Characterization of transforming growth factors produced by the insulin-independent teratoma-derived cell line 1246-3A

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Abstract
The 1246-3A cell line is an insulin-independent variant derived from the adipogenic cell line 1246. Data presented in this paper indicate that the 1246-3A cell line releases in its culture medium two types of transforming growth factors, TGF-α and TGF-β-like polypeptides, and a growth inhibitor. TGF-α like polypeptide eluted from Biogel P60 column into two fractions with an apparent molecular weight of 50 kDa and 13 kDa. These high-molecular-weight TGF-α-like factors competed with 125l-EGF for binding to epidermal growth factor (EGF) receptors and were specifically immunoprecipitated by incubation with antirat TGF-α antibody, not by incubation with anti-EGF antibody. Both fractions promoted anchorage-independent growth of normal rat kidney NRK cells in the absence of EGF and stimulated DNA synthesis in quiescent Balb/c-3T3 cells in a fashion similar to EGF and synthetic TGF-α. In addition to secreting TGF-α-like polypeptides, 1246-3A cells produce TGF-β. This polypeptide, eluted from Biogel P60 chromatography with an apparent molecular weight of 25 kDa, promoted anchorage-independent growth of NRK cells in the presence of EGF and was growth inhibitory for Chinese hamster lung fibroblasts CCL 39 cells. Interestingly, another growth inhibitory activity was detected in Biogel P60 fractions and eluted with an apparent molecular weight of between 9.5-11 kDa. This fraction was different from TGF-β and TGF-α as determined by specific radioreceptor competition assays. TGF-α and TGF-β-like polypeptides could represent autocrine growth stimulators for the insulin-independent 1246-3A cells and act in synergy with insulin-related factor (IRF) for an optimal stimulation of 1246-3A cell proliferation in serum-free medium.

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