Transfection of the c-erbB2/neu gene upregulates the expression of sialyl Lewis X, α1,3-fucosyltransferase VII, and metastatic potential in a human hepatocarcinoma cell line

Abstract

The pCMV4 plasmid containing the cancer-promoting gene, c-erbB2/neu, was cotransfected into the human hepatocarcinoma cell line 7721 with the pcDNA3 vector, which contains the 'neo' selectable marker. Several clones showing stable expression of c-erbB2/neu were established and characterized by determination of c-erbB2/neu mRNA and its encoded protein p185. Expression of Lewis antigens and α1,3-fucosyltransferases and the biological behavior of 7721 cells after c-erbB2/neu transfection were studied using mock cells transfected with the vectors pCMV4 and pcDNA3 as controls. SLex expression on the surface of mock cells was high, whereas expression of SDLex, Lex and SLea was absent or negligible. This is compatible with the abundant expression of α1,3-fucosyltransferase VII, very low expression of αfucosyltransferase III/VI, and almost absent expression of α1,3-fucosyltransferase IV in the mock cells. After transfection of c-erbB2/neu, expression of SLex and α1,3-fucosyltransferase VII were simultaneously elevated, but that of αfucosyltransferase III/VI was not altered. The expression of both SLex and α1,3-fucosyltransferase VII correlated positively with the expression of c-erbB2/neu in different clones, being highest in clone 13, medium in clone 6, and lowest in clone 7. In addition, the adhesion of 7721 cells to human umbilical vein endothelial cells (HUVECs) or P-selectin, as well as cell migration and invasion, were increased in c-erbB2/neu-transfected cells. These increases also correlated positively with the expression intensities of c-erbB2/neu, SLex and α1,3-fucosyltransferase VII in the different clones, whereas cell adhesion to fibronectin correlated negatively with these variables. mAbs to SLex (KM93) and SDLex (FH6) significantly and slightly, respectively, abolished cell adhesion to HUVECs or P-selectin and cell migration and invasion. mAbs to SDLex and SLea did not suppress cell adhesion to HUVECs nor inhibit cell migration and invasion. Transfection of α1,3-fucosyltransferase VII cDNA into 7721 cells showed similar results to transfection of c-erbB2/neu, and the increased adhesion to HUVECs, cell migration, and invasion were also inhibited significantly by KM93 and slightly by FH6. These results indicate that expression of α1,3-fucosyltransferase VII and its specific product, SLex, and their capacity for cell adhesion, migration and invasion are closely related. Therefore, the c-erbB2/neu gene is proposed to be a metastasis-promoting gene, and its effects are at least partially mediated by the increased expression of α1,3-fucosyltransferase VII and SLex.