PIK3CA mutations activate the PI3K-PTEN-AKT pathway which is downstream from both the EGFR and the RAS-RAF-MAPK pathways.The somatic mutations found thus far in PIK3CA are oncogenic, and the majority of them are clustered within exon 9 and 20 (helical and kinase domains), with 80% of the identified mutations found within three hotspot: E542K, E545K, and H1047R. PIK3CA mutations are often found in hormone receptor positive breast cancer and have been associated with resistance to anti-EGFR therapy in some studies but not in others.

PIK3CA is the the p110 catalytic subunit-alpha of phosphatidylinositol 3 kinase. Activating mutations of PIK3CA occur in various types. PIK3CA mutations have been reported in approximately 8% of cases of diffuse large B cell lymphoma and are typically mutually exclusive of PTEN loss in that tumor type. PIK3CA mutations are very rare in chronic lymphocytic leukemia and believed to be absent in acute myeloid leukemia and myelodysplastic syndromes. PIK3CA mutations are potentially targetable in some settings and pathway inhibitors are currently under investigation .

The catalytic subunit (p110a) of phosphatidylinositol-3-kinase (PI3K) is encoded by the PIK3CA gene and acts to activate several signaling cascades, including the well-characterized AKT-mTOR pathway that promotes cell survival, proliferation, growth and motility. PIK3CA is among the most commonly mutated genes in cancer and aberrant activation of PI3K is a transforming event. Somatic mutations in PIK3CA have been found in 1--3% of NSCLC and genetic alteration in PIK3CA have been identified in 7% of lung adenocarcinomas. These mutations typically occur within specific hotspot regions. PIK3CA mutations activate the PI3K-PTEN-AKT pathway which is downstream from both the EGFR and the RAS-RAF-MAPK pathways. The somatic mutations found thus far in PIK3CA are oncogenic, and the majority of them are clustered within exon 9 and 20 (helical and kinase domains), with three hotspots (E542K, E545K, and H1047R/L). PIK3CA mutations have been reported in 8-21% and 20-33% of head/neck and anal squamous cell carcinoma, respectively. PIK3CA mutations, especially ones involving the helical domain, in these types of squamous cell carcinoma are highly associated with HPV. The predictive and prognostic significance of PIK3CA mutations in squamous cell carcinoma is unclear and needs further elucidation. Clinical trials targeting PI3K/Akt/mTor pathway inhibitors are available for patients with PIK3CA mutated tumors.

PIK3CA mutations activate the PI3K-PTEN-AKT pathway which is downstream from both the EGFR and the RAS-RAF-MAPK pathways. The somatic mutations found thus far in PIK3CA are oncogenic, and the majority of them are clustered within exon 9 and 20 (helical and kinase domains), with three hotspots (E542K, E545K, and H1047R/L). PIK3CA mutations have been reported in various tumor types including up to 36% and 11% of hepatocellular carcinoma and gastric cancer, respectively. They are detected less frequently in cholangiocarcinoma (~6%) and pancreatic adenocarcinoma (~4%). The predictive and prognostic significance of PIK3CA mutations is unclear and needs further elucidation. Clinical trials targeting PI3K/Akt/mTor pathway inhibitors are available for patients with PIK3CA mutated tumors.

Somatic mutations in PIK3CA have been found in 10-30% of colorectal cancers. KRAS, NRAS, BRAF and PIK3CA and non-functional PTEN predict resistance to anti-EGFR therapies in metastatic colorectal cancer. According to some reports, co-occurrence of both exon 9 and exon 20 PIK3CA mutations, when present, may be associated with a poor prognosis. Recent 'molecular pathological epidemiology' (MPE) research has shown that aspirin use may be associated with better prognosis and clinical outcome in PIK3CA-mutated colorectal carcinoma, suggesting somatic PIK3CA mutation may be a molecular biomarker that predicts response to aspirin therapy. PIK3CA may also be a target of directed therapy in some clinical settings.

PIK3CA mutations activate the PI3K-PTEN-AKT pathway which is downstream from both the EGFR and the RAS-RAF-MAPK pathways. The somatic mutations found thus far in PIK3CA are oncogenic, and the majority of them are clustered within exons 9 and 20 (helical and kinase domains), with three hotspots (E542K, E545K, and H1047R/L). PIK3CA mutations have been reported in various tumor types including up to 36% and 11% of hepatocellular carcinoma and gastric cancer, respectively. They are detected less frequently in cholangiocarcinoma (~6%) and pancreatic adenocarcinoma (~4%). The predictive and prognostic significance of PIK3CA mutations is unclear and needs further elucidation. Clinical trials targeting PI3K/Akt/mTor pathway inhibitors are available for patients with PIK3CA mutated tumors.