SV40-transformed human diploid cells that remain transformed throughout their limited lifespan

Of ninety-one subcultured foci of SV40-transformed WI-38 human diploid fibroblasts, none yielded cells that grew indefinitely, but all cells in each subculture continued to produce T antigen and to look morphologically transformed throughout their lifespan. These results are consistent with the commitment theory of fibroblast senescence, but predict that a special transformation event is necessary to accout for the rare survivors.