The use of fibroblast and epidermal growth factors to lower the serum requirement for growth of normal diploid cells in early passage: a new method for cloning.
The proliferation of animal cells in tissue culture requires unidentified macromolecules that are contained in serum. Since serum is an extremely complex mixture, efforts to purify these growth-promoting components of serum have met only limited success. On the assumption that these growth-promoting macromolecules in serum are synthesized in active form in some tissue other than blood, we investigated the possibility that they may be purified more readily from specific organs than from serum. We have concentrated our efforts on two likely sources: the pituitary gland, since partially-purified preparations of pituitary hormones have been reported to stimulate the growth of cells in vitro and brain, since neural tissue is essential for the regrowth of amputated limbs in lower vertebrates capable of regeneration. Both pituitary and brain have yielded a strongly mitogenic polypeptide that we call Fibroblast Growth Factor (FGF). FGF was named on the basis of early studies demonstrating its effect on fibroblastic cells: 3T3 cells, amniotic fluid-derived cells, and fibroblasts from human foreskin and mouse embryos. Further work has revealed that FGF promotes the growth of several other mesoderm-derived cell types including adrenal cells, chondrocytes, myoblasts, vascular smooth muscle cells, and vascular endothelial cells. The effect of FGF will be compared to that of EGF and its use for cloning mammalian cells will be described.