Epigenetic Modifications of DAPK and p16 Genes Contribute to Arsenic-Induced Skin Lesions and Nondermatological Health Effects

Over 26 million people in West Bengal, India, are exposed to very high levels of arsenic through drinking water, leading to several deleterious endpoints including cancers. To elucidate the role of promoter methylation in arsenic-induced dermatological and nondermatological health effects, methylation status of p16 and DAPK genes was determined. A case-control study was conducted involving 72 individuals with arsenic-induced skin lesions (cases) and 50 individuals without skin lesions (controls), having similar arsenic exposure through drinking water. Methylation status was determined by bisulfite conversion of genomic DNA and methylation-specific PCR. Expression of the genes was determined by real-time PCR and Western blot analysis. Associations between the promoter methylation status and nondermatological health effects were determined from epidemiological survey data. Significant hypermethylation was found in the promoters of both DAPK and p16 genes in the cases compared with the controls resulting in downregulation of both the genes in the cases. There was a 3.4-fold decrease in the expression of death-associated protein kinase and 2.2-fold decrease in gene expression of p16 in the cases compared to the controls, the lowest expression being in the cancer tissues. Promoter hypermethylation of the genes was also associated with higher risk of developing arsenic-induced skin lesions, peripheral neuropathy, ocular and respiratory diseases. This study for the first time makes an attempt to correlate epigenetic modifications of the tumor suppressor genes with dermatological and nondermatological health outcomes in a population chronically exposed to arsenic.