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International audience; NFAT1 is a transcription factor that elicits breast carcinoma cells to become invasive, thus contributing to metastasis. The molecular mechanisms by which NFAT1 operates in this respect are still poorly known. Here, we report that NFAT1 increases lipocalin 2 (LCN2) mRNA and protein expression by binding to specific sites in the LCN2 gene promoter region. We show that the LCN2 protein is required downstream of NFAT1 to increase breast cancer cell invasion. We demonstrate that the NFAT1-LCN2 axis is sufficient to regulate expression of the TNF-like receptor TWEAKR at the RNA level and of its ligand, TWEAK, at the protein level. We show, however, that TWEAKR mediates an anti-invasive effect in breast cancer cells whereas, depending on LCN2 expression, TWEAK has either anti- or pro-invasive capacities. Thus, we identify LCN2 and TWEAKR-TWEAK as crucial downstream effectors of NFAT1 that regulate breast cancer cell motility and invasive capacity.

We have previously shown that CD4 ligands inhibit interleukin-2 (IL-2) production and T cell proliferation in human peripheral CD4+ T lymphocytes, in an MHC-independent way. Two major pathways implicated in T cell activation are inhibited by binding of CD4 ligands to the CD4 molecule, i.e. Ca2+ signaling by phospholipase Cgamma1 (PLCgamma1), and ERK-2 activation, suggesting a p21ras inhibition. We have correlated these inhibitions with the disruption of multifunctional complexes containing PLCgamma1, p120GAP and Sam68, induced by T cell activation. We report here that T cell activation through the TCR/CD3 induces an association of the phosphoinositide 3 kinase (PI3 kinase) with PLCgamma1, both in peripheral CD4+ T lymphocytes and the HUT-78 CD4+ T cell line. PI3 kinase is present in the multifunctional complexes that we have described previously. Preincubation of human peripheral CD4+ T cells and HUT-78 CD4+ T cells with gp160 or a peptide analogue of the HLA class II DR molecule precludes the association of PLCgamma1 with PI3 kinase. We also demonstrate, using two specific inhibitors of PI3 kinase activity (LY294002 and wortmannin), that this activity plays a key role in the association of PLCgamma1 with PI3 kinase. Moreover, we demonstrate the implication of the PI3 kinase activity in the negative signal mediated by HIV gp160 binding to CD4 molecules. We propose that the products of the PI3 kinase are important mediators of the negative signaling induced by the binding of CD4 ligands to the CD4 molecule implicated in the regulation of the formation of multifunctional complexes.

International audience; Luminal breast cancers represent 70% of newly diagnosed breast cancers per annum and have a relatively good prognosis compared with triple-negative breast cancers. Luminal tumors that are responsive to hormonal therapy are particularly associated with a favorable prognosis. Nonetheless, the absolute number of metastatic relapses in luminal cancers is larger than in triple-negative breast cancers. A better understanding of the biology of luminal cancers, control of metastases formation, and identification of predictive markers of their evolution are therefore still necessary. In this context, we previously disclosed the key role of NFAT3 in regulating luminal breast cancer invasion. We have now identified a specific inhibitory region, in the C-terminal part of NFAT3, required for the inhibition of invasion of the human luminal breast cancer cell line T-47D. Indeed, we showed that this 85 amino acid C-terminal region acts as a dominant negative form of NFAT3 and that its overexpression in the T-47D cell line led to increased cell invasion. Mechanistically, we have revealed that this region of NFAT3 interacts with the small Ras GTPase RERG (RAS like estrogen regulated growth inhibitor) and shown that RERG expression is required for NFAT3 to impede T-47D cell invasion. We have validated the association of NFAT3 with RERG in human luminal breast cancer tissues. We have shown an increase of the quantity of the NFAT3/RERG complexes in patients without axillary lymph node colonization and therefore proposed that the detection of this complex may be a non-invasive marker of axillary lymph node colonization.

Metastases are the main cause of cancer-induced deaths worldwide. To block tissue invasion, development of extracellular vesicles (EVs) as therapeutic carriers, appears as an exciting challenge. To this aim, we took advantage of the anti-invasive function of NFAT3 transcription factor we identified previously in breast cancer and addressed the opportunity to transfer this inhibitory function by EVs. We show here that EVs produced by poorly invasive NFAT3-expressing breast cancer cell lines are competent to block in vitro invasion of aggressive cancer cells from different origins and, in cooperation with macrophages, inhibit cell proliferation and induce apoptosis. Moreover, this inhibitory effect can be improved by overexpression of NFAT3 in the EVs-producing cells. These results were extended in a mouse breast cancer model, with clear impact of inhibitory EVs on tumor growth and metastases spreading. This work identifies EVs produced by NFAT3-expressing breast cancer cells as an anti-tumoral tool to tackle cancer development and metastases dissemination.