SMAD7 and glioblastoma: In contrast, SMAD7, a negative regulator of TGFβ pathway that often was induced upon TGFβ stimulation in vitro (Additional file 1), was downregulated in the strong TGFβ response group (fold change -1.48, p < 0.0007), suggesting the tumor-specific escape of the negative feedback mechanism may also contributed to TGFβ activation in glioblastomas.