Phosphorylation at tyrosine 317 and 508 are crucial for PIK3CA/p110[alpha] to promote CRC tumorigenesis

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 p110[alpha] of PI3K complex, is one of the most frequently mutated oncogenes in human cancers. However, phosphorylation sites of PIK3CA/p110[alpha] and their underlying mechanism in tumorigenesis are largely unknown. Tyrosine phosphorylation sites of PIK3CA/p110[alpha] 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/p110[alpha] tyrosine phosphorylation. In vitro kinase assay is applied to identify the kinase of PIK3CA/p110[alpha] tyrosine phosphorylation. Tyrosine phosphorylation of PIK3CA/p110[alpha] is stimulated by growth factors such as EGF, HGF and PDGF. Two tyrosine residues, Y317 and Y508, are identified on PIK3CA/p110[alpha]. Either Y317 or Y508 phosphorylation is essential for tumorigenesis of CRC. Mutation at Y317 of p110[alpha] reduces the proliferation, migration, and invasion of cancer cells through Src-MLC2 pathway, while mutation at Y508 of p110[alpha] impairs AKT signaling. Moreover, Src interacts with and phosphorylates p110[alpha]. PIK3CA/p110[alpha] phosphorylation at Y317 and Y508 play important role in tumorigenesis of colorectal cancer through two independent pathways.