RBMX suppresses tumorigenicity and progression of bladder cancer via interaction with hnRNP A1 protein to regulate PKM alternative splicing

Bladder cancer (BCa) is one of the most common malignant tumors of urinary system and has high incidence rate and mortality but there is a lack of effective treatment. Therefore, an in-depth study of the molecular mechanisms involved in BCa is of great significance for improving the survival of patients with advanced BCa. We found that the expression of RBMX was significantly declined in BCa, especially in muscle-invasive BCa. BCa patients with low levels of RBMX had poor prognoses. By in vitro and in vivo experiments, RBMX was shown to inhibit BCa cells growth and metastasis. Co-IP coupled with MS and GO analysis identified hnRNP A1 as a RBMX-binding protein. Mechanistically, RBMX competitively bond to the RGG box of hnRNP A1 and antagonized the hnRNP A1-mediated regulation of PKM splicing by blocking the binding of the RGG motif of hnRNP A1 to the sequences flanking PKM exon 9, resulting in downregulation of PKM2 and upregulation of PKM1. By decreasing the PKM2/PKM1 ratio, RBMX suppressed BCa cells aerobic glycolysis, which further inhibited tumorigenicity and progression of BCa. Overall design: Overexpression of RBMX by plasmid transfection followed by examining alternative splicing changes by RNA-seq or examining cancer phenotype by established assays.