Implications of endogenous tumor cell surface lectins as mediators of cellular interactions and lung colonization.

A monoclonal antibody (mAb) designated 5D7 that is directed against endogenous, galactoside-specific lectin and binds to the surface of various tumor cells was used to examine the involvement of cell surface lectin molecules in cellular interactions in vitro and in vivo. The mAb 5D7 was found to inhibit asialofetuin-induced homotypic aggregation of B16 melanoma and UV-2237 fibrosarcoma cell variants by up to 80%. The rate at which these cells, as well as the virally transformed fibroblasts (SVPy-3T3), adhere to tissue culture dishes was reduced in the presence of mAb 5D7 to less than 50% of the control. The anti-lectin mAb had no effect on the adhesion rate of untransformed 3T3 fibroblasts. Treatment of B16 and UV-2237 cells with mAb 5D7 in vitro before their injection into the tail vein of syngeneic mice resulted in a decrease of up to 90% in the appearance of tumor lung colonies. These findings imply that tumor cell surface lectins might play a role in mediation of cell-to-cell and cell-to-substratum adhesion in vitro as well as in similar interactions in vivo that are relevant for metastasis.