Abstract 3734: Neuroendocrine differentiation (ND) in sensitivity of neuroendocrine tumor (NET) cells to ONC201/TIC10 cancer therapeutic

Abstract

Abstract Neuroendocrine tumors (NETs) harbor neuroendocrine differentiation (ND) with specific markers including protein gene product 9.5 (PGP9.5) and Chromogranin A (CgA). In prostate cancers (PC), ND is induced by BRN2/SOX2 transcription factors. NET-like cells with low or absent androgen receptor (AR) signaling cause hormone therapy resistance and poor prognosis in PC. Small cell lung carcinoma (SCLC), a high-grade NET, presents with metastasis early and has poor survival. ONC201/TIC10 is a small molecule inducer of TRAIL signaling in clinical trials. ONC201 antagonizes dopamine D2 or D3 receptors (DRD2/DRD3) and is an agonist of mitochondrial caseinolytic protease P (ClpP) resulting in activation of DR5/TRAIL-dependent apoptosis involving the integrated stress response (ISR). ONC201 is active in various malignancies including H3K27M-mutated glioma and NETs expressing high levels of DRD2. We hypothesized that altered BRN2/SOX2 may impact NET apoptosis by ONC201 through the ISR and TRAIL/DR5. We analyzed the expression of neuroendocrine markers PGP9.5, CgA, SOX2, and BRN2, as well as markers of TRAIL signaling pathway markers ATF4, DR5, ClpP, ClpX, and DRD2/DRD3 in PC and SCLC cell lines (N=6) ± treatment with ONC201. Specifically, we compared pre-treatment protein expression levels with the IC50. Our results reveal that DU145 (IC50=3.11μM), PC3 (IC50=3.02μM), and LNCaP (IC50=1.33μM) are ONC201 sensitive. H1417 SCLC expresses CgA, unlike PC3 and DU145. PGP9.5 is expressed in these lines. PGP9.5 is expressed in PC3, DU145, H1417, and H1048 but not in LNCaP and 22RV1. BRN2 is expressed in PC3, H1417, and H1048 but not DU145, LNCaP, or 22RV1. ClpX is expressed in all 6 lines but at lower levels in SCLC. ClpP is expressed in the 6 lines. DR5 is expressed at higher levels in PC3, DU145, LNCaP, and 22RV1 PC versus H1417 and H1048 SCLC. SOX2 is expressed at high levels in H1417 cells. These results are establishing the landscape of ND in PC and SCLC lines for further experimentation and testing of our hypothesis. To characterize the association of BRN2 dysregulation with ONC201 sensitivity, we are performing BRN2/SOX2 knockdown experiments using siRNA and evaluating effects towards ONC201 sensitivity. Our results provide insights into molecular mechanisms of ND in PC and SCLC sensitivity to ONC201. We are also currently working to overexpress BRN2 and SOX2 in cell lines to analyze the impact on neuroendocrine differentiation and ONC201 sensitivity. Citation Format: Elizabeth C. Ding, Wafik S. El-Deiry. Neuroendocrine differentiation (ND) in sensitivity of neuroendocrine tumor (NET) cells to ONC201/TIC10 cancer therapeutic. [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 3734.