Abstract 134: ZEB2 as a therapeutic target in fusion-positive rhabdomyosarcoma

Abstract

Abstract Rhabdomyosarcoma (RMS) is a highly aggressive childhood soft tissue cancer with skeletal muscle histogenesis. It is classified at the molecular level into fusion-negative (FN) and fusion-positive (FP) subtypes, with FP subtypes being defined by their signature oncofusions between the transcription factors PAX3 (or PAX7) and a variety of 3’ partners. Patients with FP-RMS have a five-year survival of &lt30%, and current treatments remain ineffective against the driving oncofusions. To address this challenge, we are interested in identifying proteins that interact with the oncofusions as alternate therapeutic targets, and conducted an unbiased proximity labeling screen for seven of the known RMS oncofusions. This approach revealed that ZEB2 is a common member of the interactome for all seven FP-RMS subtypes. ZEB2 is a DNA-binding transcriptional repressor that interacts with SMAD proteins and is known to be important for coordinating muscle and nerve development during embryogenesis. ZEB2 has been identified as an oncogene in various cancer types such as leukemia, glioblastoma, lung, and breast cancers. Further analysis of ZEB2's expression in FP-RMS cell lines, compared to skeletal muscle and other cancer cell lines, showed significantly higher levels of expression. In silico analyses of genomic CRISPR and RNAi screens in DepMap suggested a strong dependency of FP-RMS on ZEB2, with ZEB2 being one of the top four differential CRISPR dependencies in RMS cell lines compared to all other cancer cell lines. To investigate the functional consequences of ZEB2 suppression, we employed a loss-of-function approach using RNAi (siRNA and shRNA) in human FP-RMS cells. Our experiments confirmed the knockdown of ZEB2 through qRT-PCR and immunoblotting. Interestingly, the extent of ZEB2 knockdown determined whether FP-RMS cells underwent apoptosis or differentiation, potentially towards a neurodifferentiation pathway. We hypothesize that ZEB2 holds potential as a therapeutic target for FP-RMS patients. We aim to elucidate ZEB2's phenotypic role and mechanism of action in FP-RMS tumorigenesis, and assess its value as a therapeutic target in vivo. Our long-term goals for this project are to contribute to the development of innovative therapies that can mitigate the oncogenic activity driven by oncofusions in FP-RMS. Citation Format: Assil Fahs, Aanandi Munshi, Leen Barbar, Seth Zimmerman, Chris Counter, Corinne Linardic. ZEB2 as a therapeutic target in fusion-positive rhabdomyosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 134.