Transforming growth factor type β has been purified from serum-free culture fluids of transformed mouse L-929 cells which are capable of continual growth in serum-free medium in the absence of any exogenously added polypeptide growth factors. TGFΒ has been purified to homogeneity as judged by NH2-terminal amino acid sequence analysis. Analysis of the purified polypeptide by gel electrophoresis indicates that TGF is composed of two polypeptide chains of Mr12,500 cross-linked by disulfide bonds. TGF was characterized by its ability to induce anchorage-dependent normal rat kidney (NRK) cells to grow in soft agar in the presence of epidermal growth factor (EGF). TGFΒ was also able to enhance both EGF-induced DNA synthesis and cell proliferation on growth-arrested NRK cells in monolayer cultures under serum-free conditions. We also show that in mouse melanoma B-16 cells under serum-free conditions TGFΒ stimulates both DNA synthesis in monolayer cultures and anchorage-independent growth in soft agar. Paradoxically, the anchorage-independent growth in the presence of serum of many human cell lines, including melanomas, and mammary, prostatic, vulvar, and lung carcinomas is inhibited by TGFΒ at saturating concentrations similar to those that stimulate colony formation of the rodent cell lines L-929 and B-16 under serum-free conditions. The peculiar action of TGFΒ is further revealed by the observations that while EGF and TGFΒ synergize to induce inhibition of anchorage-independent growth of A-431 human vulvar carcinoma cells, their effects on the anchorage-independent growth of one human lung carcinoma cell line (A-549) and two human prostatic carcinoma cell lines (PC-3 and DU-145) are antagonistic. Moreover, we show that in the rodent and human cell lines TGFΒ interacts with specific cellular receptors which may mediate the actions of TGFΒ. We conclude that (a) the expression of both TGFΒ and TGFΒ receptors by L-929 cells and the stimulation of growth of L-929 cells in serum-free medium by TGFΒ suggests that TGFΒ may be important for maintaining the transformed state of this tumor cell line, and (b) the way in which a cell responds to TGFΒ is dependent on the presence or absence of growth factors contained in the serum.
|Number of pages||9|
|State||Published - Oct 1 1986|