Abstract 3962: Mechanisms of tumor recurrence and drug resistance in rhabdomyosarcoma

Abstract

Abstract Rhabdomyosarcoma (RMS) is an aggressive pediatric soft tissue sarcoma, which constitutes of two main histological subtypes. Alveolar Rhabdomyosarcoma (FP-RMS) is characterized by a fusion protein PAX3-FKHR, whereas embryonal Rhabdomyosarcoma (FN-RMS), which is the focus of this project, is more genetically heterogeneous. The prognosis for RMS has improved over the years, however the cure rates for recurrent or relapse disease remains dismal, warranting further identification of novel therapeutic interventions, which is the aim of this project. To this end, we performed two CRISPR knockout screens, using a kinome sgRNA library and a whole genome sgRNA library in combination with etoposide at a concentration of IC10, in order to identify genes that might confer resistance to chemotherapeutic drugs. In addition, the kinome screen was also designed to identify essential genes by using the treatment control samples as further time points. For treatment associated genes, we identified components of the JNK/P38 and Hippo signaling pathways among the top hits. We also found enrichment of a novel pathway involving HIFα stabilization via the genes LRRK2 and PTK6. Further and as expected, many DNA damage repair pathways were enriched. Finally in this category, players of the Wnt signaling pathway including JNK1, which is involved in non-canonical Wnt signaling were found to be enriched. As for essential gene identification, many cell cycle genes such as CDK6, PLK3 and PLK4 were among the top hits, as well as WEE1, which has been implicated in the context of RMS, were common between all the time points. Taken together, the CRISPR screens identified potential pathways that might be involved in resistance of FN-RMS cells towards etoposide. Selected candidates are being validated via an in vitro competition assay and drug screening is being performed to identify inhibitors that could be used to re-sensitize cells to treatment with standard chemotherapy. Citation Format: Devmini C. Moonamale, Marco Wachtel, Beat W. Schäfer. Mechanisms of tumor recurrence and drug resistance in rhabdomyosarcoma [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 3962.