MTOR and prostate cancer: In addition, a decrease in the pS6/S6 ratio, one of the major downstream targets of mTORC1, has been found to lead to increase PI3K/Akt signaling in MCF-7 and MDA-MB-468 human breast cancer cells or DU-145 human prostate cancer cells [28, 14], suggesting that the combined use of mTOR and PI3K/Akt signaling inhibitors might provide effective therapy against tumors.