Abstract 2612: Neuropilin-2 promotes enzalutamide-resistant neuroendocrine prostate cancer
Authors: Wang Jing , Li Jingjing , Wu Boyang , Yin Lijuan 
Published: September 2020

Abstract
Background: Neuroendocrine prostate cancer (NEPC) is a lethal subtype of prostate cancer (PC) that emerges after androgen deprivation therapy in advanced PC patients, with incidence significantly increased in recent years due to the widespread use of highly potent antiandrogens such as enzalutamide (ENZ). This study investigated the role of neuropilin-2 (NRP2) in the development and progression of ENZ-induced NEPC.
Methods: Human PC tissue microarrays with different characteristics, including hormone naïve, castration resistant (CR) and neuroendocrine (NE), were analyzed for NRP2 expression by immunohistochemistry. Human PC cells were manipulated for stable knockdown or overexpression of NRP2, and then subjected to cell proliferation, cell colony formation and tumorsphere formation assays, and Western blot/RT-qPCR examination of NE marker expression.
Results: NRP2 expression was elevated in CRPC and NEPC patient samples compared to hormone-naïve counterparts, which was supported by association of higher NRP2 expression with hormone-refractory and NE status of PC from additional clinical data sets. Increased NRP2 expression was found in LNCaP cells treated with ENZ (10 µM, up to 7 days) as well as in the ENZ-resistant C4-2BENZR cells (with acquired resistance to ENZ at 20 µM). Both cell lines exhibited treatment-induced NEPC features, including NE differentiation cell morphology, AR suppression and NE marker induction. Silencing of NRP2 in C4-2BENZR and 22Rv1 (with inherent ENZ resistance and NE traits) cells decreased cell proliferation by 50% and 75% respectively, which was corroborated in colony formation and tumorsphere assays. Silencing of NRP2 also increased apoptosis in both cell lines. NRP2 silencing further led to reduced expression of NE markers, including CHGA, SYP, CD56 and SOX2. Conversely, enforced expression of NRP2 in LNCaP and 22Rv1 cells accelerated cell proliferation by up to 4-fold, which was paralleled by increased cell colony and tumorsphere formation, reduced cell apoptosis, upregulation of NE marker expression (CHGA, SYP, NSE, CD56 and SOX2), and downregulation of AR and AR target genes (PSA, TMPRSS2, FKBP5 and KLK2). Mechanistically, NRP2 induced phosphorylation of STAT3 in C4-2BENZR and 22Rv1 cells as revealed by phospho-kinase antibody arrays, which will be further investigated for downstream effectors mediating NRP2's function in NEPC.
Conclusion: NRP2 contributes to PC disease progression towards a NE phenotype following ENZ treatment and subsequent emergence of ENZ resistance, which provides new insights into understanding the mechanism underlying development of antiandrogen-induced NEPC and developing a new target for treating this lethal disease.
Citation Format: Jing Wang, Jingjing Li, Boyang Wu, Lijuan Yin. Neuropilin-2 promotes enzalutamide-resistant neuroendocrine prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2612.