Project description:This study chronically exposed human lung epithelial BEAS-2B cells to low-dose arsenic trioxide in vitro to elucidate cancer promoting gene signaling networks (GSNs) associated with As-transformed (B-As) cells. Following a six month exposure, exposed cells were assessed for enhanced cell proliferation, colony formation, invasion ability and in vivo tumor formation compared to control cell lines. Collected mRNA was subjected to whole genome expression microarray profiling followed by in silico Ingenuity Pathway Analysis (IPA) to identify lung carcinogenesis modes of action. B-As cells displayed significant increases in proliferation, colony formation and invasion ability compared to BEAS-2B cells. B-As injections into nude mice resulted in development of primary and secondary metastatic tumors. As exposure resulted in widespread up-regulation of genes associated with mitochondrial metabolism and increased ROS protection suggesting mitochondrial dysfunction. Carcinogenic initiation via ROS and epigenetic mechanisms was further supported by altered DNA repair, histone, and ROS-sensitive signaling. NF-ÎºB, MAPK and NCOR1 signaling disrupted PPARÎ±/Î´-mediated lipid homeostasis. A âpro-cancerâ GSN identified increased survival, proliferation, inflammation, metabolism, anti-apoptosis and mobility signaling. IPA-ranked signaling networks identified altered p21, EF1Î±, Akt, MAPK, and NF-ÎºB signaling networks promoting genetic disorder, altered cell cycle, cancer and changes in nucleic acid and energy metabolism. In conclusion, transformed B-As cells with their whole genome GSN profile provide an in vitro As model for future lung cancer signaling research and data for chronic As exposure risk assessment. Whole genome expression profiling was conducted on arsenic (III) oxide-exposed human immortalized lung epithelial cells (BEAS-2B) following 6 month in vitro chronic exposure. As2O3 exposed cells (B-As) gene expression were compared to unexposed, passage control (B-Control) cell gene expression. Three B-As and four B-Control biological replicate cDNA samples were analyzed.

Project description:Chronic arsenic exposure can lead to various health issues including cancer. There has been a growing concern about co-exposure to various prevalent lifestyle habits and their role in the enhancement of arsenic toxicity. Smokeless tobacco (SLT) products are extensively consumed in many South Asian countries, where their use frequently co-occurs with exposure to arsenic from contaminated groundwater. To decipher the oral epithelial cell responses to arsenic and SLT alone and in co-exposure, we performed multi-omics analyses of DNA methylome, transcriptomic reprogramming and genotoxic effects in controlled experimental settings. Chronic exposure studies revealed hypomethylation of genes involved in inflammation response and apoptosis, further corroborated by the upregulation of genes involved in these processes due to arsenic and the combined treatment in acute exposure setting. Next, to validate the omics results at the phenotypic level, we observed a dose dependent decrease in cell viability, induction of DNA damage, cell cycle changes, and an increase in apoptotic cells, with the most pronounced effects observed under arsenic and SLT co-exposure conditions. The observed DNA damage was likely the result of apoptosis induction, as chronic exposure experiments based on whole-exome sequencing did not reveal increased mutagenicity following the arsenic and/or SLT exposure. Our integrative omics study provides insights into both chronic and acute responses to arsenic and SLT co-exposure, with both types of responses converging on some of the same mechanisms. We identified large-scale epigenomic and transcriptomic reprograming associated with arsenic and SLT co-exposure, alongside genotoxic effects presumably manifesting as consequences of apoptosis induction. The findings point to a role of arsenic and SLT in altering key molecular responses, especially in the context of the co-exposure, and call for further studies in humans in the areas of exposure, to validate the observed mechanisms.

Project description:Arsenic (As) exposure is a significant worldwide environmental health concern. Low dose, chronic arsenic exposure has been associated with higher risk of skin, lung, and bladder cancer, as well as cardiovascular disease and diabetes. While arsenic-induced biological changes play a role in disease pathology, little is known about the dynamic cellular changes due to arsenic exposure and withdrawal. In these studies, we seek to understand the molecular mechanisms behind the biological changes induced by chronic low doses of arsenic exposure. We used a comprehensive approach involving chromatin structural studies and mRNA microarray analyses to determine how chromatin structure and gene expression patterns change in response to chronic low dose arsenic exposure and its subsequent withdrawal. Our results show that cells exposed to low doses of sodium arsenite have distinct temporal and coordinated chromatin, gene expression and miRNA changes that are consistent with differentiation and activation of multiple biochemical pathways. Most of these temporal patterns in gene expression are reversed when arsenic was withdrawn. However, some of the gene expression patterns remained altered, plausibly as a result of an adaptive response by these cells. Additionally, these gene expression patterns correlated with changes in chromatin structure, further solidifying the role of chromatin structure in gene regulatory changes due to arsenite exposure. Lastly, we show that arsenite exposure influences gene regulation both at the transcription initiation as well as at the splicing level. Thus our results suggest that general patterns of alternative splicing, as well as expression of particular gene regulators, can be indicative of arsenite-induced cell transformation. A total of eight (8) samples with two biological replicates under four separate conditions: wild-type treated with deionized H2O for 36 days (NT); chronic low-dose arsenic exposure of 1 uM of sodium arsenite (iAs-T) for 36 days; chronic arsenic exposure of 1 uM of sodium arsenite for 26 days followed by removal of sodium arsenite for 10 days, measured at day 36 (iAs-Rev); and chronic arsenic exposure of 1 uM of sodium arsenite for 26 days, followed by removal of sodium arsenite exposure for 10 days, followed by 1 uM of chronic sodium arsenite exposure for 10 days (measured at day 46) (iAs-Rev-T).

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