Human embryonal carcinoma cells in culture do not synthesize fibronectin until they differentiate.

The expression of fibronectin by clones of 2102Ep, a human cell line derived from a testicular germ-cell tumor, was studied. In high-density cultures these cells retain an embryonal carcinoma phenotype and do not express the cell surface antigen SSEA-1. They do not synthesize fibronectin. However, when grown at low densities, many of the cells appear to differentiate, as indicated by a change in their morphology and their expression of SSEA-1. Such cultures also synthesize fibronectin. Further, when low-density cultures were fractionated into SSEA-1-positive and SSEA-1-negative subpopulations by fluorescence-activated cell sorting, fibronectin synthesis was confined to the SSEA-1-positive cells. The fibronectin produced by these cells exhibits an apparent molecular weight (261,000) slightly greater than that produced by diploid fibroblasts (250,000) and may represent an embryonic form. It is not laid down as an extracellular matrix and cannot be detected by immunofluorescence analysis of cell monolayers.