Abstract 1918: Patient-derived hormone-naive prostate cancer xenograft models reveal GRB10 as an AR-repressed gene driving the development of castration-resistant prostate cancer

Abstract

Abstract Prostate cancer is the most commonly diagnosed noncutaneous cancer and the leading cause of cancer-related death in North American men. Although androgen-deprivation therapy is initially effective in controlling the growth of hormone-naive prostate cancers (HNPC) in patients, currently incurable castration-resistant prostate cancer (CRPC) inevitably develops. Thus, we aim to identify CRPC driver genes that may provide new targets to enhance CRPC therapy. In this study, patient-derived xenografts (PDXs) of HNPCs that develop CRPC following host castration were examined for changes in expression of genes at various time points after castration using transcriptome profiling analysis; particular attention was given to pre-CRPC changes in expression indicative of genes acting as potential CRPC drivers. Eighty genes were found to be significantly upregulated at the CRPC stage while 7 of them also showed elevated expression prior to CRPC development. Among the latter, Growth Factor Receptor Bound Protein 10 (GRB10) was the most significantly and consistently upregulated gene. Moreover, we found GRB10 expression was elevated in clinical CRPC compared to HNPC in several clinical cohorts. Further investigation suggests that GRB10 is transcriptionally regulated by androgen receptor through an androgen-responsive element located in GRB10's intron. Functionally, we found that GRB10 knockdown markedly reduced prostate cancer cell proliferation and activity of AKT, a well-established CRPC mediator. Also, a positive correlation between AKT activity and GRB10 expression was found in clinical cohorts. In conclusion, GRB10 acts as a driver of CRPC and sensitizes AR pathway inhibitors, and hence GRB10-targeting provides a novel therapeutic strategy for the disease. Citation Format: Jun Hao, Xinpei Ci, Hui Xue, Rebecca Wu, Xin Dong, Fang Zhang, Sifeng Qu, Fan Zhang, Anne M. Haegert, Peter W. Gout, Colin Collins, Martin E. Gleave, Dong Lin, Yuzhuo Wang. Patient-derived hormone-naive prostate cancer xenograft models reveal GRB10 as an AR-repressed gene driving the development of castration-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1918.