TGFB1 and glioblastoma: In addition, FOXG1 has been shown to inhibit expression of the cyclin-dependent kinase (CDK) inhibitor p21WAF1/CIP1, which is normally transcriptionally activated by TGF-β signalling, in glioblastoma and the neuroepithelium (Pardali et al, 2000; Seoane et al, 2004).