PD59-11 TARGETING BCL2 TO INCREASE ENZALUTAMIDE SENSITIVITY TO BETTER SUPPRESS PROSTATE CANCER PROGRESSION THROUGH ALTERING ARV7 PROTEIN DEGRADATION

You have accessJournal of UrologyProstate Cancer: Basic Research & Pathophysiology III (PD59)1 Apr 2020PD59-11 TARGETING BCL2 TO INCREASE ENZALUTAMIDE SENSITIVITY TO BETTER SUPPRESS PROSTATE CANCER PROGRESSION THROUGH ALTERING ARV7 PROTEIN DEGRADATION Hua Xu* Hua Xu*Hua Xu* More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000000969.011AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Androgen deprivation therapy (ADT) with antiandrogens targeting androgens/androgen receptor (AR) signaling is the standard used to treat prostate cancer in different clinical settings besides surgical treatment. However, most prostate cancer patients will eventually develop cancer progression despite castrate levels of testosterone, into castration resistant prostate cancer (CRPC). The recently developed antiandrogen, Enzalutamide, has reformed the standard of care for castration resistant prostate cancer patients. However, Enzalutamide resistance inevitably emerges despite success of Enzalutamide in prolonging castration resistant prostate cancer patients’ survival. Here we found that Enzalutamide resistant prostate cancer cells had higher BCL2 expression. We aimed to test whether targeting BCL2 would influence Enzalutamide sensitivity of prostate cancer and identify the potential mechanism. METHODS: The study was designed to target Enzalutamide induced BCL2 with inhibitor ABT263 and test Enzalutamide sensitivity in Enz-resistant prostate cancer cells by MTT assay. Cellular reactive oxygen species levels were detected with dihydroethidium staining, and in vitro deubiquitinating enzyme activity assay was used to evaluate ubiquitin specific protease 26 (USP26) activity. RESULTS: We retrospectively performed an RNA sequencing among 625 CRPC patients and 625 matched hormone-sensitive prostate cancer (HSPC) patients and revealed that BCL2 was significant increased in CRPC, which indicated that targeting BCL2 might be a potential option. BCL2 inhibitor, ABT263 could increase Enzalutamide sensitivity and increase the ubiquitination of androgen receptor (AR) and AR splice variant 7 (ARv7) and their ubiquitin/proteasome-dependent degradation in both Enzalutamide sensitive and Enzalutamide resistant prostate cancer cells. As BCL2 is a classical anti-apoptosis protein, we then tested the potential linkage of its anti-apoptotic activity to its ability to alter the AR and ARv7 expression. The results revealed that inhibition of BCL2 activity by ABT263 (with and without Enz treatment) resulted in cleaved-PARP expression in both EnzS1-C4-2 and EnzR1-C4-2 and EnzR3-CWR22Rv1 PCa cells, suggesting that ABT263 could promote PCa apoptosis. However, blocking apoptosis through inhibition of caspase activity with Z-VAD-FMK (pan-caspase inhibitor) failed to reverse the decrease of AR and ARv7 protein expression, suggesting that the apoptotic pathway was unlikely responsible for the decrease of AR and ARv7 expression. As BCL2 is a mitochondria protein that may alter the mitochondria function via modulating the ROS, we then tested weather ABT263 could function via altering the cellular ROS to decrease the AR and ARv7 expression to further influence Enzalutamide sensitivity. ABT263 treatment could significantly induce cellular ROS level in both EnzS1-C4-2 and EnzR1-C4-2 and EnzR3-CWR22Rv1 PCa cells. Elevated cellular reactive oxygen species levels might then inhibit USP26 activity to increase the ubiquitination of androgen receptor (AR) and AR splice variant 7 (ARv7) and their ubiquitin/proteasome-dependent degradation, which contributed to the increase of Enz sensitivity. In vivo mouse model also demonstrates that ABT263 will suppress the prostate cancer progression. CONCLUSIONS: This study demonstrated that targeting Enzalutamide induced BCL2 with inhibitor ABT263 could increase Enzalutamide sensitivity in both Enzalutamide sensitive and Enzalutamide resistant prostate cancer cells through induction of cellular reactive oxygen species levels and suppression of USP26 activity with a consequent increase of ubiquitin/proteasome-dependent degradation of AR and ARv7 protein expression. This preclinical study established the foundation to use ABT263 in combination with Enzalutamide to treat prostate cancer patients, especially those resistant to Enzalutamide. Source of Funding: National Natural Science Foundation of China (No. 81472377 and 81802570) © 2020 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 203Issue Supplement 4April 2020Page: e1209-e1209 Advertisement Copyright & Permissions© 2020 by American Urological Association Education and Research, Inc.MetricsAuthor Information Hua Xu* More articles by this author Expand All Advertisement PDF downloadLoading ...