Growth factor requirements of Chinese hamster lung fibroblasts in serum free media: high mitogenic action of thrombin.

We have defined a chemical medium to grow an anchorage and highly serum-dependent Chinese Hamster Lung fibroblast cell line (CCl 39) in the absence of serum. This serum-free medium referred to as DM4, contains Transferrin (5 microgram/ml), Insulin (10 microgram/ml), Epidermal Growth Factor (10 ng/ml) and Thrombin (0.05 U/ml). Thrombin appeared to be a very potent mitogen for Chinese Hamster Lung cells. DM4 allows exponential growth of CCl 39 cells plated in serum-coated dishes without any lag and with a generation time of 15 hours. Continuous subculturing and clonal growth can be obtained by passaging the cells with Ca++, Mg++ free phosphate-buffered saline in fibronectin coated dishes. The entire definition of growth factor requirements for this anchorage dependent cell line is of great value to approach the mechanisms of escape of growth control by these cells.