MTOR and cancer: Conversely, PIK3IP1 knockdown significantly restored activation of the PI3K/Akt/mTOR pathway and suppressed cell death induced by inhibition of MEK and ERK (Fig. 5e), further indicating positive cross-talk between the Ras and PI3K pathways via the Ras˧PIK3IP1˧PI3K signaling network for cancer cell proliferation and survival (Fig. 5f).