Abstract 5503: Targeting CDK12-mediated DNA damage response to overcome cisplatin resistance in human urothelial carcinoma

Abstract

Abstract Urothelial carcinoma (UC) accounts for more than 90% of bladder cancer. According to the 2019 Surveillance, Epidemiology and End Results (SEER) Program database, the 5-year survival rates of regional and metastatic bladder cancer are 36.3% and 4.6%, respectively. Patients who received radical cystectomy suffer from a high recurrence rate of up to 30%. As for metastatic UC, only half of the patients respond to standard platinum-based chemotherapy, with 20% of 5-year overall survival. CDK12 shows transcription regulatory effects via regulating RNA polymerase II CTD phosphorylation. In our research, we used CDK12 selective inhibitor SR-4835 to treat the UC cell lines including T24, BFTC905, RT4, and cisplatin-resistant T24/R. MTT assay result has demonstrated the cytotoxicity of SR-4835 against UC cells. Using q-RT-PCR and immunoblotting, we have confirmed the reduction of ATM mRNA and protein expression after the treatment of SR-4835. The expression of DNA damage marker gamma-H2AX was also elevated. Flow cytometry data indicated an increase in apoptotic population after treatment. According to these findings, we presume SR-4835 can lead to a DNA damage-induced apoptosis process. Furthermore, we also observed the inhibition of AKT pathway, which is related to cell survival and proliferation. Due to the effects of DNA-repair inhibition, we aim to combine SR-4835 to enhance the anti-cancer effects of cisplatin. The results of UC mice xenograft have confirmed that SR-4835 and cisplatin display a synergistic effect against UC tumor growth in vivo. We will further dissect the mechanisms of the in vitro synergistic effects between SR-4835 and cisplatin using immunoblotting, RNA-sequencing, comet assay, and various functional assays. Conclusively, our study aims to explore the role of CDK12 in urothelial carcinoma and the therapeutic effects of SR-4835, especially its potential to overcome cisplatin resistance and manage metastatic disease. Citation Format: Po-Ming Chow, Jun-Ren Dong, Chung-Sheng Shi, Kuo-How Huang. Targeting CDK12-mediated DNA damage response to overcome cisplatin resistance in human urothelial carcinoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5503.