Pluripotent cells in embryogenesis and in teratoma formation.

Pluripotent cells of the early preimplantation embryo originate all types of somatic cell and germ cells of the adult organism. Permanent pluripotent cell lines (ES and EG cells) that were derived from an inner cell mass of blastocysts and primordial germ cells have a high proliferative potential and ability to differentiate in vitro into a wide variety of somatic and extraembryonic tissues as well as germ cells and to contribute to different organs of chimeric animals. In some cases pluripotent cells and primordial germ cells can generate teratomas, teratocarsinomas and some kinds of seminomas as the results of damages of differentiation programme of these cells. Experimental teratomas which formed after transplantation of undifferentiated ES and EG cells into immunocompromiced mice may provide a unique opportunity to study pluripotent cell specification and to develop novel approaches in carcinogenesis investigations. Research of signaling and metabolic pathways regulating the pluripotent cell maintenance and their multilineage differentiation are essential to search molecular targets to eliminate undifferentiated cells in tumors. Analysis of interactions between pluripotent cells and differentiated cells of the recipient animals, identification of the factors that may drive differentiation ES and EG cells in vivo contribute in understanding the mechanisms involved in the determination of cell fate during normal development and tumorigenesis. These data are important for development of effective and safe stem cell based technologies for prospective clinical treatment.