Significance of glycosylation patterns of rat Zajdela ascitic hepatocellular carcinoma: Effect of enzymatic removal of surface sialic acid on humoral response

Abstract

Rat Zajdela ascitic hepatocellular carcinoma (ZAH) is a malignant cell type with some properties in common with rat hepatocytes. The aim of this study was to determine the glycosylation patterns of surface glycoproteins of two cell lines C and D of ZAH by lectin binding for identification and characterization of tumor-specific markers. Plasma membrane proteins from these cells were separated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, and probed using radio-iodinated lectins. We observed a decrease in the binding of concavalin A, and an increase in the binding of wheat germ agglutinin (WGA) to glycoproteins from the tumor cell lines as compared with those from normal liver cells. We showed that the increase in binding of WGA was mainly due to increased sialylation of the surface glycoproteins of the tumor cells. The major sialylated glycoproteins of the tumor cells contained O-linked carbohydrate chains. It was also shown that removal of surface sialic acid by neuraminidase significantly decreased the lethality of the tumor and led to increased survival of tumor-bearing animals. The decreased lethality of the tumor appears to be due to increased antigenicity of the desialylated tumor cells. Taken together, the presence of highly sialylated O-linked glycosylation of gp120 in ZAH tumor cells and its absence in normal liver cells is of significance with respect to the biological properties of this tumor.