In GBM, exosomal circCMTM3 derived from GBM stem cells (GSCs) has been shown to promote the phenotypic transition from differentiated glioma cells (DGCs) to VM. Once internalized by DGCs, circCMTM3 binds to CNOT4, suppressing the ubiquitination and degradation of STAT5A and STAT5B. Here, STAT5B is linked to glioblastoma.