Epigenetic Modifications of RASSF1A Gene through Chromatin Remodeling in Prostate Cancer

• Published in: Clinical cancer research Vol. 13; no. 9; pp. 2541 - 2548
• Main Authors: KAWAMOTO, Ken, OKINO, Steven T, MAJID, Shahana, ENOKIDA, Hideki, NAKAGAWA, Masayuki, DAHIYA, Rajvir, PLACE, Robert F, URAKAMI, Shinji, HIRATA, Hiroshi, KIKUNO, Nobuyuki, KAWAKAMI, Toshifumi, TANAKA, Yuichiro, POOKOT, Deepa, ZHONG CHEN
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 01.05.2007
• Subjects: Acetylation; Aged; Aged, 80 and over; Antineoplastic agents; Biological and medical sciences; Chromatin - metabolism; Chromatin Assembly and Disassembly; CpG methylation; DNA Methylation; Epigenesis, Genetic; Gene Expression Regulation, Neoplastic; Gynecology. Andrology. Obstetrics; histone modification; Histones - metabolism; Humans; Male; Male genital diseases; Medical sciences; Middle Aged; Nephrology. Urinary tract diseases; Pharmacology. Drug treatments; prostate cancer; Prostatic Neoplasms - genetics; Prostatic Neoplasms - metabolism; RASSF1A gene; Tumor Suppressor Proteins - genetics; Tumors; Tumors of the urinary system; Urinary tract. Prostate gland; Modification; Chromatin; Urinary system disease; Prostate disease; Epigenetics; Malignant tumor; Remodeling; Male genital diseases; Prostate cancer
• ISSN: 1078-0432; 1557-3265
• DOI: 10.1158/1078-0432.CCR-06-2225

Purpose: The RAS-association domain family 1, isoform A ( RASSF1A ) gene is shown to be inactivated in prostate cancers. However, the molecular mechanism of silencing of the RASSFIA gene is not fully understood. The present study was designed to investigate the mechanisms of inactivation of the RASSF1A gene through the analysis of CpG methylation and histone acetylation and H3 methylation associated with the RASSF1A promoter region. Experimental Design: Methylation status of the RASSF1A gene was analyzed in 131 samples of prostate cancer, 65 samples of benign prostate hypertrophy (BPH), and human prostate cell lines using methylation-specific PCR. Histone acetylation (acetyl-H3, acetyl-H4) and H3 methylation (dimethyl-H3-K4, dimethyl-H3-K9) status associated with the promoter region in prostate cells were analyzed by chromatin immunoprecipitation (ChIP) assay. Results: Aberrant methylation was detected in 97 (74.0%) prostate cancer samples and 12 (18.5%) BPH samples. The methylation frequency of RASSF1A showed a significant increase with high Gleason sum and high stage. The ChIP assays showed enhancement of histone acetylation and dimethyl-H3-K4 methylation on the unmethylated RASSF1A promoter. TSA alone was unable to alter key components of the histone code. However, after 5-aza-2′-deoxy-cytidine treatment, there was a complete reversal of the histone components in the hypermethylated promoter. Levels of acetyl-H3, acetyl-H4, and dimethyl-H3-K4 became more enriched, whereas H3K9me2 levels were severely depleted. Conclusions: This is the first report suggesting that reduced histone acetylation or H3K4me2 methylation and increased dimethyl-H3-K9 methylation play a critical role in the maintenance of promoter DNA methylation–associated RASSF1A gene silencing in prostate cancer.