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In Vivo. 2010 May-Jun;24(3):249-55.
Pharmacological ascorbic acid suppresses syngeneic tumor growth and metastases in hormone-refractory prostate cancer.
Pollard HB, Levine MA, Eidelman O, Pollard M.
Department of Anatomy, Physiology and Genetics, Uniformed Services University School of Medicine, USUHS, Bethesda, MD 20814, USA. hpollard@usuhs.mil
Abstract
AIM: The aim of this study was to test for the influence of ascorbic acid on tumorigenicity and metastases of implanted PAIII prostate cancer adenocarcinoma cells in syngeneic LW rats.
MATERIALS AND METHODS: Hormone-refractory prostate cancer PAIII cells were implanted subcutaneously into immunologically intact, Lobund-Wistar (LW) rats. Intraperitoneal pharmacological doses of ascorbic acid were administered each day for the ensuing 30 days. On the 40th day, animals were sacrificed. Local tumor weights were measured, and metastases were counted.
RESULTS: At the end of the 40 day experimental period, the primary tumors were found to be significantly reduced in weight (p=0.026). In addition, sub-pleural lung metastases were even more profoundly reduced in number and size (p=0.009). Grossly enlarged ipsilateral lymph node metastases declined from 7 of 15 rats to 1 of 15 rats.
CONCLUSION: Pharmacological doses of ascorbic acid suppress tumor growth and metastases in hormone-refractory prostate cancer.
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2.
Clin Cancer Res. 2010 Jan 15;16(2):509-20. Epub 2010 Jan 12.
Mechanisms of ascorbate-induced cytotoxicity in pancreatic cancer.
Du J, Martin SM, Levine M, Wagner BA, Buettner GR, Wang SH, Taghiyev AF, Du C, Knudson CM, Cullen JJ.
Department of Surgery, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA.
Abstract
PURPOSE: Pharmacologic concentrations of ascorbate may be effective in cancer therapeutics. We hypothesized that ascorbate concentrations achievable with i.v. dosing would be cytotoxic in pancreatic cancer for which the 5-year survival is <3%.
EXPERIMENTAL DESIGN: Pancreatic cancer cell lines were treated with ascorbate (0, 5, or 10 mmol/L) for 1 hour, then viability and clonogenic survival were determined. Pancreatic tumor cells were delivered s.c. into the flank region of nude mice and allowed to grow at which time they were randomized to receive either ascorbate (4 g/kg) or osmotically equivalent saline (1 mol/L) i.p. for 2 weeks.
RESULTS: There was a time- and dose-dependent increase in measured H(2)O(2) production with increased concentrations of ascorbate. Ascorbate decreased viability in all pancreatic cancer cell lines but had no effect on an immortalized pancreatic ductal epithelial cell line. Ascorbate decreased clonogenic survival of the pancreatic cancer cell lines, which was reversed by treatment of cells with scavengers of H(2)O(2). Treatment with ascorbate induced a caspase-independent cell death that was associated with autophagy. In vivo, treatment with ascorbate inhibited tumor growth and prolonged survival.
CONCLUSIONS: These results show that pharmacologic doses of ascorbate, easily achievable in humans, may have potential for therapy in pancreatic cancer.
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3.
Free Radic Biol Med. 2009 Jul 1;47(1):27-9. Epub 2009 Apr 8.
Losing and finding a way at C: new promise for pharmacologic ascorbate in cancer treatment.
Molecular and Clinical Nutrition Section, Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-1372, USA. MarkL@mail.nih.gov
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4.
Proc Natl Acad Sci U S A. 2008 Aug 12;105(32):11105-9. Epub 2008 Aug 4.
Pharmacologic doses of ascorbate act as a prooxidant and decrease growth of aggressive tumor xenografts in mice.
Chen Q, Espey MG, Sun AY, Pooput C, Kirk KL, Krishna MC, Khosh DB, Drisko J, Levine M.
Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, and Radiation Biology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Abstract
Ascorbic acid is an essential nutrient commonly regarded as an antioxidant. In this study, we showed that ascorbate at pharmacologic concentrations was a prooxidant, generating hydrogen-peroxide-dependent cytotoxicity toward a variety of cancer cells in vitro without adversely affecting normal cells. To test this action in vivo, normal oral tight control was bypassed by parenteral ascorbate administration. Real-time microdialysis sampling in mice bearing glioblastoma xenografts showed that a single pharmacologic dose of ascorbate produced sustained ascorbate radical and hydrogen peroxide formation selectively within interstitial fluids of tumors but not in blood. Moreover, a regimen of daily pharmacologic ascorbate treatment significantly decreased growth rates of ovarian (P < 0.005), pancreatic (P < 0.05), and glioblastoma (P < 0.001) tumors established in mice. Similar pharmacologic concentrations were readily achieved in humans given ascorbate intravenously. These data suggest that ascorbate as a prodrug may have benefits in cancers with poor prognosis and limited therapeutic options.
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Proc Natl Acad Sci U S A. 2007 May 22;104(21):8749-54. Epub 2007 May 14.
Ascorbate in pharmacologic concentrations selectively generates ascorbate radical and hydrogen peroxide in extracellular fluid in vivo.
Chen Q, Espey MG, Sun AY, Lee JH, Krishna MC, Shacter E, Choyke PL, Pooput C, Kirk KL, Buettner GR, Levine M.
Molecular and Clinical Nutrition Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Abstract
Ascorbate (ascorbic acid, vitamin C), in pharmacologic concentrations easily achieved in humans by i.v. administration, selectively kills some cancer cells but not normal cells. We proposed that pharmacologic ascorbate is a prodrug for preferential steady-state formation of ascorbate radical (Asc(*-)) and H(2)O(2) in the extracellular space compared with blood. Here we test this hypothesis in vivo. Rats were administered parenteral (i.v. or i.p.) or oral ascorbate in typical human pharmacologic doses ( approximately 0.25-0.5 mg per gram of body weight). After i.v. injection, ascorbate baseline concentrations of 50-100 microM in blood and extracellular fluid increased to peaks of >8 mM. After i.p. injection, peaks approached 3 mM in both fluids. By gavage, the same doses produced ascorbate concentrations of <150 microM in both fluids. In blood, Asc(*-) concentrations measured by EPR were undetectable with oral administration and always <50 nM with parenteral administration, even when corresponding ascorbate concentrations were >8 mM. After parenteral dosing, Asc(*-) concentrations in extracellular fluid were 4- to 12-fold higher than those in blood, were as high as 250 nM, and were a function of ascorbate concentrations. By using the synthesized probe peroxyxanthone, H(2)O(2) in extracellular fluid was detected only after parenteral administration of ascorbate and when Asc(*-) concentrations in extracellular fluid exceeded 100 nM. The data show that pharmacologic ascorbate is a prodrug for preferential steady-state formation of Asc(*-) and H(2)O(2) in the extracellular space but not blood. These data provide a foundation for pursuing pharmacologic ascorbate as a prooxidant therapeutic agent in cancer and infections.
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Proc Natl Acad Sci U S A. 2005 Sep 20;102(38):13604-9. Epub 2005 Sep 12.
Pharmacologic ascorbic acid concentrations selectively kill cancer cells: action as a pro-drug to deliver hydrogen peroxide to tissues.
Chen Q, Espey MG, Krishna MC, Mitchell JB, Corpe CP, Buettner GR, Shacter E, Levine M.
Molecular and Clinical Nutrition Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Abstract
Human pharmacokinetics data indicate that i.v. ascorbic acid (ascorbate) in pharmacologic concentrations could have an unanticipated role in cancer treatment. Our goals here were to test whether ascorbate killed cancer cells selectively, and if so, to determine mechanisms, using clinically relevant conditions. Cell death in 10 cancer and 4 normal cell types was measured by using 1-h exposures. Normal cells were unaffected by 20 mM ascorbate, whereas 5 cancer lines had EC(50) values of <4 mM, a concentration easily achievable i.v. Human lymphoma cells were studied in detail because of their sensitivity to ascorbate (EC(50) of 0.5 mM) and suitability for addressing mechanisms. Extracellular but not intracellular ascorbate mediated cell death, which occurred by apoptosis and pyknosis/necrosis. Cell death was independent of metal chelators and absolutely dependent on H(2)O(2) formation. Cell death from H(2)O(2) added to cells was identical to that found when H(2)O(2) was generated by ascorbate treatment. H(2)O(2) generation was dependent on ascorbate concentration, incubation time, and the presence of 0.5-10% serum, and displayed a linear relationship with ascorbate radical formation. Although ascorbate addition to medium generated H(2)O(2), ascorbate addition to blood generated no detectable H(2)O(2) and only trace detectable ascorbate radical. Taken together, these data indicate that ascorbate at concentrations achieved only by i.v. administration may be a pro-drug for formation of H(2)O(2), and that blood can be a delivery system of the pro-drug to tissues. These findings give plausibility to i.v. ascorbic acid in cancer treatment, and have unexpected implications for treatment of infections where H(2)O(2) may be beneficial.
