Protein synthesis and tumorigenicity of the cytoplasmic hybrid between rat yolk sac tumor and mouse fibroblastic cell line.

Cytoplasmic hybrid (cybrid) cell lines were formed by fusing whole cells of rat yolk sac tumor cell line (EST-II) with cytoplasts of mouse fibroblastic cell line (B-82cap), a variant of mouse L cell line that is deficient in thymidine kinase (TK-) and resistant to chloramphenicol (capr). The cybrid cell line with the nucleus of EST-II and cytoplasma of B-82cap was successfully obtained using double selection with HAT and chloramphenicol-containing medium. The cybrid's ability to synthesize proteins such as albumin, alpha-fetoprotein, gamma-EST, and gamma-GTP was found to be approximately one-fourth that of the nuclear donor, EST-II, at a early time of growth in culture, but this was followed by a gradual increase during the period of observation. The nude mice undergoing subcutaneous transplantation of 1 X 10(6) cells of EST-II and cybrid were killed by the tumor growth, with the survival time being 56 +/- 11 and 105 +/- 25 days, respectively. The histologic findings of cybrid tumor closely resembled those of the nuclear donor, EST-II. These facts suggest that factors from both the nucleus and cytoplasma will be able to affect the gene expression of the cybrid cell line.