Human mena (hMENA), a member of the actin cytoskeleton regulators Ena/VASP, is overexpressed in high-risk preneoplastic lesions and in primary breast tumors and has been identified as playing a role in invasiveness and poor prognosis in breast cancers that express HER2. Here we identify a unique isoform, hMENAΔv6, derived from the hMENA alternative splicing program. In an isogenic model of human breast cancer progression, we show that hMENA 11a is expressed in premalignant cells, whereas hMENAΔv6 expression is restricted to invasive cancer cells. "Reversion" of the malignant phenotype leads to concurrent down-regulation of all hMENA isoforms. In breast cancer cell lines, isoform-specific hMENA overexpression or knockdown revealed that in the absence of hMENA 11a , overexpression of hMENAΔv6 increased cell invasion, whereas overexpression of hMENA 11a reduced the migratory and invasive ability of these cells. hMENA 11a splicing was shown to be dependent on the epithelial regulator of splicing 1 (ESRP1), and forced expression of ESRP1 in invasive mesenchymal breast cancer cells caused a phenotypic switch reminiscent of a mesenchymal-to-epithelial transition (MET) characterized by changes in the cytoskeletal architecture, reexpression of hMENA 11a, and a reduction in cell invasion. hMENA-positive primary breast tumors, which are hMENA 11a -negative, are more frequently E-cadherin low in comparison with tumors expressing hMENA 11a . These data suggest that polarized and growth-arrested cellular architecture correlates with absence of alternative hMENA isoform expression, and that the hMENA splicing program is relevant to malignant progression in invasive disease.ENA along with VASP and EVL comprise the Ena/VASP family of actin regulatory proteins, which modulate cell adhesion and migration by antagonizing actin capping proteins (1, 2), bundling actin filaments, and nucleating and extending filopodia (1-7). The MENA gene encodes the 570-aa hMENA protein and different alternative splicing-derived isoforms, often expressed in a tissue-specific manner, have been reported in human (8, 9) and mouse (1, 10, 11). The neuronal variant is characterized by an extended exon 6 (1, 8), the spleen-specific variant lacks the proline-rich region (10), and an invasion-specific splice variant (MENA INV ), with an additional exon just after the EVH1 domain, has been shown to regulate chemotaxis in mouse and rat mammary tumor cells (12). Previously, we characterized hMENA 11a , an epithelial-associated hMENA splice variant with an additional exon (exon 11a) (9). hMENA 11a , expressed in human pancreatic (13) and breast cancer cells (9), is phosphorylated downstream of HER2 and EGFR following EGF and NRG1 treatment and in turn influences the mitogenic signals of these receptors in luminal breast cancer cell lines (9,14).hMENA isoforms, undetectable in normal breast tissue, are progressively expressed in premalignant breast lesions, suggesting that their presence could be used as an early stage marker of breast neoplasia in women at a hig...

We have studied the gene expression pattern of invasive primary mammary tumor cells using a unique in vivo invasion assay that isolates the invasive tumor cells by chemotaxis. One of the genes upregulated in the invasive tumor cells is Mena, an actin binding protein involved in the regulation of cell motility. There are multiple known splice variants of Mena accounted for by four alternatively included exons, +, ++, +++ and 11a. Using the in vivo invasion assay in rats and

hMena (ENAH), an actin regulatory protein involved in the control of cell motility and adhesion, is modulated during human breast carcinogenesis. In fact, whereas undetectable in normal mammary epithelium, hMena becomes overexpressed in high-risk benign lesions and primary and metastatic tumors. In vivo, hMena overexpression correlates with the HER-2 +

