Transcriptional Modulation of the ERK1/2 MAPK and NF-κB Pathways in Human Urothelial Cells After Trivalent Arsenical Exposure: Implications for Urinary Bladder Cancer

Abstract

Chronic exposure to drinking water contaminated with inorganic arsenic (iAs) is associated with an increased risk of urinary bladder (UB) cancers in humans. The exact role of specific iAs metabolite(s) in As-mediated carcinogenesis remains largely unknown. Experimental evidence suggests that trivalent arsenicals, namely arsenite (iAs^III) and two of its metabolites, monomethylarsonous acid (MMA^III) and dimethylarsinous acid (DMA^III), are possible proximate UB carcinogens. Here, we used a transcriptomics approach to examine perturbed molecular pathways in a human urothelial cell line (UROtsa) after short-term exposure to iAs^III, MMA^III and DMA^III. Molecular pathways containing genes that encode proteins implicated in UB cancer development were perturbed by both MMA^III and DMA^III. These pathways included those of the extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase (ERK 1/2 MAPK) and nuclear factor kappa beta (NF-κB). Together, these results may inform the current understanding of effects in the UB induced by acute As exposure and the relationship of these effects with As-mediated carcinogenesis.

Keywords: Arsenite; DMAIII; MMAIII; UROtsa; dimethylarsinous acid; extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase; gene expression; inflammation; microarray; monomethylarsonous acid; nuclear factor kappa beta; urinary bladder cancer.

Figure 1

(A). Venn diagrams displaying shared and unique UROtsa DEGs among the iAs^III, MMA^III and DMA^III treatment groups. The total number of DEGs in each treatment group is in parentheses. (B). Hierarchical clustering of the 830 unique genes in UROtsas that were differentially expressed vs. controls after 24 h exposure to at least one trivalent arsenical. Z scores of fold change values are shown.

Figure 2

Comparison of gene expression changes determined by microarrays and quantitative reverse transcription-PCR (qRT-PCR) of selected genes. Statistically significant changes in gene expression compared to vehicle-treated controls are indicated as determined by microarrays (*) and qRT-PCR (**).

Figure 3

A-B. Large interacting molecular networks associated with the MMA^III and DMA^III treatment groups, respectively; (C). MMA^III–induced ERK 1/2 MAPK network; (D). DMA^III –induced ERK 1/2 MAPK network; (E). MMA^III–induced NF-κB network; (F). DMA^III–induced NF-κB network. Upregulated and downregulated genes are displayed in red and green, respectively and interacting genes that are not differentially expressed are not shaded.