Insulin and Cancer – biblio growing and growing

Study protocol: Insulin and its role in cancer.

Harish K, Dharmalingam M, Himanshu M.

ABSTRACT: BACKGROUND: Studies have shown that metabolic syndrome and its consequent biochemical derangements in the various phases of diabetes may contribute to carcinogenesis. A part of this carcinogenic effect could be attributed to hyperinsulinism. High levels of insulin decrease the production of IGF-1 binding proteins and hence increase levels of free IGF-1. It is well established that bioactivity of free insulin growth factor 1 (IGF-1) increases tumor turnover rate. The objective is to investigate the role of insulin resistance/sensitivity in carcinogenesis by studying the relation between insulin resistance/sensitivity and IGF-1 levels in cancer patients. We postulate that hyperinsulinaemia which prevails during initial phases of insulin resistance (condition prior to overt diabetes) increases bioactivity of free IGF-1, which may contribute to process of carcinogenesis. Methods / Design: Based on our pilot study results and power analysis of the same, we have designed a two group case-control study. 800 proven untreated cancer patients (solid epithelial cell tumors) under age of 50 shall be recruited with 200 healthy subjects serving as controls. Insulin resistance/sensitivity and free IGF-1 levels shall be determined in all subjects. Association between the two parameters shall be tested using suitable statistical methods.

DISCUSSION: Well controlled studies in humans are essential to study the link between insulin resistance, hyperinsulinaemia, IGF-1 and carcinogenesis. This study could provide insights to the role of insulin, insulin resistance, IGF-1 in carcinogenesis although a precise role and the extent of influence cannot be determined. In future, cancer prevention and treatment strategies could revolve around insulin and insulin resistance.

Ann Surg Oncol. 1998 Mar;5(2):194-201.Links

Altered serum levels of insulin-like growth-factor binding proteins in breast cancer patients.

Ng EH, Ji CY, Tan PH, Lin V, Soo KC, Lee KO.

Department of Surgery, Singapore General Hospital, Republic of Singapore.

BACKGROUND: Insulin-like growth factor 1 (IGF-1) has mitogenic properties for breast cancer cell lines and has been proposed to be an important factor in breast carcinogenesis. We hypothesized that differences in IGF-1 or its binding proteins might increase susceptibility to breast cancer. This case-control study was designed to investigate whether patients with breast cancer have altered levels of either IGF-1 or its intermediary modulatory proteins, the IGF binding proteins (BP). METHODS: Serum was collected from 90 patients (63 with breast cancer and 27 with benign breast disease) after an overnight fast and before surgery. IGF-1, BP1, and BP3 levels were determined by immunoradiometric assays. In a subset of 66 patients, Western ligand blots were also performed for a semiquantitative measurement of functioning BP levels. A forward stepwise logistic regression model to adjust for other confounding variables (age, menopausal status, parity, age at menarche, use of oral contraceptives, history of breast biopsy, family history of breast cancer, hormone replacement therapy, and body-mass index) was used in the multivariate analysis.

RESULTS: Serum IGF-1 levels were similar in cases and controls. However, levels of BP3 (p < 0.001), BP4 (p < 0.01), and BP1 (p < 0.05) were significantly associated with risk of breast cancer. The level of BP3 was the most significant factor predictive of breast cancer. The odds ratio for breast cancer in women with BP3 levels >2066 ng/ml was 0.18 (95% CI, 0.05-0.55). Correspondingly, women with BP1 levels higher than 39 ng/ml had an odds ratio of 0.21 (95% CI, 0.07-0.68) for breast cancer. When considering only cancer patients (n = 63), decreasing levels of BP4 (p < 0.01) and increasing levels of BP1 (p < 0.02) were significantly associated with progesterone receptor positivity (PR+) in the tumor. The odds ratio of PR+ in patients with BP1 levels higher than 34 ng/ml was 7.49 (95% CI, 1.5-37.4). Better grade of tumor (well and moderately differentiated) was observed in patients with higher levels of BP3 (p < 0.03).

CONCLUSIONS: Distinct differences in BP profiles exist among patients with breast cancer and also among those with high-grade, hormonal receptor-negative tumors. These findings suggest that the bioavailability of IGF-1 as mediated by its binding proteins may participate in both breast carcinogenesis and selection of more aggressive breast carcinomas.

 

added 12-07

INSULIN RECEPTORS AND CANCER



1: J Immunol  2002 Jun 15;168(12):6215-23 
 
Over-expression of insulin receptor substrate-1, but not insulin receptor substrate-2, protects a T cell hybridoma from activation-induced cell death.
 
Li L, Qi X, Williams M, Shi Y, Keegan AD.
 
Department of Immunology, Jerome Holland Laboratories, American Red Cross, Rockville, MD 20852, USA.
 
The insulin receptor substrate (IRS) family of signaling molecules is expressed in lymphocytes, although their functions in these cells is largely unknown. To investigate the role of IRS in the protection of T cells from activation-induced cell death (AICD), we transfected the T cell hybridoma A1.1, which is IL-4 responsive but lacks expression of IRS family members with cDNA encoding IRS1 or IRS2. Stimulation of these clones with immobilized anti-CD3-induced expression of CD69 to the same level as the parental A1.1 cells. However, the A1.1 IRS1-expressing cells were markedly resistant to AICD, while the A1.1
IRS2-expressing cells were not. Inhibition of phosphatidylinositol 3'-kinase in
the A1.1 IRS1-expressing cells did not abrogate their resistance to AICD. Fas
mRNA was induced similarly by anti-CD3 in A1.1, A1.1 IRS1-expressing, and A1.1
IRS2-expressing cells. However, induction of Fas ligand (FasL) mRNA and
functional FasL protein was delayed and decreased in IRS1-expressing cells, but
not in IRS2-expressing cells. The induction of transcription from a 500-bp FasL
promoter and a minimal 16-mer early growth response element linked to luciferase
was also impaired in the IRS1-expressing cells. These results suggest that
overexpression of IRS1, but not IRS2, protects A1.1 cells from AICD by
diminishing FasL transcription through a pathway that is independent of the
tyrosine phosphorylation of IRS1 and phosphatidylinositol 3'-kinase activity.
 
 
2: Int J Obes Relat Metab Disord  2002 Jun;26(6):747-53 
 
Upper abdominal obesity, insulin resistance and breast cancer risk.
 
Stoll BA.
 
Oncology Department, St Thomas' Hospital, London, UK.
 
PURPOSE: A majority of prospective studies show breast cancer risk to be higher
in obese postmenopausal women with upper abdominal adiposity than in those with
overall adiposity. The evidence is more limited and inconsistent in the case of
premenopausal women. The review examines evidence that aberrant insulin
signalling may be involved in the promotion of mammary carcinogenesis. The
aetiology and concomitants of abdominal visceral obesity are examined.
MECHANISMS: Clinical and experimental evidence suggests that the higher breast
cancer risk associated with greater abdominal visceral obesity may be related to
aberrant insulin signalling through the insulin receptor substrate 1 pathway,
leading to insulin resistance, hyperinsulinaemia and increased concentrations of
endogenous oestrogen and androgen. The putative role of aberrant insulin
signalling in the promotion of mammary carcinogenesis may help to explain
clinical relationships between breast cancer risk and age at menarche,
pregnancies and onset of obesity. CONCLUSION: Overall adiposity in women
adversely affects breast cancer risk mainly by greater exposure of mammary
epithelial tissue to endogenous oestrogen. Upper abdominal adiposity appears to
involve an additional effect related to the presence of insulin resistance.
Aetiological factors in the development of hyperinsulinaemic insulin resistance
are still uncertain but may involve aberrant susceptibility genes in adipocyte
insulin receptors or in the insulin receptor substrate 1 pathway. Epigenetic
factors are also likely to contribute, including high free fatty acid levels and
obesity. Dietary fatty acids, particularly polyunsaturated fatty acids, are
known to regulate adipocyte differentiation through the nuclear peroxisome
proliferator-activated receptor gamma, and may also have a role in insulin
resistance. These aetiological factors are likely to be relevant to the high
risk of postmenopausal breast cancer in industrialised Western populations.
 
3: Am J Med Sci  2002 Mar;323(3):140-5 
 
Insulin: a novel factor in carcinogenesis.
 
Gupta K, Krishnaswamy G, Karnad A, Peiris AN.
 
Department of Internal Medicine, Mountain Home VA Medical Center and East
Tennessee State University, Johnson City, Tennessee, USA.
 
Cancer is a leading cause of mortality in the United States. Despite much
research on specific carcinogens, the cause of many cancers remains unclear. The
identification of novel causative agents offers the potential for cancer
prevention. Diseases such as obesity and diabetes mellitus, characterized by
hyperinsulinemia, are associated with increased risk of endometrial, colorectal,
and breast carcinomas. There is increasing evidence that insulin is a growth
factor for tumor formation. The mechanisms underlying insulin-mediated neoplasia
may include enhanced DNA synthesis with resultant tumor cell growth, inhibition
of apoptosis, and altered sex hormone milieu. The reduced insulin levels seen
with physical activity, weight loss, and a high fiber diet may account for
decreased cancer risk. The role of newer drugs that restore sensitivity to
insulin, thereby reducing hyperinsulinemia, is an exciting potential area of
cancer prevention. In this review, we discuss the potential role of insulin as a
tumor growth factor.
 
 
4: J Clin Endocrinol Metab  2002 Jan;87(1):245-54 
 
A novel autocrine loop involving IGF-II and the insulin receptor isoform-A
stimulates growth of thyroid cancer.
 
Vella V, Pandini G, Sciacca L, Mineo R, Vigneri R, Pezzino V, Belfiore A.
 
Istituto di Medicina Interna e di Malattie Endocrine e del Metabolismo, Cattedra
di Endocrinologia, University of Catania, Ospedale Garibaldi, 95123 Catania,
Italy.
 
The insulin receptor (IR) occurs in two isoforms (IR-A and IR-B) resulting from
alternative splicing of exon 11 of the gene. The IR-A isoform is predominantly
expressed in fetal tissues and malignant cells and binds IGF-II with high
affinity. We previously observed that IRs are overexpressed in thyroid cancer
cells; now we evaluated whether these cells preferentially express IR-A and
produce IGF-II, which would activate a growth-promoting autocrine loop. The IR
content ranged 6.0-52.6 ng/100 microg cell membrane protein in thyroid cancer
primary cultures (n = 8) and permanent cell lines (n = 6) vs. 1.2-1.7 in normal
thyroid cells (n = 11 primary cultures; P < 0.0001). IR-A isoform relative
abundance ranged from 36-79% in cancer cells (with the highest values in
undifferentiated cancers) vs. 27-39% in normal cells. Similar results were
obtained in normal vs. cancer thyroid tissue specimens. IGF-II caused IR
autophosphorylation with an ED(50) of 1.5-40.0 nM in cancer cells vs. more than
100 nM in normal cells; IGF-II affinity correlated with the relative abundance
of IR-A (r = 0.628; P < 0.0001). IGF-II was expressed in all cancer cells,
highly expressed in anaplastic cells, and less expressed in normal cells. In
conclusion, malignant thyrocytes, especially when poorly differentiated, produce
IGF-II and overexpress IR, predominantly as IGF-II-sensitive isoform A. A
growth-promoting autocrine loop is activated, therefore, and may affect thyroid
cancer biology.
 
5: Diabetes Metab  2001 Sep;27(4 Pt 2):S7-12 
 
[Resistance to insulin and polycystic ovary syndrome]
 
[Article in French]
 
Ducluzeau PH, Laville M, Vidal H, Pugeat M.
 
Federation d'Endocrinologie, Hopital de l'Antiquaille, Hospices Civils de Lyon.
michel.pugeat@chu-lyon.fr
 
 
6: Brain Res Mol Brain Res  2001 Dec 30;97(2):161-70 
 
Altered insulin receptor processing and function in scrapie-infected
neuroblastoma cell lines.
 
Ostlund P, Lindegren H, Pettersson C, Bedecs K.
 
Department of Neurochemistry and Neurotoxicology, University of Stockholm,
Svante Arrhenius v. 21A, S-10691 Stockholm, Sweden.
 
The underlying neurochemical changes contributing to prion-induced
neurodegeneration remain largely unknown. This study shows that scrapie
infection induced a 2-fold increase of insulin receptor (IR) protein and
aberrantly processed IR beta-chain in scrapie-infected N2a neuroblastoma cells
(ScN2a) as measured by Western blot of immunoprecipitated IR, in the absence of
increased IR mRNA. Elevated IR protein level was further confirmed in an
independently scrapie-infected neuroblastoma cell line N1E-115 (ScN1E-115).
Proliferation studies showed that the increased IR level in ScN2a did not result
in an increased insulin-mediated cell growth compared to normal N2a cells.
Binding studies indicated that this apparent paradox was due to a 65% decrease
in specific [(125)I]insulin binding sites in ScN2a when compared to the amount
of immunoreactive IR, although the IR binding affinity was unchanged. Analysis
of insulin stimulated IR tyrosine phosphorylation showed a slight but not
significant reduction in ScN2a, when related to the increased level of
immunoreactive IR. However, comparing the IR tyrosine phosphorylation to the
loss of binding sites in ScN2a, we demonstrated an increased IR tyrosine
phosphorylation of the remaining functional IR. In addition to these differences
in IR properties, the basal extracellular signal regulated kinase-2 (ERK2)
phosphorylation detected by Western blot, was significantly elevated and the
insulin stimulated ERK2 phosphorylation was subsequently decreased in ScN2a.
Together, these data show that scrapie infection affects the level and
processing of the IR and signal transduction mediated by the IR in neuroblastoma
cells, as well as induces an elevated basal ERK2 phosphorylation. Aberrant
regulation of neuroprotective receptors may contribute to neurodegeneration in
prion diseases.
 
 
7: J Endocrinol  2001 Nov;171(2):285-92 
 
Expression of insulin target genes in skeletal muscle and adipose tissue in
adult patients with growth hormone deficiency: effect of one year recombinant
human growth hormone therapy.
 
Khalfallah Y, Sassolas G, Borson-Chazot F, Vega N, Vidal H.
 
INSERM U.449, Rene Laennec Faculty of Medicine, Lyon, France.
 
Our aim was to investigate the effects of one year recombinant human growth
hormone (rhGH) therapy on the regulation by insulin of gene expression in muscle
and adipose tissue in adults with secondary GH deficiency (GHD). Six GHD
subjects without upper-body obesity were submitted to a 3-h euglycemic
hyperinsulinemic clamp before and after one year of rhGH therapy. Muscle and
abdominal subcutaneous adipose tissue biopsies were taken before and at the end
of each clamp. The mRNA levels of insulin receptor, p85
alpha-phosphatidylinositol-3 kinase (p85 alpha PI-3K), insulin dependent glucose
transporter (Glut4), hexokinase II, glycogen synthase, lipoprotein lipase (LPL)
in muscle and in adipose tissue, hormone sensitive lipase and peroxisome
proliferator-activated receptor gamma (PPAR gamma) in adipose tissue were
quantified by RT-competitive PCR. One year treatment with rhGH (1.25 IU/day)
increased plasma IGF-I concentrations (54+/-7 vs 154+/-11 ng/ml, P<0.01) but did
not affect insulin-stimulated glucose disposal rate measured during the
hyperinsulinemic clamp (74+/-9 vs 85+/-5 micromol/kg free fat mass/min). Insulin
significantly increased p85 alpha PI-3K, hexokinase II and Glut4 mRNA levels in
muscle both before and after rhGH treatment. One year of GH therapy increased
LPL mRNA levels in muscle (38+/-2 vs 70+/-7 amol/microg total RNA, P<0.05) and
in adipose tissue (2490+/-260 vs 4860+/-880 amol/microg total RNA, P<0.05), but
did not change the expression of the other mRNAs. We conclude from this study
that GH therapy did not alter whole body insulin sensitivity and the response of
gene expression to insulin in skeletal muscle of adult GHD patients, but it did
increase LPL expression in muscle and adipose tissue. This result could be
related to the documented beneficial effect of GH therapy on lipid metabolism.
 
 
8: J Biol Chem  2001 Oct 26;276(43):40362-7 
 
Regulation of insulin/insulin-like growth factor-1 signaling by
proteasome-mediated degradation of insulin receptor substrate-2.
 
Rui L, Fisher TL, Thomas J, White MF.
 
Howard Hughes Medical Institute, Joslin Diabetes Center, Harvard Medical School,
One Joslin Place, Boston, MA 02215, USA.
 
