High-Throughput Drug Screening Identifies Pazopanib and Clofilium Tosylate as Promising Treatments for Malignant Rhabdoid Tumors

Abstract

Summary: Rhabdoid tumors (RTs) are aggressive tumors of early childhood characterized by SMARCB1 inactivation. Their poor prognosis highlights an urgent need to develop new therapies. Here, we performed a high-throughput screening of approved drugs and identified broad inhibitors of tyrosine kinase receptors (RTKs), including pazopanib, and the potassium channel inhibitor clofilium tosylate (CfT), as SMARCB1-dependent candidates. Pazopanib targets were identified as PDGFRα/β and FGFR2, which were the most highly expressed RTKs in a set of primary tumors. Combined genetic inhibition of both these RTKs only partially recapitulated the effect of pazopanib, emphasizing the requirement for broad inhibition. CfT perturbed protein metabolism and endoplasmic reticulum stress and, in combination with pazopanib, induced apoptosis of RT cells in vitro. In vivo, reduction of tumor growth by pazopanib was enhanced in combination with CfT, matching the efficiency of conventional chemotherapy. These results strongly support testing pazopanib/CfT combination therapy in future clinical trials for RTs. : Rhabdoid tumors (RTs) are aggressive pediatric tumors characterized by SMARCB1 inactivation. Chauvin et al. identify two SMARCB1-dependent targeted therapies for RT: pazopanib, which inhibits PDGFR and FGFR2, and the potassium channel inhibitor clofilium tosylate, which induces endoplasmic reticulum stress. Combining both drugs induces cell apoptosis and reduces PDX tumor growth. Keywords: rhabdoid tumors, SMARCB1, pazopanib, clofilium tosylate, high-throughput drug screening, tyrosine kinase inhibitors