Genistein reverses hypermethylation and induces active histone modifications in tumor suppressor gene B-Cell translocation gene 3 in prostate cancer.
BACKGROUND
: B-cell translocation gene 3 (BTG3/ANA/APRO4) is a candidate tumor suppressor gene in some malignancies. We report here that B-cell translocation gene 3 (BTG3) is transcriptionally down-regulated in prostate cancer and the mechanism of inactivation is through promoter hypermethylation.


METHODS
: Prostate cancer and normal cell lines were treated with different doses of genistein and 5-aza-2'-deoxycytidine (5Aza-C). BTG3 messenger ribonucleic acid (mRNA) expression was determined by quantitative real-time polymerase chain reaction in tissues and cell lines. Bisulfate-modified polymerase chain reaction, cloning and sequencing were used to examine promoter methylation in tumor samples and cell lines. Enzyme activity/inhibition assays were done to check the effect of genistein and 5Aza-C on DNA methyltransferases. ChIP assay was performed to analyze chromatin modifications caused by genistein treatment.


RESULTS
: BTG3 mRNA expression was down-regulated in cancer tissues and cells. Genistein and 5Aza-C induced BTG3 mRNA expression in all PC cell lines. Complete methylation of BTG3 promoter in tumor samples and cancer cell lines was observed. Genistein and 5Aza-C treatment significantly decreased promoter methylation, reactivating BTG3 expression. Genistein and 5Aza-C increased levels of acetylated histones 3, 4, histone 3 dimethylated at lysine 4, histone 3 trimethylated at lysine 4, and RNA polymerase II, decreased DNA methyl transferase and methyl-binding domain protein 2 activity, and increased histone acetyl transferase (HAT) activity.


CONCLUSIONS
: This is the first report to show that BTG3 is silenced in prostate cancer and can be reactivated by genistein-induced promoter demethylation and active histone modification. Genistein showed similar effects to that of 5Aza-C, which is currently undergoing phase 2 clinical trials as a treatment for prostate cancer. Because genistein is a natural, nontoxic, and dietary isoflavone, these results indicate that genistein is a novel, advantageous therapeutic agent for treating prostate cancer.
Majid
Shahana
S
Department of Urology, Veterans Affairs Medical Center and University of California, San Francisco, San Francisco, CA 94121, USA.
Dar
Altaf A
AA
Shahryari
Varahram
V
Hirata
Hiroshi
H
Ahmad
Ardalan
A
Saini
Sharanjot
S
Tanaka
Yuichiro
Y
Dahiya
Angela V
AV
Dahiya
Rajvir
R
D001483:Base Sequence; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D042002:Chromatin Assembly and Disassembly / Q000187:drug effects; D019175:DNA Methylation / Q000187:drug effects*; D016147:Genes, Tumor Suppressor; D019833:Genistein / Q000494:pharmacology*; D006657:Histones / Q000378:metabolism*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D011471:Prostatic Neoplasms / Q000235:genetics*; D011506:Proteins / Q000235:genetics*
C424522:BTG3 protein, human; D018797:Cell Cycle Proteins; D006657:Histones; D011506:Proteins; D019833:Genistein