Determination of granulocyte/macrophage-colony-stimulating factor secretion by human melanoma cells and its effects on human melanoma cell proliferation.

Recently, granulocyte/macrophage-colony-stimulating factor (GM-CSF) became available for overcoming chemotherapy-induced granulocytopenia. GM-CSF not only has a prominent role in the regulation of proliferation and differentiation of haematopoietic cells but it is also secreted by a variety of solid tumours and is capable of exerting growth-stimulatory effects. To evaluate the safety of GM-CSF administration in the treatment of malignant melanoma, we investigated GM-CSF secretion, GM-CSF receptor expression and the effect of GM-CSF on the proliferation of human melanoma cells in vitro. A panel of eight human melanoma cell lines and two fresh tumour specimen was studied. GM-CSF protein was not detectable in culture supernatants by ELISA without stimulation. Interleukin-1 and tumour necrosis factor alpha induced GM-CSF secretion in all four melanoma cell lines tested. When biotinylated GM-CSF was used, the corresponding receptor was not detectable by immunohistochemical or FACScan analysis. The proliferation of eight human melanoma cell lines and two fresh melanoma specimens was determined by the MTT test after 4-6 days of growth in the presence of different concentrations of GM-CSF (0.1-1000 U/ml). Neither proliferation nor growth inhibition was observed. Therefore the effect of GM-CSF on residual tumour cells in vivo may not present a problem during clinical use to stimulate marrow regeneration after or during chemotherapy of metastatic malignant melanoma.