Abstract 5451: Arsenic induced altered pathways in bladder cancer

Abstract

Abstract Background: Urine excretion is the primary route for arsenic elimination. The bladder may thus be exposed to higher concentrations of arsenic due to the bioconcentration of urine by the kidneys. The molecular etiology of cancer linked to arsenic exposure is complex and multiple factors have been described as playing a role in this process. Although there is extensive epidemiologic evidence of increased risk for the development of urothelial cell carcinoma (UCC) associated with arsenic exposure, the mechanisms by which arsenic participates in tumorigenesis are not fully elucidated. Materials and Methods: To prepare in vitro model we chronically exposed immortalized normal human bladder cell line (HUC-1) to arsenic. Briefly, HUC1 cells were cultured in 25cm flask in F12K complete medium with or without 1µM As2O3. Medium and arsenic was changed every two days. Cells were sub-cultured as necessary and frozen down each month for future studies. Morphology differences were monitored over the entire treatment schedule, using a light microscope. Cell growth was monitored by MTT assay. Tumorigenic properties were analyzed by soft agar and invasion assay. Expression of several key molecules of PI3K-AKT signaling pathway was determined by western blot analysis. Results: At 6 months arsenic treated HUC1 cells started to became more rounded and had a tendency to pile on to one another. MTT was performed for each month of treatment in order to determine any changes in cell proliferation due to arsenic treatment. As expected the growth of the HUC1 cells was increased in a time dependent manner after arsenic treatment. Anchorage independent growth was evaluated using soft agar assay. Colonies were observed only in arsenic treated cells and the number of colonies was gradually increased with longer period of treatment. Similarly invaded cells were determined only in arsenic treated cells after 8 months. Withdrawal of arsenic for 2.5 months from 8 and 10 months arsenic treated cells does not reverse the tumorigenic properties. Western Blot analysis of AKT pathway genes, PTEN decreased and AKT and mTOR increased in arsenic treated HUC cells. Conclusion: Our study suggests that the exposure of HUC-1 to arsenic rapidly induces a multifaceted dedifferentiation program characterized by increased cell proliferation, anchorage independent growth and invasion, a motive that is also present after the end of the arsenic treatment indicating that such a manifestation seems to be irreversible. Further studies are needed in order to delineate the molecular effect of arsenic exposal to primary urothelial cancer tissue collected from patients exposed to arsenic. Studies are in progress to understand the mechanisms that induce this tumorigenic properties and potential stem cells activities in arsenic exposed urothelial cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5451. doi:1538-7445.AM2012-5451