To test whether Akt can suppress the phosphorylation of Smad3 in NAG-1-overexpressed glioblastoma cells, the PI3K inhibitors wortmannin and LY294002 were used to inhibit the Akt phosphorylation, and then the Smad3 phosphorylation was analyzed by western blot. The gene discussed is GDF15; the disease is glioblastoma.