BackgroundThe ETS transcription factor ETV4 is involved in the main steps of organogenesis and is also a significant mediator of tumorigenesis and metastasis, such as in breast cancer. Indeed, ETV4 is overexpressed in breast tumors and is associated with distant metastasis and poor prognosis. However, the cellular and molecular events regulated by this factor are still misunderstood. In mammary epithelial cells, ETV4 controls the expression of many genes, MMP13 among them. The aim of this study was to understand the function of MMP13 during ETV4-driven tumorigenesis.MethodsDifferent constructs of the MMP13 gene promoter were used to study the direct regulation of MMP13 by ETV4. Moreover, cell proliferation, migration, invasion, anchorage-independent growth, and in vivo tumorigenicity were assayed using models of mammary epithelial and cancer cells in which the expression of MMP13 and/or ETV4 is modulated. Importantly, the expression of MMP13 and ETV4 messenger RNA was characterized in 456 breast cancer samples.ResultsOur results revealed that ETV4 promotes proliferation, migration, invasion, and anchorage-independent growth of the MMT mouse mammary tumorigenic cell line. By investigating molecular events downstream of ETV4, we found that MMP13, an extracellular metalloprotease, was an ETV4 target gene. By overexpressing or repressing MMP13, we showed that this metalloprotease contributes to proliferation, migration, and anchorage-independent clonogenicity. Furthermore, we demonstrated that MMP13 inhibition disturbs proliferation, migration, and invasion induced by ETV4 and participates to ETV4-induced tumor formation in immunodeficient mice. Finally, ETV4 and MMP13 co-overexpression is associated with poor prognosis in breast cancer.ConclusionMMP13 potentiates the effects of the ETV4 oncogene during breast cancer genesis and progression.Electronic supplementary materialThe online version of this article (10.1186/s13058-018-0992-0) contains supplementary material, which is available to authorized users.

Ets-1 overexpression in human breast cancers is associated with invasiveness and poor prognosis. By overexpressing Ets-1 or a dominant negative mutant in MMT breast cancer cells, we previously highlighted the key role of Ets-1 in coordinating multiple invasive features of these cells. Interestingly, we also noticed that Ets-1 decreased the density of breast cancer cells cultured in three-dimensional extracellular matrix gels. The 3D context was instrumental to this phenomenon, as such downregulation was not observed in cells grown on two-dimensional plastic or matrix-coated dishes. Ets-1 overexpression was deleterious to anchorage-independent growth of MMT cells in soft agar, a standard model for in vitro tumorigenicity. The relevance of this mechanism was confirmed in vivo, during primary tumor growth and in a metastatic assay of lung colonization. In these models, Ets-1 was associated with epithelial-to-mesenchymal transition features and modulated the ratio of Ki67-positive cells, while hardly affecting in vivo apoptotic cell death. Finally, siRNA-mediated knockdown of Ets-1 in human breast cancer cell lines also decreased colony growth, both in anchorage-independent assays and 3D extracellular matrix cultures. These in vitro and in vivo observations shed light on an unsuspected facet of Ets-1 in breast tumorigenesis. They show that while promoting malignancy through the acquisition of invasive features, Ets-1 also attenuates breast tumor cell growth and could therefore repress the growth of primary tumors and metastases. This work also demonstrates that 3D models may reveal mechanisms of tumor biology that are cryptic in standard 2D models.Breast cancer is the foremost cause of cancer-related deaths of women worldwide. The natural history of breast cancer classically involves progression from in situ hyperproliferative lesions to invasive carcinomas, eventually leading to metastatic disease. 1 The standard model of tumor progression relies on the sequential acquisition of genetic mutations conferring enhanced cell proliferation, survival, and invasiveness. Besides the high diversity among breast tumors, these malignancies are also characterized by great intratumoral heterogeneity. This is notably observed in terms of angiogenic, invasive and metastatic potential, and probably reflects a mixed population of cells at different stages of tumoral evolution. 2 Besides the genetic alterations driving tumor cell malignancy, cancer cells are also subjected to external stimuli from their microenvironment, which can foster their aggressiveness. In particular, epithelial-tomesenchymal transition (EMT) can be induced by tumorassociated reactive stroma, endowing carcinoma cells with the invasive properties required for intravasation. Elucidating the molecular mechanisms and master regulators of these transformative events is key to identifying new targets for anticancer therapy.The Ets-1 proto-oncogene is the prototype of the ETS family of transcription factors involved in the regulation of various biological functions. ...