Hypomethylation and hypohydroxymethylation of DNA in hepatocellular carcinoma and cholangiocarcinoma

MTHFR Gene Polymorphism Is Associated With DNA Hypomethylation and Genetic Damage Among Benzene-Exposed Workers in Southeast China

OBJECTIVE AND METHODS

To analyze the association between global DNA methylation and single-nucleotide polymorphisms (SNPs) in methylenetetrahydrofolate reductase (MTHFR). MTHFR polymorphisms rs1801133 and rs1801131 were detected using the restriction fragment length polymorphism method, and cytokinesis-block micronucleus (MN) frequency and global DNA methylation was measured in workers from 410 shoe factories.

RESULTS

A multilinear regression analysis demonstrated that DNA methylation of the TT variant allele of rs1801133 was lower than that of the CC wild type allele (Exp(β) [95% CI], 0.76 [0.56, 1.02], P = 0.071), with a P-value approaching significance. A significantly increased MN frequency was observed for carriers of the TT genotype (frequency ratio = 1.27, 95% CI: 1.07-1.51, P < 0.01).

CONCLUSION

The results imply that the TT genotype in rs1801133 is associated with global DNA hypomethylation, which may influence the induction of MN following exposure to benzene.

Do mutations in DNMT3A/3B affect global DNA hypomethylation among benzene-exposed workers in Southeast China?: Effects of mutations in DNMT3A/3B on global DNA hypomethylation

Global DNA hypomethylation is commonly observed in benzene-exposed workers, but the underlying mechanisms remain unclear. We sought to discover the relationships among reduced white blood cell (WBC) counts, micronuclear (MN) frequency, and global DNA methylation to determine whether there were associations with mutations in DNMT3A/3B. Therefore, we recruited 410 shoe factory workers and 102 controls from Wenzhou in Zhenjiang Province. A Methylated DNA Quantification Kit was used to quantify global DNA methylation, and single nucleotide polymorphisms (SNPs) in DNMT3A (rs36012910, rs1550117, and R882) and DNMT3B (rs1569686, rs2424909, and rs2424913) were identified using the restriction fragment length polymorphism method. A multilinear regression analysis demonstrated that the benzene-exposed workers experienced significant global DNA hypomethylation compared with the controls (β = -0.51, 95% CI: -0.69 to -0.32, P < 0.001). The DNMT3A R882 mutant allele (R882H and R882C) (β = -0.25, 95% CI: -0.54 to 0.04, P = 0.094) and the DNMT3B rs2424909 GG allele (β = -0.37, 95% CI: -0.70 to -0.03, P = 0.031) were significantly associated with global DNA hypomethylation compared with the wild-type genotype after adjusting for confounding factors. Furthermore, the MN frequency in the R882 mutant allele (R882H and R882C) (FR = 1.18, 95% CI: 0.99 to 1.40, P = 0.054) was higher than that of the wild-type. The results imply that hypomethylation occurs due to benzene exposure and that mutations in DNMTs are significantly associated with global DNA methylation, which might have influenced the induction of MN following exposure to benzene. Environ. Mol. Mutagen. 58:678-687, 2017. © 2017 Wiley Periodicals, Inc.