Bladder cancer is the sixth leading cause of cancer in the United States. Patients with bladder stones are at an increased risk for developing bladder cancer. Bladder stones are an established cause of bladder irritation and inflammation. Proliferative and phenotypic changes induced by chronic inflammation are the proposed etiology for the development of bladder cancer in individuals with chronically irritated bladders. The purpose of this study was to identify the early genetic changes associated with bladder inflammation that may be associated with the development of bladder cancer. Slc3a1 knockout male mice develop cystine bladder stones from the second month of life. Prior investigations demonstrated bladder inflammation in these mice, which may closely mimic inflammation inducing the earliest stages of bladder cancer in humans. To investigate changes in cell structure, proliferation, and differentiation, we performed PCR expression arrays on tissue from bladders of Slc3a1 knockout mice and compared them to wild-type mice. We tested genes in the uroplakin (UP), cytokeratin (CK), and tissue inhibitor of mellatoprotease (TIMP) families of proteins, as well as genes involved in EMT. We localized expression of selected markers by immunofluorescence. Results demonstrated pronounced alterations in expression of E-cadherin, TIMP-1, TIMP-2, UP1A, UP2, UP3A, UP3B and CK 14 and CK17. E-cadherin and TIMP proteins are involved in cell motility underpinning epithelial-mesenchymal transition. CKs are structural proteins believed to be indicative of the stem-cell population in urothelial cancers. Metastatic potential and stem-cell behavior are key features of cancer cells, and expression changes in genes underpinning these functions may represent the earliest steps in the progression to bladder cancer. Prior studies had shown UP2 to be up-regulated in bladder cancer, suggesting that it could serve as a marker for the disease. We found up-regulation of UP2, as well as up-regulation of UP1A, UP3A, and UP3B in our model, indicating that changes in expression of these genes may occur before the disease is clinically evident. Thus, they have the potential to serve as biomarkers for this disease in its early, silent stages. Genetic changes discovered in Slc3a1 knockout mice may closely mirror the early cellular changes seen in bladder cancer. Our study has provided insight into the earliest genes exhibiting altered expression by inflammation-induced changes in the bladder, including a set of potential biomarkers for early detection of the disease. These genes require in-depth analysis to identify the mechanistic contribution of each one to the development and progression of bladder cancer in the hopes of generating molecular targets for future therapy.

Citation Format: Kathleen M. Capaccione, Min Yang, Lourdes Serrano, Jay A. Tishfield, Amrik Sahota. Cystine stones as a potential cause of bladder cancer in Slc3a1 knockout male mice. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 808. doi:10.1158/1538-7445.AM2015-808