AKT1 and central nervous system cancer: With regard to the underlying mechanism, it was found that activation of cGK-II (a cGMP-dependent protein kinase) led to the phosphorylation and inhibition of the SOX9 protein, which in turn suppressed AKT phosphorylation and arrested cultured glioma cells in the G1 phase; siRNA-induced suppression of SOX9 was also found to reduce glioma cell proliferation [13].