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7.
Arch Biochem Biophys. 2004 Mar 1;423(1):109-15.
Short-term and long-term vitamin C supplementation in humans dose-dependently increases the resistance of plasma to ex vivo lipid peroxidation.
Polidori MC, Mecocci P, Levine M, Frei B.
Institute of Biochemistry and Molecular Biology I, Heinrich-Heine University, Duesseldorf, Germany.
Abstract
To assess the effects of short-term and long-term vitamin C supplementation in humans on plasma antioxidant status and resistance to oxidative stress, plasma was obtained from 20 individuals before and 2h after oral administration of 2g of vitamin C, or from eight subjects enrolled in a vitamin C depletion-repletion study using increasing daily doses of vitamin C from 30 to 2500 mg. Plasma concentrations of ascorbate, but not other physiological antioxidants, increased significantly after short-term supplementation, and increased progressively in the long-term study with increasing vitamin C doses of up to 1000 mg/day. Upon incubation of plasma with a free radical initiator, ascorbate concentrations were positively correlated with the lag phase preceding detectable lipid peroxidation. We conclude that vitamin C supplementation in humans dose-dependently increases plasma ascorbate concentrations and, thus, the resistance of plasma to lipid peroxidation ex vivo. Plasma and body saturation with vitamin C in humans appears desirable to maximize antioxidant protection and lower risk of oxidative damage.
PMID: 14871474 [PubMed – indexed for MEDLINE]
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8.
CMAJ. 2001 Feb 6;164(3):353-5.
New insights into the physiology and pharmacology of vitamin C.
Molecular and Clinical Nutrition Section, Bldg. 10, Rm. 4D52-MSC 1372, National Institutes of Health, Bethesda, MD 20892-1372, USA.
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9.
J Am Coll Nutr. 2000 Aug;19(4):423-5.
Reevaluation of ascorbate in cancer treatment: emerging evidence, open minds and serendipity.
Molecular and Clinical Nutrition Section, Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Abstract
Some clinicians and alternative therapy practitioners advocate megadose intravenous and oral ascorbate treatment of cancer. Randomized control studies using oral ascorbate showed no benefit. Recent data show that intravenous but not oral administration of ascorbate can produce millimolar plasma concentrations, which are toxic to many cancer cell lines. We propose that ascorbate treatment of cancer should be reexamined by rigorous scientific scrutiny in the light of new evidence.
Altern Med Rev. 2010 Dec;15(4):345-51.
The vitamin C:vitamin K3 system – enhancers and inhibitors of the anticancer effect.
Lamson DW, Gu YH, Plaza SM, Brignall MS, Brinton CA, Sadlon AE.
Bastyr University, Kenmore, WA, USA. davisl@seanet.com
Abstract
The oxidizing anticancer system of vitamin C and vitamin K₃ (VC:VK₃, producing hydrogen peroxide via superoxide) was combined individually with melatonin, curcumin, quercetin, or cholecalciferol (VD₃) to determine interactions. Substrates were LNCaP and PC-3 prostate cancer cell lines. Three of the tested antioxidants displayed differences in cell line cytotoxicity. Melatonin combined with VC:VK₃ quenched the oxidizing effect, while VC:VK₃ applied 24 hours after melatonin showed no quenching. With increasing curcumin concentrations, an apparent combined effect of VC:VK₃ and curcumin occurred in LNCaP cells, but not PC-3 cells. Quercetin alone was cytotoxic on both cell lines, but demonstrated an additional 50-percent cytotoxicity on PC-3 cells when combined with VC:VK₃. VD₃ was effective against both cell lines, with more effect on PC-3. This effect was negated on LNCaP cells with the addition of VC:VK₃. In conclusion, a natural antioxidant can enhance or decrease the cytotoxicity of an oxidizing anticancer system in vitro, but generalizations about antioxidants cannot be made.
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