MiRNA expression changes in arsenic-induced skin cancer in vitro and in vivo.

Arsenic is a naturally prevalent metalloid. Chronic arsenic ingestion through drinking water causes skin cancer. Arsenic-induced cancer mechanisms are not well defined. Epigenetic changes, including microRNA expression changes, might be playing a role. This dissertation investigates the impact of miRNA expression changes in arsenic-induced skin cancer. MiRNA expression was measure and compared using 3 different techniques, RTq-PCR, hybridization arrays and RNA-sequencing. MiRNAs differential expression in skin lesions was phenotype- and stage-related. Immortalized human keratinocytes (HaCaT) were transformed by chronic low arsenite exposure serving as a model for arsenic-induced skin carcinogenesis. Early changes in miRNAs and target mRNAs contribute to arsenic-induced carcinogenesis. Throughout the time course of arsenic exposure, dysregulation of cells’ growth and cancer-related pathways were identified. Comparisons between the miRNA profiles in lesions and cells predict some miRNAs may serve as biomarkers and/or therapeutic targets for arsenic-induced tumors. This dissertation provides strong evidences of epigenetic changes related to carcinogenesis in arsenic-induced skin cancer

The role of pesticides in non-alcoholic fatty liver disease (NAFLD).

NAFLD, the most common form of liver disease worldwide, is caused by various factors including industrial chemicals and pesticides exposure. Annually, 5.2 billion pounds of pesticides are used worldwide and can contribute to liver disease, but their role is modestly studied. We hypothesize that pesticides contaminating food supply can worsen diet-induced steatosis via xenobiotic receptor activation. Two human and two rodent databases were utilized and 85% of the 330 chemicals identified associated with NAFLD were pesticides. Eight were selected for evaluating hepatic receptor activation in vitro. The majority including DDT activated hPXR/CAR and mPXR. DDT (100 mg/kg) was studied in vivo in a diet-induced obesity (DIO) model. DDT upregulated Cyp2b10 (CAR target) in control diet-fed mice. DDT decreased adiposity, but it did not affect weight gain, food consumption or insulin resistance. In conclusion, DDT improved steatosis, but it did not affect NAFLD, obesity, liver damage or diabetes caused by DIO

Data from: Differentially expressed mRNA targets of differentially expressed miRNAs predict changes in the TP53 axis and carcinogenesis related pathways in human keratinocytes chronically exposed to arsenic

Background: Arsenic is a widely distributed toxic natural element. Chronic arsenic ingestion causes several cancers, especially skin cancer. Arsenic-induced cancer mechanisms are not well defined, but several studies indicate that mutation is not the driving force and that microRNA expression changes play a role. Chronic low arsenite exposure malignantly transforms immortalized human keratinocytes (HaCaT), serving as a model for arsenic-induced skin carcinogenesis. Hypothesis: Early changes in miRNA expression in HaCaT cells chronically exposed to arsenite will reveal early steps in transformation. Methods: HaCaT cells were maintained with 0/100 nM NaAsO2 for 3 and 7 weeks. Total RNA was purified. miRNA and mRNA expression was assayed using Affymetrix microarrays. Targets of differentially expressed miRNAs were collected from TargetScan 6.2, intersected with differentially expressed mRNAs using Partek Genomic Suite™ software, and mapped to their pathways using MetaCore™ software. MDM2, HMGB1 and TP53 mRNA and protein levels were assayed by western blot. Results: Numerous miRNAs and mRNAs involved in carcinogenesis pathways in other systems were differentially expressed at 3 and 7 weeks. A TP53 regulatory network including MDM2 and HMGB1 was predicted by the miRNA and mRNA networks. Total TP53 and TP53-S15-phosphorylation were induced. However, TP53-K382-hypoacetylation suggested that the induced TP53 is inactive in arsenic exposed cells. Conclusions: Our data provide strong evidence that early changes in miRNAs and target mRNAs may contribute to arsenic-induced carcinogenesis

Supplementary table 2

Filtered differentially expressed 38 predicted targets of differentially expressed miRNA at 3 and 7 weeks

Supplementary table 3

Filtered differentially expressed mRNA targets of differentially expressed miRNAs (3 weeks time point