Two multipotent embryonal carcinoma cell lines irreversibly differentiate in defined media

Two unrelated multipotent embryonal carcinoma cell lines, OC-15S1 and 1003, have been cultured in hormone-supplemented defined media in order to identify the signals that influence their differentiation. Previous studies have shown that F9 embryonal carcinoma cells can be grown for many generations in the defined medium, EM-3, which contains fibronectin, insulin, and transferrin in place of serum. F9 cells, which only differentiate into a few cell types, undergo little or no differentiation in EM-3 unless an inducer is present (A. Rizzino and C. Crowley, 1980, Proc. Nat. Acad. Sci. USA 77, 457-461). This report demonstrates that, in contrast to F9, OC-15S1 and 1003 embryonal carcinoma cells do not proliferate in EM-3. Instead, the cells differentiate. However, the differentiated cells do not survive in EM-3 unless it is supplemented with factors such as purified serum lipoproteins. In EM-3 containing high-density lipoprotein, a population of differentiated cells, devoid of embryonal carcinoma cells, is formed. The differentiated cells that appear exhibit an epitheloid morphology throughout the culture. These cells also secrete plasminogen activator and two different criteria argue that it is the type released by parietal endoderm. This suggests that, under the influence of the defined medium, both multipotent embryonal carcinoma cell lines differentiate at high frequency into parietal endoderm. It was also determined that fibronectin promotes the differentiation of OC-15S1 and 1003 in serum-containing media, and this suggests that fibronectin is at least partly responsible for the differentiation observed in EM-3 plus high-density lipoprotein. In light of these findings, it is suggested that fibronectin may directly influence cellular differentiation during early mammalian development.