Insulin and insulin-like growth factor-1 (IGF-1) regulate metabolism and body
growth through homologous receptor tyrosine kinases that phosphorylate the
insulin receptor substrate (IRS) proteins. IRS-2 is an important IRS protein, as
it mediates peripheral insulin action and beta-cell survival. In this study, we
show that insulin, IGF-1, or osmotic stress promoted
ubiquitin/proteasome-mediated degradation of IRS-2 in 3T3-L1 cells, Fao
hepatoma, cells and mouse embryo fibroblasts; however, insulin/IGF-1 did not
promote degradation of IRS-1 in 3T3-L1 preadipocytes or mouse embryo
fibroblasts. MG132 or lactacystin, specific inhibitors of 26S proteasome,
blocked insulin/IGF-1-induced degradation of IRS-2 and enhanced the detection of
ubiquitinated IRS-2. Insulin/IGF1-induced ubiquitination and degradation of
IRS-2 was blocked by inhibitors of phosphatidylinositol 3-kinase (wortmannin or
LY294002) or mTOR (rapamycin). Chronic insulin or IGF-1 treatment of
IRS-1-deficient mouse embryo fibroblasts inhibited IRS-2-mediated activation of
Akt and ERK1/2, which was reversed by lactacystin pretreatment. By contrast,
IRS-1 activation of Akt and ERK1/2 was not inhibited by chronic insulin/IGF-1
stimulation in IRS-2-deficient mouse embryo fibroblasts. Thus, we identified a
novel negative feedback mechanism by which the ubiquitin/proteasome-mediated
degradation of IRS-2 limits the magnitude and duration of the response to
insulin or IGF-1.
 
 
9: Physiologist  1993 Feb;36(1 Suppl):S160-1 
 
Enhancement of insulin receptor mediated endocytosis in cultured osteoblastic
cells under hypergravity.
 
Malouvier A, Holy X, Zerath E, Marie PJ, Schmitt DA.
 
CERMA, Division Histophysiologie, Centre d'Essais en Vol, Bretigny Sur Orge,
France.
 
 
10: Clin Endocrinol (Oxf)  2001 Aug;55(2):191-9 
 
Tissue insulin sensitivity and body weight in polycystic ovary syndrome.
 
Marsden PJ, Murdoch AP, Taylor R.
 
Department of Obstetrics and Gynaecology, University Hospital of North Durham,
Durham, UK. Philippa_Marsden@hotmail.com
 
OBJECTIVE: Polycystic ovarian syndrome (PCOS) and obesity both affect insulin
sensitivity. This study was designed to investigate the biochemical indices of
PCOS and tissue insulin sensitivity in groups of lean and obese women with
clinically equivalent degrees of the syndrome, relative to control subjects.
DESIGN: A prospective study of in vivo parameters and in vitro study of
adipocytes to assess insulin sensitivity. PATIENTS: Six lean and 14 overweight
patients fulfilling formal diagnostic criteria for PCOS were studied. The degree
of hirsutism and amenorrhoea was similar in each group. Eight control subjects
were also studied. MEASUREMENTS: Endocrine and metabolic parameters were
measured in lean and overweight patients with PCOS and control subjects. In
vitro studies of adipocyte insulin receptor binding and adipocyte insulin action
were performed. RESULTS: The mean plasma LH level was elevated in both groups of
PCOS but was significantly higher in the lean group (LH levels were 25.1 +/- 3.1
and 14.5 +/- 1.6 iu/l in lean PCOS and obese PCOS, respectively (P = 0.01)).
There was a strong inverse correlation between BMI and LH levels (R = - 0.70, P
= 0.001). Fasting insulin levels were elevated in both lean and obese groups
(11.5 +/- 2.8 and 26.8 +/- 8.1 mU/l, respectively; P = 0.068). Mean serum
testosterone and serum androstenedione levels were also elevated in PCOS
compared to control subjects but there was no difference between the two groups
of PCOS subjects. Insulin receptor binding in amenorrhoeic subjects with PCOS
was low in both lean and obese patients with PCOS but was not significantly
different between the two groups (0.79 +/- 0.17% and 0.66 +/- 0.07% per 10 cm2
cell membrane, respectively). Maximally insulin-stimulated rates of
3-O-methylglucose transport were low in both groups compared to previously
studied normal subjects (0.96 +/- 0.21 and 0.64 +/- 0.07 pmol per 10 cm2
membrane in lean and obese PCOS subjects, respectively; P = NS). CONCLUSIONS:
Lean subjects with a given phenotypic expression of PCOS have an equivalent
degree of tissue insulin resistance compared to obese PCOS subjects. This
implies that the insulin resistance may be a primary feature of PCOS. If this is
so, a similar clinical degree of the syndrome may be brought about by
genetically determined insulin resistance in lean subjects or by insulin
resistance which is secondary to obesity.
 
PMID: 11531925 [PubMed - indexed for MEDLINE]
 
 
 
11: Med Hypotheses  2001 Aug;57(2):146-50 
 
Insulin secretion as a determinant of pancreatic cancer risk.
 
McCarty MF.
 
Pantox Laboratories, 4622 Santa Fe St, San Diego, CA 92109, USA.
 
New epidemiology confirms that glucose intolerance is a risk factor for
pancreatic cancer, and that this association cannot be accounted for by an
adverse impact of early pancreatic cancer on beta cell function. Previous
reports indicate that risk for pancreatic cancer is increased in adult-onset
diabetics. Since streptozotocin diabetes inhibits carcinogen-mediated induction
of pancreatic cancer in hamsters, the most reasonable interpretation of these
findings is that insulin (or some other beta cell product) acts as a promoter
for pancreatic carcinogenesis. This view is consistent with a report that human
pancreatic adenocarcinomas express insulin receptors that can stimulate mitosis;
an additional possibility is that high insulin levels indirectly promote
pancreatic carcinogenesis by boosting effective IGF-I activity via hepatic
actions. In international ecologic epidemiology, pancreatic cancer rates
correlate tightly with dietary intake of animal products; this may reflect the
fact that vegan diets are associated with low diurnal insulin secretion. There
is also suggestive evidence that macrobiotic vegan diets, which are low in
glycemic index, may increase mean survival time in pancreatic cancer. However,
other types of diets associated with decreased postprandial insulin response,
such as high-protein diets or 'Mediterranean' diets high in oleic acid, may also
have the potential for pancreatic cancer prevention. The huge increases of
age-adjusted pancreatic cancer mortality in Japan and among African-Americans
during the last century imply that pancreatic cancer is substantially
preventable; a low-insulin-response diet coupled with exercise training, weight
control, and smoking avoidance, commendable for a great many other reasons, may
slash pancreatic cancer mortality dramatically. Copyright 2001 Harcourt
Publishers Ltd.
 
PMID: 11461162 [PubMed - indexed for MEDLINE]
 
 
 
12: Eur J Endocrinol  2001 Aug;145(2):213-21 
 
Effects of IGF-I and -II, IGF binding protein-3 (IGFBP-3), and transforming
growth factor-beta (TGF-beta) on growth and apoptosis of human osteosarcoma
Saos-2/B-10 cells: lack of IGF-independent IGFBP-3 effects.
 
Schmid C, Ghirlanda-Keller C, Zapf J.
 
Division of Endocrinology and Diabetes, Department of Medicine, University
Hospital, 8091 Zurich, Switzerland. ndozaj@usz.unizh.ch
 
OBJECTIVE: Insulin-like growth factor binding protein-3 (IGFBP-3) inhibits cell
growth. Previous reports have suggested the existence of plasma membrane IGFBP-3
receptors that could mediate direct, IGF-independent effects. Thus far, however,
the only well-defined putative IGFBP-3 receptor is the type V transforming
growth factor-beta (TGF-beta) receptor, a membrane glycoprotein that mediates
TGF-beta-induced growth inhibition in selected cells. The aim of the study was
to test whether IGFBP-3 and TGF-beta exert short-term effects in an osteosarcoma
cell line that produces no IGF but contains type 1 IGF receptors. DESIGN: DNA
synthesis and apoptosis in Saos-2/B-10 cells were measured in response to IGF-I,
IGF-II, IGFBP-3 and TGF-beta2, and to type 1 IGF receptor ligands with poor
affinity for IGFBP-3 ([QAYL]-IGF-I and insulin). RESULTS: IGF-I and IGF-II
stimulated thymidine incorporation into DNA and suppressed apoptosis in a
dose-dependent manner with maximal effects at 1 and 3 nM respectively. TGF-beta2
slightly increased thymidine incorporation into DNA but had no effect on
apoptosis. IGFBP-3 had no effect by itself. Whereas it blocked the above effects
of 1 nmol/l IGF-I, it did not block those of 1 nmol/l [QAYL]-IGF-I or 100 nmol/l
insulin. CONCLUSIONS: IGFBP-3 does not affect DNA synthesis or apoptosis in an
IGF-independent manner in IGF-responsive osteosarcoma cells. It therefore
appears to act essentially by sequestration of IGF.
 
PMID: 11454519 [PubMed - indexed for MEDLINE]
 
 
 
13: Am J Physiol Endocrinol Metab  2001 Aug;281(2):E392-9 
 
Defects in insulin receptor signaling in vivo in the polycystic ovary syndrome
(PCOS).
 
Dunaif A, Wu X, Lee A, Diamanti-Kandarakis E.
 
Division of Women's Health, Department of Medicine, Brigham and Women's
Hospital, Boston, Massachusetts 02115, USA.
 
Women with polycystic ovary syndrome (PCOS) are insulin resistant secondary to a
postbinding defect in insulin signaling. Sequential euglycemic glucose clamp
studies at 40 and 400 mU. m(-2). min(-1) insulin doses with serial skeletal
muscle biopsies were performed in PCOS and age-, weight-, and ethnicity-matched
control women. Steady-state insulin levels did not differ, but insulin-mediated
glucose disposal was significantly decreased in PCOS women (P < 0.05). Insulin
receptor substrate (IRS)-1-associated phosphatidylinositol 3-kinase (PI 3K)
activity was significantly decreased in PCOS (n = 12) compared with control
skeletal muscle (n = 8; P < 0.05). There was no significant difference in the
abundance of IR, IRS-1, or the p85 regulatory subunit of PI 3K in PCOS (n = 14)
compared with control (n = 12) muscle. The abundance of IRS-2 was significantly
increased (P < 0.05) in PCOS skeletal muscle, suggesting a compensatory change.
We conclude that there is a physiologically relevant defect in insulin receptor
signaling in PCOS that is independent of obesity and type 2 diabetes mellitus.
 
Publication Types:
Clinical Trial
Controlled Clinical Trial
 
PMID: 11440917 [PubMed - indexed for MEDLINE]
 
 
 
14: Mol Cell Biol Res Commun  2000 Oct;4(4):234-8 
 
Complexes formation between insulin receptor and extracellular signal-regulated
kinases ERKs.
 
Lin YL, Mettling C, Chou CK.
 
Institut de Genetique Humaine, Centre National de la Recherche Scientifique, 141
rue de la Cardonille, Montpellier Cedex 5, 34396, France
 
A property of signal transduction pathways that might explain their efficiency
and specificity is the formation of signaling complexes. The recent
demonstration that adaptor proteins can interact with many components of the
extracellular signal-regulated kinases (ERKs) signaling cascade leads us to
investigate whether such complexes may include the transmembrane receptor. The
present work shows that in human hepatoma Hep3B cells, insulin receptor (IR) can
be coimmunoprecipitated with other components of the ERKs cascade: insulin
receptor substrate (IRS), Raf-1, and ERKs. Furthermore, these complexes formed
near the cytoplasmic membrane even prior to insulin stimulation. Copyright 2001
Academic Press.
 
PMID: 11409918 [PubMed - indexed for MEDLINE]
 
 
 
15: Mol Pathol  2001 Jun;54(3):138-44 
 
The IGF axis and hepatocarcinogenesis.
 
Scharf JG, Dombrowski F, Ramadori G.
 
Department of Medicine, Division of Gastroenterology and Endocrinology,
Georg-August-Universitat, D-37075 Gottingen, Germany.
jscharf@med.uni-goettingen.de
 
Deregulation of the insulin-like growth factor (IGF) axis, including the
autocrine production of IGFs, IGF binding proteins (IGFBPs), IGFBP proteases,
and the expression of the IGF receptors, has been identified in the development
of hepatocellular carcinoma (HCC). Characteristic alterations detected in HCC
and hepatoma cell lines comprise the increased expression of IGF-II and the
IGF-I receptor (IGF-IR), which have emerged as crucial events in malignant
transformation and the growth of tumours. Alterations of IGFBP production and
the proteolytic degradation of IGFBPs resulting in an excess of bioactive IGFs,
as well as the defective function of the IGF degrading IGF-II/mannose
6-phosphate receptor (IGF-II/M6PR), may further potentiate the mitogenic effects
of IGFs in the development of HCC.
 
Publication Types:
Review
Review, Tutorial
 
PMID: 11376124 [PubMed - indexed for MEDLINE]
 
 
 
16: Mol Pathol  2001 Jun;54(3):121-4 
 
The IGF system in thyroid cancer: new concepts.
 
Vella V, Sciacca L, Pandini G, Mineo R, Squatrito S, Vigneri R, Belfiore A.
 
Cattedra di Endocrinologia, Istituto di Medicina Interna, Malattie Endocrine e
del Metabolismo, University of Catania, Ospedale Garibaldi, Catania, Italy.
 
In recent years, the activation of the insulin-like growth factor (IGF) system
in cancer has emerged as a key factor for tumour progression and resistance to
apoptosis. Therefore, a variety of strategies have been developed to block the
type I IGF receptor (IGF-I-R), which is thought to mediate the biological
effects of both IGF-I and IGF-II. However, recent data suggest that the IGF
signalling system is complex and that other receptors are involved. To unravel
the complexity of the IGF system in thyroid cancer, IGF-I and IGF-II production,
and the expression and function of their cognate receptors were studied. Both
IGFs were found to be locally produced in thyroid cancer: IGF-I by stromal cells
and IGF-II by malignant thyrocytes. Values were significantly higher in
malignant tissue than in normal tissue. IGF-I-Rs were overexpressed in
differentiated papillary carcinomas but not in poorly differentiated or
undifferentiated tumours, whereas insulin receptors (IRs) were greatly
overexpressed in all tumour hystotypes, with a trend for higher values in
dedifferentiated tumours. As a consequence of IR overexpression, high amounts of
IR/IGF-I-R hybrids (which bind IGF-I with high affinity) were present in all
thyroid cancer histotypes. Because of recent evidence that isoform A of IR
(IR-A) is a physiological receptor for IGF-II in fetal life, the relative
abundance of IR-A in thyroid cancer was measured. Preliminary data indicate that
overexpressed IRs mainly occur as IR-A in thyroid cancer. These data indicate
that both IR/IGF-I-R hybrids and IR-A play an important role in the
overactivation of the IGF system in thyroid cancer and in IGF-I mitogenic
signalling in these tumours. J Clin PATHOL: Mol Pathol
 
Publication Types:
Review
Review, Tutorial
 
PMID: 11376121 [PubMed - indexed for MEDLINE]
 
 
 
17: J Biol Chem  2001 Apr 27;276(17):14459-65 
 
Insulin stimulates PKCzeta -mediated phosphorylation of insulin receptor
substrate-1 (IRS-1). A self-attenuated mechanism to negatively regulate the
function of IRS proteins.
 
Liu YF, Paz K, Herschkovitz A, Alt A, Tennenbaum T, Sampson SR, Ohba M, Kuroki
T, LeRoith D, Zick Y.
 
Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot
76100, Israel.
 
Incubation of rat hepatoma Fao cells with insulin leads to a transient rise in
Tyr phosphorylation of insulin receptor substrate (IRS) proteins. This is
followed by elevation in their P-Ser/Thr content, and their dissociation from
the insulin receptor (IR). Wortmannin, a phosphatidylinositol 3-kinase (PI3K)
inhibitor, abolished the increase in the P-Ser/Thr content of IRS-1, its
dissociation from the IR, and the decrease in its P-Tyr content following 60 min
of insulin treatment, indicating that the Ser kinases that negatively regulate
IRS-1 function are downstream effectors of PI3K. PKCzeta fulfills this
criterion, being an insulin-activated downstream effector of PI3K.
Overexpression of PKCzeta in Fao cells, by infection of the cells with
adenovirus-based PKCzeta construct, had no effect on its own, but it accelerated
the rate of insulin-stimulated dissociation of IR.IRS-1 complexes and the rate
of Tyr dephosphorylation of IRS-1. The insulin-stimulated negative regulatory
role of PKCzeta was specific and could not be mimic by infecting Fao cells with
adenoviral constructs encoding for PKC alpha, delta, or eta. Because the
reduction in P-Tyr content of IRS-1 was accompanied by a reduced association of
IRS-1 with p85, the regulatory subunit of PI3K, it suggests that this negative
regulatory process induced by PKCzeta, has a built-in attenuation signal. Hence,
insulin triggers a sequential cascade in which PI3K-mediated activation of
PKCzeta inhibits IRS-1 functions, reduces complex formation between IRS-1 and
PI3K, and inhibits further activation of PKCzeta itself. These findings
implicate PKCzeta as a key element in a multistep negative feedback control
mechanism of IRS-1 functions.
 
