Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) gain-of-function mutants (PI3Kα mutants)

Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha (PI3Kα) is a lipid kinase that converts PIP2 to PIP3, initiating the PI3K/AKT/mTOR signaling cascade (UniProt P42336). Gain-of-function mutations in the PIK3CA gene are among the most common drivers in human cancers, including breast and colorectal malignancies (Samuels et al., Science, 2004). These mutations are predominantly clustered in the helical domain (e.g., E542K, E545K) and the kinase domain (e.g., H1047R), leading to constitutive pathway activation and promoting cell proliferation and survival (Maira et al., Mol. Cancer Ther., 2012). Helical domain mutations typically disrupt the inhibitory contact with the p85 regulatory subunit, whereas kinase domain mutations increase the enzyme's affinity for the plasma membrane (Zhao & Vogt, PNAS, 2008). Targeted therapies such as alpelisib (Piqray) specifically inhibit the p110α subunit and are FDA-approved for PIK3CA-mutated, hormone receptor-positive breast cancer (FDA, 2019). However, because PI3Kα is essential for insulin signaling, these drugs often cause hyperglycemia as a primary side effect, necessitating careful patient management (Hopkins et al., Nature, 2018). Current research is focused on developing mutant-selective inhibitors to improve the therapeutic index and reduce off-target metabolic effects.

Other names

PIK3CA mutantsp110α mutantsPhosphoinositide 3-kinase alpha mutantsHelical domain PIK3CA mutantsKinase domain PIK3CA mutantsPIK3CA E542KPIK3CA E545KPIK3CA H1047R

Small-molecule inhibition of the p110α catalytic subunit by competing with ATP binding, thereby preventing the phosphorylation of PIP2 to PIP3 and subsequent downstream AKT signaling (Fritsch et al., Mol. Cancer Ther., 2014).