Hypermethylation of CpG islands is associated with increasing chromosomal damage in chinese lead-exposed workers

Lead is a widely existing environmental pollutant with potential carcinogenicity. To investigate the association of blood lead level (B-Pb) with potential chromosomal damage and cancer, we analyzed micronucleus (MN) frequency of peripheral blood lymphocytes (PBLs) and the methylation status of six human tumor suppressor genes (TSGs) post lead exposure. In the study, 147 lead-exposed workers were divided into two groups according to their B-Pb P-50 value, with other 50 lead-unexposed workers as a control group. The cytokinesis-blocked micronucleus (CBMN) assay was performed to detect chromosomal damage of PBLs of both lead-exposed and -unexposed workers. The methylation-specific polymerase chain reaction (MSP-PCR) was further used to examine the methylation status of six TSGs (GSTP1, hMLH1, MGMT, p14, p15, and p16). Results showed that MN frequencies of high B-Pb workers 8.1 +/- 3.1 parts per thousand and low B-Pb workers 5.7 +/- 2.3 parts per thousand were significantly higher than that of control group 2.8 +/- 1.9 parts per thousand (P<0.01), while the MN frequency of high B-Pb workers was also higher than that of the low B-Pb workers (P<0.01). The MN frequency in PBLs of lead-exposed group with the methylated TSGs was significantly higher than that in PBLs with the unmethylated TSGs (P<0.05). Notably, the CpG island methylator phenotype (CIMP) correlated with chromosome damage (P<0.05). Additionally, workers with high B-Pb had higher chromosome damage than those with low B-Pb (P<0.05). Taken altogether, the results suggest that lead-exposed workers with CIMP positive and high B-Pb have a higher risk of being vulnerable to tumorigenesis. Environ. Mol. Mutagen. 59:549-556, 2018. (c) 2018 Wiley Periodicals, Inc.