SMAD2 and glioma: Moreover, TGF-β expression and extent of Smad2/3 phosphorylation were attenuated in glioma cells transfected with siRNA-PVT1, while siRNA-p53 transfection led to opposite effects, and co-treatment of siRNA-p53 and siRNA-PVT1 counteracted the effect of siRNA-p53 (Figure 4c).