Abstract P178: RBM39 degradation leads to exceptional responses in high-risk neuroblastoma by targeting the spliceosome

Abstract

Abstract Genome-wide studies of thousands of human tumors have revealed dysregulated pre-mRNA splicing as a critical pathway in tumorigenesis, which may consequently create vulnerabilities for cancer cells. Indeed, C-MYC-dependent cancers are specifically susceptible to perturbation of spliceosome function. The MYC oncogenes (C-MYC, MYCN, and MYCL1), which are known transcriptional drivers of large numbers of genes, are among the most common genetic abnormalities in human cancer. We found that neuroblastoma, a MYC-driven cancer characterized by splicing dysregulation and spliceosomal dependency, requires splicing factor RBM39 for survival. Indisulam, a “molecular glue” that selectively recruits RBM39 to the CRL4-DCAF15 E3 ubiquitin ligase for proteasomal degradation, is highly efficacious against neuroblastoma, leading to exceptional responses in multiple high-risk disease models, without overt toxicity. Genetic depletion or indisulam-mediated degradation of RBM39 induces significant genome-wide splicing anomalies and cell death. Mechanistically, the dependency on RBM39 and high-level expression of DCAF15 determine the exquisite sensitivity of neuroblastoma to indisulam. Our data indicate that targeting the dysregulated spliceosome by precisely inhibiting RBM39, a vulnerability in neuroblastoma, is a valid therapeutic strategy. In summary, our study has validated the mechanism by which “molecular glues” targeting RNA binding proteins can be exploited for drug development in cancer, and has a broad impact on understanding of the splicing dependency of MYC-driven cancers and the identification of novel therapeutic approaches against them. Citation Format: Jun Yang. RBM39 degradation leads to exceptional responses in high-risk neuroblastoma by targeting the spliceosome [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P178.