PMID: 11278339 [PubMed - indexed for MEDLINE]
 
 
 
18: Exp Cell Res  2001 Apr 1;264(2):388-96 
 
Loss of insulin-like growth factor II receptor expression promotes growth in
cancer by increasing intracellular signaling from both IGF-I and insulin
receptors.
 
Osipo C, Dorman S, Frankfater A.
 
Division of Molecular and Cellular Biochemistry, Loyola University Medical
Center, Maywood, Illinois 60153, USA.
 
The insulin-like growth factor-II receptor (IGF-IIR) is frequently mutated or
deleted in some malignant human tumors, suggesting that the IGF-IIR is a tumor
suppressor. However, the exact mechanism by which IGF-IIR suppresses growth in
tumors has not been definitively established. We demonstrate that
IGF-IIR-deficient murine L cells (D9) have higher growth rates than
IGF-IIR-positive L cells (Cc2) in response to IGF-II. IGF-II levels are higher
in growth-conditioned medium from D9 versus Cc2 cells. Receptor neutralization
studies and measurements of insulin receptor substrate 1 phosphorylation confirm
that the enhanced growth of D9 cells is due to increased stimulation of the
IGF-I and insulin receptors by IGF-II. In contrast, the levels of secreted
latent and active transforming growth factor beta (TGF-beta) are similar for
both D9 and Cc2 cells, indicating that the slower growth of Cc2 cells is not due
to activation of latent TGF-beta by IGF-IIR and growth inhibition. The results
directly demonstrate that down regulation of the IGF-IIR promotes the growth of
transformed D9 cells by sustaining IGF-II, which binds to and activates IGF-IR
and insulin receptor to increase intracellular growth signals. Copyright 2001
Academic Press.
 
PMID: 11262195 [PubMed - indexed for MEDLINE]
 
 
 
19: Srp Arh Celok Lek  2000 Sep-Oct;128(9-10):335-9 
 
[The role of insulin and hyperinsulinemia in the pathogenesis of the polycystic
ovary syndrome]
 
[Article in Serbo-Croatian (Cyrillic)]
 
Vasiljevic M.
 
Publication Types:
Review
Review, Academic
 
PMID: 11255689 [PubMed - indexed for MEDLINE]
 
 
 
20: Cancer Lett  2001 Jan 26;162(2):253-60 
 
Expression levels of insulin-like growth factor binding proteins and insulin
receptor isoforms in hepatoblastomas.
 
von Horn H, Tally M, Hall K, Eriksson T, Ekstrom TJ, Gray SG.
 
Laboratory for Molecular Development and Tumor Biology, Experimental Alcohol and
Drug Addiction Research Section, Department of Clinical Neuroscience, Karolinska
Institute, CMM, L8 01, S-171 76, Stockholm, Sweden.
 
Hepatoblastoma, a rare pediatric liver tumour, is a poorly understood disease.
While expression studies for some members of the Insulin-like growth factor axis
have been studied in hepatoblastoma, a systematic analysis of the IGF-axis has
not been carried out. We have examined a series of hepatoblastomas with matched
normal liver tissue for gene expression differences with emphasis on members of
the insulin-like growth factor binding proteins. The expression profiles
obtained reveal that the expression of these genes are altered in these tumors.
The results indicate that the IGF-axis is seriously disturbed in the tumors.
 
PMID: 11146233 [PubMed - indexed for MEDLINE]
 
 
 
21: Toxicol Sci  2001 Jan;59(1):178-84 
 
Effects of dichloroacetate (DCA) on serum insulin levels and insulin-controlled
signaling proteins in livers of male B6C3F1 mice.
 
Lingohr MK, Thrall BD, Bull RJ.
 
Washington State University, Pullman, Washington 99164-6510, USA.
 
DCA is hepatocarcinogenic in rodents. At carcinogenic doses, DCA causes a large
accumulation of liver glycogen. Thus, we studied the effects of DCA treatment on
insulin levels and expression of insulin-controlled signaling proteins in the
liver. DCA treatment (0.2-2.0 g/l in drinking water for 2 weeks) reduced serum
insulin levels. The decrease persisted for at least 8 weeks. In livers of mice
treated with DCA for 2-, 10-, and 52-week periods, insulin receptor (IR) protein
levels were significantly depressed. Additionally, protein kinase B (PKBalpha)
expression decreased significantly with DCA treatment. In normal liver, glycogen
levels were increased as early as at 1 week, and this effect preceded changes in
insulin and IR and PKBalpha. In contrast to normal liver, IR protein was
elevated in DCA-induced liver tumors relative to that in liver tissue of
untreated animals and to an even greater extent when compared to adjacent normal
liver in the treated animal. Mitogen-activated protein kinase (MAP kinase)
phosphorylation was also increased in tumor tissue relative to normal liver
tissue and tissue from untreated controls. These data suggest that normal
hepatocytes down-regulate insulin-signaling proteins in response to the
accumulation of liver glycogen caused by DCA. Furthermore, these results suggest
that the initiated cell population, which does not accumulate glycogen and is
promoted by DCA treatment, responds differently from normal hepatocytes to the
insulin-like effects of this chemical. The differential sensitivity of the 2
cell populations may contribute to the tumorigenic effects of DCA in the liver.
 
PMID: 11134557 [PubMed - indexed for MEDLINE]
 
 
 
22: Laryngorhinootologie  2000 Jul;79(7):438-41 
 
[Detection of overexpression of insulin receptor gene in laryngeal carcinoma
cells by using differential display method]
 
[Article in German]
 
Maune S, Gorogh T.
 
Klinik fur Hals-, Nasen-, Ohrenheilkunde, Kopf- und Halschirurgie,
Christian-Albrechts-Universitat zu Kiel. maune@hno.uni-kiel.de
 
BACKGROUND: The insulin receptor (IR) is an essential protein localized on the
surface of almost all cell types. IR belongs to the tyrosine-kinase growth
factor receptor family. Insulin mediates proliferative responses in a variety of
tumor cells, however, the role of the IR molecule in carcinogenesis has not yet
exactly been established. METHODS: Messenger RNA from mucosal keratinocytes and
laryngeal carcinoma cells were transcribed in cDNA using reverse transcriptase
and amplified by PCR by means of a number of oligonucleotides. PCR products were
analyzed electrophoretically. RESULTS: Comparing the electrophoretic pattern of
both cell types the overexpression of a 127 bp fragment could be detected in
laryngeal carcinoma cells in contrast to benign keratinocytes. Cloning and
sequencing this fragment exact homologous match was found with exon-2 of the IR
gene. The overexpression of the IR gene in laryngeal carcinoma cells was
confirmed by Northern hybridization. CONCLUSIONS: The results show up-regulation
of IR-mRNA in laryngeal carcinoma cells suggesting that the number of IR is
enhanced in these cells. Hence it follows, that the overexpression of IR plays a
possible role in laryngeal cancer initiation and/or progression.
 
PMID: 11005099 [PubMed - indexed for MEDLINE]
 
 
 
23: Eur J Nutr  2000 Apr;39(2):67-70 
 
Paleolithic vs. modern diets--selected pathophysiological implications.
 
Eaton SB, Eaton SB 3rd.
 
Dept Anthropology, Emory University, Atlanta, GA 30327, USA. sboydeaton@aol.com
 
The nutritional patterns of Paleolithic humans influenced genetic evolution
during the time segment within which defining characteristics of contemporary
humans were selected. Our genome can have changed little since the beginnings of
agriculture, so, genetically, humans remain Stone Agers--adapted for a
Paleolithic dietary regimen. Such diets were based chiefly on wild game, fish
and uncultivated plant foods. They provided abundant protein; a fat profile much
different from that of affluent Western nations; high fibre; carbohydrate from
fruits and vegetables (and some honey) but not from cereals, refined sugars and
dairy products; high levels of micronutrients and probably of phytochemicals as
well. Differences between contemporary and ancestral diets have many
pathophysiological implications. This review addresses phytochemicals and
cancer; calcium, physical exertion, bone mineral density and bone structural
geometry; dietary protein, potassium, renal acid secretion and urinary calcium
loss; and finally sarcopenia, adiposity, insulin receptors and insulin
resistance. While not, yet, a basis for formal recommendations, awareness of
Paleolithic nutritional patterns should generate novel, testable hypotheses
grounded in evolutionary theory and it should dispel complacency regarding
currently accepted nutritional tenets.
 
Publication Types:
Historical Article
 
PMID: 10918987 [PubMed - indexed for MEDLINE]
 
 
 
24: J Biol Chem  2000 Jul 7;275(27):20880-6 
 
Selective attenuation of metabolic branch of insulin receptor down-signaling by
high glucose in a hepatoma cell line, HepG2 cells.
 
Nakajima K, Yamauchi K, Shigematsu S, Ikeo S, Komatsu M, Aizawa T, Hashizume K.
 
Department of Aging Medicine and Geriatrics, Shinshu University School of
Medicine, 3-1-1 Asahi, Matsumoto 390-8621, Japan.
 
The effects of a high concentration of glucose on the insulin receptor-down
signaling were investigated in human hepatoma (HepG2) cells in vitro to
delineate the molecular mechanism of insulin resistance under glucose toxicity.
Treatment of the cells with high concentrations of glucose (15-33 mm) caused
phosphorylation of serine residues of the insulin receptor substrate 1 (IRS-1),
leading to reduced electrophoretic mobility of it. The phosphorylation of IRS-1
with high glucose treatment was blocked only by protein kinase C (PKC)
inhibitors. The high glucose treatment attenuated insulin-induced association of
IRS-1 and phosphatidylinositol 3-kinase and insulin-stimulated phosphorylation
of Akt. A metabolic effect of insulin, stimulation of glycogen synthesis, was
also inhibited by the treatment. In contrast, insulin-induced association of Shc
and Grb2 was not inhibited. Treatment of the cells with high glucose promoted
the translocation of PKCepsilon and PKCdelta from the cytosol to the plasma
membrane but not that of other PKC isoforms. Finally, PKCepsilon and PKCdelta
directly phosphorylated IRS-1 under cell-free conditions. We conclude that a
high concentration of glucose causes phosphorylation of IRS-1, leading to
selective attenuation of metabolic signaling of insulin. PKCepsilon and PKCdelta
are involved in the down-regulation of insulin signaling, and they may lie in a
pathway regulating the phosphorylation of IRS-1.
 
PMID: 10764799 [PubMed - indexed for MEDLINE]
 
 
 
25: J Clin Endocrinol Metab  2000 Mar;85(3):1232-8 
 
The intracellular mechanism of insulin resistance in pancreatic cancer patients.
 
Liu J, Knezetic JA, Strommer L, Permert J, Larsson J, Adrian TE.
 
Department of Biomedical Sciences, Creighton University School of Medicine,
Omaha, Nebraska 68178, USA.
 
The diabetes that frequently occurs in pancreatic cancer patients is
characterized by profound peripheral insulin resistance. The intracellular
mechanism of this insulin resistance was investigated in skeletal muscle
biopsies from pancreatic cancer patients with or without diabetes and control
subjects. Insulin receptor (IR) binding, tyrosine kinase activity, IR messenger
RNA (mRNA), IR substrate-1 content, GLUT-4, and GLUT-4 mRNA content were all
normal in pancreatic cancer patients. In contrast, multiple defects in glycogen
synthesis were found in pancreatic cancer patients, especially in those with
diabetes. Glycogen synthase I activity, total activity, and mRNA levels were
significantly decreased in pancreatic cancer patients compared with controls.
The fractional velocity of glycogen synthase was decreased only in the diabetic
pancreatic cancer group. Glycogen phosphorylase a and b activities were
increased in diabetic pancreatic cancer patients, but glycogen phosphorylase
mRNA levels were not significantly different. The insulin resistance associated
with pancreatic cancer is associated with a post-IR defect, which impairs
skeletal muscle glycogen synthesis and glycogen storage.
 
Publication Types:
Clinical Trial
 
PMID: 10720068 [PubMed - indexed for MEDLINE]
 
 
 
26: Diabetes Metab Res Rev  2000 Jan-Feb;16(1):26-32 
 
High insulin levels do not influence PC-1 gene expression and protein content in
human muscle tissue and hepatoma cells.
 
Frittitta L, Sbraccia P, Costanzo BV, Tassi V, D'Adamo M, Spampinato D, Ercolino
T, Purrello F, Tamburrano G, Vigneri R, Trischitta V.
 
Institute of Internal Medicine, Endocrine and Metabolic Diseases, University of
Catania, Garibaldi Hospital, Catania, Italy. segmeint@mbox.unict.it
 
BACKGROUND: To verify whether insulin levels influence PC-1 tissue content, we
studied PC-1 gene expression and protein content in skeletal muscle of patients
with insulinoma, a model of primary hyperinsulinemia. Data were compared with
those obtained in matched insulin sensitive or resistant healthy subjects. In
addition, the effect of high insulin concentration on PC-1 protein content was
studied in HepG2 cells. METHODS: The following measurements were performed:
insulin sensitivity by euglycemic clamp; PC-1 protein content and insulin
receptor autophosphorylation by specific ELISAs; PC-1 gene expression by
competitive polymerase chain reaction (PCR); phosphatidyl-inositol-3 kinase by
immunoprecipitation and thin layer chromatography; glycogen synthesis by
(14)C-glucose incorporation. RESULTS: Muscle PC-1 content was similar in the
insulinoma patients and in insulin sensitive controls but higher (p<0.01) in
insulin resistant controls (21.9+/-4.6 ng/mg protein, 23.8+/-3.9, 48.0+/-8.7,
respectively). PC-1 protein content was inversely correlated with insulin
sensitivity (r=-0.5, p<0.015) but with neither plasma insulin nor glucose
levels. PC-1 protein content was correlated with PC-1 gene expression (r=0.53,
p<0.05, n=14). Exposure to high insulin (100 nmol/l for 16 h) caused a
significant (p<0.05-0.01) impairment of insulin receptor autophosphorylation,
phosphatidyl-inositol-3 kinase activity and glycogen synthesis, but not of PC-1
protein content (114+/-3 vs 102+/-14 ng/mg protein) in HepG2 cells. CONCLUSION:
These findings suggest that chronic high insulin levels do not influence PC-1
expression. Copyright 2000 John Wiley & Sons, Ltd.
 
PMID: 10707036 [PubMed - indexed for MEDLINE]
 
 
 
27: J Cell Biochem  1999;Suppl 32-33:68-75 
 
Differentiation and malignant transformation: two roads diverged in a wood.
 
Baserga R, Morrione A.
 
Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania
19107, USA. r_baserga@lac.jci.tju.edu
 
Growth factors and their receptors are known to send at times contradictory
signals, such as proliferation or differentiation. Recent developments in our
knowledge of growth factor receptors and their signaling pathways have clarified
the basis for this puzzling behavior. Separate domains of a receptor and/or the
availability of specific substrates determine the fate of a cell stimulated by
the same growth factor. In some models, the difference between malignant
transformation and differentiation (leading to cell death) may depend on the
presence or absence of a single agonist or antagonist molecule. The type 1
insulin-like growth factor receptor will serve as the paradigm for this review.
J. Cell. Biochem. Suppls. 32/33:68-75, 1999. Copyright 1999 Wiley-Liss, Inc.
 
Publication Types:
Review
Review, Tutorial
 
PMID: 10629105 [PubMed - indexed for MEDLINE]
 
 
 
28: FEBS Lett  1999 Dec 31;464(3):159-63 
 
Insulin selectively activates STAT5b, but not STAT5a, via a JAK2-independent
signalling pathway in Kym-1 rhabdomyosarcoma cells.
 
Storz P, Doppler H, Pfizenmaier K, Muller G.
 
