The secreted glycoprotein CREG enhances differentiation of NTERA-2 human embryonal carcinoma cells

Differentiation of the human embryonal carcinoma cell Line NTERA-2 is chara cterized by changes in morphology, altered patterns of gene expression, red uced proliferative potential, and a loss of tumorigenicity. The cellular re pressor of E1A-stimulated genes, CREG, was previously shown to antagonize t ranscriptional activation and cellular transformation by the Adenovirus EIA oncoprotein. These properties suggested that CREG may function to inhibit cell growth and/or promote differentiation, Here we show that CREG is a sec reted glycoprotein which enhances differentiation of NTERA-2 cells. Norther n blot analysis reveals that, although CREG mRNA is widely expressed in adu lt tissues, CREG mRNA is not significantly expressed in pluripotent mouse e mbryonic stem cells or NTERA-2 embryonal carcinoma cells. CREG mRNA is rapi dly induced upon in vitro differentiation of both mouse embryonic stem cell s and human NTERA-2 cells, We show that constitutive expression of CREG in NTERA-2 cells enhances neuronal differentiation upon treatment with retinoi c acid. Media enriched in CREG was also found to promote NTERA-2 differenti ation in the absence of an inducer such as retinoic acid. These studies sug gest that secreted CREG protein participates in a signaling cascade importa nt for differentiation of pluripotent stem cells such as those found in ter atocarcinomas.