PIK3CA and cancer: Moreover, the co-administration of the MDM2 antagonist RG7388 and the dual inhibitor PI3K/mTOR BEZ235 was also able to significantly reduce tumor growth rate, thus indicating that the combination strategy designed to inhibit the AKT/mTOR signaling and to re-activate p53 signaling at once, may be potentially effective in different cancer types, including GBM.