Purpose: hMena (ENAH), a cytoskeleton regulatory protein involved in the regulation of cell motility and adhesion, is overexpressed in breast cancer. The aim of this study was to define at what stage of breast carcinogenesis hMena is overexpressed and to correlate hMena overexpression with established prognostic factors in breast cancer, focusing on human epidermal growth factor receptor-2 (HER-2). Experimental Design: hMena expression was assessed immunohistochemically in a prospective cohort of cases (n = 360) encompassing a highly representative spectrum of benign breast diseases associated with different risk of transformation, in situ, invasive, and metastatic tumors. Correlations with conventional pathologic and prognostic variables, such as proliferation index, hormonal receptor status, and HER-2 overexpression, were also evaluated. In vitro experiments were done to study the effect of neuregulin-1and Herceptin treatments on hMena expression. Results: hMena protein is undetectable in normal breast and is weakly expressed in a small percentage of low-risk benign diseases (9%), but displays a progressive and significant increase of positivity in benign lesions at higher risk of transformation (slightly increased risk 43%; moderate increased risk 67%), in in situ (72%), invasive (93%), and metastatic breast cancer (91%).A significant direct correlation with tumor size (P = 0.04), proliferation index (P < 0.0001), and HER-2 overexpression (P < 0.0001) and an inverse relationship with estrogen (P = 0.036) and progesterone receptors (P = 0.001) are found in invasive carcinomas. In vitro experiments show that neuregulin-1up-regulates, whereas Herceptin down-regulates, hMena expression. Conclusions: Our data provide new insights into the relevance of actin-binding proteins in human breast carcinogenesis and indicate hMena overexpression as a surrogate indicator in breast disease management. Management of breast cancer, and other malignancies, islikely to benefit from the identification of early markers of transformation. In this context, major efforts are ongoing in the areas of genomic and proteomic profiling aimed at identifying genetic or biochemical markers related to proliferative lesions heralding the development of breast cancer. In view of the increasing evidence that the host immune response contributes to the editing of the tumor phenotype (1), we have recently isolated, by serologic analysis of cDNA expression libraries (SEREX), hMena (ENAH) protein, the human orthologue of murine Mena, which is overexpressed in over 70% of primary breast cancers (2). Mena belongs to the Ena/VASP protein family, which, by controlling the geometry of the actin filament network (3, 4), represents key regulator molecules of cell movement and shape in a large variety of cell types and organisms (5). It has been suggested that Ena/VASP proteins are members of the adherens junction structures and are required for the actin dynamics necessary to seal membranes into epithelial sheets (6), a process frequently deregula...

BackgroundWe have previously shown that in pancreatic ductal adenocarcinoma (PDA) cells, the glycolytic enzyme alpha-enolase (ENO1) also acts as a plasminogen receptor and promotes invasion and metastasis formation. Moreover, ENO1 silencing in PDA cells induces oxidative stress, senescence and profoundly modifies PDA cell metabolism. Although anti-ENO1 antibody inhibits PDA cell migration and invasion, little is known about the role of ENO1 in regulating cell-cell and cell-matrix contacts. We therefore investigated the effect of ENO1 silencing on the modulation of cell morphology, adhesion to matrix substrates, cell invasiveness, and metastatic ability.MethodsThe membrane and cytoskeleton modifications that occurred in ENO1-silenced (shENO1) PDA cells were investigated by a combination of confocal microscopy and atomic force microscopy (AFM). The effect of ENO1 silencing was then evaluated by phenotypic and functional experiments to identify the role of ENO1 in adhesion, migration, and invasion, as well as in senescence and apoptosis. The experimental results were then validated in a mouse model.ResultsWe observed a significant increase in the roughness of the cell membrane due to ENO1 silencing, a feature associated with an impaired ability to migrate and invade, along with a significant downregulation of proteins involved in cell-cell and cell-matrix adhesion, including alpha v/beta 3 integrin in shENO1 PDA cells. These changes impaired the ability of shENO1 cells to adhere to Collagen I and IV and Fibronectin and caused an increase in RGD-independent adhesion to vitronectin (VN) via urokinase plasminogen activator receptor (uPAR). Binding of uPAR to VN triggers integrin-mediated signals, which result in ERK1-2 and RAC activation, accumulation of ROS, and senescence. In shENO1 cancer cells, the use of an anti-uPAR antibody caused significant reduction of ROS production and senescence. Overall, a decrease of in vitro and in vivo cell migration and invasion of shENO1 PDA cells was observed.ConclusionThese data demonstrate that ENO1 promotes PDA survival, migration, and metastasis through cooperation with integrins and uPAR.Electronic supplementary materialThe online version of this article (doi:10.1186/s13045-016-0385-8) contains supplementary material, which is available to authorized users.