Effects of H-ras and v-sis overexpression on N-acetylglucosaminyltransferase V and metastasis-related phenotypes in human hepatocarcinoma cells

Oncogenes and N-acetylglucosaminyltransferase (GnT-V) are both commonly ass ociated with carcinogenesis and metastasis, in order to elucidate the relat ionship between oncogenes and GnT-V, two oncogenes, H-ras and v-sis/PDGF (p latelet-derived growth factor), were selected, and the effects of their ove rexpression on GnT-V in 7721 human hepatocarcinoma cells were investigated. The results showed that the over expression of H-ras or v-sis/PDGF-B up-re gulated the activities of GnT-V to various degrees in the transfected cells , In H-ras- and PDGF-B-overexpressing cells, the activity of GnT-V was up-r egulated to double the normal value. The transient expression of v-sis, whi ch produces a protein almost identical to PDGF-B, stimulated the GnT-V acti vity by 80.3%, and the effect was more pronounced (increased by 182.5%) in 7721 cells with stable expression of v-sis. The stimulating effect was enti rely abolished by treatment with PDGF-B antibody. The staining of asparagin e-linked glycans (N-glycans) in the H-ras- and v-sis-overexpressing 7721 ce lls was intensified when horseradish peroxidase-labeled leucoagglutinating phytohemogglutinin was used as a probe, indicating the increased content of beta 1,6GlcNAc branching on the N-glycans. The enhancement of GnT-V mRNA e xpression was also observed in H-ras- and v-sis- overexpressing cells, indi cating that H-ras and v-sis regulated GnT-V via the transcription of GnT-V mRNA and the synthesis of GnT-V protein. The cells in metastasis-related ph enotypes, including acceleration of cell growth, decline of cell adhesion t o fibronectin, and an increase of cell adhesion to laminin, as well as incr eased invasiveness through Matrigel. These results indicated that thee alte ration of cell adhesion and invasion induced by oncogenes is closely relate d to the up-regulation of GnT-V activity and its product, beta 1,6GlcNAc br anching in N-glycans on the cell surface.