Glycogen Synthase Kinase-3b (GSK-3b) 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-3b nuclear expression in urothelial cancer (UC) and renal cell carcinoma (RCC), and demonstrated that GSK-3b positively regulated UC and RCC cell survival and proliferation. Our objective was to evaluate the antitumor effects of clinically viable agent 9-ING-41, a maleimide-based ATP-competitive GSK-3 inhibitor, which demonstrated broad spectrum antitumor activity and marked activity in reversing chemoresistance in a variety of human cancers.
We used flow cytometry, Western immunoblotting, quantitative RT-PCR, BrDU incorporation and MTS assays to examine the pre-clinical antitumor activity of 9-ING-41 in UC (T24, HT1376 and RT4 cell lines) and RCC (ACHN, Caki2, A498 and KRC/Y cell lines).
A dose-dependent decrease in cancer cell proliferation was observed by MTS assay and BrdU incorporation assay with GI50 ranging from 0.7 to 4.7 mM (UC) and 7.2 to 11.5 mM (RCC). Treatment with 9-ING-41 induced prominent cell cycle arrest (predominantly G2 arrest) in UC and RCC cell lines. Expression of cell cycle related proteins, including Cyclin D, and anti-apoptotic proteins, such as XIAP and Bcl-2, were 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 both UC and RCC cell lines.
Our data provide a rationale for the inclusion of patients with advanced and/or chemo-refractory UC or RCC in 9-ING-41 clinical studies.
Clinical trial identification
Legal entity responsible for the study
D. Schmitt: President, CEO, equity interest: Actuate Therapeutics, Inc. A. Mazar: Equity interest, scientific advisor: Actuate Therapeutics, Inc. A. Ugolkov: Equity interest, consulting scientific Director: Actuate Therapeutics, Inc.
All authors have declared no conflicts of interest.