The relationship between embryonic, embryonal carcinoma and embryo-derived stem cells.

Two types of pluripotent stem cell lines of embryonic origin are available as tools for the study of molecular and cellular differentiation in vitro. Tumor-derived embryonal carcinoma (EC) cell lines and the more recently developed embryo-derived stem (ES) cell lines have many characteristics similar to those of pluripotent cells within the embryo itself, the major difference being the cell lines' capacity for continued proliferation as undifferentiated cells. It is not known whether all EC/ES cell lines are derived from the same or different embryonic stem cells. Some differences between cell lines would be compatible with the latter. The advent of ES cells, which appear to be closer to embryonic cells, may allow the resolution of this question.