Inhibitory effects of transforming growth factor-β on laminin production and growth exhibited by endoderm-like cells derived from embryonal carcinoma cells

Previous studies have shown that two mouse embryonal carcinoma (EC) cell lines do not express cell surface receptors for transforming growth factor type-β (TGF-β) until they are induced to differentiate. To understand the effects of TGF-β in this model system, we have examined the effects of TGF-β on parietal endoderm-like cells derived from EC cells. We have determined that TGF-β exerts three effects on these cells. TGF-β inhibits proliferation of the parietal endoderm-like cells, and this occurs even in the presence of growth factors that stimulate their proliferation. TGF-β also alters the morphology of the parietal endoderm-like cells by increasing their spreading. Moreover, the morphological effect of TGF-β is observed in the presence of dibutyryl cyclic AMP (dbcAMP), which reduces the spreading of these cells. Lastly, TGF-β, but not other growth factors, decreases the production of laminin by the parietal endoderm-like cells. This was unexpected since TGF-β has been shown to increase the production of extracellular matrices in other systems. Thus, our findings indicate that parietal endoderm-like cells provide a useful system for broadening the study of TGF-β. Furthermore, our findings provide additional support for the possibility that TGF-β plays important roles during the early stages of mammalian development.