Abstract 4812: 9-ING-41, a novel inhibitor of glycogen synthase kinase-3beta (GSK-3β), is active as a single agent and within combination therapies in bladder cancer cell lines

Glycogen synthase kinase-3beta (GSK-3β) is a serine/threonine protein kinase that has been established as a therapeutic target in a broad spectrum of human malignancies. We have previously identified aberrant GSK-3β nuclear expression in bladder cancer (BC), and demonstrated that GSK-3β positively regulated BC cell survival and proliferation. Our objective was to evaluate the antitumor effects of the clinically viable agent 9-ING-41, a maleimide-based ATP-competitive GSK-3 inhibitor, which has broad spectrum antitumor activity and marked activity in reversing chemoresistance in a variety of pre-clinical models of human cancers. We used flow cytometry, Western immunoblotting, quantitative RT-PCR, BrDU incorporation and MTS assays to examine antitumor activity of 9-ING-41 in BC (T24, HT1376, RT4 cell lines). Additionally, we studied combination therapy of 9-ING-41 with gemcitabine and cisplatin, standard agents used for the treatment of patients with advanced BC, with cabozantinib, a multi kinase inhibitor, and with chloroquine, an autophagy inhibitor. A dose-dependent decrease in cancer cell proliferation was observed by MTS assay and BrdU incorporation assay with GI50 0.7μM (T24), 4.7 μM(HT1376), 2.2μM(RT4). Treatment with 9-ING-41 induced prominent cell cycle arrest (predominantly G2 arrest) in BC cells. Expression of cell cycle related proteins, including Cyclin D, and anti-apoptotic proteins, such as XIAP and Bcl-2, were significantly decreased as detected by Western immunoblotting and real time RT-PCR. Treatment with 9-ING-41 significantly potentiated the growth inhibitory effect of cisplatin and gemcitabine in cultured cells. In addition, combination therapy with 9-ING-41 and cabozantinib or chloroquine, significantly potentiated the effect of either single agent. Our data proved that a single treatment using 9-ING-41 is effective in BC cells. Combination treatment of 9-ING-41 with standard chemotherapeutic drugs or novel agents may provide a new therapeutic approaches in BC. These data provide a rational for the inclusion of patients with advanced BC in clinical studies of 9-ING-41. Citation Format: Hiroo Kuroki, Tsutomu Anraku, Vladimir Bilim, Masayuki Tasaki, Daniel Schmitt, Andrew Mazer, Francis J. Giles, Andrey Ugolkov, Yoshihiko Tomita. 9-ING-41, a novel inhibitor of glycogen synthase kinase-3beta (GSK-3β), is active as a single agent and within combination therapies in bladder cancer cell lines [abstract]. In: Proceedings of the American Associ