PI3K/Akt signaling in human cancer can be driven by tyrosine kinase receptors, G-coupled protein receptors, or mutant RAS. PI3K catalyzes the production of the lipid second messenger, phosphatidylinositol (3,4,5) trisphosphate (PIP3) from phosphatidylinositol (4,5) bisphosphate (PIP2). Here, NTRK1 is linked to cancer.