Regulation of stem cell-like phenotype and response to chemotherapy in bladder cancer by beta-arrestins.

Abstract

461 Background: Identification of molecular drivers that promote a muscle invasive phenotype and chemoresistance in bladder cancer, as well as an understanding of their mechanism of action should help in designing potential prognostic markers and effective targeted treatments for patients with advanced bladder cancer. β-arrestins (ARRBs) are classic attenuators of G-Protein coupled receptor signaling. However, they have multiple roles in cellular physiology, including carcinogenesis. Methods: β-arrestin-1 (ARRB1) and β-arrestin-2 (ARRB2) mRNA levels were measured by quantitative RT-PCR in two clinical specimen cohorts (n = 63; n = 43). The role of ARRBs in regulating a stem cell-like phenotype and response to chemotherapy treatments was investigated using CRISPR-Cas9 mediated gene-knockout of ARRB1. The consequence of forced expression of ARRBs on tumor growth and response to gemcitabine in vivo were investigated using bladder tumor xenografts in nude mice. Results: ARRB1 levels were significantly elevated and ARRB2 levels downregulated in cancer tissues compared to normal tissues. In multivariate analysis only ARRB2 was an independent predictor of metastasis, disease-specific-mortality and failure to Gemcitabine + Cisplatin (G+C) chemotherapy; ~ 80% sensitivity and specificity to predict clinical outcome. ARRBs were found to regulate stem cell characteristics in bladder cancer cells. Depletion of ARRB2 resulted in increased cancer stem cell markers but ARRB2 overexpression reduced expression of stem cell markers (CD44, ALDH2, and BMI-1), and increased sensitivity towards gemcitabine. Overexpression of ARRB2 resulted in reduced tumor growth and increased response to Gemcitabine in tumor xenografts. Conclusions: β-Arrestins regulate response towards gemcitabine and are therefore potential targets and predictive markers for chemotherapy failure in bladder cancer. The present work shows for the first time that β-arrestins have prognostic significance for predicting metastasis and response to chemotherapy in bladder cancer.