Interaction of human embryonal carcinoma cells and differentiated derivatives in vitro with simian virus 40, human adenovirus type 7, or PARA

Polyclonal antibodies were used to assay human embryonal carcinoma (EC), differentiating EC, yolk sac carcinoma, and teratoma cells for expression of viral early antigen (T-Ag) after infection with simian virus 40 (SV40). Cells of four EC lines were induced to differentiate by cultivation at low density or by exposure to retinoic acid or dimethyl sulfoxide. After infection with SV40, T-Ag was expressed by 1%, or less, of the cells (presumed to be differentiated derivatives) in only some EC cultures whereas the antigen was synthesized by a significant percentage of the yolk sac carcinoma, teratoma, and differentiating EC cells. Also, viral late proteins were produced by EC cells infected with human adenovirus type 7 (Ad7), and SV40 T-Ag was expressed by EC cells after infection with PARA, which is an Ad7-SV40 hybrid virus containing the SV40 T-Ag sequence controlled by Ad7 late regulatory sequences. Thus, T-Ag is not synthesized by the parental EC cells infected with SV40, but it is expressed in cultures of infected differentiated derivatives. The EC cells produce T-Ag, however, when expression of the viral protein is controlled by the Ad7 regulatory sequences in PARA particles. These results demonstrate that expression of T-Ag after infection with SV40 is an indicator of EC cell differentiation and also raise the possibility that, as in mouse EC cells infected with the virus, the SV40 regulatory sequences controlling T-Ag synthesis are not active in human EC cells.