Institute of Cell Biology, University of Stuttgart, Allmandring 31, 70569,
Stuttgart, Germany. peter.storz@po.uni-stuttgart.de
 
The STAT multigene family of transcriptional regulators conveys signals from
several cytokines and growth factors upon phosphorylation by janus kinases
(JAK). Activation of STAT5 is typically mediated by JAK2, but more recent data
indicate a direct activation by the insulin receptor kinase. STAT5 exists in two
closely homologous isoforms, STAT5a and b. We here describe the selective
tyrosine phosphorylation of STAT5b in Kym-1 cells in response to insulin.
Blocking insulin signalling by HNMPA-(AM)(3), an insulin receptor kinase
inhibitor, resulted in the loss of insulin-induced STAT5b tyrosine
phosphorylation, whereas the inhibition of JAK2 by the JAK selective inhibitor
tyrphostin AG490 had no effect. By contrast, in the same cells, IFNgamma-induced
STAT5b activation was JAK2-dependent, indicating that this signal pathway is
functional in Kym-1 cells. We conclude from this rhabdomyosarcoma model that
STAT5b, but not STAT5a is a direct target of the insulin receptor kinase.
 
PMID: 10618497 [PubMed - indexed for MEDLINE]
 
 
 
29: Hum Reprod  1999 Sep;14(9):2216-22 
 
Adipocyte insulin action following ovulation in polycystic ovarian syndrome.
 
Marsden PJ, Murdoch AP, Taylor R.
 
Department of Obstetrics and Gynaecology, Sunderland Royal Hospital, Kayll Road,
Sunderland SR4 7TP, UK.
 
The role of anovulation and insulin resistance in the pathogenesis of polycystic
ovarian syndrome (PCOS) remains to be determined. The aim of this study was to
investigate whether the metabolic abnormality of insulin resistance in PCOS
reflects, rather than causes, the ovarian dysfunction. Eight subjects with
classical PCOS were studied on two occasions. Adipocyte insulin sensitivity
together with hormonal and metabolic changes were investigated in patients with
PCOS following prolonged amenorrhoea and then again in the early follicular
phase after ovulation. Insulin receptor binding in amenorrhoeic subjects with
PCOS was low at 0.78 +/- 0.08% and this increased to 1.18 +/- 0.19% after an
ovulatory cycle (P < 0.05). Maximal insulin stimulated 3-O-methylglucose uptake
was 0.70 +/- 0. 14 during amenorrhoea and increased to 1.08 +/- 0.25 pmol/10
cm(2) cell membrane (P < 0.05). Plasma testosterone fell (4.0 +/- 0.4 to 2. 3
+/- 0.2 nmol/l; P < 0.001), luteinizing hormone fell (17.6 +/- 2.3 to 6.7 +/-
0.8 IU/l; P < 0.001) but plasma insulin concentrations remained unchanged
following ovulation (14.6 +/- 1.9 and 15.7 +/- 3. 8 pmol/l during amenorrhoea
and after ovulation respectively). The results of this study suggest that
chronic anovulation per se appears to modify the factors contributing to
cellular insulin resistance seen in PCOS.
 
PMID: 10469683 [PubMed - indexed for MEDLINE]
 
 
 
30: Clin Endocrinol (Oxf)  1999 Aug;51(2):247-53 
 
Comment in:
 Clin Endocrinol (Oxf). 1999 Aug;51(2):147.
 
Hypoglycaemia associated with the production of insulin-like growth factor II
and insulin-like growth factor binding protein 6 by a haemangiopericytoma.
 
Hoekman K, van Doorn J, Gloudemans T, Maassen JA, Schuller AG, Pinedo HM.
 
Department of Medical Oncology, Free University Hospital, Amsterdam, The
Netherlands. hoekman@azvu.nl
 
Non-islet-cell tumour-induced hypoglycaemia (NICTH) is, in most cases,
attributable to tumour production of insulin-like growth factor II (IGF-II).
Tumour-derived IGF-II has a higher than normal molecular weight (big 'IGF-II')
and an impaired ability to form the normal ternary 150 kD complex with IGF
binding protein-3 (IGFBP-3) and the acid-labile subunit (ALS). Consequently,
tumoral IGF-II circulates mainly in smaller binary complexes which have a higher
bioavailability than the ternary complex. We had the opportunity to analyze IGFs
and IGF-related factors in both pre- and post-operative blood, tumour tissue and
tumour cyst fluid from a patient with a disseminated haemangiopericytoma and
severe hypoglycaemia. In addition, the effect of serum and tumour cyst fluid on
autophosphorylation of the insulin receptor was examined. Patient serum
contained low levels of IGF-I, IGFBP-3 and ALS, while the concentrations of
IGFBP-2 and IGFBP-6 were markedly elevated. The total level of circulating
IGF-II was within the normal range, but Biogel P-60 gel filtration of patient
serum revealed that 77% of the IGF-II was present in high molecular weight forms
(normal: 10-15%), which decreased to 53% after partial removal of the tumour.
Most of the IGF-II immunoreactivity in pre- and post-operative patient serum was
associated with 50-60 kD complexes with only a minimal contribution (<10%) from
the 150 kD complex. Tumour cyst fluid contained excessive amounts of both big
IGF-II and IGFBP-6. Northern blot analysis of total mRNA isolated from the
tumour demonstrated high expression of the IGF-II gene and abundant 1.1 kb
IGFBP-6 transcript, while the genes encoding IGFBP-3, -4 and -5 were only weakly
expressed and mRNA of IGFBP-1, -2 and IGF-I could not be detected. mRNAs for the
IGF type II receptor could be easily demonstrated, whereas those for the
insulin- and IGF type I receptor were hardly detectable. In contrast to patient
serum tumour cyst fluid strongly stimulated the insulin receptor in vitro. The
present study suggests an important role of the simultaneous production of
IGF-II and IGFBP-6 in the pathophysiology of tumour-induced hypoglycaemia.
 
PMID: 10468998 [PubMed - indexed for MEDLINE]
 
 
 
31: Endocr Rev  1999 Aug;20(4):535-82 
 
The insulin-related ovarian regulatory system in health and disease.
 
Poretsky L, Cataldo NA, Rosenwaks Z, Giudice LC.
 
Department of Medicine, New York Presbyterian Hospital and Weill Medical College
of Cornell University, New York, New York 10021, USA.
 
Publication Types:
Review
Review, Academic
 
PMID: 10453357 [PubMed - indexed for MEDLINE]
 
 
 
32: Exp Cell Res  1999 Aug 25;251(1):22-32 
 
Characterization of an antibody that can detect an activated IGF-I receptor in
human cancers.
 
Rubini M, D'Ambrosio C, Carturan S, Yumet G, Catalano E, Shan S, Huang Z,
Criscuolo M, Pifferi M, Baserga R.
 
University of Ferrara, Via L. Borsari 46, Ferrara, 44100, Italy.
 
The type 1 insulin-like growth factor receptor (IGF-IR) plays an important role
in malignant transformation and in apoptosis. Its role in human cancer has now
been firmly established. IGF-IR signaling occurs only when the receptor is
activated by its ligands, which induce autophosphorylation of the receptor at
several tyrosine residues. Although the IGF-IR (phosphorylated or not) can be
detected in human cancers with conventional antibodies, it would be desirable to
obtain antibodies that can detect the IGF-IR only when activated by its ligands.
We describe and characterize in this paper such an antibody and show that it can
be used in sections of human cancers to detect an autophosphorylated IGF-IR.
This antibody will be useful in detecting autocrine or paracrine influences on
normal and tumor cells and could eventually be also useful in diagnostic and
prognostic studies of human primary and metastatic cancer. Copyright 1999
Academic Press.
 
PMID: 10438568 [PubMed - indexed for MEDLINE]
 
 
 
33: Clin Cancer Res  1999 Jul;5(7):1935-44 
 
Insulin and insulin-like growth factor-I (IGF-I) receptor overexpression in
breast cancers leads to insulin/IGF-I hybrid receptor overexpression: evidence
for a second mechanism of IGF-I signaling.
 
Pandini G, Vigneri R, Costantino A, Frasca F, Ippolito A, Fujita-Yamaguchi Y,
Siddle K, Goldfine ID, Belfiore A.
 
Istituto di Medicina Interna, Malattie Endocrine e del Metabolismo, Universita
di Catania, Ospedale Garibaldi, Italy.
 
The insulin receptor (IR) form hybrids with the closely related insulin-like
growth factor-I (IGF-I) receptor (IGF-I-R). Because most human breast carcinomas
overexpress both the IR and the IGF-I-R, we evaluated whether the insulin/IGF-I
hybrid receptor (Hybrid-R) is also overexpressed in these tumors and what role
it plays in breast cancer biology. Using specific ELISAs and Western blots, we
measured Hybrid-R content and function in 8 human cultured breast cancer cell
lines and 39 human breast cancer specimens. Hybrid-R content and function were
also compared to the content and function of the IR and the IGF-I-R. Hybrid-R
content exceeded the IGF-I-R content in >75% of breast cancer specimens and was
directly related to the molar ratio of both the IR and IGF-I-R content,
suggesting that Hybrid-R formation occurred by random assembly of IR and IGF-I-R
half-receptors. Hybrid-Rs became tyrosine autophosphorylated when breast cancer
cells were exposed to IGF-I but not when they were exposed to insulin. In cells
with an elevated Hybrid-R content, Hybrid-R autophosphorylation in response to
IGF-I exceeded IGF-I-R autophosphorylation, suggesting that most of the IGF-I
effect occurred via the Hybrid-R. Furthermore, Hybrid-Rs mediated growth in
response to IGF-I, as indicated by experiments with blocking antibodies to the
IGF-I-R. These data indicated therefore that: (a) Hybrid-Rs are present and play
a major role in mediating the IGF-I signal in breast cancer; (b) their
expression is directly related to IR overexpression; and (c) potential therapies
designed to block IGF-I actions in breast cancer must take into account the role
of these Hybrid-Rs.
 
PMID: 10430101 [PubMed - indexed for MEDLINE]
 
 
 
34: Cancer Res  1999 Jul 15;59(14):3527-34 
 
Differential reconstitution of mitochondrial respiratory chain activity and
plasma redox state by cysteine and ornithine in a model of cancer cachexia.
 
Ushmorov A, Hack V, Droge W.
 
Deutsches Krebsforschungszentrum, Division of Immunochemistry, Heidelberg,
Germany.
 
The mechanism of wasting, as it occurs in malignant diseases and various
etiologically unrelated conditions, is still poorly understood. We have,
therefore, studied putative cause/effect relationships in a murine model of
cancer cachexia, C57BL/6 mice bearing the fibrosarcoma MCA-105. The plasma of
these mice showed decreased albumin and increased glutamate levels, which are
typically found in practically all catabolic conditions. Skeletal muscles from
tumor-bearing mice were found to have an abnormally low mitochondrial
respiratory chain activity (mito.RCA) and significantly decreased glutathione
(GSH) levels. The decrease in mito.RCA was correlated with an increase in the
i.m. GSH disulfide/GSH ratio, the plasma cystine/thiol ratio, and the GSH
disulfide/GSH ratio in the bile. This is indicative of a generalized shift in
the redox state extending through different body fluids. Treatment of
tumor-bearing mice with ornithine, a precursor of the radical scavenger
spermine, reversed both the decrease in mito.RCA and the change in the redox
state, whereas treatment with cysteine, a GSH precursor, normalized only the
redox state. Treatment of normal mice with difluoromethyl-ornithine, a specific
inhibitor of ornithine decarboxylase and spermine biosynthesis, inhibited the
mito.RCA in the skeletal muscle tissue, thus illustrating the importance of the
putrescine/spermine pathway in the maintenance of mito.RCA. Ornithine, cysteine,
and N-acetyl-cysteine (NAC) also reconstituted the abnormally low concentrations
of the GSH precursor glutamate in the skeletal muscle tissue of tumor-bearing
mice. Higher doses, however, enhanced tumor growth and increased the plasma
glucose level in normal mice. In the latter, cysteine and NAC also decreased
i.m. catalase and GSH peroxidase activities. Taken together, our studies on the
effects of ornithine, cysteine, and NAC illuminate some of the mechanistic
pathways involved in cachexia and suggest targets for therapeutic intervention.
 
PMID: 10416620 [PubMed - indexed for MEDLINE]
 
 
 
35: Biochimie  1999 Apr;81(4):403-7 
 
Insulin/IGF-I hybrid receptors play a major role in IGF-I signaling in thyroid
cancer.
 
Belfiore A, Pandini G, Vella V, Squatrito S, Vigneri R.
 
Istituto di Medicina Interna, Malattie Endocrine e del Metabolismo, Universita
di Catania, Ospedale Garibaldi, Italy.
 
The insulin-like growth factor-I (IGF-I) plays an important role in determining
the biological behavior of a variety of malignancies. We measured IGF-I, its
receptor and related receptors in thyroid cancer. IGF-I was present both in
normal thyroid tissue and in thyroid cancer tissue and it was produced by
stromal cells but not by thyrocytes. Values were significantly higher in
malignant than in normal tissue. IGF-I receptors (IGF-I-Rs) and the homologous
insulin receptors (IRs) were found overexpressed in both thyroid cancer cell
lines (n = 4) and specimens (n = 17) as compared to normal values. In addition,
high levels of hybrid IGF-I/insulin receptors (IR/IGF-I-Rs) were present in both
thyroid cancer specimens and cell lines. IR/IGF-I-R hybrids were the most
represented type of receptor in 14/17 specimens and exceeded the IGF-I-R content
in all cases. Hybrid content correlated with the IR and IGF-I-R content,
suggesting that in thyroid tissue hybrid formation occurs by random assembly of
IR and IGF-I-R half receptors. Hybrid receptor autophosphorylation was
stimulated by IGF-I with high affinity. In cells with a high IR/IGF-I-Rs
content, blocking antibodies specific to these receptors substantially inhibited
IGF-I induced cell growth. These data indicate that the IGF-I system is
overactivated in thyroid cancer and that IR/IGF-I-R hybrid receptors play an
important role in IGF-I mitogenic signaling in these tumors.
 
PMID: 10401676 [PubMed - indexed for MEDLINE]
 
 
 
36: J Intern Med  1999 Jun;245(6):621-5 
 
The role of TNFalpha and TNF receptors in obesity and insulin resistance.
 
Hotamisligil GS.
 
Department of Nutrition, Harvard University, School of Public Health, Boston,
Massachusetts 02115, USA. ghota-mis@hsph.harvard.edu
 
Insulin resistance, a smaller than expected response to a given dose of insulin,
is associated with many common diseases including, ageing, polycystic ovarian
disease, syndrome X, cancer, infections, trauma and, most significantly, obesity
and type 2 diabetes mellitus. The biochemical basis of insulin resistance in
type 2 diabetes has been the subject of many studies. Earlier studies have
indicated that quantitative regulation of the insulin sensitive glucose
transporters (Glut-4) and insulin receptors themselves may contribute to this
disorder, however, these two factors are probably inadequate to explain the
extent of insulin resistance. This point also became apparent by the development
of only mild hyperinsulinaemia in mice with a targeted mutation in the Glut-4
gene. Studies on postreceptor defects in type 2 diabetes has recently focused on
the intrinsic catalytic activity of the insulin receptor and downstream
signalling events. A reduction in tyrosine phosphorylation of both the insulin
receptor (IR) and the insulin receptor substrate-1 (IRS-1) has been noted in
both animal and human type 2 diabetes. Importantly, this appears to occur in all
of the major insulin-sensitive tissues, namely the muscle, fat and liver. It is
now clear that decreased signalling capacity of the insulin receptor is an
important component of this disease. I will review some of the potential
mechanisms underlying this deficiency.
 
Publication Types:
Review
Review, Tutorial
 
PMID: 10395191 [PubMed - indexed for MEDLINE]
 
 
 
37: Endocrinol Metab Clin North Am  1999 Jun;28(2):361-78 
 
Insulin action in the normal and polycystic ovary.
 
Franks S, Gilling-Smith C, Watson H, Willis D.
 
Department of Reproductive Science and Medicine, Imperial College School of
Medicine, St. Mary's Hospital, London, United Kingdom. s.franks@ic.ac.uk
 
Insulin has a stimulatory effect on steroidogenesis by granulosa cells of normal
and polycystic ovaries and interacts with gonadotropins in an additive or, as in
the case of LH, a synergistic manner. These actions seem to be mediated
specifically by the insulin receptor rather than by cross-reaction with the type
I IGF receptor, even in tissue obtained from women with PCOS with biochemical
evidence of insulin resistance. The authors suggest that hyperinsulinemia makes
a significant contribution to premature arrest of follicle growth, which is
characteristic of anovulation in women with PCOS, and that the interaction of
insulin with LH is a key element in this process. Insulin may also have a role
in amplifying LH-induced androgen production by theca cells, which may help
explain the prominence of symptoms of hyperandrogenism in obese subjects with
PCOS. The results of recent clinical studies of insulin-sensitizing agents such
as metformin and the thiazoladinedione troglitazone in PCOS have provided
encouragement that improvement of insulin sensitivity and consequent lowering of
circulating insulin levels by these agents may be of therapeutic value in the
management of both anovulation and hirsutism.
 
