Neuraminidase and Cell Viability: Failure to Detect Cytotoxic Effects With Dye-Exclusion Techniques

Summary

The effects of in vitro incubation of line-1 carcinoma cells with Vibrio cholerae neuraminidase (VCN) were studied in vivo and in vitro. At 25-200 U/10⁶ cella/ml, VCN had no effect on the ability of line-1 cells to exclude either eosin or trypan blue; i.e., VCN did not affect viability. When, however, the viability of these same cells was assayed in vitro by either colony formation or ³H-thymidine incorporation, a concentration-dependent reduction in viability was observed. At the highest concentration tested, 200 U/10⁶ cells/ml, 73–84% cytotoxicity was observed. This toxicity of VCN was not related to the prior treatment of the cells with trypsin and could be abolished by heat-inactivation of the VCN before use. After correction of the data for VCN-induced toxicity, VCN-treated cells were as efficient as untreated cells in producing tumors in vivo and gave no evidence of a heightened ability to sensitize the mice to subsequent tumor challenge. We concluded, therefore, that VCN was toxic to line-1 cells, that this toxicity was not detectable by dye-exclusion techniques, and that VCN treatment did not increase the antigenicity of line-1 cells.