ZEB1 and glioblastoma: The effect of TGF-β on GG14 neurosphere size is in line with a previous report showing TGF-β-dependent enhancement of GBM neurosphere growth.33 Moreover, TGF-β treatment induced phosphorylation of SMAD2 and enhanced ZEB1 expression in GG14 that was associated with a reduction of PDGFR-α, whereas OLIG2 expression remained the same, and a gain of YKL40 expression.