Publication Types:
Review
Review, Tutorial
 
PMID: 10352923 [PubMed - indexed for MEDLINE]
 
 
 
38: Biochemistry  1999 May 4;38(18):5896-904 
 
Reversible change in thiol redox status of the insulin receptor alpha-subunit in
intact cells.
 
Garant MJ, Kole S, Maksimova EM, Bernier M.
 
Diabetes Section, Laboratory of Clinical Investigation, National Institute on
Aging, National Institutes of Health, Baltimore, Maryland 21224-6825, USA.
 
In this study, we used maleimidobutyrylbiocytin to examine possible alteration
that may occur in the redox state of the insulin receptor (IR) sulfhydryl groups
in response to reduced glutathione (GSH) or N-acetyl-L-cysteine (NAC).
Short-term treatment of intact cells expressing large numbers of IR with GSH or
NAC led to a rapid and reversible reduction of IR alpha-subunit disulfides,
without affecting the receptor beta-subunit thiol reactivity. The overall
integrity of the oligomeric structure of IR was maintained, indicating that
neither class I nor class II disulfides were targeted by these agents. Similar
findings were obtained in cells transfected with IR mutants lacking cysteine524,
one of the class I disulfides that link the two IR alpha-subunits.
Membrane-associated thiols did not participate in GSH- or NAC-mediated reduction
of IR alpha-subunit disulfides. No difference in insulin binding was observed in
GSH-treated cells; however, ligand-mediated increases in IR autophosphorylation,
tyrosine phosphorylation of cellular substrates, and dual phosphorylation of the
downstream target mitogen-activated protein kinase were inhibited at
concentrations of GSH (10 mM or greater) that yielded a significant increase in
IR alpha-subunit thiol reactivity. GSH did not affect IR signaling in the
absence of insulin. Our results provide the first evidence that the IR
alpha-subunit contains a select group of disulfides whose redox status can be
rapidly altered by the reducing agents GSH and NAC.
 
PMID: 10231542 [PubMed - indexed for MEDLINE]
 
 
 
39: Oncogene  1999 Apr 15;18(15):2471-9 
 
Insulin receptor activation by IGF-II in breast cancers: evidence for a new
autocrine/paracrine mechanism.
 
Sciacca L, Costantino A, Pandini G, Mineo R, Frasca F, Scalia P, Sbraccia P,
Goldfine ID, Vigneri R, Belfiore A.
 
Istituto di Medicina Interna, Malattie Endocrine e del Metabolismo, Universita
di Catania, Ospedale Garibaldi, Italy.
 
IGF-II, produced by breast cancer epithelial and stromal cells, enhances tumor
growth by activating the IGF-I receptor (IGF-I-R) via autocrine and paracrine
mechanisms. Previously we found that the insulin receptor (IR), which is related
to the IGF-I-R, is overexpressed in breast cancer cells. Herein, we find that,
in breast cancer the IR is activated by IGF-II. In eight human breast cancer
cell lines studied there was high affinity IGF-II binding to the IR, with
subsequent IR activation. In these lines, IGF-II had a potency up to 63% that of
insulin. In contrast, in non malignant human breast cells, IGF-II was less than
1% potent as insulin. Via activation of the IR tyrosine kinase IGF-II stimulated
breast cancer cell growth. Moreover, IGF-II also activated the IR in breast
cancer tissue specimens; IGF-II was 10-100% as potent as insulin. The IR occurs
in two isoforms generated by alternative splicing of exon 11; these isoforms are
IR-A (Ex11-) and IR-B (Ex11+). IR-A was predominantly expressed in breast cancer
cells and specimens and the potency of IGF-II was correlated to the expression
of this isoform (P<0.0001). These data indicate, therefore, that the IR-A, which
binds IGF-II with high affinity, is predominantly expressed in breast cancer
cells and represents a new autocrine/paracrine loop involved in tumor biology.
 
PMID: 10229198 [PubMed - indexed for MEDLINE]
 
 
 
40: J Surg Res  1999 May 1;83(1):32-5 
 
Human insulin receptor and insulin signaling proteins in hepatic disease.
 
Spector SA, Olson ET, Gumbs AA, Friess H, Buchler MW, Seymour NE.
 
Surgical Service, VA Connecticut Healthcare System, West Haven, Connecticut
06516, USA.
 
Insulin regulates hepatocellular metabolism and growth following insulin
receptor (IR) autophosphorylation and activation of the intracellular adapter
protein, insulin receptor substrate 1 (IRS-1). IRS-1 activates SH2 domain
proteins such as Grb2, which may be vital to hepatocyte growth. To determine if
these substances are abnormally expressed under pathophysiologic conditions, IR,
IRS-1, Grb2 protein, and IR mRNA were studied in normal human liver (n = 10),
cirrhotic liver (n = 10), and hepatocellular carcinoma (HCC) (n = 10) that had
been procured during operative procedures. IR mRNA was quantified by S1-nuclease
assay using a 195-bp digoxigenin-labeled IR DNA probe and normalized to the
level of expression of the glyceraldehyde 3-phosphate dehydrogenase (GAPDH)
gene. Protein concentrations were determined by immunoblot analysis following
SDS-PAGE of liver homogenate samples. Labeled DNA and antibody-complexed protein
were detected by chemiluminescent means and quantified by densitometric analysis
(mean densitometric units +/- standard error). Similar levels of IR mRNA were
observed in normal tissue, cirrhosis, and HCC. IR protein concentration was
significantly greater in HCC than in normal liver (1.82 +/- 0.2 vs 1. 25 +/-
0.17; P < 0.05). IRS-1 was significantly increased in cirrhosis compared to
normal liver (1.61 +/- 0.31 vs 0.86 +/- 0.21; P < 0.05). No differences were
observed in Grb2 in the three tissue types. Insulin receptor overexpression,
previously seen in other tumor types, may confer an insulin-mediated growth
advantage in HCC if added receptors reflect functional high affinity binding
sites. Although an altered mass of IRS-1 protein was not observed in HCC, an
IRS-1 increase in cirrhosis may favor hepatic regeneration. Copyright 1999
Academic Press.
 
PMID: 10210639 [PubMed - indexed for MEDLINE]
 
 
 
41: Diabetologia  1999 Mar;42(3):317-25 
 
Modulation of insulin receptor signalling by pancreastatin in HTC hepatoma
cells.
 
Sanchez-Margalet V.
 
Department of Medical Biochemistry and Molecular Biology, School of Medicine,
Virgen Macarena Hospital, University of Seville, Spain.
 
Pancreastatin, a neuropeptide derived from chromogranin A, has a glycogenolytic
and counterregulatory effect to insulin in the rat liver. This effect is
mediated by calcium and protein kinase C activity. Our aim was to study the
possible cross-talk between pancreastatin and the insulin signalling system, by
using the well-studied insulin sensitive rat hepatoma HTC cells. First, we
checked the counterregulatory effect of pancreastatin on insulin action.
Pancreastatin dose-dependently inhibited insulin stimulated glycogen synthesis.
This effect was not due to competition for insulin receptors. Moreover, when
protein kinase C activation was blocked with staurosporine, this effect of
pancreastatin was not observed. Next, we found a dose-dependent inhibition of
insulin receptor autophosphorylation by pancreastatin. In addition,
phosphorylation of the major substrates of insulin receptor in HTC, i. e.
insulin-receptor substrate (IRS)-1/IRS-2 and p62 was also blunted and so was its
association with p85 regulatory subunit of phosphatidylinositol-3-kinase.
Moreover, the insulin activation of S6 kinase was also blocked by pancreastatin.
Again, all these inhibitory effects of pancreastatin were prevented by
staurosporine. Furthermore, pancreastatin produced Ser/Thr phosphorylation of
insulin receptor by a staurosporine-sensitive mechanism. Finally, we checked the
pancreastatin activation of protein kinase C in HTC cells and found that a
"classical" isoform of this protein is translocated to the plasma membrane.
These findings suggest that pancreastatin could exert its anti-insulin effect in
the hepatocyte by interrupting the stimulation of early insulin receptor
signalling as a result of phosphorylation. This interaction might have a role in
the mechanisms of insulin resistance.
 
PMID: 10096784 [PubMed - indexed for MEDLINE]
 
 
 
42: Cell Mol Life Sci  1999 Jan;55(1):142-7 
 
Insulin activates G alpha il,2 protein in rat hepatoma (HTC) cell membranes.
 
Sanchez-Margalet V, Gonzalez-Yanes C, Santos-Alvarez J, Najib S.
 
Departamento de Bioquimica Medica y Biologia Molecular, Facultad de Medicina,
Hospital Universitario Virgen Macarena, Sevilla, Spain.
 
Insulin action is initiated by binding to its cognate receptor, which then
triggers multiple cellular responses by activating different signaling pathways.
There is evidence that insulin receptor signaling may involve G protein
activation in different target cells. We have studied the activation of G
proteins in rat hepatoma (HTC) cells. We found that insulin stimulated binding
of guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-35S) to plasma membrane
proteins of HTC cells, in a dose-dependent manner. This effect was completely
blocked by pertussis toxin treatment of the membranes, suggesting the
involvement of G proteins of the G alpha i/G alpha o family. The expression of
these G alpha proteins was checked by Western blotting. Next, we used blocking
antibodies to sort out the specific G alpha protein activated by insulin
stimulation. Anti-G alpha il,2 antibodies completely prevented
insulin-stimulated GTP binding, whereas anti-G alpha o,i3 did not modify this
effect of insulin on GTP binding. Moreover, we found physical association of the
insulin receptor with G alpha il,2 by copurification studies. These results
further support the involvement of a pertussis toxin-sensitive G protein in
insulin receptor signaling and provides some evidence of specific association
and activation of G alpha il,2 protein by insulin. These findings suggest that G
alpha il,2 proteins might be involved in insulin action.
 
PMID: 10065161 [PubMed - indexed for MEDLINE]
 
 
 
43: Cancer  1999 Jan 15;85(2):492-8 
 
Functional insulin receptors are overexpressed in thyroid tumors: is this an
early event in thyroid tumorigenesis?
 
Frittitta L, Sciacca L, Catalfamo R, Ippolito A, Gangemi P, Pezzino V, Filetti
S, Vigneri R.
 
Istituto di Medicina Interna, Malattie Endocrine e del Metabolismo, Universita
di Catania, Ospedale Garibaldi, Italy.
 
BACKGROUND: Insulin receptor (IR), a member of the receptor tyrosine kinase
family, is expressed in normal thyroid cells and affects thyroid cell
proliferation and differentiation. METHODS: The authors measured IR content in
benign and malignant thyroid tumors by three independent methods: a specific
radioimmunoassay, 125I-insulin binding studies, and immunohistochemistry. The
results obtained were compared with the IR content in paired, adjacent, normal
thyroid tissue. To assess IR function in thyroid carcinoma cells, glucose uptake
responsiveness to insulin was also studied in a human transformed thyroid cell
line (B-CPAP) and in follicular carcinoma cells in primary culture. RESULTS: In
9 toxic adenomas, the average IR content was similar to that observed in the 9
paired normal thyroid tissue specimens from the same patients (2.2+/-0.3 vs.
2.1+/-0.3). In 13 benign nonfunctioning, or "cold," adenomas, the average IR
content was significantly higher (P < 0.001) than in paired normal tissue
specimens (4.3+/-0.5 vs. 1.8+/-0.1). In 12 papillary and 10 follicular
carcinomas, IR content was significantly higher (P < 0.001) than in the adjacent
normal thyroid tissue (4.0+/-0.4 vs. 1.6+/-0.2 and 5.6+/-1.0 vs. 1.8+/-0.2,
respectively). The finding of a higher IR content in benign "cold" adenomas and
in thyroid carcinomas was confirmed by both binding and immunostaining studies.
CONCLUSIONS: The current studies indicate that 1) IR content is elevated in most
follicular and papillary differentiated thyroid carcinomas, and 2) IR content is
also elevated in most benign follicular adenomas ("cold" nodules) but not in
highly differentiated, hyperfunctioning follicular adenomas ("hot" nodules),
which very rarely become malignant. This observation suggests that increased IR
expression is not restricted to the thyroid malignant phenotype but is already
present in the premalignant "cold" adenomas. It may contribute, therefore, to
thyroid tumorigenesis and/or represent an early event that gives a selective
growth advantage to transformed thyroid cells.
 
PMID: 10023720 [PubMed - indexed for MEDLINE]
 
 
 
44: Biochem Biophys Res Commun  1998 Dec 18;253(2):315-9 
 
Role of IRS-1 signaling in insulin-induced modulation of estrogen receptors in
breast cancer cells.
 
Ando' S, Panno ML, Salerno M, Sisci D, Mauro L, Lanzino M, Surmacz E.
 
Dipartimento di Biologia Cellulare, Universita' degli Studi della Calabria,
Cosenza, Italy. sando@diemme.it
 
Cross-talk between steroid hormones and polypeptide growth factors regulates the
growth of hormone-responsive breast cancer cells. For example, in the MCF-7
human breast cancer cell line, insulin up-regulates estrogen receptor (ER)
content and binding capacity. Since the insulin receptor (IR) substrate 1
(IRS-1) is one of the core signaling elements transmitting mitogenic and
metabolic effects of insulin, we investigated whether IRS-1 is also required for
the insulin-induced function of the ER. The effects of insulin on the ER were
compared in MCF-7 cells and MCF-7-derived cell lines with decreased levels (by
approximately 80%) of IRS-1 due to the expression of IRS-1 antisense RNA. The
severe IRS-1 deficiency in MCF-7 cells was associated with (1) reduced mitogenic
response to 20 ng/ml insulin and 10% calf serum (CS), but not to 1 nM estradiol
(E2); (2) loss of insulin-E2 synergism; (3) up-regulation of ER protein
expression and binding capacity; and (4) loss of insulin-induced regulation of
ER tyrosine phosphorylation. In conclusion, the data confirm the existence of
the IR-ER cross-talk and suggest that IRS-1-dependent signaling may contribute
to the negative regulation of the ER expression and function in MCF-7 cells.
Copyright 1998 Academic Press.
 
PMID: 9878535 [PubMed - indexed for MEDLINE]
 
 
 
45: Pancreas  1998 Nov;17(4):359-66 
 
The intracellular mechanism of insulin resistance in the hamster pancreatic
ductal adenocarcinoma model.
 
Liu J, Kazakoff K, Pour PM, Adrian TE.
 
Department of Biomedical Sciences, Creighton University School of Medicine,
Omaha, Nebraska 68178, USA.
 
Diabetes associated with pancreatic cancer is characterized by profound
peripheral insulin resistance. The intracellular mechanism of insulin resistance
was investigated in skeletal muscles from N-nitrosobis(2-oxopropyl)amine
(BOP)-treated hamsters. Effects of high-fat diet and exercise also were studied.
BOP (20 mg/kg body weight) was administrated weekly for 2 weeks.
Hyperinsulinemia was found in BOP-treated hamsters at 20 weeks after BOP
treatment, suggesting the peripheral insulin resistance is an early feature in
pancreatic cancer. Hamsters were killed at 42 weeks, and soleus muscles were
taken for the analysis. Skeletal muscle insulin-receptor binding and insulin
receptor tyrosine kinase activities were similar between the control and
BOP-treated hamsters. However, maximal muscle glycogen synthase activity was
significantly reduced in BOP-treated hamsters compared with the control group.
Muscle glycogen phosphorylase activity was increased in the BOP-treated group
fed with high-fat diet as well as in BOP-treated groups with exercise. These
findings indicate that insulin resistance in the hamster pancreatic cancer model
is caused by a postreceptor defect, which led to significant decrease of muscle
glycogen synthase activity. Whereas a high-fat diet causes more severe insulin
resistance in BOP-treated hamsters, high-fat diet and exercising had no
significant effects on skeletal muscle insulin-receptor function and glycogen
synthase activity. Furthermore, both high-fat diet and exercise enhanced
glycogen phosphorylase activity in BOP-treated hamsters.
 
PMID: 9821177 [PubMed - indexed for MEDLINE]
 
 
 
46: Clin Cancer Res  1995 Nov;1(11):1429-36 
 
Overexpression of insulin receptor substrate 1 (IRS-1) in the human breast
cancer cell line MCF-7 induces loss of estrogen requirements for growth and
transformation.
 
Surmacz E, Burgaud JL.
 
Jefferson Cancer Institute, Thomas Jefferson University, Philadelphia,
Pennsylvania 19107, USA.
 
