Abstract
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. Cancer 2010. © 2010 American Cancer Society.