CHARACTERISTICS OF AN INFINITE LIFE-SPAN DIPLOID HUMAN FIBROBLAST CELL STRAIN AND A NEAR-DIPLOID STRAIN ARISING FROM A CLONE OF CELLS EXPRESSING A TRANSFECTED V-MYC ONCOGENE

Diploid human fibroblasts were transfected with a plasmid carrying av-myconcogene linked to theneo gene or with a vector control carrying aneo gene. Drug-resistant clones were isolated and subcultured as needed. All populations went into crisis and eventually senesced. But while they were senescing, viable-appearing clones were noted among the progeny of a transfected population that expressed thev-myc oncogene. After several months, these cells began replicating more rapidly. Karyotype analysis indicated that they were clonally derived since all of them had 45 chromosomes, including 2 marker chromosomes. This cell strain was designated MSU-1.1. Similar analysis showed that cells from an earlier passage were diploid. These cells were designated MSU-1.0. Both strains have undergone more than 200 population doublings since their siblings senesced, without any change in chromosome complement. Both strains express thev-mycprotein and have the same integration site for the transfectedv-mycandneo genes. The MSU-1.0 cells cannot grow without exogenously added growth factors. The MSU-1.1 cells grow moderately well under the same conditions and grow to a higher saturation density than MSU-1.0 cells. Since the chance of human cells acquiring an infinite life span in culture is very rare, the data suggest that MSU-1.1 cells are derived from MSU-1.0 cells. The expression ofv-myc is probably required for acquisition of an infinite life span, since this phenotype did not develop in populations not expressing this oncogene. However, expression ofv-myc is clearly not sufficient, since all of the progeny of the clone that gave rise to the MSU-1.0 cells expressed this oncogene, but the vast majority of them senesced. © 1991 Academic Press, Inc. All rights of reproduction in any form reserved.