MTOR and cancer: In PDAC, oncogenic KRAS drives the transcriptional expression of PI3K (phosphatidylinositol 3-kinase)/AKT (alpha serine/threonine-protein kinase)/mTOR (mammalian target of rapamycin) and RAF (rapidly accelerated fibrosarcoma)/MEK/MAPK (mitogen-activated protein kinase), which have been shown to regulate cancer cell proliferation and survival as well as resistance to chemotherapy [20–24].