Junction protein shrew-1 influences cell invasion and interacts with invasion-promoting protein CD147

Shrew-1 was previously isolated from an endometriotic cell line in our search for invasion-associated genes. It proved to be a membrane protein that targets to the basolateral membrane of polarized epithelial cells, interacting with E-cadherin-catenin complexes of adherens junctions. Paradoxically, the existence of adherens junctions is incompatible with invasion. To investigate whether shrew-1 can indeed influence cellular invasion, we overexpressed it in HT1080 fibrosarcoma cells. This resulted in enhanced invasiveness, accompanied by an increased matrix metalloprotease (MMP)-9 level in the supernatant, raising the question about the role of shrew-1 in this process. Logic suggested we looked for an interaction with CD147, a known promoter of invasiveness and MMP activity. Indeed, genetics-based, biochemical, and microscopy experiments revealed shrew-1- and CD147-containing complexes in invasive endometriotic cells and an interaction in epithelial cells, which was stronger in MCF7 tumor cells, but weaker in Madin-Darby canine kidney cells. In contrast to the effect mediated by overexpression, small interfering RNA-mediated down-regulation of either shrew-1 or CD147 in HeLa cells decreased invasiveness without affecting the proliferation behavior of HeLa cells, but the knockdown cells displayed decreased motility. Altogether, our results imply that shrew-1 has a function in the regulation of cellular invasion, which may involve its interaction with CD147.     

Phagocytized Beads Reduce the α5β1 Integrin Facilitated Invasiveness of Cancer Cells by Regulating Cellular Stiffness

Cell invasion through the extracellular matrix (ECM) of connective tissue is an important biomechanical process, which plays a prominent role in tumor progression. The malignancy of tumors depends mainly on the capacity of cancer cells to migrate and metastasize. A prerequisite for metastasis is the invasion of cancer cells through connective tissue to targeted organs. Cellular stiffness and cytoskeletal remodeling dynamics have been proposed to affect the invasiveness of cancer cells. Here, this study investigated whether highly invasive cancer cells are capable of invading into dense 3D-ECMs with an average pore-size of 1.3 or 3.0 μm when phagocytized beads (2.7 and 4.5 μm diameter) increased their cellular stiffness and reduced their cytoskeletal remodeling dynamics compared to weakly invasive cancer cells. The phagocytized beads decreased the invasiveness of the α5β1^high cancer cells into 3D-ECMs, whereas the invasiveness of the α5β1^low cancer cells was not affected. The effect of phagocytized beads on the highly invasive α5β1^high cells was abolished by specific knock-down of the α5 integrin subunit or addition of an anti-α5 integrin blocking antibody. Furthermore, the reduction of contractile forces using MLCK and ROCK inhibitors abolished the effect of phagocytized beads on the invasiveness of α5β1^high cells. In addition, the cellular stiffness of α5β1^high cells was increased after bead phagocytosis, whereas the bead phagocytosis did not alter the stiffness of α5β1^low cells. Taken together, the α5β1 integrin dependent invasiveness was reduced after bead phagocytosis by altered biomechanical properties, suggesting that the α5β1^high cells need an appropriate intermediate cellular stiffness to overcome the steric hindrance of 3D-ECMs, whereas the α5β1^low cells were not affected by phagocytized beads.     

A Highlights from MBoC Selection: Soft matrix is a natural stimulator for cellular invasiveness

Directional mesenchymal cell invasion in vivo is understood to be a stimulated event and to be regulated by cytokines, chemokines, and types of extracellular matrix (ECM). Instead, by focusing on the cellular response to ECM stiffness, we found that soft ECM (low stiffness) itself is sufficient to prevent stable cell-to-cell adherens junction formation, up-regulate matrix metalloproteinase (MMP) secretion, promote MMP activity, and induce invadosome-like protrusion (ILP) formation. Consistently, similar ILP formation was also detected in a three-dimensional directional invasion assay in soft matrix. Primary human fibroblasts spontaneously form ILPs in a very narrow range of ECM stiffness (0.1–0.4 kPa), and such ILP formation is Src family kinase dependent. In contrast, spontaneous ILP formation in malignant cancer cells and fibrosarcoma cells occurs across a much wider range of ECM stiffness, and these tumor cell ILPs are also more prominent at lower stiffness. These findings suggest that ECM softness is a natural stimulator for cellular invasiveness.     

Contractile forces contribute to increased glycosylphosphatidylinositol-anchored receptor CD24-facilitated cancer cell invasion

