Inhibition of metastasis by a dialysable factor in fetal bovine serum in B16 melanoma cells

Fetal bovine serum (FBS) supplemented to the culture medium inhibited the metastasis of B16BL6 melanoma cells in a dose-dependent manner. This metastasis-inhibiting activity was accompanied by growth-promoting activity, up to the concentration of 10% FBS. However, among the clones isolated from B16BL6 cells, there were clones in which FBS significantly inhibited the metastasis without promoting their growth. Dialysis (cutoff M.W. 8000 Da) removed the metastasis-inhibiting activity but not the growth-promoting activity from FBS. These results indicate that FBS has metastasis-inhibiting activity which is independent of growth-promoting activity, and that the metastasis-inhibiting activity is carried by molecules removed by dialysis.