Abstract B056: Homoharringtonine, a translational inhibitor, induces dramatic apoptosis in prostate cancer xenografts

Abstract Introduction: We have previously shown that prostate cancer is primed to undergo apoptosis with BH3 mimetics targeting anti-apoptotic proteins, including BCL2, BCLXL, and MCL1 (Arai S, Balk SP et al. Clin Cancer Res 2018). We have also revealed that receptor tyrosine kinase inhibitors induced MCL1 degradation through integrated stress response and mitochondrial E3 ubiquitin ligase MARCH5 (Arai S, Balk SP et al. eLife 2020). Thus, we hypothesized that drugs targeting mitochondria might decrease MCL1 and induce apoptosis in prostate cancer. Methods: In this study, we have conducted a small-scale screening of a commercially available drug library (84 compounds) that is supposed to target mitochondria in prostate cancer cells. We have selected the top 5 drugs that could decrease prostate cancer cell growth at 1 μM levels. Results: Homoharringtonine, an FDA-approved translational inhibitor for chronic myelogenous leukemia, decreased cell growth within nM levels in multiple prostate cancer cell lines in vitro. Mechanistically, homoharringtonine rapidly reduced several proteins (MCL1, AR, AR-V7, and c-MYC) through translational inhibition and significantly induced apoptosis in prostate cancer cells in vitro. Importantly, homoharringtonine dose-dependently led to the regression of prostate cancer xenografts in vivo. Conclusions: Homoharringtonine might be a good candidate drug to treat prostate cancer. Citation Format: Akira Ohtsu, Seiji Arai, Tatsuhiro Sawada, Mai Kato, Yuta Maeno, Yoshiyuki Miyazawa, Yoshitaka Sekine, Kazuhiro Suzuki. Homoharringtonine, a translational inhibitor, induces dramatic apoptosis in prostate cancer xenografts [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr B056.