FBXO7 Confers Mesenchymal Properties and Chemoresistance in Glioblastoma by Controlling Rbfox2‐Mediated Alternative Splicing

Abstract

Abstract Mesenchymal glioblastoma (GBM) is highly resistant to radio‐and chemotherapy and correlates with worse survival outcomes in GBM patients; however, the underlying mechanism determining the mesenchymal phenotype remains largely unclear. Herein, it is revealed that FBXO7, a substrate‐recognition component of the SCF complex implicated in the pathogenesis of Parkinson's disease, confers mesenchymal properties and chemoresistance in GBM by controlling Rbfox2‐mediated alternative splicing. Specifically, FBXO7 ubiquitinates Rbfox2 Lys249 through K63‐linked ubiquitin chains upon arginine dimethylation at Arg341 and Arg441 by PRMT5, leading to Rbfox2 stabilization. FBXO7 controls Rbfox2‐mediated splicing of mesenchymal genes, including FoxM1, Mta1, and Postn. FBXO7‐induced exon Va inclusion of FoxM1 promotes FoxM1 phosphorylation by MEK1 and nuclear translocation, thereby upregulates CD44, CD9, and ID1 levels, resulting in GBM stem cell self‐renewal and mesenchymal transformation. Moreover, FBXO7 is stabilized by temozolomide, and FBXO7 depletion sensitizes tumor xenografts in mice to chemotherapy. The findings demonstrate that the FBXO7‐Rbfox2 axis‐mediated splicing contributes to mesenchymal transformation and tumorigenesis, and targeting FBXO7 represents a potential strategy for GBM treatment.

Keywords

• alternative splicing
• chemoresistance
• FBXO7
• glioblastoma
• mesenchymal transformation