Cell-Surface Glycoproteins of Normal and Malignant Rat Liver Cells

Malignant transformation is accompanied by cell-surface alterations which are directly involved in many of the aberrant properties displayed by the transformed cell ( 1 ). Lectins have been used extensively as probes to study these membrane alterations because, in several in vitro cell systems, non-transformed cells are not agglutinated at lectin concentrations sufficient to agglutinate transformed or protease-treated non-transformed cells ( 2 ). Despite extensive investigation, the molecular mechanism(s) responsible for lectin-induced cytoagglutination is (are) still not clear, although several hypotheses have been proposed: exposure of cryptic lectin-binding sites ( 3, 4 ); clustering and lateral mobility of lectin receptors ( 5 - 8 ); reduction of surface charge repulsive forces ( 2 ); increased membrane deformabi1ity ( 2 ); increased density of lectin-binding sites due to altered surface morphology ( 9 ); and structural alterations of lectin receptors ( 10, 11 ). Two such lectins, concanavalin A (Con A) and wheat germ agglutinin (WGA), have been used to probe the membrane structure of normal and malignant rat liver cells.