Expression of TGF-beta signaling genes in the normal, premalignant, and malignant human trophoblast: Loss of smad3 in choriocarcinoma cells

We had earlier shown that TGF-beta controls proliferation, migration, and i nvasiveness of normal human trophoblast cells, whereas premalignant and mal ignant trophoblast cells are resistant to TGF-beta. To identify signaling d efects responsible for TGF-beta resistance in premalignant and malignant tr ophoblasts, we have compared the expression of TGF-beta signaling molecules in a normal trophoblast cell line (HTR-8), its premalignant derivative (RS VT2/C), and two choriocarcinoma cell lines (JAR and JEG-3). RT-PCR analysis revealed that all these cell lines expressed the mRNA of TGF-beta1, -beta2 , and -beta3, TGF-beta receptors type I, II, and III, and post-receptor sig naling genes smad2, smad3, smad4, smad6, and smad7 with the exception that TGF-beta2 and smad3 were undetectable in JAR and JEG-3 cells. Immunoblot an alysis confirmed the absence of smad3 protein in choriocarcinoma cells. Tre atment with TGF-beta1 induced smad3 phosphorylation and smad3 translocation to the nucleus in the normal and premalignant trophoblast cells. These res ults suggest that loss of smad3 may account for a functional disruption in the TGF-beta signaling pathway in choriocarcinomas, but not in the premalig nant trophoblast. (C) 2001 Academic Press.