These findings suggest that in GBM patients, although the RBFOX2 expression is not altered, RBFOX2-mediated cassette exon inclusion events are significantly impaired when SON and hnRNP A2B1 are overexpressed due to the competitive action of the SON-hnRNP A2B1 complex blocking RBFOX2 function, revealing a previously unrecognized mechanism repressing RBFOX2 activity in GBM. This evidence concerns the gene SON and glioblastoma.