STIMULATION OF THYMIDINE UPTAKE AND CELL-PROLIFERATION IN MOUSE EMBRYO FIBROBLASTS BY CONDITIONED MEDIUM FROM MAMMARY CELLS IN CULTURE

  • 1 January 1976
    • journal article
    • research article
    • Vol. 36  (12) , 4543-4551
Abstract
Undialyzed conditioned medium from several cell culture sources did not stimulate thymidine incorporation or cell overgrowth in quiescent, density-inhibited mouse embryo fibroblasts. Dialyzed conditioned medium (DCM) from clonal mouse mammary cell lines MCG-V14, MCG-T14, MCG-T10; HeLa [human cervical cancer] cells; primary mouse adenocarcinoma cells and BALB/c normal mouse mammary epithelial cells promoted growth in quiescent fibroblasts. The amount of growth promoting activity produced per cell varied from 24% (HeLa) to 213% (MCG-V14) of the activity produced by primary tumor cells. The production of growth promoting activity was not unique to tumor derived cells or cells of high tumorigenicity. The amount of growth promoting activity produced per cell in active cultures was not correlated with any of the following: tumorigenicity, growth rate, cell density achieved at saturation, cell type or species of cell origin. Transformed and nontransformed cells of diverse origin, cell type and tumorigenicity can produce growth factors in culture. The growth promoting potential of the active media from primary tumor cultures accumulated with time of contact with cells and was too great to be accounted for entirely by the removal of low molecular weight inhibitors by dialysis. The results are consistent with the hypothesis that conditioned medium from active cultures contained dialyzable, growth promoting activity. Different cell lines exhibited differential sensitivity to tumor cell DCM and fetal bovine serum. Quiescent fibroblasts were stimulated by primary tumor cell DCM in the presence of saturating concentrations of fetal bovine serum. These observations support the notion that the active growth promoting principle in primary tumor cell DCM may not be a serum factor(s).

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