title: Tumor promoters retard the loss of a transient subpopulation of cells in low passage Syrian hamster cell cultures.
abstract: Early passage normal diploid Syrian hamster (SH) fetal cell cultures contain a transient subpopulation of contact-insensitive (CS-) cells which lack density-dependent inhibition of cell division. The size of this CS- subpopulation decreases during in vitro passage by conversion of the CS- cells to contact-sensitive (CS+) cells. Approximately 10-15 population doublings after the frequency of the CS- cells has declined to below 0.001%, mass cultures cease proliferating and exhibit cellular senescence. Cultures with higher initial numbers of CS- cells exhibit longer in vitro proliferative life spans than cultures with smaller initial numbers of CS- cells. Active tumor promoting phorbol esters (12-O-tetra-decanoyl-phorbol-13-acetate [TPA] and phorbol-12,13-didecanoate [PDD]) retard the decline in the proportion of CS- cells during in vitro passage, while the inactive tumor promoting phorbol ester, 4 alpha-phorbol-12,13-didecanoate (4 alpha PDD) has no effect on the rate of loss of the CS- cells. In addition, continuous treatment from secondary culture with TPA or PDD extends by approximately twofold the in vitro proliferative life span of SH fetal cell cultures. Treatment must, however, begin at passage 1 or 2 when the CS- cells are still present. After the proportion of the CS- cells has decreased to less than 0.001% as in passage 6 cultures, promoters have no effect on the life span of the culture. This finding that exposure to promoters results in both a prolonged maintenance of the CS- cellular subpopulation, as well as an extension of in vitro proliferative life span, suggests that the conversion of CS- cells to CS+ cells is involved in the mechanism of in vitro senescence.
authors.affiliation: Division of Biophysics, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, MD 21205.
authors.forename: H
authors.initials: H
authors.lastname: Ueo
authors.forename: S
authors.initials: S
authors.lastname: Nakano
authors.forename: P O
authors.initials: PO
authors.lastname: Ts'o
authors.forename: S A
authors.initials: SA
authors.lastname: Bruce
mesh_terms: D000818:Animals; D002273:Carcinogens / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects*; D002478:Cells, Cultured / Q000166:cytology / Q000187:drug effects; D003260:Contact Inhibition / Q000187:drug effects; D006224:Cricetinae; D008647:Mesocricetus; D010703:Phorbol Esters / Q000494:pharmacology; D010969:Plastics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D002273:Carcinogens; D010703:Phorbol Esters; D010969:Plastics; C008876:phorbol-12,13-didecanoate; D013755:Tetradecanoylphorbol Acetate