Functional role and tobacco smoking effects on methylation of CYP1A1 gene in prostate cancer
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Yozo Mitsui1,2,3,*, Inik Chang4,*, Taku Kato1,2, Yutaka Hashimoto1,2, Soichiro Yamamura1,2, Shinichiro Fukuhara5, Darryn K. Wong1, Marisa Shiina1, Mitsuho Imai-Sumida1,2, Shahana Majid1,2, Sharanjot Saini1,2, Hiroaki Shiina3, Koichi Nakajima6, Guoren Deng1,2, Rajvir Dahiya1,2, Yuichiro Tanaka1,2
1Department of Surgery/Urology, Veterans Affairs Health Care System, San Francisco, California 94121, USA
2Department of Urology, University of California, San Francisco, California 94121, USA
3Department of Urology, Shimane University Faculty of Medicine, Izumo, 693-8501, Japan
4Department of Oral Biology, Yonsei University College of Density, Seoul, 120-752, South Korea
5Department of Urology, Osaka University Graduate School of Medicine, Suita, 565-0871, Japan
6Department of Urology, Toho University Faculty of Medicine, Tokyo, 143-8540, Japan
*These authors contributed equally to this work
Yozo Mitsui, email: firstname.lastname@example.org
Yuichiro Tanaka, email: email@example.com
Keywords: cytochrome P450 1A1, methylation, prostate cancer, tobacco smoking
Received: March 01, 2016 Accepted: May 04, 2016 Published: May 19, 2016
Cytochrome P450 (CYP) 1A1 is a phase I enzyme that can activate various compounds into reactive forms and thus, may contribute to carcinogenesis. In this study, we investigated the expression, methylation status, and functional role of CYP1A1 on prostate cancer cells. Increased expression of CYP1A1 was observed in all cancer lines (PC-3, LNCaP, and DU145) compared to BPH-1 (P < 0.05); and was enhanced further by 5-aza-2’-deoxycytidine treatment (P < 0.01). Methylation-specific PCR (MSP) and sequencing of bisulfite-modified DNA of the xenobiotic response element (XRE) enhancer site XRE-1383 indicated promoter methylation as a regulator of CYP1A1 expression. In tissue, microarrays showed higher immunostaining of CYP1A1 in prostate cancer than normal and benign prostatic hyperplasia (BPH; P < 0.001), and methylation analyses in clinical specimens revealed significantly lower methylation levels in cancer compared to BPH at all enhancer sites analyzed (XRE-1383, XRE-983, XRE-895; P < 0.01). Interestingly, smoking affected the XRE-1383 site where the methylation level was much lower in cancer tissues from smokers than non-smokers (P < 0.05). CYP1A1 levels are thus increased in prostate cancer and to determine the functional effect of CYP1A1 on cells, we depleted the gene in LNCaP and DU145 by siRNA. We observe that CYP1A1 knockdown decreased cell proliferation (P < 0.05) and increased apoptosis (P < 0.01) in both cell lines. We analyzed genes affected by CYP1A1 silencing and found that apoptosis-related BCL2 was significantly down-regulated. This study supports an oncogenic role for CYP1A1 in prostate cancer via promoter hypomethylation that is influenced by tobacco smoking, indicating CYP1A1 to be a promising target for prostate cancer treatment.
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