Formation and fate of heterokaryons involving embryonal carcinoma cells.

We have shown that murine embryonal carcinoma (EC) cells will readily fuse to non-EC cells following treatment with polyethylene glycol (PEG). Heterokaryons were detected by autoradiography and by the induction of premature chromosome condensation (PCC). Those heterokaryons formed between EC cells and certain of the non-EC cell types did not proliferate to form viable hybrids. For example, hybrids were not recovered from EC/HeLa heterokaryons in spite of the fact that both EC/3T3 and HeLa/3T3 heterokaryons gave rise to hybrids at high frequency. No hybrids were recovered from fusion mixtures involving Chinese hamster (CHO) cells and EC; however, if the differentiated progeny of the EC cells were used, hybrids were recovered. These results suggest that both developmental and phylogenetic differences between parental cells may contribute to the ability of heterokaryons to proliferate indefinitely.