Longevity of Strains From Individual Foci of Human Amnion Cells Transformed by Simian Virus 40

Summary

Sixteen cell strains, derived from isolated individual foci (“focus srrains”) in cultures of primary human amnion cells transformed by simian virus 40 (SV40), varied considerably in longevity (170–268 days after infection) and in number of cell divisions (16–45) before “crisis.” The comparison with strains composed of pools of cells derived from these foci (“pool strains”), and with strains derived from whole cultures of transformed primary amnion cells (“whole culture strains”), supported the following conclusion: The longevity of a cell strain derived from a culture containing several foci is expressed by the strain component with the highest longevity potentials. This observation provides an explanation for the increased longevity observed for strains of SV40-transformed amnion cells initially infected with a high multiplicity of virus and under favorable cultural conditions. Some focus strains consisted of cells of fibroblast-like morphology. However, the cells in most of these strains, in the pool strains, and in all whole culture strains were epithelial-like. Four focus strains and three whole culture strains were recovered as postcrisis cell lines. It is proposed that many changes during the precrisis period after SV40 transformation reflect variations in the relative representation of the components derived from individual foci. This representation, at any time, appears to be determined by the different times at which the individual components cease to divide.