Identification of tyrosine phosphoproteins in signaling pathway triggered TGF-a by using functional proteomics technology.

Although several groups had conducted proteomics of nasopharyngeal carcinoma (NPC), little study was involved in phosphoproteomics, oncogenic signaling, and cancer research about NPC. Analysis of phosphotyrosine proteins from transforming growth factor alpha (TGF-a) triggered phosphotyrosine proteome permitted the identification of novel downstream substrates of the epidermal growth factor receptor (EGFR). Using functional proteomics technology based on 2-DE, 2-D western blotting, and mass spectrometry, we identified and quantified the tyrosine phosphorylation levels of 16 proteins between control and TGF-a-treated CNE2 human NPC cells. Among these proteins, tyrosine phosphorylated levels of ten proteins were increased, and those of six proteins were decreased in TGF-a-treated CNE2 cells compared with control. In addition, among these identified proteins, ANXA3, KRT8, and KRT18 were validated to be novel tyrosine-phosphorylation targets of EGFR signaling by IP-western blotting and part of a complex EGFR phosphotyrosine signaling network. These novel findings will provide new insights into the complex EGFR phosphorylation signaling and may have implications in molecular cancer therapy of NPC.