[Isolation of growth modulating factors secreted by human malignant melanoma cells]

Novel low molecular mass growth-modulating factors-F0.5 (0.5-1.0 kDa), F1 (approximately 1 kDa) and fraction F8 (8-12 kDa)-have been isolated from a serum-free culture of human malignant pigmented melanoma mS cells using ultrafiltration, affinity and low and medium pressure gel chromatography. Factor F0.5 (10(-9)-10(-7) M) had a growth-stimulating effect on melanoma mS cells exceeding by a factor of 2 and 3 that of 5% embryonic calf serum. Factor F1 and fraction F8 inhibited melanoma cell growth when used at concentrations of 10(-9)-10(-5) M and higher than 10(-6) mg/ml, respectively. The effect of fraction F8 was concentration-dependent; that of factor F1 was more complex. The inhibiting action of fraction F8 was more pronounced when amelanotic cells of human malignant melanoma BRO were used at concentrations above 10(-8) mg/ml. Neither factors F0.5 and F1 nor fraction F8 influenced the growth of human lung fibroblast Lech 240 cells. The growth-modulating factors can participate in the autocrine regulation of malignant melanoma cell growth.