TGFB1 and glioblastoma: To obtain insight into the mechanisms underlying TGF-β-induced mesenchymal shift in GBM, the expression of various transcription factors associated with EMT, such as Snail1, Snail2/Slug, ZEB1 (zinc-finger E-box-binding homeobox 1), Twist and β-Catenin, was examined in U87 and U251 cells.