Abstract
Basic fibroblast growth factor (bFGF) stimulates the proliferation of many cells and it is found in a wide variety of normal or transformed tissues. As demonstrated here, bFGF is also present in cultured human Ewing's sarcoma cells. Unexpectedly, however, bFGF isolated from these cells inhibits their own proliferation, indicating that bFGF can act as an endogenous (autocrine) growth inhibitor for cultured Ewing's sarcoma cells. Since bFGF also inhibits the proliferation of some further tumor cells, but stimulates that of others, it can be considered a bifunctional regulator of tumor cell proliferation. The autocrine growth-inhibitory effect of bFGF in Ewing's sarcoma cells may explain the low mitotic activity of Ewing's sarcomas.