Phosphorylation at tyrosine 317 and 508 are crucial for PIK3CA/p110a to promote CRC tumorigenesis

Background PI3K/AKT signaling pathway plays important role in tumorigenesis of human cancer. Protein phosphorylation is crucial for signaling transduction of this pathway. PIK3CA, encoding the catalytic subunit p110a of PI3K complex, is one of the most frequently mutated oncogenes in human cancers. However, phosphorylation sites of PIK3CA/p110a and their underlying mechanism in tumorigenesis are largely unknown.Methods Tyrosine phosphorylation sites of PIK3CA/p110a are identified with Mass-Spectrum. Crispr/CAS9 strategy is applied to generate Y317F and Y508F mutant knock-in cell clones. The growth and metastasis abilities of cells are evaluated in vitro and in vivo. Phospho-proteomics analysis and Western blots are used to demonstrate downstream signaling pathways of PIK3CA/p110a tyrosine phosphorylation. In vitro kinase assay is applied to identify the kinase of PIK3CA/p110a tyrosine phosphorylation.Results Tyrosine phosphorylation of PIK3CA/p110a is stimulated by growth factors such as EGF, HGF and PDGF. Two tyrosine residues, Y317 and Y508, are identified on PIK3CA/p110a. Either Y317 or Y508 phosphorylation is essential for tumorigenesis of CRC. Mutation at Y317 of p110a reduces the proliferation, migration, and invasion of cancer cells through Src-MLC2 pathway, while mutation at Y508 of p110a impairs AKT signaling. Moreover, Src interacts with and phosphorylates p110a.Conclusions PIK3CA/p110a phosphorylation at Y317 and Y508 play important role in tumorigenesis of colorectal cancer through two independent pathways.