Reversal of hypermethylation and reactivation of p16INK4a, RARbeta, and MGMT genes by genistein and other isoflavones from soy.
OBJECTIVE
We have previously shown the reactivation of some methylation-silenced genes in cancer cells by (-)-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.


METHODS
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 beta (RARbeta), p16INK4a, and O6-methylguanine methyltransferase (MGMT) in KYSE 510 esophageal squamous cell carcinoma cells treated with genistein alone or in combination with trichostatin, sulforaphane, or 2'-deoxy-5-aza-cytidine (5-aza-dCyd).


RESULTS
Genistein (2-20 micromol/L) reversed DNA hypermethylation and reactivated RARbeta, p16INK4a, and MGMT in KYSE 510 cells. Genistein also inhibited cell growth at these concentrations. Reversal of DNA hypermethylation and reactivation of RARbeta by genistein were also observed in KYSE 150 cells and prostate cancer LNCaP and PC3 cells. Genistein (20-50 micromol/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 RARbeta, 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.
Fang
Ming Zhu
MZ
Susan Lehman Cullman Laboratory for Cancer Research, Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-8020, USA.
Chen
Dapeng
D
Sun
Yi
Y
Jin
Zhe
Z
Christman
Judith K
JK
Yang
Chung S
CS
D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism*; D019175:DNA Methylation; D000077209:Decitabine; D004305:Dose-Response Relationship, Drug; D004938:Esophageal Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D019833:Genistein / Q000494:pharmacology*; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D007529:Isoflavones / Q000737:chemistry / Q000494:pharmacology; D017879:Isothiocyanates; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013025:Glycine max / Q000378:metabolism*; D013447:Sulfites / Q000494:pharmacology; D013454:Sulfoxides; D013662:Tea; D013861:Thiocyanates / Q000494:pharmacology
D016588:Anticarcinogenic Agents; D000970:Antineoplastic Agents; D019941:Cyclin-Dependent Kinase Inhibitor p16; D006877:Hydroxamic Acids; D007529:Isoflavones; D017879:Isothiocyanates; D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; D013447:Sulfites; D013454:Sulfoxides; D013662:Tea; D013861:Thiocyanates; C082925:retinoic acid receptor beta; C012589:trichostatin A; C004742:daidzein; D000077209:Decitabine; D019833:Genistein; D019853:O(6)-Methylguanine-DNA Methyltransferase; C016766:sulforaphane; D001374:Azacitidine; C004541:biochanin A