Identification of target proteins of N-acetylglucosaminyl transferase V in human colon cancer and implications of protein tyrosine phosphatase kappa in enhanced cancer cell migration

To gain a better understanding of the mechanism underlying colon cancer and to search for potential markers of colon cancer prognosis, a comparative proteomic analysis of colon cancer WiDr cells was conducted using 2-DE and lectin blot, followed by identification based on ESI-MS. Through these approaches 14 proteins were identified as candidate target proteins for N-acetylglucosaminyl transferase V (GnT-V) that would be expected to be implicated in the progression of colon cancer. We selected protein tyrosine phosphatase kappa (PTP kappa) as a model protein to validate this approach to the discovery of novel biomarkers in colon cancer. PTP kappa underwent an aberrant glycosylation in GnT-V-overexpressing WiDr cells, and the aberrantly glycosylated PTP kappa was vulnerable to proteolytic cleavage. The enhanced cleavage of PTP kappa in GnT-V-overexpressing cells was responsible for the mitigation of the homophilic binding capacity, resulting in an increase in cancer cell migration.