Indisulam targets RNA splicing and metabolism to serve as a novel therapeutic strategy for high risk neuroblastoma

Neuroblastoma is the most common solid tumour in childhood. Prognosis remains poor for high risk cases despite the use of multimodal treatment, highlighting the urgent need for novel therapeutic strategies. Analysis of cell line drug sensitivity data suggested that among solid tumours neuroblastoma could be the most sensitive to treatment with indisulam (E7070). Indisulam is a clinical aryl sulphonamide and selective promoter of DCAF15-E3-ubiquitin ligase dependent degradation of the RNA splicing factor and transcriptional coactivator RBM39. Here, we demonstrate for the first time that indisulam is highly efficacious in vitro and in vivo in experimental models of neuroblastoma. Indisulam induced rapid depletion of RBM39, accumulation of splicing errors in mRNA and growth inhibition in a DCAF15-dependent manner. Global analysis of protein and RNA alterations in IMR32 cells demonstrated a significant overlap between mis-spliced RNA and decrease in protein levels. Pathway analysis indicated an enrichment for genes involved in cell cycle and one-carbon metabolism, including CDK4 and TYMS. Finally, indisulam induces mitochondrial dysfunction, metabolome perturbations, alterations to redox balance and NAD/NADH ratio in vitro. Metabolic changes were validated in IMR32 xenografts in vivo. Collectively, our data suggest that high-risk neuroblastomas, which are frequently MYCN/MYC-driven, may be particularly susceptible to the dual targeting of metabolism and RNA splicing with anticancer sulfonamides such as indisulam RNA was extracted from IMR-32 cells which were treated with two doses of indisulam at two time points