PIK3CA codon(s) 542, 545, 1047 any
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.
DeRoock W, Claes B, Bernasconi D, et al. Effects of KRAS, BRAF, NRAS, and PIK3CA mutations of the efficacy of cetuximab plus chemotherapy in chemotherapy-refractory metastatic colorectal cancer: A retrospective consortium analysis. Lancet Oncol. 2010;11:753-762.
Prenan H, DeSchutter J, Jacobs B, et al. PIK3CA mutations are not a major determinant of resistance to the epidermal growth factor inhibitor cetuximab in metastatic colorectal cancer. Clin Cancer Res.2009;15:3184-3188
Stephens PJ et al. The landscape of cancer genes and mutational processes in breast cancer. 2012 Nature;486(7403):400-4
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