LAUSR

Background: Therapy-induced neuroendocrine prostate cancer (NEPC) is an aggressive variant of castration-resistant prostate cancer (CRPC) that is increasing in incidence with the widespread use of second generation of androgen receptor (AR)-pathway inhibitors (APIs) such as Enzalutamide (ENZ). NEPC arises from CRPC-Adenocarcinomas (CRPC-Adeno) via a reversible trans-differentiation process, referred to as neuroendocrine differentiation (NED) wherein prostate cancer cells (PCa) undergo a lineage switch. As a result of this lineage switching, PCa cells exhibit neuroendocrine (NE) features, characterized by expression of neuronal markers such as enolase 2 (ENO2), chromogranin A (CHGA) and synaptophysin (SYP). Due to lack of AR signaling, these PCa variants are impervious to anti-androgen therapy and constitute an aggressive variant of advanced CRPC with survival times < 1 year. Clinically, NEPC manifests as the presence of visceral metastatic disease including metastasis to liver, lung, central nervous system or bone despite low serum PSA levels. Current therapeutic options for NEPC are limited to highly toxic platinum drugs. The primary objective of our study is to evaluate novel, exosome-based therapies for NEPC. Methods: Exosomes were isolated from HEK-293T cells by ultracentrifugation. Isolated exosomes were characterized by Nanoparticle Tracking Analyses and electron microscopy. These exosomes were engineered to express biotinylated CEACAM-5 antibody on their cell surface. Exosomes were packaged with a combination of drugs (EZH2 inhibitor and AR inhibitor) by sonication. Engineered exosomes were tested in vitro using NEPC cell line NCI-H660 and in vivo using LuCaP 145.1 patient-derived xenograft model. Results: Engineered exosomes reduced the viability of NEPC cells. CEACAM5-labelled exosomes trafficked to tumor cells as CECAM5 is a surface protein expressed by NEPC cells. Conclusions: Engineered-exosome based therapy may provide a new avenue as a targeted therapy for NEPC. Citation Format: Amritha Sreekumar, Sharanjot Saini. Exosome-based therapeutic strategy for neuroendocrine prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3064.