Tumors induced with hamster kidney cells transformed by the adeno 2-, adeno 3-, adeno 7-, and adeno 12-SV40 hybrid viruses, and by adenovirus type 12, were examined histologically. The tumors induced with adeno 2-, adeno 3-, and adeno 7-SV40-transformed cells were similar to tumors induced with SV40-transformed hamster kidney cells but contained cells intermediate in morphology between SV40 and adenovirus tumor cells and occasionally contained nests of adenovirus-like cells. Cells transformed by the adeno 12-SV40 hybrid and by adenovirus type 12 gave rise to morphologically similar tumors.
The results suggest that both viral genomes are operative in hybrid-transformed cells but that one genome is apparently responsible for the predominant morphology of the tumor. Evidence that the morphology of a single transformed target cell is determined by the transforming genome was discussed.