mTORC1 functions as a downstream effector for many frequently mutated oncogenic pathways including the PI3K/AKT and Ras/RAF/MEK/ERK (MAPK) pathways, and mTOR signaling is hyperactive in a range of 40–90% in different tumor entities [158], which makes mTOR an attractive target for cancer therapy. The gene discussed is PIK3CA; the disease is cancer.