Effect of enzymatic removal of cell surface sialic acid on the adherence of Walker 256 tumor cells to mesothelial membrane.

When cells of the Walker 256 rat tumor were incu bated in vitro with neuraminidase, free sialic acid accu mulated in the medium without detectable loss of tumor cell viability, as indicated by the unchanged survival of rats given i.p. injections of 50, 100, or 250 cells. For de termination of the effect of neuraminidase treatment of the tumor cells on their adherence to living mesothelium, 1 testis of each of a group of rats was bathed, under standard conditions in vitro, in a suspension of either un treated or neuraminidase-pretreated tumor cells, at each of several cell concentrations. The testis was washed and, with its circulation still intact, placed in the peritoneal cavity of the same animal, and the incision was closed. In rats exposed to 100 to 4,000 cells/ml, host survival was longer when the cells had been pretreated with neuraminidase. Similarly, after the direct i.p. injection of 500 to 10,000 cells, host survival was longer after neura minidase treatment of the tumor cells. The effect was shown to be due to reduced attachment of the treated tumor cells and did not involve any increase in tumor cell antigenicity. The results indicate that the adhesion of dissociated Walker 256 tumor cells to mesothelial membrane depends in part on the presence of sialic acid at the tumor cell surface.