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.     

Expression of various viral and cellular enhancer-promoters during differentiation of human embryonal carcinoma cells

Alterations in the pattern of gene expression were studied during differentiation of the human embryonal carcinoma (EC) cell line NEC14. NEC14 cells can be induced to differentiate by the addition of 10(-2) M N,N'-hexamethylene-bis-acetamide (HMBA). The efficiency of DNA transfection of undifferentiated and differentiated NEC14 cells was compared by measuring the activities of endogenous and exogenously introduced promoters for the beta-actin gene and heat shock protein 70 gene. The results indicated that the efficiency was not significantly different in cells of these two states. Under the conditions used, all the viral enhancer-promoters tested showed very little or no activity in undifferentiated cells, but activities of SV40, BKV, adenovirus and RSV enhancers were greatly increased after differentiation. Activities of these viral enhancers in differentiated cells were completely repressed by cotransfection with the adenovirus E1A gene. An E1A-inducible promoter of the adenovirus E2 gene showed stronger activity in differentiated than in undifferentiated cells, and was not activated efficiently by cotransfection with the E1A gene in either undifferentiated or differentiated cells. These results indicate that factor(s) regulating activities of various enhancer-promoters in NEC14 cells is or are different from E1A-like factor(s) present in mouse EC F9 cells.