Lectin-like activities associated with human and murine neoplastic cells

Single-cell suspensions of several tumor cell lines, including five human melanomas (A375, SH4, Hs294, Hs852, and Hs939), a human cervical adenocarcinoma (HeLa-S3), a murine melanoma (B16-F1), and a murine fibrosarcoma (UV-2237P), undergo extensive homotypic aggregation in the presence of the glycoproteins fetuin and its desialated derivative, asialofetuin. This phenomenon was observed even at very low glycoprotein concentrations (less than 10 micrograms/ml). Fluorescent derivatives of fetuin and asialofetuin bind to the surface B16-F1 melanoma cells; this binding can be inhibited by lactose (0.1 M). Since the above results suggested the presence of a carbohydrate-binding component(s) on the tumor cells, we tested the possibility that the cells contain endogenous lectin(s). Extracts prepared from the neoplastic cell lines used in this study exhibited a potent capacity to agglutinate trypsin-treated, glutaraldehyde-fixed rabbit erythrocytes. This activity was abolished by treating the extracts with trypsin and could be inhibited by millimolar concentrations of lactose, whereas D-galactose, D-galactosamine, and N-acetyl-D-galactosamine were much less potent inhibitors. D-Mannose, L-fucose, and N-acetyl-D-glucosamine failed to inhibit hemagglutination at 0.2 M. These results demonstrate the presence of a galactoside-specific lectin in the tumor cells. The implications of the existence of a carbohydrate-binding protein(s) on the surface of malignant cells on their in vivo behavior, especially as it may relate to metastatic spread, are discussed.