Carcinogenesis Advance Access published online on February 12, 2009
Carcinogenesis, doi:10.1093/carcin/bgp042
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BTG3 tumor suppressor gene promoter demethylation, histone modification and cell cycle arrest by genistein in renal cancer
1 Department of Urology, Veterans Affairs Medical Center and University of California, San Francisco, San Francisco, California
2 Department of Dermatology, University of California, San Francisco, San Francisco, California
* To whom correspondence should be addressed: Rajvir Dahiya, Ph.D., Professor and Director, Urology Research Center (112F), Veterans Affairs Medical Center and University of California at San Francisco, 4150 Clement Street, San Francisco, CA 94121. Phone: 415-750-6964; Fax: 415-750-6639, E-mail: rdahiya{at}urology.ucsf.edu.
BTG3/ANA/APRO4 has been reported to be a tumor suppressor gene in some malignancies. It constitutes important negative regulatory mechanism for Src-mediated signaling, a negative regulator of the cell cycle and inhibits transcription factor E2F1. We report that BTG3 is down-regulated in renal cancer () and that the mechanism of inactivation is through promoter hypermethylation. Quantitative-RT-PCR showed that BTG3 was down-regulated in cancer tissues and cells. Genistein and 5-aza-2-deoxycytidine (5Aza-C) induced BTG3 mRNA expression in A498, ACHN and HEK-293 RCC cell lines. Bisulfite-modified-PCR and DNA sequencing results showed complete methylation of BTG3 promoter in tumor samples and cancer cell lines. Genistein and 5Aza-C treatment significantly decreased promoter methylation, reactivating BTG3 expression. ChIP assay revealed that genistein and 5Aza-C increased levels of acetylated histones 3, 4, 2H3K4, 3H3K4 and Pol II at the BTG3 promoter indicative of active histone modifications. Enzymatic assays showed genistein and 5Aza-C decreased DNMTase, MBD2 activity and increased HAT activity. Cell cycle and MTT cell proliferation assays showed that genistein has antiproliferative effect on cancer cell growth through induction of cell cycle arrest. This is the first report to show that BTG3 is epigenetically silenced in RCC and can be reactivated by genistein induced promoter demethylation and active histone modification. Genistein had similar effects to that of 5Aza-C, which is a potent demethylating agent with high toxicity and instability. Genistein being a natural, non-toxic, dietary isoflavone, is effective in retarding the growth of RCC cells, making it a promising candidate for epigenetic therapy in renal carcinoma.
Key Words: Renal carcinoma genistein BTG3 gene DNA methylation Histone modification
Received November 20, 2008; revised February 5, 2009; accepted February 5, 2009.