Abstract 5667: EZH2 inhibition targets B7-H3 in Myc amplified medulloblastoma

Abstract

Abstract Medulloblastoma (MB) is the most common malignant pediatric brain tumor. The most aggressive MB subtype Group 3, is characterized by Myc amplifications. However, targeting Myc has proven unsuccessful, necessitating alternative therapies for MB. The histone methyltransferase, enhancer of zeste homolog 2 (EZH2), is well-known for its role in catalyzing the tri-methylation of H3K27 (H3K27me3). Recent studies have demonstrated that EZH2 is overexpressed in Group 3 MB and that Myc and EZH2 regulate the expression of the B7 homolog 3 (B7-H3). As we previously showed the oncogenic functions of B7-H3 in Group 3 MB, this study aims to investigate the efficacy of EZH2 inhibition to reduce B7-H3 levels in an effort to improve treatment options and patient survival. Datamining studies conducted using MB patient datasets showed a positive correlation between EZH2 and B7-H3 transcripts. Additionally, we showed that inhibition of EZH2 using EPZ005687 in Myc-amplified MB cell lines downregulated B7-H3 and Myc expression. Furthermore, targeting EZH2 through shRNA and pharmacological inhibition reduced the viability and augmented apoptosis, as indicated by LDH, MTT, clonogenic, and FACS assays. We additionally tested the consequences of EZH2 inhibition on the C17.2, murine neural stem cells, and C17.2 NSC transformed with EZH2 oncogene (C17.2_EZH2OX). Furthermore, the C17.2_EZH2OXcells were susceptible to EPZ005687 treatment compared to C17.2 control cells, as demonstrated by MTT and FACS. Collectively, our study highlights the therapeutic benefits of targeting EZH2 in Myc-amplified MB cell survival. Citation Format: Katherine Shishido, Sujatha Venkataraman, Rajeev Vibhakar, Kiran Velpula, Swapna Asuthkar. EZH2 inhibition targets B7-H3 in Myc amplified medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5667.