Abstract 992: Patient-derived tumor organoids of neuroendocrine prostate cancer

Abstract

Abstract Background: The development of neuroendocrine prostate cancer (NEPC) is one mechanism of treatment resistance to androgen receptor (AR)-targeted therapies for a subset of patients with advanced prostate cancer. This is associated with transition from a prostate adenocarcinoma to small cell/NEPC histology, low AR signaling signaling, and expression of neuroendocrine markers as Chromogranin A (CGHA), Synaphophysin (SYP) and CD56). Patient derived preclinical models recapitulating the NEPC phenotype may be used to address NEPC pathogenesis and test emerging therapeutic targets. Methods: Tumor organoids were developed according to protocols previously described (Gao et al, Cell 2015). Briefly the tissue biopsies (liver and bone biopsy) were washed, enzymatically digested and then seeded in Matrigel (BD) droplets. Organoids were characterized at genomic (WES), RNA and protein level (IHC) to confirm the expression of specific markers. Lentiviral infections were performed using shRNAs against EZH2 to knock down EZH2 in organoids. Organoids were also subcutaneously injected in NSG mice to generate patient derived xenografts (PDXs) for drug treatment in vivo. Results: We developed and characterized two NEPC tumor organoids from tumor biopsies (liver and bone) of two patients both in vitro and in vivo (as PDXs). NEPC tumor organoid models retained the molecular and histological characteristic of their matched patient samples. We successfully manipulated the activity of the histone methyltransferase EZH2 by using a catalytic inhibitor and its expression by infecting organoids with shEZH2. We showed that the absence of EZH2 affects the expression of neuroendocrine-associated programs as stem cell and neuronal pathway. Moreover treatment with EZH2 inhibitor decreased tumor organoids viability and PDXs tumor volume. Drug screening approaches on NEPC organoids were used to discovery novel drug targets and combinations that could potentially benefit NEPC patients. Top single agent hits included previously identified targets such as EZH2, AURKA, as well as novel synergies. Conclusions NEPC patient tumor organoids are clinically relevant tumor models to study the NEPC phenotype in advanced prostate cancer and may be used to elucidate novel drug targets. Citation Format: Loredana Puca, Rohan Bareja, Reid Shaw, Wouter Karthaus, Dong Gao, Chantal Pauli, Juan Miguel Mosquera, Joanna Cyrta, Rachele Rosati, Rema Rao, Andrea Sboner, Carla Grandori, Giorgio Inghirami, Yu Chen, Mark A. Rubin, Himisha Beltran. Patient-derived tumor organoids of neuroendocrine prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 992. doi:10.1158/1538-7445.AM2017-992