Differences in glycosylation state of fibronectin from two rat colon carcinoma cell lines in relation to tumoral progressiveness.

We have investigated the biosynthesis and carbohydrate structure of fibronectin secreted by two rat colon carcinoma cell lines. The cell line Prob yields progressive tumors after s.c. injection in syngeneic BD IX rats while tumors developed by Regb cells disappear after 20 days. No difference was observed in the fibronectin biosynthesis from both cell lines; however, the glycosylation degree was higher in Regb than in Prob cells indicating probable differences in the posttransductional process. The analysis of the glycosylation nature shows that fibronectin doesn't bear O-linked carbohydrate chains. The fibronectin of progressive Prob cells is more sialylated than that of the regressive Regb ones. In addition, the tri- and tetraantennary glycans are more important in Prob, while the fucosylated triantennary glycans are three times higher in Regb cells. These differences in the glycosylation state of the fibronectins could explain their differential susceptibility to the proteases treatment. In fact, the low glycosylated fibronectin from the progressive Prob cells was more rapidly degraded by several proteases than that of regressive Regb cells. The identification of the specific sites of proteolytic cleavage by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the cell attachment domain as well as the collagen binding domain of Regb cell fibronectin are particularly protected against proteolytic degradation.