Arsenic-Associated Differential DNA Methylation in Human Uroepithelial Cells

There is strong epidemiologic evidence supporting that exposure to inorganic arsenic (iAs) exposure is responsible for a myriad of adverse health effects, including carcinogenesis of the bladder. This research aimed to identify novel epigenetic biomarkers of iAs exposure in target cells within a human population. Here we assessed genome-wide, gene-specific promoter DNA methylation levels assessed in exfoliated human bladder uroepithelial cells (BECs) in relationship to BEC iAs, monomethylated As (MMAs), dimethylated As (DMAs), and total As (tAs) concentrations from 46 individuals with varying levels of As exposure in Chihuahua, Mexico. These analyses identified genes with increased methylation associated with BEC iAs(III+V), MMAs(III+V), and tAs(III+V). These genes were enriched for signaling related to metabolic disease and cancer. Individuals participating in the present study (n=46) represent a subcohort of a larger study (n=374) among residents of Chihuahua, Mexico, recruited between 2008 and 2013. Study participants were required to be at least 18 years of age and have at least 5 years of uninterrupted residency in the study area. Urine samples were collected and uroepithelial cell isolation occurred immediately. Exfoliated bladder uroepithelial cells (BECs) were isolated from freshly collected urine. As species in BECs were measured using hydride generation (HG) with preconcentration by cryotrapping (CT) and inductively coupled plasma-mass spectrometry (ICP-MS) (HG-CT-ICP-MS). DNA was extracted from the exfoliated BECs of 46 subjects using the QIAamp DNA Blood Mini Kit (Qiagen, Valenica, CA) according to manufacturer’s instruction. CpG-methylated DNA was isolated using the MethylMinerTM Methylated DNA Enrichment Kit (Invitrogen/Life Technologies, Grand Island, NY), amplified, and hybridized to Affymetrix Human Promoter 1.0R arrays.