Stimulation of colony formation of various human carcinoma cell lines by rhGM-CSF and rhIL-3.

We studied the effects human recombinant granulocyte-macrophage colony-stimulating factor and human recombinant interleukin-3 on the colony formation of three human solid tumor cell lines. Using a modified double-layer soft agar clonogenic assay rhGM-CSF enhanced colony formation of all cell lines tested in a dose dependent manner (up to twofold for the breast cancer cell line BT-20, up to 163% of the control for the hypernephroma cell line C 94 and up to 147% for the non-small cell lung cancer cell line CCL 185 at a concentration of 100 ng/ml). RhIL-3 stimulated colony formation of the cell lines C 94 and BT-20, whereas on the cell line CCL 185 rhIL-3 had no effect even at the highest dose level tested (100 ng/ml). Combinations of growth factors showed subadditive stimulation on two cell lines tested (BT-20, C 94). These data indicate that haematopoietic growth factors exert a growth promoting activity on certain solid tumor cells in vitro at physiological concentrations. Therefore our results suggest that the application of these factors in immuno- and myelosuppressed cancer patients after high dose chemotherapy should be seen in light of a possible co-stimulation of the malignant cells.