The synergistic action of estrogens and insulin-like growth factors (IGFs)
promotes the growth of many human breast cancer cell lines. This synergistic
effect involves estrogen-dependent induction of the IGF system, i.e., estrogens
augment the number of IGF-I receptors, stimulate the secretion of IGF-II, and
promote the synthesis of certain IGF-binding proteins. On the other hand, the
sustained activation of the IGF-I receptor (IGF-IR) by the overexpression of
IGF-II has been found to contribute to the development of the
estrogen-independent phenotype in breast cancer cells. In this study, we have
investigated whether the amplification of the IGF-IR intracellular signaling in
MCF-7 cells can abolish or reduce estrogen requirements for growth and
transformation. To this end we developed several MCF-7 clones that overexpressed
insulin receptor substrate 1 (IRS-1), one of the principal substrates of the
IGF-IR. We report here that in MCF-7 cells overexpressing IRS-1, estrogen
requirements for growth in monolayer culture as well as in soft agar were
reduced. The decreased estrogen requirements depended on the level of the
overexpressed IRS-1 protein, and in cells which contained several-fold more
functional IRS-1 than the parental cells, we observed total loss of estrogen
dependence for growth. In addition, the importance of IRS-1 in proliferation of
MCF-7 cells has been confirmed through the use of antisense strategies.
 
PMID: 9815941 [PubMed - indexed for MEDLINE]
 
 
 
47: Am J Physiol  1998 Nov;275(5 Pt 1):E748-56 
 
Adenovirus-mediated transfer of a modified human proinsulin gene reverses
hyperglycemia in diabetic mice.
 
Short DK, Okada S, Yamauchi K, Pessin JE.
 
Department of Physiology and Biophysics, The University of Iowa, Iowa City, Iowa
52242-1109, USA.
 
The human proinsulin cDNA was introduced into a replication-defective adenovirus
and was found to confer proinsulin expression to a hepatocyte (H4-II-E) cell
line upon infection. A second virus was constructed in which the dibasic
prohormone convertase recognition sequence was mutated to a tetrabasic furin
cleavage site. Cells infected with this virus synthesized both proinsulin and
mature insulin. Gel filtration chromatography, competition of insulin binding,
and activation of the insulin receptor kinase activity demonstrated that this
mature insulin was functionally identical to that of authentic processed
insulin. Injection of these viral constructs into the external jugular vein of
mice resulted in insulin gene expression in the liver. Expression from the
mutated proinsulin virus dramatically improved the glycemic state of diabetic
mice. However, the effects of the viral infection were transient, being maximal
at approximately 5-7 days and returning to steady-state levels by 14-21 days.
These data demonstrate that somatic cell insulin gene delivery by the use of
recombinant adenovirus can be used to transiently reverse the diabetic state in
mice.
 
PMID: 9814992 [PubMed - indexed for MEDLINE]
 
 
 
48: Am J Med  1998 Oct;105(4):331-45 
 
Insulin action and insulin resistance: diseases involving defects in insulin
receptors, signal transduction, and the glucose transport effector system.
 
Hunter SJ, Garvey WT.
 
Department of Medicine, Medical University of South Carolina, Ralph H. Johnson
Veterans Affairs Medical Center, Charleston 29425, USA.
 
Publication Types:
Review
Review, Tutorial
 
PMID: 9809695 [PubMed - indexed for MEDLINE]
 
 
 
49: Gynecol Endocrinol  1998 Aug;12(4):277-92 
 
Insulin and polycystic ovary syndrome: a new look at an old subject.
 
Ciampelli M, Lanzone A.
 
Department of Obstetrics and Gynecology, Catholic University of Sacred Heart,
Rome, Italy.
 
In recent years the metabolic implications of polycystic ovary syndrome (PCOS)
have received a great deal of attention; in fact 50% of women with PCOS are
obese and a similar percentage of subjects was found to show exaggerated insulin
secretion and reduced insulin-stimulated glucose uptake. The presence of these
features in women with PCOS has profound clinical implications in terms of
morbidity due to diabetes mellitus, dyslipidemia, hypertension and
cardiovascular disease. Moreover, hyperinsulinemia has recently been proposed as
a possible independent risk factor for endometrial and breast cancer. In the
light of these considerations, the importance of metabolic screening in patients
with PCOS in order to improve their quality of life cannot be underestimated. In
this review we analyze all the clinical pathologies in which hyperinsulinemia of
PCOS could be involved. Furthermore, in order to clarify the possible mechanisms
leading to the insulin disorders of the syndrome, we review the available data
about the insulin receptor abnormalities, as well as those concerning the
insulin resistance and the exaggerated insulin secretion. Finally, we examine
the main therapeutic strategies to ameliorate the insulinemic status of PCOS
patients in order to potentially be able to prevent the long-term consequences
of this syndrome.
 
Publication Types:
Review
Review, Academic
 
PMID: 9798138 [PubMed - indexed for MEDLINE]
 
 
 
50: Head Neck  1998 Oct;20(7):634-9 
 
Focal adhesion kinase expression in oral cancers.
 
Kornberg LJ.
 
Department of Otolaryngology, University of Florida, Gainesville 32610, USA.
 
BACKGROUND: Evidence suggests that focal adhesion kinase (FAK) is involved in
the pathogenesis of certain cancers. Focal adhesion kinase is overexpressed in
invasive and metastatic cancers of the breast, colon, thyroid, and prostate. The
objective of this study was to determine the presence and cellular distribution
of FAK in oral cancer and determine whether there is a difference in FAK
expression in preinvasive and invasive oral cancers. METHODS:
Immunohistochemistry was used to detect FAK expression in 20 archival oral
cancer specimens. RESULTS: Focal adhesion kinase immunoreactivity was detected
in all specimens that were examined. In tumors, there was an increase in the
intensity of FAK staining and in the percentage of FAK-positive cells.
Preinvasive tumors had populations of cancer cells which stained more intensely
than neighboring cancer cells. CONCLUSIONS: Focal adhesion kinase expression
appears to be increased in invasive and preinvasive oral cancers. It is
speculated that enhanced expression of FAK may contribute to the aggressive
phenotype of oral cancers.
 
PMID: 9744465 [PubMed - indexed for MEDLINE]
 
 
 
51: Am J Obstet Gynecol  1998 Jul;179(1):6-12 
 
Specific binding and growth-promoting activity of insulin in endometrial cancer
cells in culture.
 
Nagamani M, Stuart CA.
 
Department of Obstetrics and Gynecology, University of Texas Medical Branch,
Galveston 77555, USA.
 
OBJECTIVE: Insulin is known to be mitogenic to a variety of cells in culture.
The purpose of this study was to investigate the possible role of insulin in the
growth and development of endometrial cancers. STUDY DESIGN: Specific binding
and growth effects of insulin were studied in 5 different human endometrial
cancer cell lines derived from cancers with different degrees of
differentiation: HEC-1-A and HEC-1-B (from a moderately well-differentiated
adenocarcinoma), RL95-2 (from a moderately well-differentiated adenosquamous
carcinoma), KLE (from poorly differentiated carcinoma), and AN3 CA (from a
metastatic undifferentiated endometrial carcinoma). The receptors were further
characterized by competitive binding and chemical cross-linking studies.
RESULTS: Binding studies with 125I-insulin revealed the presence of
high-affinity binding sites for insulin on all the 5 cell lines. Binding of
insulin was found to be highly specific. Competitive binding studies with
125I-insulin revealed that insulin was most effective in displacing the labeled
hormone, whereas insulin-like growth factor-I and insulin-like growth factor-II
competed for binding only at very high concentrations. Scatchard analysis of the
binding data revealed that the association constant for the high-affinity
binding sites ranged from 0.72 to 1.91 x 10(9) L/mol. Estrogen-receptor-negative
cell lines HEC-1-A and HEC-1-B had the highest number of insulin receptors,
whereas the estrogen-receptor-positive cell line RL95-2 had the least number of
receptors. The effect of insulin on cell proliferation was studied by monitoring
cell number and incorporating [3H]thymidine into deoxyribonucleic acid of the
cells. Insulin stimulated cell growth of all the cell lines. CONCLUSIONS: The
results of this study indicate the potential role of hyperinsulinemia in the
growth and development of endometrial cancer.
 
PMID: 9704758 [PubMed - indexed for MEDLINE]
 
 
 
52: J Clin Endocrinol Metab  1998 Jun;83(6):2001-5 
 
Insulin stimulates testosterone biosynthesis by human thecal cells from women
with polycystic ovary syndrome by activating its own receptor and using
inositolglycan mediators as the signal transduction system.
 
Nestler JE, Jakubowicz DJ, de Vargas AF, Brik C, Quintero N, Medina F.
 
Department of Internal Medicine, Medical College of Virginia/Virginia
Commonwealth University, Richmond 23298, USA. nestler@hsc.vcu.edu
 
To determine whether insulin stimulates human ovarian testosterone production in
the polycystic ovary syndrome by activating its own receptor and using
inositolglycan mediators as the signal transduction system, thecal cells from
polycystic ovary syndrome women were isolated and cultured. Insulin and
insulin-like growth factor I stimulated thecal testosterone biosynthesis.
Antibody blockade of the insulin receptor abolished insulin's stimulatory
action, whereas effective antibody blockade of the insulin-like growth factor I
receptor did not alter insulin's stimulation of thecal testosterone
biosynthesis. A chiro-inositol containing glycan (INS-2) increased thecal
testosterone biosynthesis. Preincubation of cells with an antiinositolglycan
antibody (A23939 or alpha IGP) abolished insulin's stimulatory effect, but not
that of hCG. These findings suggest that inositolglycans serve as the signal
transduction system for insulin's stimulation of human thecal testosterone
biosynthesis.
 
PMID: 9626131 [PubMed - indexed for MEDLINE]
 
 
 
53: J Biol Chem  1998 Apr 17;273(16):9994-10003 
 
Insulin receptor substrate-1 is the predominant signaling molecule activated by
insulin-like growth factor-I, insulin, and interleukin-4 in estrogen
receptor-positive human breast cancer cells.
 
Jackson JG, White MF, Yee D.
 
Division of Medical Oncology, Department of Medicine, University of Texas Health
Science Center, San Antonio, Texas 78284-7884, USA.
 
Because insulin-like growth factor-I (IGF-I), insulin, and interleukin-4 (IL-4)
have known biological effects in breast cancer cells and signal through
insulin-receptor substrate (IRS) adaptor proteins, we examined the expression
and function of IRS-1 and IRS-2 in breast tumors and cell lines. IRS-1 and IRS-2
were expressed by cell lines and primary breast tumor specimens. IGF-I, insulin,
and IL-4 treatment of MCF-7 and ZR-75, and IGF-I treatment of T47-D breast
cancer cells, resulted in much greater tyrosine phosphorylation of IRS-1
compared with IRS-2. Furthermore, IGF-I stimulated greater tyrosine
phosphorylation of IRS-1 than either insulin or IL-4. IGF-I treatment also
enhanced association of the p85 regulatory subunit of phosphatidylinositol
3-kinase with IRS-1 and stimulated increased enzymatic activity compared with
IL-4 and insulin in all three cell lines. Similarly, mitogen-activated protein
kinase activity was greater in IGF-I-stimulated cells. To determine the
functional significance of the activation of these pathways, we inhibited
activation of phosphatidylinositol 3-kinase with wortmannin and
mitogen-activated protein kinase with PD098059. Both compounds inhibited
IGF-stimulated growth, suggesting that both pathways contributed to the
mitogenic response to IGF-I. We conclude that IRS-1, and not IRS-2, is the
predominant signaling molecule activated by IGF-I, insulin, and IL-4.
Furthermore, enhanced tyrosine phosphorylation of IRS-1 by IGF-I, compared with
either insulin or IL-4, is associated with greater activation of mitogenic
downstream signaling pathways resulting in enhanced cell growth.
 
PMID: 9545345 [PubMed - indexed for MEDLINE]
 
 
 
54: Surgery  1998 Mar;123(3):315-20 
 
Variable effect of streptozotocin-diabetes on the growth of hamster pancreatic
cancer (H2T) in the Syrian hamster and nude mouse.
 
Fisher WE, Muscarella P, Boros LG, Schirmer WJ.
 
Department of Surgery, Ohio State University, Columbus 43210, USA.
 
BACKGROUND: Streptozotocin-diabetes prevents induction of pancreatic tumors in
several animal models and inhibits the growth of established human pancreatic
cancer implants in nude mice. However, it also promotes growth of the hamster
pancreatic cancer cell line, H2T, in the Syrian hamster. To test the hypothesis
that these contradictory effects are due to tumor host differences, the growth
of the H2T cell line was examined in the streptozotocin-diabetic nude mouse.
METHODS: H2T cells were implanted subcutaneously into streptozotocin-diabetic
nude mice (n = 10) and untreated control mice (n = 10). After 21 days, tumors
were excised and weighed. Plasma insulin and somatostatin were determined by
radioimmunoassay. RESULTS: After 3 weeks, tumors in the control group weighed
118 mg and tumors in the diabetic group weighed 28 mg (p < 0.001). Plasma
insulin was significantly decreased in the streptozotocin-treated animals
compared with control animals (insulin, 23 microU/ml vs 31 microU/ml; p <
0.001). In contrast, somatostatin was significantly elevated in the
streptozotocin-diabetic group compared with the control group (somatostatin, 179
pg/ml versus 54 pg/ml, p < 0.001). Competitive binding studies revealed specific
cell surface receptors for insulin (Kd, 15.5 nmol/L), and somatostatin (Kd, 2.5
nmol/L) on the H2T cells. In an in vitro cell proliferation assay, cell division
was promoted by insulin (p < 0.01, maximum +11%) and inhibited by somatostatin
(p < 0.01, maximum -18%). CONCLUSIONS: The variable effect of
streptozotocin-diabetes on pancreatic cancer growth is due to differences in the
tumor host. The growth of pancreatic cancer, particularly in
streptozotocin-diabetic nude mice, may be influenced by gut peptides in a
receptor-dependent fashion.
 
PMID: 9526524 [PubMed - indexed for MEDLINE]
 
 
 
55: Cancer Res  1998 Mar 15;58(6):1159-64 
 
Elevated insulin-like growth factor I receptor autophosphorylation and kinase
activity in human breast cancer.
 
Resnik JL, Reichart DB, Huey K, Webster NJ, Seely BL.
 
Department of Medicine, University of California, San Diego, La Jolla 92093,
USA.
 
Insulin-like growth factor I action has been implicated in the pathogenesis of
many different malignancies, including breast cancer. Insulin-like growth factor
I receptors (IGF-IRs) are overexpressed in virtually all breast cancer cell
lines, in which they are believed to enhance growth and inhibit apoptosis. In
this study, the functional activity of IGF-IRs from normal and malignant human
breast tissue was assessed. IGF-IR expression was 14-fold higher in malignant
breast tissue than in normal breast tissue. IGF-IR autophosphorylation and
kinase activity were 2-4-fold higher in purified receptor preparations from
malignant breast tissue as compared to normal breast tissue when normalized for
receptor number. This increase in receptor function, coupled with the enhanced
receptor expression, amounts to a 40-fold elevation in IGF-IR tyrosine kinase
activity in malignant breast tissue. The enhanced receptor autophosphorylation
and kinase activity were observed in the absence of hormonal stimulation and
seem to result from an alteration in the intrinsic activity of the receptor
itself. Protein tyrosine phosphatase activity is also increased in malignant
breast tissue. These data suggest that the IGF-IR is an important target for
breast cancer therapy.
 
PMID: 9515800 [PubMed - indexed for MEDLINE]
 
 
 
56: Diabetes  1998 Jan;47(1):87-92 
 
Expression of insulin/IGF-I hybrid receptors is increased in skeletal muscle of
patients with chronic primary hyperinsulinemia.
 
Federici M, Lauro D, D'Adamo M, Giovannone B, Porzio O, Mellozzi M, Tamburrano
G, Sbraccia P, Sesti G.
 
Laboratory of Molecular Medicine, University of Rome, Italy.
 
