Type , 8 Transforming Growth Factor from Feline Sarcoma Virus - transformed Rat Cells

We have isolated a strongly mitogenic, type B transforming growth factor (BTGF) released by SnyderTheilen feline sarcoma virus-transformed rat embryo (FeSV-Fre) cells that induces phenotypic transformation of normal NRK cells when they are concomitantly stimulated by analogues of epidermal growth factor (EGF). Molecule filtration chromatography separates BTGF from an EGF-like TGF (eTGF) which is also present in acid extracts from medium conditioned by FeSV-Fre cells (J. Massague, (1983) J. Biol. Chem. 258, 13606-13613). Final purification of BTGF is achieved by reverse phase high pressure liquid chromatography (HPLC) on octadecyl support, molecular filtration HPLC, and nonreducing dodecyl sulfate-polyacrylamide gel electrophoresis steps, yielding a 300,000-fold purified polypeptide with a final recovery of 21%. The purified rat BTGF consists of two M, = 11,000-12,000 polypeptide chains disulfide-linked as a M, = 23,000 dimer. Induction of anchorage-independent proliferation of NRK cells by rat BTGF depends on the simultaneous presence of eTGF or EGF. In the presence of a saturating (300 pM) concentration of either rat eTGF or mouse EGF, half-maximal anchorage-independent proliferation of NRK cells is obtained with 4-6 PM rat BTGF. In the presence of a saturating (20 PM) concentration of rat BTGF, halfmaximal anchorage-independent proliferation of NRK cells is obtained with either rat eTGF or mouse EGF at a 50-70 PM concentration. Rat BTGF is also able to induce DNA synthesis and cell proliferation on growtharrested NRK, human lung, and Swiss mouse 3T3 fibroblast monolayers, this effect being half-maximal at 2-3 PM BTGF for NRK cells. These results identify eTGF and BTGF as the two synergistically acting factors responsible for the transforming action of culture fluids from FeSV-Fre cells.