An 18,000 molecular weight polypeptide induces early events and stimulates DNA synthesis in cultured cells.

Extracts of serum-free medium, conditioned by contact with SV40-transformed BHK cells, stimulate DNA synthesis in cultured fibroblasts. From this source, we have purified a homogenous basic protein of 18,000 molecular weight, termed fibroblast derived growth factor. In submicrogram quantities, fibroblast derived growth factor stimulates DNA synthesis in mouse 3T3 cells, in the absence of added serum. Prior to the onset of DNA synthesis, both serum and fibroblast derived growth factor induce an array of nearly simultaneous biochemical changes in the membrane to 3T3 cells that include stimulation of the uptake of nucleosides, 2-deoxyglucose, and 86Rb+. These results strongly suggest that the early events are integral components of the proliferative response, rather than coincidental effects of nonmitogenic molecules present in serum.