Nanog is a regulatory protein that is associated with undifferentiated pluripotent cells. The expression of Nanog, which is suppressed in all adult tissues, is restricted to embryonic stem cells and to certain pluripotent cancer cells. Decreased expression of Nanog is strongly correlated with cell differentiation. Nanog, most likely, acts as an intracellular regulator, which maintains pluripotency and self renewal via a STAT3 independent pathway. Recombinant human Nanog is a 35 kDa protein, which is synthesized as a 304 amino acid polypeptide lacking a signal sequence for secretion.