Functional role and tobacco smoking effects on methylation ofCYP1A1gene in prostate cancer

Abstract

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.

Association between NAT2, CYP1A1, and CYP1A2 genotypes, heterocyclic aromatic amines, and prostate cancer risk: a case control study in Japan

“…CYP1A1 is a member of the phase I cytochrome P450 family, which is highly active in the liver, acting on the metabolic activation of HAAs [ 28 ]. Similar to NAT2 , CYP1A1 mRNA is also expressed in prostate tissue [ 48 – 50 ]. CYP1A1 in individuals harboring the mutant G allele (GA or GG genotype) in exon 7, which substitutes valine for isoleucine, has a higher catalytic activity compared to that found in individuals who are homozygous AA [ 51 ].…”

First evidence of association between past environmental exposure to dioxin and DNA methylation of CYP1A1 and IGF2 genes in present day Vietnamese population

“…(chr11:2154089-2154542) is part of a CpG island and shore but it is located in the gene body. DNA methylation of CYP1A1 was associated with exposure to dioxin and external pollutants in different studies (Mitsui et al, 2014;Okino and Whitlock, 1995). DNA methylation of IGF2 was associated with environmental chemical exposure (Hou et al, 2012), while a previous study reported that exposure of mouse preimplantation embryos to dioxin alters the methylation status of imprinted genes H19 and IGF2 (Wu et al, 2004).…”

“…In this context the aim of the present study was to investigate the DNA methylation patterns of two candidate genes, CYP1A1 and IGF2 in order to address the question whether exposure to dioxin in Vietnam is associated with persistent differences in methylation as previously suggested (Manikkam et al, 2012;Skinner et al, 2013) including, for the first time, a very detailed description of historical data (in terms of number of spray runs and spray dates for each district). The rationale beyond the selection of the two genes was the following: CYP1A1 belongs to the cytochrome 450 family, which is involved in the metabolism of various molecules and chemicals within cells (Ko et al, 1996;Mitsui et al, 2014;Okino and Whitlock, 1995;Whitlock et al, 1997) . Dioxin is known to be a CYP1A1 inducer (Tsyrlov and Pokrovsky, 1993).…”

AhR regulates the expression of human cytochrome P450 1A1 (CYP1A1) by recruiting Sp1

“…Recently, numerous studies have shown that the upregulation of CYP1A1 results in the malignancy of various types of tumor cells . CYP1A1 was found to have an oncogenic role in prostate cancer, indicating that CYP1A1 could be a promising target for prostate cancer therapeutics, and to promote breast cancer proliferation and survival through the suppression of AMPK signaling . In addition, CYP1A1 protected against nonalcoholic fatty liver disease (NAFLD) and hepatic inflammation caused by a western diet plus benzo [a] pyrene in mice, indicating that CYP1A1 protected against NAFLD pathogenesis .…”

“…Agonists such as β‐NF and TCDD facilitate AhR binding to the xenobiotic‐responsive element (XRE) and consequently upregulate the expression of CYP1A1 . In addition, the XRE is a conserved sequence among the CYP1 subfamily, and up to 10 high‐affinity binding sites for the AhR complex have been identified in the human CYP1A1 promoter . Moreover, multiple copies of consensus XRE sequences are found in the 5'‐flanking region of CYP1A1 .…”