ABSTRACT
Lung is a major target for arsenic carcinogenesis in humans by both oral and inhalation routes. However, the carcinogenic mode of action of arsenicals is unknown. We investigated the effects of inorganic arsenic (iAsIII), monomethylarsonous acid (MMAIII), dimethylarsinous acid (DMAIII) and dimethylthioarsinic acid (DMTA), a sulfur containing dimethyl arsenic metabolite, in human bronchial epithelial (BEAS-2B) cells. Cells were exposed to 3, 15 microM-iAsIII; 0.3, 1 microM-MMAIII; 0.2, 1 microM-DMAIII; 0.2, 0.9 microM-DMTA as non-cytotoxic and minimally cytotoxic ( approximately 20%) concentrations based on Neutral Red uptake assays after 24h of culture. Total RNA was isolated and gene expression analysis conducted using Affymetrix Human Genome 133 Plus 2.0 arrays. Differentially expressed genes (DEGs) were determined using a one-way ANOVA (p < or =0.05) by Rosetta Resolver, a Benjamini-Hochberg FDR (false discovery rate) multiple testing correction (< 0.05) followed by a Scheffe's post hoc test. For all compounds except DMTA, > 90% of DEG altered in the low concentration were also changed at the high concentration. There was a clear dose-response seen in the number of DEGs for all four compounds. iAsIII showed the highest number of DEG at both concentrations (2708 and 123, high and low, respectively). 1749, 420 and 120 DEGs were unique to the high concentrations of iAsIII, MMAIII and DMAIII, respectively. Transferrin receptor is a common DEG in low concentration arsenical treated cells. Ingenuity Pathway Analysis revealed p53 signaling (E2F1 and 2, SERPIN), and cell cycle related genes (cyclin D1) were altered by the high concentrations of DMTA, MMAIII and iAsIII. Oxidative stress (DUSP1, GPX2, NQO1, GCLC) and NF-kappaB signaling (TLR4, NF-kappaB) pathways were changed by the high concentrations of MMAIII and iAsIII. The genes identified in this study can be a valuable tool to determine the mechanism of arsenic toxicity and cancer formation. A number of similarities were observed in the gene expression profiles of DMAIII and DMTA and also iAsIII and MMAIII. These findings reveal some biological effects of arsenicals that will aid in creating a better risk assessment model for arsenical-induced lung cancer.
