Abstract B040: Novel immunotherapy strategies targeting PTEN and TP53 defects in advanced prostate cancer

Abstract

Abstract Prostate cancer is the most diagnosed cancer in men worldwide and the leading cause of cancer death in men worldwide. Genetic inactivation of PTEN and TP53 are common in advanced prostate cancers. Checkpoint immunotherapy has yielded meaningful responses across many cancers but shown modest activity in advanced prostate cancer. Prior studies showed that overexpression of immune checkpoint B7-H3 (CD276) correlates with the increased risks of clinical recurrence, disease spread, and poor outcomes in various cancer types, including prostate cancer. However, the roles of B7-H3 in prostate cancer development and its tumor microenvironment remain unclear, partially due to the lack of tissue-specific deletion mouse models. This gap in knowledge hinders the application of immunotherapy targeting B7-H3 in prostate cancers. To identify PTEN- and p53-associated immune checkpoints, we performed multi-omics analyses of expression patterns of 51 checkpoint molecules in human prostate cancer samples and found that B7-H3 is one of the most significantly overexpressed immune checkpoints in prostate tumors containing PTEN and TP53 genetic inactivation. Mechanistically, we found that the PTEN-AKT pathway co-operates with p53 pathway in modulating B7-H3 expression in cancer cells. In Pten/Trp53 genetically engineered mouse (GEM) models, prostate-specific deletion of Cd276 resulted in markedly delayed tumor progression and reversed immunosuppression in the tumor microenvironment. Furthermore, we developed and evaluated novel combinatorial immunotherapy strategies targeting B7-H3 in advanced prostate cancer with PTEN and TP53 deficiencies. Citation Format: Wei Shi, Yin Wang, Yuehui Zhao, Di Zhao. Novel immunotherapy strategies targeting PTEN and TP53 defects in advanced prostate cancer [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 B040.