Role of B-arrestins in bladder cancer progression and response to chemotherapy

Bladder cancer is the most expensive cancer to treat. Frequent recurrence and treatment refractoriness are the most common causes of morbidity and high cost of treatment of this disease. Males are three times more likely to develop bladder cancer. Therefore, the United States Veterans are at higher risk of developing bladder cancer. The high-grade, muscle invasive bladder cancers are difficult to treat and neoadjuvant and adjuvant chemotherapies have only modest benefits for overall survival. The investigators identified a pair of molecular markers that potentially determine response to chemotherapy, especially towards the Gemcitabine + Cisplatin chemotherapy combination. The markers β-Arrestin 1 (BARR1) and β-Arrestin 2 (BARR2) are members of the intracellular signaling complex triggered by chemokine receptors. The research group investigated muscle invasive bladder cancer tissues and found that BARR1 and BARR2 expressions are associated with treatment failure and metastasis. Further, in vitro studies using established bladder cancer cell lines showed an inverse correlation between BARR2 levels and the cancer stem cell phenotype, metastatic potential, and resistance to Gemcitabine induced cytotoxicity. Conversely, BARR1 expression correlated with metastasis and cancer stem cell properties. The principal hypothesis of this project is BARR1 and BARR2 are regulators of BC cell growth, differentiation into basal or luminal cell phenotype, and BC cell motility. BARR1 and BARR2 regulate malignant progressions, such as muscle invasion, metastasis, and resistance to chemotherapy drugs. Three specific aims are proposed: 1. To investigate the mechanism by which BARR1 and BARR2 regulate BC growth, cancer stem cell phenotype, and invasive/metastatic potential; 2. To investigate whether modulation of the levels of BARR1 and BARR2 alters the response to Gem treatment in preclinical BC models. Also, test the potential of tetrahydrouridine, an inhibitor of intracellular Gemcitabine metabolism, to sensitize chemotherapy-resistant Patient-derived bladder tumor xenografts (PDX) towards Gemcitabine; 3. To investigate the potential of BARR1 and BARR2 expression as a predictor of chemotherapy response and clinical outcome in MIBC. The investigators consider the high impact of this project on improving the prediction of treatment-response in high- grade bladder cancers as well as therapy response using a combination of a non-toxic drug and an established chemotherapy drug. The proposed studies have the potential to improve bladder cancer treatment and outcome for U.S. Veterans.