Abstract 1446: The elevated expression of INSM1 is correlated with EZH2 in neuroendocrine prostate cancer

Abstract Background: Neuroendocrine prostate cancer (NEPCa) is the most aggressive and non-targetable prostate cancer (PCa). It is well accepted that NEPCa arises from prostate adenocarcinoma (AdPCa) via trans-differentiation. NEPCa tumors exhibit a similar mutation burden but a different transcriptome profile from AdPCa. This suggests that the acquisition of the NE phenotype is driven by epigenetic, transcriptional reprogramming but not genetic alterations. Enhancer of zeste homolog 2 (EZH2), a histone methyltransferase, is an epigenetic regulator and upregulated in NEPCa. The upregulation of EZH2 in PCa has been considered to be correlated with therapy-induced plasticity and NE differentiation. Insulinoma-associated 1 (INSM1), is a zinc-finger transcription factor, which is predominantly expressed in neuroendocrine (NE) cells and important for the NE developmental pathways. INSM1 has been considered as a biomarker for multiple types of NE tumors, like pancreatic, lung, and prostate. Also, the increase level of INSM1 is associated with NE differentiation in PCa. Analysis of PCa transcriptomic profiles suggests that EZH2 and INSM1 have positive correlation in PCa and function together in NEPCa. Methods: To study the expression of INSM1 and EZH2, we did immunofluorescence (IF), immunohistochemistry (IHC), Western blot and RT-qPCR in prostate cancer cell lines, mouse tissues, and human patients samples. The bioinformatics analysis was done using the publicly available RNA-Seq data obtained from the cBioportal, the Cancer Genome Atlas (TCGA), and the Cancer Cell Line Encyclopedia websites (CCLE). Results and Conclusion: Our IHC results confirmed that INSM1 is highly expressed in NEPCa rather that AdPCa in both human and mouse tissues. By IF, we further found that INSM1 also expresses in PCa amphicrine cells. Additionally, we found that the expression of INSM1 is positively associated with EZH2 expression in PCa. These data indicates that INSM1 may act as a marker for not only NE cells but also amphicrine cells in PCa. Also the correlation between INSM1 and EZH2 further indicates the importance of INSM1 in NEPCa. Our further study will focus on how INSM1 functions and whether there’s a direct regulation between INSM1 and EZH2. Acknowledgement: This work was supported by NIH R01 CA226285, and the Feist-Weiller Cancer Center (FWCC). Citation Format: Lin Li, Siyuan Cheng, Xiuping Yu. The elevated expression of INSM1 is correlated with EZH2 in 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 1446.