CpG site-specific hypermethylation of p16INK4α in peripheral blood lymphocytes of PAH-exposed workers.
BACKGROUND
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.


CONCLUSIONS
p16(INK4α) hypermethylation might be an essential biomarker for the exposure to PAHs and for early diagnosis of cancer.
Department of Toxicology, Guangdong Provincial Key Laboratory of Food, Nutrition and Health, School of Public Health, Sun Yat-sen University, Guangzhou, China.
Ping
P
Yang
Junxiang
J
Ma
Bo
B
Zhang
Huawei
H
Duan
Zhini
Z
He
Junling
J
Zeng
Xiaowen
X
Zeng
Daochuan
D
Li
Qing
Q
Wang
Yongmei
Y
Xiao
Caixia
C
Liu
Qin
Q
Xiao
Liping
L
Chen
Xiaonian
X
Zhu
Xiumei
X
Xing
Zhifang
Z
Li
Shixin
S
Zhang
Zhengbao
Z
Zhang
Lu
L
Ma
Erman
E
Wang
Zhixiong
Z
Zhuang
Yuxin
Y
Zheng
Wen
W
Chen
D000328:Adult; D015415:Biomarkers / Q000097:blood / Q000378:metabolism / Q000652:urine; D002460:Cell Line; D018899:CpG Islands; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D019175:DNA Methylation; D019942:Genes, p16 / Q000187:drug effects*; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects* / Q000502:physiology; D015162:Micronucleus Tests / Q000379:methods; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D016273:Occupational Exposure / Q000009:adverse effects / Q000032:analysis; D011084:Polycyclic Aromatic Hydrocarbons / Q000097:blood* / Q000506:poisoning*; D011401:Promoter Regions, Genetic; D011721:Pyrenes / Q000378:metabolism; D012307:Risk Factors
D015415:Biomarkers; C000614131:CDKN2A protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D009363:Neoplasm Proteins; D011084:Polycyclic Aromatic Hydrocarbons; D011721:Pyrenes; C033146:1-hydroxypyrene