PIK3CA and neoplasm: In brief, PI3K—encoded by the PI3KCA gene—is activated by different receptor tyrosine kinases (such as IGFR, EGFR, VEGFR, FGFR, RET) and in turn activates AKT which leads to inhibition of TSC1/2 and consequently to disinhibition/activation of mTORC1/p70S6K, phosphorylation of 4EBP1, activation of eIF-4E, cell proliferation and tumor growth (analogous to RAS/RAF/MEK/ERK signaling).