Reversal of Hypermethylation and Reactivation of p16INK4a, RARβ, and MGMT Genes by Genistein and Other Isoflavones from Soy

Abstract

Purpose: We have previously shown the reactivation of some methylation-silenced genes in cancer cells by (À)-epigallocatechin-3-gallate, the major polyphenol from green tea. To determine whether other polyphenolic compounds have similar activities, we studied the effects of soy isoflavones on DNA methylation. Experimental Design: Enzyme assay was used to determine the inhibitory effect of genistein on DNA methyltransferase activity in nuclear extracts and purified recombinant enzyme. Methylation-specific PCR and quantitative real-time PCR were employed to examine the DNA methylation and gene expression status of retinoic acid receptor h (RARb), p16INK4a , and O 6 -methylguanine methyltransferase (MGMT) in KYSE 510 esophageal squamous cell carcinoma cells treated with genistein alone or in combination with trichostatin, sulforaphane, or 2V -deoxy-5-aza-cytidine (5-aza-dCyd). Results: Genistein (2-20 Amol/L) reversed DNA hypermethylation and reactivated RARb, p16INK4a , and MGMT in KYSE 510 cells. Genistein also inhibited cell growth at these concentrations. Reversal of DNA hypermethylation and reactivation of RARb by genistein were also observed in KYSE 150 cells and prostate cancer LNCaP and PC3 cells. Genistein (20-50 Amol/L) dose-dependently inhibited DNA methyltransferase activity, showing substrate-and methyl donor^dependent inhibition. Biochanin A and daidzein were less effective in inhibiting DNA methyltransferase activity, in reactivating RARb, and in inhibiting cancer cell growth. In combination with trichostatin, sulforaphane, or 5-aza-dCyd, genistein enhanced reactivation of these genes and inhibition of cell growth. Conclusions:These results indicate that genistein and related soy isoflavones reactivate methylation-silenced genes, partially through a direct inhibition of DNA methyltransferase, which may contribute to the chemopreventive activity of dietary isoflavones.

Inhibition of cell proliferation, induction of apoptosis, reactivation of DLC1, and modulation of other gene expression by dietary flavone in breast cancer cell lines

“…Promoter hypermethylation is a major mechanism of DLC1 down-regulation and inactivation in many other types of solid tumors and hematological malignancies [13,17,49], and reactivation of DLC1 expression by dietary constituents thus warrants further investigation. Various dietary compounds have been shown to have potential therapeutic benefits [48,50,51,52]. Our present results obtained with cell lines derived from aggressive or metastatic breast tumors suggest the possibility that administration of flavone, alone or in combination with DNA methyltransferase and histone deacetylase inhibitors, may be an effective adjunct to chemotherapy.…”

“…(-)Epigallocatechin-3-gallate, the major polyphenol in green tea, was shown to inhibit DNA methyltransferase activity and to reverse the methylation of several genes including that of a tumor suppressor gene in cancer cell lines [47]. Genistein and related soy isoflavones were also shown to reactivate the gene for the tumor suppressor p16INK4a as well as those for retinoic acid receptor β, O6-methylguanine methyltransferase, and mut L homolog 1 in colon, esophageal, and prostate cancer cell lines [48]. Our results now suggest that flavone manifests a similar activity in breast cancer cells.…”

Flavonoid consumption and esophageal cancer among black and white men in the United States

“…22 Isoflavonoids inhibit the growth of ESCC cell lines. 23,24 The differences in risk estimates in white men for EAC and ESCC in this and other epidemiological studies suggest that chemopreventive properties of bioactive food components might differ in their effects on EAC and ESCC. 25 A major strength of our study is the large number of histologically classified cases, providing power to detect differences in histological subtypes and flavonoid intakes when present.…”

Epigenetic deregulation of miR-29a and miR-1256 by isoflavone contributes to the inhibition of prostate cancer cell growth and invasion

“…20 TRIM68 could functionally interact to reverse the methylation status of several genes including BTG3, GSTP1, RASSF1A, EPH2, BRCA1, p16, RARβ and MGMT. [32][33][34][35] Studies have also shown the regulatory effects of isoflavone genistein on the methylation of miR-221/222 and miR-145 in PCa cells. 36,37 These findings suggest the demethylating function of isoflavone.…”