EGF increases retinoid X receptor-α expression in human trophoblastic cells in culture: relationship with retinoic acid induced human chorionic gonadotropin secretion

Abstract

In the present study, the effect of retinoic acid (RA) and epidermal growth factor (EGF) on the functions of human trophoblastic cells in culture were analysed. In these cells, RA potentiated the hCG secretion increase induced by EGF. To gain a better understanding of such a synergistic effect, the expression of retinoic acid receptors (RARα and β) and retinoid X receptor (RXRα) was studied by immunoblotting in RA- and EGF-treated cells. EGF treatment specifically increased the level of RXRα protein and RXRα transcripts. In parallel, we demonstrated that the choriocarcinoma cells JEG 3, which respond to RA by an increase in hCG secretion, express constitutively high levels of RXRα protein. Furthermore, RXRα-transfected trophoblastic cells also become RA responsive for hCG secretion. All these data suggest that RXRα expression is modulated by EGF, and may be involved in the effect of RA on hCG secretion.