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Lysis of Chinese hamster embryo fibroblast mutants by human natural cytotoxic (NK) cells.

The nontransformed, nontumorigenic CHEF/18 Chinese hamster embryo fibroblast line, as well as nontumorigenic CHEF/18 mutants that had become anchorage independent or acquired a reduced serum requirement for growth, and fully transformed, tumorigenic CHEF cell lines were analyzed for their sensitivity to killing in vitro by human natural killer (NK) cells. Nontumorigenic but transformed anchorage-independent and low-serum-requiring mutants remained insensitive to NK-mediated lysis like the parent CHEF/18 line. Only fully tumorigenic CHEF lines were found to be sensitive to NK-mediated lysis, although a few tumorigenic lines were resistant to NK lysis. These results indicate that NK sensitivity is not the result of any cellular changes associated with acquisition of an anchorage-independent or low-serum-requiring phenotype but is the result of some additional change(s) found only in fully tumorigenic CHEF cells. Our studies also show that, whatever the NK target structure is, it is evolutionarily conserved so that human NK cells are able to distinguish between Chinese hamster tumorigenic and nontumorigenic cells.