SMAD3 and glioblastoma: Here we reported that NAG-1 overexpression could activate PI3K/Akt and Smad2/3 signaling cascades in glioblastoma cells (Fig. 3), and that NAG-1-induced apoptosis was enhanced by PI3K inhibitors and decreased by siRNAs to Smad2 and Smad3 (Fig. 4).