Department of Toxicology, Guangdong Provincial Key Laboratory of Food, Nutrition and Health, School of Public Health, Sun Yat-sen University, Guangzhou, China.
Cancer Epidemiol Biomarkers Prev. 2012 Jan;21(1):182-90. doi: 10.1158/1055-9965.EPI-11-0784. Epub 2011 Oct 25.
Sufficient epidemiologic evidence shows an etiologic link between polycyclic aromatic hydrocarbons (PAH) exposure and lung cancer risk. While the genetic modifications have been found in PAH-exposed population, it is unclear whether gene-specific methylation involves in the process of PAH-associated biologic consequence.
Sixty-nine PAH-exposed workers and 59 control subjects were recruited. Using bisulfite sequencing, we examined the methylation status of p16(INK4α) promoter in peripheral blood lymphocytes (PBL) from PAH-exposed workers and in benzo(a)pyrene (BaP)-transformed human bronchial epithelial (HBE) cells. The relationships between p16(INK4α) methylation and the level of urinary 1-hydroxypyrene (1-OHP) or the frequency of cytokinesis block micronucleus (CBMN) were analyzed.
Compared with the control group, PAH-exposed workers exhibited higher levels of urinary 1-OHP (10.62 vs. 2.52 μg/L), p16(INK4α) methylation (7.95% vs. 1.14% for 22 "hot" CpG sites), and CBMN (7.28% vs. 2.92%) in PBLs. p16(INK4α) hypermethylation in PAH-exposed workers exhibited CpG site specificity. Among the 35 CpG sites we analyzed, 22 were significantly hypermethylated. These 22 hypermethylated CpG sites were positively correlated to levels of urinary 1-OHP and CBMN in PBLs. Moreover, the hypermethylation and suppression of p16 expression was also found in BaP-transformed HBER cells.
PAH exposure induced CpG site-specific hypermethylation of p16(INK4α) gene. The degree of p16(INK4α) methylation was associated with the levels of DNA damage and internal exposure.
p16(INK4α) hypermethylation might be an essential biomarker for the exposure to PAHs and for early diagnosis of cancer.
充分的流行病学证据表明多环芳烃（PAH）暴露与肺癌风险之间存在病因联系。虽然已经在暴露于 PAH 的人群中发现了遗传改变，但基因特异性甲基化是否参与 PAH 相关生物学后果的过程尚不清楚。
招募了 69 名 PAH 暴露工人和 59 名对照者。使用亚硫酸氢盐测序，我们检测了 PAH 暴露工人外周血淋巴细胞（PBL）和苯并（a）芘（BaP）转化的人支气管上皮细胞（HBE）中 p16（INK4α）启动子的甲基化状态。分析了 p16（INK4α）甲基化与尿 1-羟基芘（1-OHP）水平或细胞有丝分裂阻断微核（CBMN）频率之间的关系。
与对照组相比，PAH 暴露工人的尿 1-OHP（10.62 与 2.52 μg/L）、PBL 中的 p16（INK4α）甲基化（22 个“热点”CpG 位点的 7.95%与 1.14%）和 CBMN（7.28%与 2.92%）水平更高。PAH 暴露工人的 p16（INK4α）过度甲基化表现出 CpG 位点特异性。在我们分析的 35 个 CpG 位点中，有 22 个显著过度甲基化。这 22 个过度甲基化的 CpG 位点与 PBL 中的尿 1-OHP 和 CBMN 水平呈正相关。此外，在 BaP 转化的 HBER 细胞中也发现了 p16 表达的过度甲基化和抑制。
PAH 暴露诱导 p16（INK4α）基因的 CpG 位点特异性过度甲基化。p16（INK4α）甲基化程度与 DNA 损伤和内暴露水平相关。
p16（INK4α）过度甲基化可能是 PAH 暴露和癌症早期诊断的重要生物标志物。
