Natural cytotoxicity: relationship to tumorigenicity of human cell lines in nude mice.

Abstract

In the microcytotoxicity assay, a stimulatory effect exerted by nonsensitized spleen cells derived from nude mice was observed on the growth of tumorigeneic human tumor cells. In contrast, the growth of non-tumor-producing cell lines (malignant and nonmalignant) was inhibited by identical effector cells. Two out of four non-tumor-producing cell lines were of malignant origin. This lack of tumorigenicity, despite a derivation from tumor tissue, might be due to a selection of stromal cells during cultivation or might reflect a variation in the sensitivity to natural cytotoxicity independent of malignancy vs nonmalignancy. Consequently, lack of tumorigenicity does not exclude the possibility that the cells are malignant.