Characterizationof the TGF-beta signalosome and of TGF-beta-dependent endometrialcell proliferation

Endometriosis is characterized by the presence of endometrial-like cells outside the uterus mostly in the ovary and peritoneum. TGF-betas are expressed significantly higher in the serum and peritoneal fluid of patients with endometriosis. TGF-betas have been also observed in endometriotic sites. Thus, TGF-betas might be involved in the pathogenesis of endometriosis. The aim of this study was to investigate the signaling pathways of the TGF-betas and possible cross-talks with other pathways. Also, we investigated the interaction of the TGF-betas to their receptors. In this study, we used four different cell lines including endometrial epithelial and stromal cell lines, endometriotic epithelial and stromal cell lines and primary endometrial stromal cells. Also, endometrial and ovarian tissues were used. Our results showed that in all four cell lines and primary cells studied: (1) TGF-beta1 or TGF-beta2 decreased cell numbers in all cells and the reduction was higher in endometrial cells compared to endometriotic cells, (2) TGF-beta1 or TGF-beta2 induced apoptosis in all cells with no significant differences between endometrial or endometriotic cells, (3) TGF-beta1 or TGF-beta2 induced Smad3 phosphorylation in all cells studied with higher phosphorylation levels observed in endometrial cells compared to endometriotic cells, (4) a TbetaRI inhibitor completely blocked the TGF-beta-induced reduction in cell numbers, apoptosis, PAI-1 secretion and Smad3 phosphorylation. A Smad3 inhibitor only partly blocked it. (5) TGF-beta1 or TGF-beta2 increased TBRII and TBRIII or TBRI and TBRII interaction with a stronger interaction observed in endometrial cells compared to endometriotic cells. (6) A BMP as well as an ALK-2 inhibitor completely blocked the TGF-beta-induced PAI-1 secretion. In contrast, ALK-3 and ALK-6 inhibitors only partly blocked it. (7) A JNK inhibitor blocked increased secretion of TGF-beta2 and TGF-beta1 in TGF-beta1-treated cells. (8) Both endometrial glands and ovarian endometriotic foci express CK 18 and MUC1 proteins. From these results, we suppose that the reduced responsiveness upon TGF-beta treatment observed in endometriotic cells compared to endometrial cells in regard to reduction in cell numbers, Smad3 phosphorylation and TBR receptor interaction indicates that endometriotic cells are more resistant to TGF-beta signals. This suggests that endometriotic cells might acquire tumor-like characteristics which might contribute to their survival, evasion of the immune system and subsequent implantation during the pathogenesis of endometriosis. In addition, we provided evidence that endometriotic cells have possibly the same origin from endometrial cells and thus are disseminated like tumor cells. Furthermore, we demonstrated for the first time that endometrial and endometriotic cells undergo apoptosis upon TGF-beta treatment and both intrinsic and extrinsic pathways are involved. In addition, we demonstrated the participation of the JNK and BMP pathways in TGF-beta signaling in endometrial, endometriotic and…