Abstract 745: Molecular landscape of arsenic-induced bladder carcinogenesis
Authors: Navin Ajit Kumar , Shukla Vaibhav , Chandrasekaran Balaji , Tyagi Ashish , Saran Uttara , Ankem Murali K. , Damodaran Chendil 
Published: June 2022

Abstract
Introduction: Epidemiological, pre-clinical, and clinical studies have linked chronic arsenic (sodium arsenite: NaAsO2) exposure to a myriad of adverse health dysfunctions including the development of bladder cancer (BCa). However, most of the studies on arsenic-induced BCa have been performed on either unsuitable cell lines or using a higher concentration of arsenic (mM), which does not reflect exposure levels in a real-world setting. We used the telomerase reverse transcriptase (HU-hTERT1) immortalized normal bladder epithelial and a median physiological concentration of NaAsO2 (250 nM: 33 mg/L), to determine the transcriptomic and phenotypic changes during malignant transformation of HU-hTERT1 cells.
Methods: HU-hTERT1 cells were exposed to 250nM arsenic for 12 months. To analyze the effect of arsenic exposure we performed cell viability, cellular proliferation, and clonogenic assays. RNA Seq data was used to perform pathway enrichment analysis, Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, and protein-protein interaction (PPI) studies.
Results: BCa patients had significantly higher (4-5 fold) levels of arsenic (20-50 mg/L) in their urine when compared to their healthy counterparts (&lt;8 mg/L). Acute exposure to high concentration of (&gt; 400nM) inhibited the HU-hTERT1 growth, whereas concentrations less than 400nM did not adversely affect the viability of these cells. HU-hTER1 cells began forming colonies after six months of chronic NaAsO2 exposure, with the number of colonies increasing concurrently with the exposure time. GO and KEGG analysis showed a total of 2174 genes that are differentially expressed in arsenic-treated HU-hTER1 transforming cells (0 vs 12 months). The upregulated genes (1392) were involved in cellular response to unfolded protein, response to endoplasmic reticulum stress, proteasome-mediated ubiquitin-dependent protein degradation, autophagy signaling, and tumor angiogenesis(P&lt;0.05). Interestingly, the PPI analysis demonstrated a significant upregulation in histone modification of genes. These genes were enriched for the binding sites of transcription factors that are key regulators of carcinogenic pathways including ataxia-telangiectasia mutated (ATM) kinase and cell cycle regulatory pathways demonstrating a novel link between NaAsO2 exposure and BCa.
Conclusion: An in vitro model of NaAsO2-induced malignant transformation was developed. Identifying precise molecular events that lead to arsenic-induced malignant transformation of normal urothelial cells would be an important step in defining therapy for BCa.
Citation Format: Ajit Kumar Navin, Vaibhav Shukla, Balaji Chandrasekaran, Ashish Tyagi, Uttara Saran, Murali K. Ankem, Chendil Damodaran. Molecular landscape of arsenic-induced bladder carcinogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 745.