Dr. Weeks’ Comment: Lunasin protects against cancer process.
Differential expression of thrombospondin (THBS1) in tumorigenic and nontumorigenic prostate epithelial cells in response to a chromatin-binding soy peptide.
Abstract
The chemopreventive properties of the chromatin-binding soy peptide, lunasin, are well documented, but its mechanism of action is unclear. To elucidate the mechanism by which lunasin reduces tumor foci formation in cultured mammalian cells, nontumorigenic (RWPE-1) and tumorigenic (RWPE-2) human prostate epithelial cells were treated with lunasin followed by gene expression profiling and characterization of the chromatin acetylation status for certain chemopreventive genes. The genes HIF1A, PRKAR1A, TOB1, and THBS1 were upregulated by lunasin in RWPE-1 but not in RWPE-2 cells. Using histone acetyltransferase (HAT) assays with acid-extracted histones as templates, we showed that lunasin specifically inhibited H4K8 acetylation while enhanced H4K16 acetylation catalyzed by HAT enzymes p300, PCAF, and HAT1A. These results suggest a novel mechanism for lunasin-dependent upregulation of gene expression. Chromatin immunoprecipitation (ChIP) revealed hypoacetylation of H4K16 in RWPE-2 cells, specifically at the 5′ end of THBS1 containing a CpG island. Moreover, bisulfite PCR (BSP) and subsequent DNA sequencing indicated that this CpG island was hypomethylated in RWPE-1 but hypermethylated in RWPE-2 cells. Histone hypoacetylation and DNA hypermethylation in the 5′ region of THBS1 may explain the inability of lunasin to upregulate this gene in RWPE-2 cells.
Lunasin suppresses E1A-mediated transformation of mammalian cells but does not inhibit growth of immortalized and established cancer cell lines.
Abstract
Lunasin, a novel and promising chemopreventive compound isolated from soybean cotyledon, is a 43-amino acid peptide that contains a -RGD-cell adhesion motif followed by 8 aspartic acid residues at the carboxyl end and a structurally conserved helix region. We showed previously that lunasin peptide applied exogenously reduces foci formation in mouse fibroblast cells treated with chemical carcinogens and inhibits skin tumorigenesis induced by chemical carcinogens in mice when applied topically. In this study, lunasin peptide applied to cell culture suppresses foci formation in E1A-transfected mouse fibroblast NIH 3T3 cells. Within 18 h of exogenous application, lunasin internalizes into the cell and localizes in the nucleus. In an initial study of genes affected by lunasin, the peptide increases p21 protein levels fivefold in cells transfected with E1A but not in untransfected cells. In contrast to its inhibitory effects on cell transformation, lunasin has no effect on growth of imicroMortalized (nontumorigenc)and established cancer cells. This is the first report that lunasin suppresses transformation of mamicroMalian cells induced by an oncogene (E1A) in addition to chemical carcinogens.
Carotenoids induce morphological changes in human mammary epithelial cell cultures.
Abstract
Epidemiological studies suggest that carotenoids may play a role in human breast carcinogenesis. To identify an anticarcinogenic mechanism, a laboratory model for examination of biologic effects is required. Efficacy of tetrahydrofuran (THF) for delivery of beta-carotene to a human mammary epithelial cell line has not been reported, and biologic effects of carotenoids on normal mammary epithelial cells or mammary epithelial cell lines have not been described. In these studies, we examined MCF-10A cells treated with 0.04%, 0.10%, and 0.35% THF (vol/vol) for morphological signs of toxicity and determined effects of THF on cell proliferation over a seven-day period. Cells treated with THF demonstrated a reduction in mean number of cells per dish (p < 0.05) but still underwent a 3.2- to 4.0-fold increase in cell number over the seven days. MCF-10A cells were also treated with a 7 mumol/l solution of beta-carotene and examined for morphological changes and effects on cell growth. Exposure to this concentration of carotenoid did not significantly affect proliferation but did induce the formation of cytoplasmic vacuoles similar to those seen in differentiating mammary epithelial cells. High-performance liquid chromatography analysis revealed a beta-carotene concentration of 0.004 nmol/10(6) cells in the treatment group. The effects of beta-carotene and the non-provitamin A carotenoid canthaxanthin were also examined in the in vitro cultures of primary human mammary epithelial cells obtained from reduction mammoplasties of two individuals. Exposure to these carotenoids induced morphological changes consistent with cellular differentiation and had a dramatic effect on the proliferative life span of these cells. Thus carotenoids may directly affect the proliferative capacity and differentiation of mammary epithelial cells, which may be among the chemoprotective activities of these compounds.
The interaction of genetic polymorphisms with lifestyle factors: implications for the dietary prevention of prostate cancer.
Abstract
Multiple studies of the impact of lifestyle factors on the development of prostate cancer have yielded inconsistent results. This may be due to unrecognized heterogeneity of the study populations, specifically genetic polymorphisms, which directly affect lifestyle interventions. We review some known polymorphisms and mechanisms of action as related to dietary and other lifestyle interventions and prostate cancer carcinogenesis. Further identification of genes affected by dietary/environmental changes will enable knowledgeable lifestyle interventions on an individual basis.