The cytoplasmic and nuclear redistribution of β-catenin and the de novo expression of vimentin are frequently involved in the epithelial-to-mesenchymal transition associated with increased invasive/migratory properties of epithelial cells. Because β-catenin can act as a coactivator of transcription through its binding to the T-cell factor (TCF)/lymphoid enhancer factor 1 transcription factor family, we have explored the possibility that βcatenin/TCF could directly transactivate vimentin. We first compared vimentin expression in relation with the localization of β-catenin in eight breast cancer cell Unes displaying various degrees of invasiveness and in a model of cell migration using human mammary MCF10A cells. We could thus show a cytoplasmic and/or nuclear distribution of β -catenin in invasive/migratory cells expressing vimentin, but not in noninvasive/stationary vimentin-negative cell lines. In addition, the human vimentin promoter was found to be up-regulated by β-catenin and TCF-4 cotransfection. Varying with the cellular background, a diminution of this up-regulation was observed when the putative β -catenin/TCF binding site of the vimentin promoter was mutated. Our results therefore demonstrate that the vimentin promoter is a target of the β-catenin/TCF pathway and strongly suggest an implication of this regulation in epithelial cell migration/invasion.

The expression of Smad interacting protein-1 (SIP1; ZEB2) and the de novo expression of vimentin are frequently involved in epithelial-to-mesenchynial transitions (EMTs) under both normal and pathological conditions. In the present study, we investigated the potential role of SIP1 in the regulation of vimentin during the EMT associated with breast tumor cell migration and invasion. Examining several breast tumor cell Unes displaying various degrees of invasiveness, we found SIP1 and vimentin expression only in invasive cell Unes. Also, using a model of cell migration with human mammary MCF10A cells, we showed that SIP1 is induced specifically in vimentin-positive migratory cells. Furthermore, transfection of SIP1 cDNA in MCF10A cells increased their vimentin expression both at the mRNA and protein levels and enhanced their migratory abilities in Boyden Chamber assays. Inversely, inhibition of SIP1 expression by RNAi strategies in BT-549 cells and MCF10A cells decreased vimentin expression. We also showed that SIP1 transfection did not activate the TOP-FLASH reporter system, suggesting that the β-catenin/ TCF pathway is not impUcated in the regulation of vimentin by SIP1. Our results therefore impUcate SIP1 in the regulation of vimentin observed in the EMT associated with breast tumor cell migration, a pathway that may contribute to the metastatic progression of breast cancer.

Estetrol (E4) is a natural estrogen with a long half-life produced only by the human fetal liver during pregnancy. The crystal structures of the estrogen receptor α (ERα) ligand-binding domain bound to 17β-estradiol (E2) and E4 are very similar, as well as their capacity to activate the two activation functions AF-1 and AF-2 and to recruit the coactivator SRC3. In vivo administration of high doses of E4 stimulated uterine gene expression, epithelial proliferation, and prevented atheroma, three recognized nuclear ERα actions. However, E4 failed to promote endothelial NO synthase activation and acceleration of endothelial healing, two processes clearly dependent on membrane-initiated steroid signaling (MISS). Furthermore, E4 antagonized E2 MISS-dependent effects in endothelium but also in MCF-7 breast cancer cell line. This profile of ERα activation by E4, uncoupling nuclear and membrane activation, characterizes E4 as a selective ER modulator which could have medical applications that should now be considered further.

The cytoplasmic/nuclear relocalization of β-catenin and ZO-1 from the adherens and tight junctions are common processes of the epithelial-mesenchymal transition (EMT) associated with tumor invasion. Data are now accumulating to demonstrate that these molecules, which shuttle between the plasma membrane and the nucleus or the cytosol, are involved in signaling pathways, and contribute to the regulation of genes such as vimentin or matrix metalloproteinase-14 which are turned on during EMT.

