Nanog, a member of the homeobox family of DNA binding transcription factors, along with SOX2 and OCT3/4 form a regulatory network that facilitates embryonic stem cell (ESC) self-renewal and differentiation. Under normal development, Nanog is localized in the nucleus, expressed in the fetal testis, ovary, and gonads. It is not expressed in most somatic organs. While Nanog and other ESC-associated proteins are important for proper development, these have been shown to contribute to tumorigenesis.

Nanog is expressed in germ cell tumors such as embryonal carcinoma, seminoma and dysgerminoma. Recently, its expression has also been reported in non-germ cell tumors, such as carcinomas of the breast, cervix, oral cavity, kidney, and ovary.