Concanavalin A and other lectins in the study of tumor cell surface organization

Cell surface structures of two mouse ascites tumors were studied using lectins. The tumors are sublines of the spontaneous mammary adenocarcinoma TA3 in strain A, differing in two main characteristics. Subline TA3-St grows only in syngeneic mice and has high expression of H-2 antigens. Subline TA3-Ha, in contrast, proliferates in all mouse strains, and has low amounts of exposed H-2 antigens. Concanavalin A (Con A), phytohemagglutinin (PHA) and Helix pomatia anti A hemagglutinin (HP) were used in agglutination tests, in binding experiments with 125I-labelled lectins and also in fluorescence studies with FITC-labelled lectins. Con A and PHA agglutinated the TA3-St cells but not the TA3-Ha cells. However, fluorescein-labelled Con A and PHA were bound to all cells (greater than 90%) of both sublines. Moreover both cell types contained an identical number of Con A receptors. The same result was obtained when the number of PHA receptors on the two sublines was compared. HP agglutinated TA3-Ha cells but not TA3-St cells. However, in this case, the difference in agglutinability between the lines was due to the presence or absence of HP receptors. All TA3-Ha cells contained large numbers of HP receptors. In contrast the majority (greater than 90%) of the TA3-St cells lacked HP receptors. (See article.) Trypsin released the HP receptors from TA3-Ha cells, at the same time making these cells agglutinable by both Con A and PHA. We conclude that the Ta3-Ha cells have a trypsin sensitive surface glycoprotein (or glycoproteins) detectable by HP, which is absent on most TA3-St cells. It is possible that this glycoprotein interferes with the agglutinability of TA3-Ha cells by Con A and PHA; whether it is also responsible for the low expression of H-2 alloantigen on this cell remains to be seen.