PIK3CA是原癌基因，编码蛋白是磷脂酰肌醇-3-激酶（PI3K）的催化亚基p110α，磷脂酰肌醇-3-激酶（PI3K）由调节亚基（p85α）和催化亚基（p110α）组成。多种受体酪氨酸激酶（包括EGFR，ERBB2（HER2），RET，MET和VEGFR等）将细胞外信号转化为细胞内信号，并通过支架蛋白如IRS1或通过激活RAS将PI3K募集至质膜。在此刺激下，PI3K-110α将其脂质底物PIP2转化为PIP3，激活几个信号级联反应，包括AKT-mTOR通路。一旦被激活，AKT-mTOR下游信号传导促进细胞存活，增殖，生长和运动。PIK3CA是癌症中最常见的突变基因之一，在多种癌症中检测到其激活突变，包括乳腺癌，子宫内膜癌和宫颈癌等。

PIK3CA, the catalytic subunit of PI3-kinase, is frequently mutated in a diverse range of cancers, including breast, endometrial and cervical cancers. Phosphatidylinositol-3-kinase (PI3K) is comprised of a regulatory subunit (p85α) as well as a catalytic subunit (p110α) and it is the catalytic subunit that is encoded by the PIK3CA gene. PIK3CA is among the most commonly mutated genes in cancer and aberrant activation of PI3K is a transforming event. Multiple receptor tyrosine kinases, including EGFR, ERBB2 (HER2), RET, MET, and VEGFR, among others, convert extracellular cues into intracellular signals and recruit PI3K to the plasma membrane via scaffold proteins such as IRS1 or by activating RAS. Upon stimulation, PI3K-110α converts its lipid substrate PIP2 (phosphatidylinositol - 4, 5 - bisphosphate) to PIP3 (phosphatidylinositol - 3, 4, 5 - bisphosphate), which activates several signaling cascades, including the well-characterized AKT-mTOR pathway. Once activated, AKT-mTOR downstream signaling promotes cell survival, proliferation, growth and motility. Adding to this complexity, exposure to some PI3K/mTOR pathway targeted drugs relieves cancer cells of self-regulatory properties inherent in the PI3K-AKT-mTOR pathway thereby promoting tumor resistance to these agents.

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