The loss of E-cadherin expression and the translocation of b-catenin to the nucleus are frequently associated with the metastatic conversion of epithelial cells. In the nucleus, b-catenin binds to the TCF/LEF-1 (T-cell factor/ lymphoid enhancer factor) transcription factor family resulting in the activation of several genes, some of them having important implications in tumour progression. In our study, we investigated the potential regulation of monocyte chemotactic protein-1 (MCP-1/CCL2) expression by the b-catenin/TCF pathway. This CC-chemokine has been implicated in tumour progression events such as angiogenesis or tumour associated macrophage (TAM) infiltration. We thus demonstrated that MCP-1 expression correlates with the reorganization of the E-cadherin/b-catenin complexes. Indeed, MCP-1 was expressed by invasive breast cancer cells (MDA-MB-231, BT549 and Hs578T), which do not express E-cadherin but was not produced by noninvasive breast cancer cell lines (MCF7 and T47D) expressing high level of E-cadherin. In addition, the MCP-1 promoter was activated in BT549 breast cancer cells transfected with b-catenin and TCF-4 cDNAs. The MCP-1 mRNA level was similarly upregulated. Moreover, we showed that MCP-1 mRNA was downregulated after transfection with a siRNA against b-catenin in both BT549 and Hs578T cells. Our results therefore identify MCP-1 as a target of the b-catenin/TCF/LEF pathway in breast tumour cells, a regulation which could play a key role in breast tumour progression. ' 2005 Wiley-Liss, Inc.Key words: MCP-1; b-catenin; breast cancer Chemokines constitute a superfamily of proinflammatory cytokines that are implicated in tumour progression, modulating not only host tumour-specific immunological response but also angiogenesis or tumour cell invasion and proliferation. 1-3 Monocyte chemotactic protein-1 (MCP-1) or CCL2 is a CC-chemokine that specifically attracts monocytes and memory T cells. It has been particularly implicated in processes characterized by mononuclear cell infiltration including breast cancer. 4,5 In some models, MCP-1 has been shown to display an antitumoral effect. 6,7 Nevertheless, a large number of studies demonstrate that MCP-1 facilitates tumour progression through its ability to recruit stromal cells including tumour associated macrophages (TAMs) and endothelial cells. 7-10 A pro-angiogenic role of MCP-1 has been demonstrated in many systems, facilitating tumour growth and dissemination. 8,9,11,12 Moreover, a direct effect of MCP-1 on tumour cell migration in vitro has also been described. 13 Recently, Lebrecht et al. 14 have correlated an increased MCP-1 serum level with an advanced breast tumour stage and the presence of lymph node metastasis. In the same way, Amann et al. 15 reported a significant association between MCP-1 urinary levels and tumour stage and grade. They suggested a use of its urinary level as prognosis marker in bladder cancer. The correlation between MCP-1 expression and a poor prognosis was also demonstrated for the squamous cell carcinoma of the oeso...

Increased risk of breast cancer is a critical side effect associated with the use of a menopausal hormone therapy (MHT). Estetrol (E4) is a natural estrogen produced by the human fetal liver and is a promising compound for clinical use in MHT. However, its impact on breast cancer is controversial and poorly defined. In this preclinical study, we show that E4 acts as a weak estrogen by stimulating the growth of hormone-dependent breast cancer only at concentrations exceeding menopausal therapeutic needs. E4 presents also an antitumor activity by decreasing the strong proliferative effect of estradiol (E2). While estrogen receptor alpha (ERα) is the predominant receptor mediating its effects, the dual weak-estrogenic/anti-estrogenic feature of E4 results from differential signaling pathways activation. Both nuclear and rapid extra-nuclear signaling pathway are necessary for a complete estrogenic effect of E4. However, the antitumor action of E4 is not due to a capacity to antagonize E2-induced nuclear activity. Altogether, our results highlight that E4 has a limited impact on breast cancer and may offer a safe therapeutic window for the treatment of menopausal symptoms.

Unlike previous studies, we observed no aromatase protein in any of the endometriosis types, and barely detectable aromatase mRNA expression, suggesting that locally produced aromatase (within endometriotic lesions) may be less implicated in endometriosis development than previously postulated. Potential factors responsible for these discrepancies are discussed.

Estetrol (E 4 ) is a natural estrogen produced exclusively by the human fetal liver during pregnancy. Its physiological activity remains unknown. In contrast to ethinyl estradiol and estradiol (E 2 ), E 4 has a minimal impact on liver cell activity and could provide a better safety profile in contraception or hormone therapy. The aim of this study was to delineate if E 4 exhibits an activity profile distinct from that of E 2 on mammary gland. Compared with E 2 , E 4 acted as a low-affinity estrogen in both human in vitro and murine in vivo models. E 4 was 100 times less potent than E 2 to stimulate the proliferation of human breast epithelial (HBE) cells and murine mammary gland in vitro and in vivo respectively. This effect was prevented by fulvestrant and tamoxifen, supporting the notion that ERa (ESR1) is the main mediator of the estrogenic effect of E 4 on the breast. Interestingly, when E 4 was administered along with E 2 , it significantly antagonized the strong stimulatory effect of E 2 on HBE cell proliferation and on the growth of mammary ducts. This study characterizes for the first time the impact of E 4 on mammary gland. Our results highlight that E 4 is less potent than E 2 and exhibits antagonistic properties toward the proliferative effect of E 2 on breast epithelial cells. These data support E 4 as a potential new estrogen for clinical use with a reduced impact on breast proliferation.