The insulin receptor (IR) shares structural and functional homology with the
IGF-I receptor (IGF-IR). Hybrid receptors composed of an IR
alphabeta-heterodimer and an IGF-IR alphabeta-heterodimer are formed in tissues
expressing both molecules. Hybrids behave as IGF-IR rather than IR with respect
to ligand binding affinity, receptor autophosphorylation, and hormone
internalization and degradation. Factors regulating hybrid formation in vivo are
unknown. We recently reported that in skeletal muscle of NIDDM patients,
expression of hybrids is increased and correlated with a decrease in IR number
and an increase in fasting insulin levels. However, it is not clear whether
increased expression of hybrid receptors is a primary defect specifically
associated with NIDDM or a secondary event caused by hyperinsulinemia. To
address this issue, we used a quantitative microwell-based immunoassay to
measure hybrid receptor abundance in skeletal muscle of 11 normal subjects and
12 patients with insulinoma, a state of primary nongenetically determined
hyperinsulinemia. Total insulin binding was lower in insulinoma patients than in
normal subjects (0.70 +/- 0.18 vs. 4.59 +/- 0.77; P < 0.0001). Total IGF-I
binding did not differ between the two groups (0.81 +/- 0.27 and 0.85 +/- 0.10,
respectively). The amount of hybrids, expressed as bound/total (B/T), was higher
in patients with insulinoma than in normal subjects (0.57 +/- 0.19 vs. 0.36 +/-
0.03; P < 0.0006) and was inversely correlated with total insulin binding (r =
-0.64, P < 0.0004). Increased abundance of hybrid receptors was positively
correlated with insulin levels (r = -0.82, P < 0.0009) and inversely correlated
with insulin-mediated glucose uptake (r = -0.80, P < 0.01). No correlations were
observed between insulin-mediated glucose uptake and maximal specific insulin
binding (r = 0.19, P = 0.64). These results indicate that insulin-induced IR
downregulation may lead to the formation of a higher proportion of hybrid
receptors, whose abundance is negatively correlated with in vivo insulin
sensitivity. These results, therefore, support a role for insulin in the
regulation of hybrid receptors formation and suggest that increased expression
of hybrids in NIDDM may be a secondary event caused by hyperinsulinemia rather
than a primary defect.
 
PMID: 9421379 [PubMed - indexed for MEDLINE]
 
 
 
57: J Soc Gynecol Investig  1994 Jan-Mar;1(1):74-8 
 
Enhanced post-receptor insulin effects in women following dehydroepiandrosterone
infusion.
 
Schriock ED, Buffington CK, Givens JR, Buster JE.
 
Department of Obstetrics and Gynecology, University of California, San
Francisco, USA.
 
OBJECTIVE: We hypothesized that intravenous dehydroepiandrosterone (DHEA) would
decrease insulin resistance in normal and insulin-resistant women. METHODS: Five
insulin-resistant women diagnosed as having polycystic ovaries (PCO) with
elevated testosterone and normal dehydroepiandrosterone sulfate (DHEAS) with
amenorrhea were recruited. Obese controls (OC) with normal menses and normal
testosterone and DHEAS were recruited and matched to each PCO woman for age and
weight. The PCO women had a mean testosterone of 3.2 +/- 0.4 nmol/L, fasting
serum insulin level of 330 +/- 55 pmol/L, and DHEAS level of 3.4 +/- 1.3
mumol/L. An oral glucose tolerance test (OGTT) was performed at 8 AM after an
overnight fast. A DHEA infusion (1 mg/hour for 17 hours) was begun at 6 PM and
continued until the completion of the second OGTT performed the following
morning at 8 AM. T-lymphocytes were drawn at 8 AM each morning. RESULTS: The
DHEA infusion had no significant effect on any of the in vivo indices of insulin
sensitivity, ie, basal and OGTT insulin, C-peptide, and ratios of
insulin/glucose. In vitro, DHEA significantly increased insulin binding to
T-lymphocytes of PCO women but caused no significant change in OC women. There
was, however, marked enhancement of T-lymphocyte pyruvate dehydrogenase (PDH)
activities in both groups of study subjects following DHEA. CONCLUSION: We
conclude that a 17-hour infusion of DHEA enhanced T-lymphocyte insulin binding
and PDH activity while producing no detectable improvements in in vivo indices
of insulin sensitivity.
 
Publication Types:
Clinical Trial
Controlled Clinical Trial
 
PMID: 9419751 [PubMed - indexed for MEDLINE]
 
 
 
58: J Endocrinol Invest  1997 Oct;20(9):531-6 
 
Sporadic amplification of the insulin receptor gene in human breast cancer.
 
Papa V, Milazzo G, Goldfine ID, Waldman FM, Vigneri R.
 
Cattedra di Endocrinologia, Universita di Catania, Ospedale Garibaldi, Italy.
 
Insulin receptor (IR) content is increased in most human breast carcinomas when
compared to normal breast tissue. In the present study we investigated IR gene
copy number by using both conventional DNA analysis (slot blot) and fluorescence
in situ hybridization (FISH). Cultured human breast cell lines and primary
breast carcinoma specimens were analyzed. In 6 breast cell lines in culture both
techniques gave similar results: the relative IR copy number determined by FISH
strongly correlated with slot blot results (r = 0.831), even if probes for
different reference loci were used in the 2 methods. We find that in human
breast cancer IR gene amplification is a sporadic event. It occurred in 1/5
cultured breast cancer cell lines (MDA-MB 231) and in 8/93 (8.6%) breast cancer
specimens. In contrast an increased copy number of the entire chromosome 19
(which contains IR gene) was frequently observed in both breast cancer cell
lines (100%) and breast cancer specimens (45%). When present, IR gene
amplification always occurred at low level. These data indicate that IR gene
amplification is an uncommon event in human breast carcinomas and that
mechanisms other than gene amplification are responsible for IR protein
overexpression in most human breast cancers.
 
PMID: 9413807 [PubMed - indexed for MEDLINE]
 
 
 
59: Proc Assoc Am Physicians  1997 Nov;109(6):565-71 
 
Insulin receptor expression and clinical outcome in node-negative breast cancer.
 
Mathieu MC, Clark GM, Allred DC, Goldfine ID, Vigneri R.
 
Department of Medicine, Mount Zion Medical Center, University of California, San
Francisco 94143-1616, USA.
 
The insulin receptor (IR), a ligand-activated tyrosine kinase, is present in
breast cancers, but its relationship to patient survival is unknown. The IR was
measured in 584 tumor specimens from patients with node-negative breast
carcinoma by frozen-section immunohistochemistry and light microscopy. The
immunostaining signal was quantitated in relation to both the staining intensity
and the proportion of positive malignant epithelial cells. Analyses indicated
that patients with tumors with undetectable IR content in malignant epithelial
cells (260 cases) had a relatively lower predicted 5-year disease-free survival
(DFS) (69% +/- 3%) than did patients with tumors with detectable IR content (324
cases; DFS 76% +/- 3%, p = .032). The significance of IR content in these breast
malignant epithelial cells was then analyzed along with patient age, tumor size,
progesterone and estrogen receptor status, p53 accumulation, and S-phase.
Multivariate analysis of these data revealed that after adjustment for these
other variables, IR content was the strongest independent predictive factor for
DFS (relative risk = 1.73, p = .005). Interestingly, in a small subset of
patients with very high IR content (n = 62), DFS was decreased. These data
indicate that IR content in node-negative breast cancers is a significant major
predictor of reduced DFS. Moreover, they raise the possibility that the
measurement of IR content might provide important information concerning breast
cancer biology.
 
PMID: 9394418 [PubMed - indexed for MEDLINE]
 
 
 
60: Life Sci  1997;61(16):1583-92 
 
Bovine fetuin is an inhibitor of insulin receptor tyrosine kinase.
 
Mathews ST, Srinivas PR, Leon MA, Grunberger G.
 
Department of Internal Medicine, Wayne State University, Detroit, MI 48201, USA.
 
Fetuin has been identified earlier as the bovine homolog of the human plasma
protein, alpha2-Heremans Schmid glycoprotein (alpha2-HSG). Although bovine
fetuin shares over 70% amino acid sequence similarity with alpha2-HSG and rat
fetuin, no common function(s) have been identified. We report that
immunoaffinity purified bovine fetuin acts as an inhibitor of insulin receptor
tyrosine kinase activity (IR-TKA) with half-maximal inhibition at 1.5 microM. In
vitro, bovine fetuin (1.5 microM) blocked insulin-induced autophosphorylation of
the human IR completely and the half-maximal inhibitory effect was observed at
0.5 microM. Incubation of HIRcB cells (rat1 fibroblasts transfected with
wild-type human insulin receptor cDNA) with bovine fetuin (1.5 microM) inhibited
insulin-induced tyrosine phosphorylation of the IR beta-subunit by 40%. In
addition, bovine fetuin (2 microM) completely blocked insulin-stimulated DNA
synthesis in H-35 rat hepatoma cells. Our results, together with earlier reports
on rat fetuin and human alpha2-HSG, indicate a common IR-TK inhibitory function
for fetuin homologs.
 
PMID: 9353167 [PubMed - indexed for MEDLINE]
 
 
 
61: Endocrinology  1997 Nov;138(11):4821-9 
 
Vanadate, but not insulin, inhibits insulin receptor gene expression in rat
hepatoma cells.
 
Bortoli S, Amessou M, Collinet M, Desbuquois B, Lopez S.
 
Unite 30 INSERM, Hopital Necker-Enfants Malades, Paris, France.
 
Insulin and vanadate treatments have recently been shown to reverse the
overexpression of the hepatic insulin receptor (IR) gene in
streptozotocin-induced diabetic rats. To better understand the mechanisms
underlying these effects, the abilities of insulin and vanadate to affect IR
gene expression have been comparatively examined in Fao hepatoma cells, an
insulin-responsive cell line. Exposure of Fao cells to insulin (1 microM) or
vanadate (500 microM) for 24 h led to a 2-fold decrease in IR number in total
cellular membranes. Insulin treatment did not affect IR messenger RNA (mRNA)
level regardless of time of exposure and concentration. In contrast, vanadate
treatment caused a time- and dose-dependent decrease in IR mRNA level, which was
maximal (4-fold change) after a 24-h exposure to 500 microM vanadate and was
fully reversible. Insulin treatment increased from 28 to 39% the relative
expression of isotype A IR mRNA, but vanadate treatment did not significantly
affect this parameter. Vanadate treatment did not modify mRNA half-life (3.5 h)
in 5, 6 dichlorobenzimidazole riboside-treated cells but decreased by 4-fold the
transcriptional activity of the IR gene. These data show for the first time
that, although both insulin and vanadate decrease total cellular IR number in
Fao cells, only vanadate decreases IR mRNA level. It does so by inhibiting
transcription of the IR gene, suggesting an action on the gene promoter which
could be mediated by changes in the level of expression and/or of
phosphorylation of trans-acting factors.
 
PMID: 9348211 [PubMed - indexed for MEDLINE]
 
 
 
62: Breast Cancer Res Treat  1997 Sep;45(2):141-7 
 
The insulin receptor content is increased in breast cancers initiated by three
different oncogenes in transgenic mice.
 
Frittitta L, Cerrato A, Sacco MG, Weidner N, Goldfine ID, Vigneri R.
 
Istituto di Medicina Interna, Endocrinologia e Malattie del Metabolismo,
Universita di Catania, Ospedale Garibaldi, Italy.
 
The Insulin Receptor (IR) is a potential oncogene for mammary epithelial cells
since its content is increased in most human breast cancer specimens, and both
ligand-dependent malignant transformation and ligand-dependent enhanced growth
occurs in cultured breast cells overexpressing the IR. To better understand
whether the IR plays a role in mammary carcinogenesis which is independent of
other initiation factors, we measured IR content in transgenic mouse models of
breast cancer induced by 3 known oncogenes (Wnt-1, Neu, and Ret). Insulin
receptor content was measured by a specific radioimmunoassay. In normal mammary
gland tissues IR content was 14.6 +/- 1.4 ng/mg of protein (mean +/- SEM, n =
6). In the 3 cancers IR content was elevated (Neu = 36.1 +/- 4.6, n = 8, p <
0.002; Wnt-1 = 38.3 +/- 2.6, n = 13, p < 0.001; and Ret = 53.6 +/- 7.1, n = 7, p
< 0.001). These data indicate that IR overexpression, in addition to being a
potential oncogene, is increased in mouse tumors initiated by other oncogenes,
and therefore may also play a supportive role in the growth of breast cancers.
 
PMID: 9342439 [PubMed - indexed for MEDLINE]
 
 
 
1: Mol Cell Endocrinol  1998 Feb;137(2):177-86 
 
Insulin receptor substrate 1 antisense expression in an hepatoma cell line
reduces cell proliferation and induces overexpression of the Src homology 2
domain and collagen protein (SHC).
 
Taouis M, Dupont J, Gillet A, Derouet M, Simon J.
 
Endocrinologie de la Croissance et du Metabolisme, Station de Recherches
Avicoles, INRA, Nouzilly, France. taouis@tours.inra.fr
 
In mammalian cells, the insulin receptor substrate 1 protein (IRS-1) is a
specific substrate for insulin and IGF-1 receptor tyrosine kinases which is
involved in mediating metabolic and mitogenic actions of insulin and IGFs. In
order to determine if IRS-1 is also essential in a chicken derived hepatoma cell
line (LMH cells), IRS-1 gene has been invalidated in these cells. For this, we
subcloned chicken IRS-1 gene in an antisense orientation into a mammalian
expression vector driven by the cytomegalovirus early promoter. LMH cells were
stably transfected with this construct or with the empty vector carrying only
the neomycin resistance gene and selected for cIRS-1 expression. One subclone,
C2, showed a complete repression of cIRS-1 expression at both protein and mRNA
levels. Proliferation of C2 cells was dramatically reduced (54%) compared with
Neo(r) cells. Furthermore this reduction was accompanied by a decrease in
insulin-dependent [3H]thymidine incorporation, indicating a reduction in DNA
synthesis. Insulin-dependent [U-14C]glucose incorporation into cellular lipids
was also significantly reduced in C2 cell line suggesting an alteration in
lipogenesis. In wild type LMH cells, SHC which is involved in Ras pathway, also
served as a substrate for insulin receptor tyrosine kinase. In C2 cells, SHC
expression, its association with the insulin receptor and its tyrosine
phosphorylation were largely increased. Two forms of the regulatory subunit of
PI 3-kinase were present: p85 and p55 forms. Furthermore, C2 cells displayed
increased basal phosphatidylinositol (PI) 3'-kinase activity. This report
demonstrates a role for cIRS-1 in the metabolic and mitogenic actions of insulin
in LMH cells. However, the overexpression of cIRS-1 antisense did not completely
abolish cell proliferation. This may be explained by the exacerbation of an
alternative pathway that only partly compensate for the knocking out of cIRS-1
gene: the overexpression of SHC.
 
PMID: 9605520 [PubMed - indexed for MEDLINE]
 
 
 
2: J Biol Chem  1998 Apr 17;273(16):9994-10003 
 
Insulin receptor substrate-1 is the predominant signaling molecule activated by
insulin-like growth factor-I, insulin, and interleukin-4 in estrogen
receptor-positive human breast cancer cells.
 
Jackson JG, White MF, Yee D.
 
Division of Medical Oncology, Department of Medicine, University of Texas Health
Science Center, San Antonio, Texas 78284-7884, USA.
 
Because insulin-like growth factor-I (IGF-I), insulin, and interleukin-4 (IL-4)
have known biological effects in breast cancer cells and signal through
insulin-receptor substrate (IRS) adaptor proteins, we examined the expression
and function of IRS-1 and IRS-2 in breast tumors and cell lines. IRS-1 and IRS-2
were expressed by cell lines and primary breast tumor specimens. IGF-I, insulin,
and IL-4 treatment of MCF-7 and ZR-75, and IGF-I treatment of T47-D breast
cancer cells, resulted in much greater tyrosine phosphorylation of IRS-1
compared with IRS-2. Furthermore, IGF-I stimulated greater tyrosine
phosphorylation of IRS-1 than either insulin or IL-4. IGF-I treatment also
enhanced association of the p85 regulatory subunit of phosphatidylinositol
3-kinase with IRS-1 and stimulated increased enzymatic activity compared with
IL-4 and insulin in all three cell lines. Similarly, mitogen-activated protein
kinase activity was greater in IGF-I-stimulated cells. To determine the
functional significance of the activation of these pathways, we inhibited
activation of phosphatidylinositol 3-kinase with wortmannin and
mitogen-activated protein kinase with PD098059. Both compounds inhibited
IGF-stimulated growth, suggesting that both pathways contributed to the
mitogenic response to IGF-I. We conclude that IRS-1, and not IRS-2, is the
predominant signaling molecule activated by IGF-I, insulin, and IL-4.
Furthermore, enhanced tyrosine phosphorylation of IRS-1 by IGF-I, compared with
either insulin or IL-4, is associated with greater activation of mitogenic
downstream signaling pathways resulting in enhanced cell growth.
 
PMID: 9545345 [PubMed - indexed for MEDLINE]
 
 
 
3: Surgery  1998 Mar;123(3):315-20 
 
Variable effect of streptozotocin-diabetes on the growth of hamster pancreatic
cancer (H2T) in the Syrian hamster and nude mouse.
 
