Tumor Suppressors and Endodermal Differentiation of P19 Embryonic Stem Cells

The P19 embryonic stem (ES) cells are derivatives of the inner cell mass of a mouse blastoderm, are multipotent and can give rise to all three germ layers [1]. They are anchorage-independent, display no contact inhibition, and are tumorigenic [2]. The P19 ES cell line was originally derived from a teratocarcinoma in C3H/HE mice, produced by grafting an embryo at 7 days of gestation to the testes of an adult male mouse [3,4]. Depending on the nature of inducers, P19 ES cells can be driven to differentiate into derivatives of all three germ layers, an advantage that has been extensively exploited to study early developmental events. Dimethyl sulfoxide (DMSO) treatment of P19 ES cell aggregates (embryoid bodies) results in differentiation into cardiacand skeletal muscle-like cells [1], whereas retinoic acid (RA) induces differentiation into neurons, glia, and fibroblast‐like cells [5]. On the other hand, monolayers of P19 ES cells, when treated with RA, differentiate into cells with endodermal and mesodermal phenotypes [6]. The type of differentiation of P19 ES cell aggregates also depends on the RA concentration; with low concentration (10 nM) of RA, these cells differentiate into primitive endoderm-like cells and with high concentrations (1 μM) of RA, differentiation is shifted towards neurons and glia [3,7,8].