Chronic arsenic exposure and hsa-miR-186 overexpression causes transcriptome-wide differential alternative splicing...

Environmental arsenic exposure causes skin cancer. Overexpression of hsa-miR-186 (mir-186) accelerated the malignant transformation of human keratinocytes by inorganic arsenic (iAs). Dysregulated alternative splicing is a key driver of carcinogenesis. iAs exposure disrupts alternative splicing. miR-186 is predicted to target several broad-spectrum splice regulators. The impact of miR-186 overexpression on differential alternative splicing alone and together in combination with iAs exposure and how that contributes to skin carcinogenesis has never been studied. We address this knowledge gap by investigating the transcriptome-wide differential alternative splicing events in preclinical HaCaT human keratinocyte clonal lines overexpressing miR-186 or scrambled control vectors concomitantly exposed to 0 or 100 nM iAs (up to 29 weeks). Differential alternative splicing events (FDR < 0.05 and IΔΨI ≥ 5%) and differentially expressed genes (p < 0.05) were identified by replicate multivariate analysis of transcript splicing (rMATS) and unpaired t test, respectively, on short-read RNA-seq data at 12- and 29-week time points. Functional impact of differential alternative splicing was assessed using Gene Ontology (GO) analysis on differentially spliced genes, as well as Ingenuity Pathway Analysis (IPA) on genes that were simultaneously differentially spliced and differentially expressed. Over 1500 alternative splicing events were detected in each pairwise comparison. miR-186 overexpression led to differential splicing of many splice regulators. Multiple cancer-related pathways were enriched and dysregulated in the miR-186 overexpressing clones with iAs exposure by GO and IPA analysis, respectively, explaining why the combination accelerates transformation. We show that dysregulated alternative splicing plays a key role in arsenic-induced cSCC development.