Tumorigenicity and its suppression in cybrids of mouse and Chinese hamster cell lines

The effect of cytoplasm upon the expression of tumorigenicity was examined with a pair of mouse and a pair of Chinese hamster cell lines, in intraspecies cybrids formed by reciprocal fusions between either tumorigenic or nontumorigenic cells and cytoplasms derived from them. With the mouse cells, 3T3 and the simian virus 40-transformed line SVT2, the cybrid clones were tumorigenic when SVT2 cells were fused with 3T3 cytoplasts, but not in the reciprocal fusion. With the hamster cells, CHEF/18 and the spontaneous transformant CHEF/16, however, tumorigenicity was partially suppressed in cybrid clones formed by fusion of tumorigenic CHEF/16 cells with CHEF/18 cytoplasts; cybrids were nontumorigenic in the reciprocal fusion. Thus, cybrid analysis has shown that tumorigenicity is not cytoplasmically transmitted in these two cell pairs, but suppression of tumor-forming ability may be cytoplasmically transmitted in the hamster cybrids.