Activities of transforming growth factors on cell lines and their modification by other growth factors

Soft agar colony-forming activity of transforming growth factors (TGFs) was examined by a simplified method of soft agar micro-assay using nontransformed mouse BALB/3T3 and normal rat kidney (NRK) cells. Bio-Gel P-60 chromatography of acid-ethanol extracts from a human placenta, a human tumor, and hamster embryos gave similar patterns of colony-forming activity towards BALB/3T3 cells and epidermal growth factor (EGF)-potentiated NRK cells, although the molecular weight ranges of the active fractions were different among the three sources. In the soft agar assay using BALB/3T3 cells, colony-forming activity of a TGF preparation from human placenta was markedly enhanced by insulin, but not by EGF. In contrast, the activity was enhanced by EGF, but not by insulin, when NRK cells were used. Fibroblast growth factor and platelet-derived growth factor induced colonies of both BALB/3T3 and NRK cells, and the induction was suppressed by the TGF preparation. TGF preparations could not induce soft agar colonies of C3H/10T1/2 cells or human foreskin diploid fibroblasts, although they increased the saturation densities of these cell types in monolayer cultures.