Fisher WE, Muscarella P, Boros LG, Schirmer WJ.
 
Department of Surgery, Ohio State University, Columbus 43210, USA.
 
BACKGROUND: Streptozotocin-diabetes prevents induction of pancreatic tumors in
several animal models and inhibits the growth of established human pancreatic
cancer implants in nude mice. However, it also promotes growth of the hamster
pancreatic cancer cell line, H2T, in the Syrian hamster. To test the hypothesis
that these contradictory effects are due to tumor host differences, the growth
of the H2T cell line was examined in the streptozotocin-diabetic nude mouse.
METHODS: H2T cells were implanted subcutaneously into streptozotocin-diabetic
nude mice (n = 10) and untreated control mice (n = 10). After 21 days, tumors
were excised and weighed. Plasma insulin and somatostatin were determined by
radioimmunoassay. RESULTS: After 3 weeks, tumors in the control group weighed
118 mg and tumors in the diabetic group weighed 28 mg (p < 0.001). Plasma
insulin was significantly decreased in the streptozotocin-treated animals
compared with control animals (insulin, 23 microU/ml vs 31 microU/ml; p <
0.001). In contrast, somatostatin was significantly elevated in the
streptozotocin-diabetic group compared with the control group (somatostatin, 179
pg/ml versus 54 pg/ml, p < 0.001). Competitive binding studies revealed specific
cell surface receptors for insulin (Kd, 15.5 nmol/L), and somatostatin (Kd, 2.5
nmol/L) on the H2T cells. In an in vitro cell proliferation assay, cell division
was promoted by insulin (p < 0.01, maximum +11%) and inhibited by somatostatin
(p < 0.01, maximum -18%). CONCLUSIONS: The variable effect of
streptozotocin-diabetes on pancreatic cancer growth is due to differences in the
tumor host. The growth of pancreatic cancer, particularly in
streptozotocin-diabetic nude mice, may be influenced by gut peptides in a
receptor-dependent fashion.
 
PMID: 9526524 [PubMed - indexed for MEDLINE]
 
 
 
4: Cancer Res  1998 Mar 15;58(6):1159-64 
 
Elevated insulin-like growth factor I receptor autophosphorylation and kinase
activity in human breast cancer.
 
Resnik JL, Reichart DB, Huey K, Webster NJ, Seely BL.
 
Department of Medicine, University of California, San Diego, La Jolla 92093,
USA.
 
Insulin-like growth factor I action has been implicated in the pathogenesis of
many different malignancies, including breast cancer. Insulin-like growth factor
I receptors (IGF-IRs) are overexpressed in virtually all breast cancer cell
lines, in which they are believed to enhance growth and inhibit apoptosis. In
this study, the functional activity of IGF-IRs from normal and malignant human
breast tissue was assessed. IGF-IR expression was 14-fold higher in malignant
breast tissue than in normal breast tissue. IGF-IR autophosphorylation and
kinase activity were 2-4-fold higher in purified receptor preparations from
malignant breast tissue as compared to normal breast tissue when normalized for
receptor number. This increase in receptor function, coupled with the enhanced
receptor expression, amounts to a 40-fold elevation in IGF-IR tyrosine kinase
activity in malignant breast tissue. The enhanced receptor autophosphorylation
and kinase activity were observed in the absence of hormonal stimulation and
seem to result from an alteration in the intrinsic activity of the receptor
itself. Protein tyrosine phosphatase activity is also increased in malignant
breast tissue. These data suggest that the IGF-IR is an important target for
breast cancer therapy.
 
PMID: 9515800 [PubMed - indexed for MEDLINE]
 
 
 
5: Diabetes  1998 Jan;47(1):87-92 
 
Expression of insulin/IGF-I hybrid receptors is increased in skeletal muscle of
patients with chronic primary hyperinsulinemia.
 
Federici M, Lauro D, D'Adamo M, Giovannone B, Porzio O, Mellozzi M, Tamburrano
G, Sbraccia P, Sesti G.
 
Laboratory of Molecular Medicine, University of Rome, Italy.
 
The insulin receptor (IR) shares structural and functional homology with the
IGF-I receptor (IGF-IR). Hybrid receptors composed of an IR
alphabeta-heterodimer and an IGF-IR alphabeta-heterodimer are formed in tissues
expressing both molecules. Hybrids behave as IGF-IR rather than IR with respect
to ligand binding affinity, receptor autophosphorylation, and hormone
internalization and degradation. Factors regulating hybrid formation in vivo are
unknown. We recently reported that in skeletal muscle of NIDDM patients,
expression of hybrids is increased and correlated with a decrease in IR number
and an increase in fasting insulin levels. However, it is not clear whether
increased expression of hybrid receptors is a primary defect specifically
associated with NIDDM or a secondary event caused by hyperinsulinemia. To
address this issue, we used a quantitative microwell-based immunoassay to
measure hybrid receptor abundance in skeletal muscle of 11 normal subjects and
12 patients with insulinoma, a state of primary nongenetically determined
hyperinsulinemia. Total insulin binding was lower in insulinoma patients than in
normal subjects (0.70 +/- 0.18 vs. 4.59 +/- 0.77; P < 0.0001). Total IGF-I
binding did not differ between the two groups (0.81 +/- 0.27 and 0.85 +/- 0.10,
respectively). The amount of hybrids, expressed as bound/total (B/T), was higher
in patients with insulinoma than in normal subjects (0.57 +/- 0.19 vs. 0.36 +/-
0.03; P < 0.0006) and was inversely correlated with total insulin binding (r =
-0.64, P < 0.0004). Increased abundance of hybrid receptors was positively
correlated with insulin levels (r = -0.82, P < 0.0009) and inversely correlated
with insulin-mediated glucose uptake (r = -0.80, P < 0.01). No correlations were
observed between insulin-mediated glucose uptake and maximal specific insulin
binding (r = 0.19, P = 0.64). These results indicate that insulin-induced IR
downregulation may lead to the formation of a higher proportion of hybrid
receptors, whose abundance is negatively correlated with in vivo insulin
sensitivity. These results, therefore, support a role for insulin in the
regulation of hybrid receptors formation and suggest that increased expression
of hybrids in NIDDM may be a secondary event caused by hyperinsulinemia rather
than a primary defect.
 
PMID: 9421379 [PubMed - indexed for MEDLINE]
 
 
 
6: J Soc Gynecol Investig  1994 Jan-Mar;1(1):74-8 
 
Enhanced post-receptor insulin effects in women following dehydroepiandrosterone
infusion.
 
Schriock ED, Buffington CK, Givens JR, Buster JE.
 
Department of Obstetrics and Gynecology, University of California, San
Francisco, USA.
 
OBJECTIVE: We hypothesized that intravenous dehydroepiandrosterone (DHEA) would
decrease insulin resistance in normal and insulin-resistant women. METHODS: Five
insulin-resistant women diagnosed as having polycystic ovaries (PCO) with
elevated testosterone and normal dehydroepiandrosterone sulfate (DHEAS) with
amenorrhea were recruited. Obese controls (OC) with normal menses and normal
testosterone and DHEAS were recruited and matched to each PCO woman for age and
weight. The PCO women had a mean testosterone of 3.2 +/- 0.4 nmol/L, fasting
serum insulin level of 330 +/- 55 pmol/L, and DHEAS level of 3.4 +/- 1.3
mumol/L. An oral glucose tolerance test (OGTT) was performed at 8 AM after an
overnight fast. A DHEA infusion (1 mg/hour for 17 hours) was begun at 6 PM and
continued until the completion of the second OGTT performed the following
morning at 8 AM. T-lymphocytes were drawn at 8 AM each morning. RESULTS: The
DHEA infusion had no significant effect on any of the in vivo indices of insulin
sensitivity, ie, basal and OGTT insulin, C-peptide, and ratios of
insulin/glucose. In vitro, DHEA significantly increased insulin binding to
T-lymphocytes of PCO women but caused no significant change in OC women. There
was, however, marked enhancement of T-lymphocyte pyruvate dehydrogenase (PDH)
activities in both groups of study subjects following DHEA. CONCLUSION: We
conclude that a 17-hour infusion of DHEA enhanced T-lymphocyte insulin binding
and PDH activity while producing no detectable improvements in in vivo indices
of insulin sensitivity.
 
Publication Types:
Clinical Trial
Controlled Clinical Trial
 
PMID: 9419751 [PubMed - indexed for MEDLINE]
 
 
 
7: J Endocrinol Invest  1997 Oct;20(9):531-6 
 
Sporadic amplification of the insulin receptor gene in human breast cancer.
 
Papa V, Milazzo G, Goldfine ID, Waldman FM, Vigneri R.
 
Cattedra di Endocrinologia, Universita di Catania, Ospedale Garibaldi, Italy.
 
Insulin receptor (IR) content is increased in most human breast carcinomas when
compared to normal breast tissue. In the present study we investigated IR gene
copy number by using both conventional DNA analysis (slot blot) and fluorescence
in situ hybridization (FISH). Cultured human breast cell lines and primary
breast carcinoma specimens were analyzed. In 6 breast cell lines in culture both
techniques gave similar results: the relative IR copy number determined by FISH
strongly correlated with slot blot results (r = 0.831), even if probes for
different reference loci were used in the 2 methods. We find that in human
breast cancer IR gene amplification is a sporadic event. It occurred in 1/5
cultured breast cancer cell lines (MDA-MB 231) and in 8/93 (8.6%) breast cancer
specimens. In contrast an increased copy number of the entire chromosome 19
(which contains IR gene) was frequently observed in both breast cancer cell
lines (100%) and breast cancer specimens (45%). When present, IR gene
amplification always occurred at low level. These data indicate that IR gene
amplification is an uncommon event in human breast carcinomas and that
mechanisms other than gene amplification are responsible for IR protein
overexpression in most human breast cancers.
 
PMID: 9413807 [PubMed - indexed for MEDLINE]
 
 
 
8: Proc Assoc Am Physicians  1997 Nov;109(6):565-71 
 
Insulin receptor expression and clinical outcome in node-negative breast cancer.
 
Mathieu MC, Clark GM, Allred DC, Goldfine ID, Vigneri R.
 
Department of Medicine, Mount Zion Medical Center, University of California, San
Francisco 94143-1616, USA.
 
The insulin receptor (IR), a ligand-activated tyrosine kinase, is present in
breast cancers, but its relationship to patient survival is unknown. The IR was
measured in 584 tumor specimens from patients with node-negative breast
carcinoma by frozen-section immunohistochemistry and light microscopy. The
immunostaining signal was quantitated in relation to both the staining intensity
and the proportion of positive malignant epithelial cells. Analyses indicated
that patients with tumors with undetectable IR content in malignant epithelial
cells (260 cases) had a relatively lower predicted 5-year disease-free survival
(DFS) (69% +/- 3%) than did patients with tumors with detectable IR content (324
cases; DFS 76% +/- 3%, p = .032). The significance of IR content in these breast
malignant epithelial cells was then analyzed along with patient age, tumor size,
progesterone and estrogen receptor status, p53 accumulation, and S-phase.
Multivariate analysis of these data revealed that after adjustment for these
other variables, IR content was the strongest independent predictive factor for
DFS (relative risk = 1.73, p = .005). Interestingly, in a small subset of
patients with very high IR content (n = 62), DFS was decreased. These data
indicate that IR content in node-negative breast cancers is a significant major
predictor of reduced DFS. Moreover, they raise the possibility that the
measurement of IR content might provide important information concerning breast
cancer biology.
 
PMID: 9394418 [PubMed - indexed for MEDLINE]
 
 
 
9: Life Sci  1997;61(16):1583-92 
 
Bovine fetuin is an inhibitor of insulin receptor tyrosine kinase.
 
Mathews ST, Srinivas PR, Leon MA, Grunberger G.
 
Department of Internal Medicine, Wayne State University, Detroit, MI 48201, USA.
 
Fetuin has been identified earlier as the bovine homolog of the human plasma
protein, alpha2-Heremans Schmid glycoprotein (alpha2-HSG). Although bovine
fetuin shares over 70% amino acid sequence similarity with alpha2-HSG and rat
fetuin, no common function(s) have been identified. We report that
immunoaffinity purified bovine fetuin acts as an inhibitor of insulin receptor
tyrosine kinase activity (IR-TKA) with half-maximal inhibition at 1.5 microM. In
vitro, bovine fetuin (1.5 microM) blocked insulin-induced autophosphorylation of
the human IR completely and the half-maximal inhibitory effect was observed at
0.5 microM. Incubation of HIRcB cells (rat1 fibroblasts transfected with
wild-type human insulin receptor cDNA) with bovine fetuin (1.5 microM) inhibited
insulin-induced tyrosine phosphorylation of the IR beta-subunit by 40%. In
addition, bovine fetuin (2 microM) completely blocked insulin-stimulated DNA
synthesis in H-35 rat hepatoma cells. Our results, together with earlier reports
on rat fetuin and human alpha2-HSG, indicate a common IR-TK inhibitory function
for fetuin homologs.
 
PMID: 9353167 [PubMed - indexed for MEDLINE]
 
 
 
10: Endocrinology  1997 Nov;138(11):4821-9 
 
Vanadate, but not insulin, inhibits insulin receptor gene expression in rat
hepatoma cells.
 
Bortoli S, Amessou M, Collinet M, Desbuquois B, Lopez S.
 
Unite 30 INSERM, Hopital Necker-Enfants Malades, Paris, France.
 
Insulin and vanadate treatments have recently been shown to reverse the
overexpression of the hepatic insulin receptor (IR) gene in
streptozotocin-induced diabetic rats. To better understand the mechanisms
underlying these effects, the abilities of insulin and vanadate to affect IR
gene expression have been comparatively examined in Fao hepatoma cells, an
insulin-responsive cell line. Exposure of Fao cells to insulin (1 microM) or
vanadate (500 microM) for 24 h led to a 2-fold decrease in IR number in total
cellular membranes. Insulin treatment did not affect IR messenger RNA (mRNA)
level regardless of time of exposure and concentration. In contrast, vanadate
treatment caused a time- and dose-dependent decrease in IR mRNA level, which was
maximal (4-fold change) after a 24-h exposure to 500 microM vanadate and was
fully reversible. Insulin treatment increased from 28 to 39% the relative
expression of isotype A IR mRNA, but vanadate treatment did not significantly
affect this parameter. Vanadate treatment did not modify mRNA half-life (3.5 h)
in 5, 6 dichlorobenzimidazole riboside-treated cells but decreased by 4-fold the
transcriptional activity of the IR gene. These data show for the first time
that, although both insulin and vanadate decrease total cellular IR number in
Fao cells, only vanadate decreases IR mRNA level. It does so by inhibiting
transcription of the IR gene, suggesting an action on the gene promoter which
could be mediated by changes in the level of expression and/or of
phosphorylation of trans-acting factors.
 
PMID: 9348211 [PubMed - indexed for MEDLINE]
 
 
 
11: Breast Cancer Res Treat  1997 Sep;45(2):141-7 
 
The insulin receptor content is increased in breast cancers initiated by three
different oncogenes in transgenic mice.
 
Frittitta L, Cerrato A, Sacco MG, Weidner N, Goldfine ID, Vigneri R.
 
Istituto di Medicina Interna, Endocrinologia e Malattie del Metabolismo,
Universita di Catania, Ospedale Garibaldi, Italy.
 
The Insulin Receptor (IR) is a potential oncogene for mammary epithelial cells
since its content is increased in most human breast cancer specimens, and both
ligand-dependent malignant transformation and ligand-dependent enhanced growth
occurs in cultured breast cells overexpressing the IR. To better understand
whether the IR plays a role in mammary carcinogenesis which is independent of
other initiation factors, we measured IR content in transgenic mouse models of
breast cancer induced by 3 known oncogenes (Wnt-1, Neu, and Ret). Insulin
receptor content was measured by a specific radioimmunoassay. In normal mammary
gland tissues IR content was 14.6 +/- 1.4 ng/mg of protein (mean +/- SEM, n =
6). In the 3 cancers IR content was elevated (Neu = 36.1 +/- 4.6, n = 8, p <
0.002; Wnt-1 = 38.3 +/- 2.6, n = 13, p < 0.001; and Ret = 53.6 +/- 7.1, n = 7, p
< 0.001). These data indicate that IR overexpression, in addition to being a
potential oncogene, is increased in mouse tumors initiated by other oncogenes,
and therefore may also play a supportive role in the growth of breast cancers.
 
PMID: 9342439 [PubMed - indexed for MEDLINE]
 
 
 
 

 

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