The malignancy of a tumor depends on the capability of cancer cells to metastasize. The process of metastasis involves cell invasion through connective tissue and transmigration through endothelial monolayers. The expression of the glycosylphosphatidylinositol-anchored receptor CD24 is increased in several tumor types and is consistently associated with increased metastasis formation in patients. Furthermore, the localization of β1-integrins in lipid rafts depends on CD24. Cell invasion is a fundamental biomechanical process and usually requires cell adhesion to the extracellular matrix (ECM) mainly through β1 heterodimeric integrin receptors. Here, we studied the invasion of A125 human lung cancer cells with different CD24 expression levels in three-dimensional ECMs. We hypothesized that CD24 expression increases cancer cell invasion through increased contractile forces. To analyze this, A125 cells (CD24 negative) were stably transfected with CD24 and sorted for high and low CD24 expression. The invasiveness of the CD24(high) and CD24(low) transfectants was determined in three-dimensional ECMs. The percentage of invasive cells and their invasion depth was increased in CD24(high) cells compared with CD24(low) cells. Knockdown of CD24 and of the β1-integrin subunit in CD24(high) cells decreased their invasiveness, indicating that the increased invasiveness is CD24- and β1-integrin subunit-dependent. Fourier transform traction microscopy revealed that the CD24(high) cells generated 5-fold higher contractile forces compared with CD24(low) cells. To analyze whether contractile forces are essential for CD24-facilitated cell invasion, we performed invasion assays in the presence of myosin light chain kinase inhibitor ML-7 as well as Rho kinase inhibitor Y27632. Cell invasiveness was reduced after addition of ML-7 and Y27632 in CD24(high) cells but not in CD24(neg) cells. Moreover, after addition of lysophosphatidic acid or calyculin A, an increase in pre-stress in CD24(neg) cells was observed, which enhanced cellular invasiveness. In addition, inhibition of the Src kinase or STAT3 strongly reduced the invasiveness of CD24(high) cells, slightly reduced that of CD24(low) cells, and did not alter the invasiveness of CD24(neg) cells. Taken together, these results suggest that CD24 enhances cell invasion through increased generation or transmission of contractile forces.     

Shifts in the abundance and distribution of shallow water fish fauna on the southeastern Brazilian coast: a response to climate change

Myriophyllum aquaticum is a semi-submerged exotic macrophyte that was introduced to China for many years. This species may be found in an emergent form in aquatic environments or in an amphibious form under drained conditions. Nuisance growth of this species has often been attributed to excessive amounts of nutrients. Therefore, we tested the following hypotheses: (1) high nutrient availability facilitates the establishment of M. aquaticum and (2) fragment type interacts with nutrient availability to determine the colonization and regeneration capacities of M. aquaticum. Two types of fragments were grown in water solutions with two levels of phosphorous. After 3 weeks, the survival rates showed no significant difference between the phosphorous treatments. However, emergent fragments showed higher RGR in the low and high phosphorous treatments than amphibious fragments. In addition, emergent fragments also showed higher regeneration capacities, indicating higher invasiveness in emergent fragments compared to amphibious fragments. Moreover, the high phosphorous concentration caused emergent fragments to produce more branches, indicating that nutrient availability may increase M. aquaticum propagule pressure. Our study highlights that nutrient supply increased emergent fragment establishment and shaped the invasion dynamics of macrophytes, which could help predict the spread and potential impact of exotic macrophytes in natural aquatic ecosystems.     

Loss of GM130 in breast cancer cells and its effects on cell migration,invasion and polarity

Spatially distinct pools of the small GTPase Cdc42 were observed, but the major focus of research so far has been to investigate its signaling at the plasma membrane. We recently showed that the Golgi pool of Cdc42 is relevant for cell polarity and that it is regulated by GM130, a Golgi matrix protein. Loss of GM130 abrogated cell polarity and consistent with the notion that polarity is frequently impaired in cancer, we found that GM130 is downregulated in colorectal cancer. Whether the loss of GM130 solely affects polarity, or whether it affects other processes relevant for tumorigenesis remains unclear. In a panel of breast cancer cells lines, we investigated the consequences of GM130 depletion on traits of relevance for tumor progression, such as survival, proliferation, adhesion, migration and invasion. We show that cellular assays that depend on polarity, such as chemotaxis and wound scratch assays, are only of limited use to investigate the role of polarity modulators in cancer. Depletion of GM130 increases cellular velocity and increases the invasiveness of breast cancer cells, therefore supporting the view that alterations of polarity contribute to tumor progression.     

Oxygen-mediated regulation of gelatinase and tissue inhibitor of metalloproteinases-1 expression by invasive cells.

The relative expression of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) is an important determinant in trophoblast invasion of the uterus and tumor invasion and metastasis. Our previous studies have shown that low oxygen levels increase the in vitro invasiveness of trophoblast and tumor cells. The present study examined whether changes in oxygen levels affect TIMP and MMP expression by cultured trophoblast and breast cancer cells. Reverse zymographic analysis demonstrated reduced TIMP-1 protein secretion by HTR-8/SVneo trophoblast cells as well as MDA-MB-231 and MCF-7 breast carcinoma cells cultured in 1% vs 20% oxygen for 24 h. While gelatin zymography revealed no changes in the levels of MMP-9 secreted by HTR-8/SVneo trophoblasts cultured under various oxygen concentrations for 24 h, human MDA-MB-231 breast carcinoma cells displayed increased MMP-9 secretion and human MCF-7 breast cancer cells exhibited reduced secretion of this enzyme when cultured under similar conditions. In contrast, MMP-2 levels remained unchanged in all cultures incubated under similar conditions. Western blot analysis of MMP-9 protein in cell extracts confirmed the results of zymography. To assess the contribution of enhanced MMP activity to hypoxia-induced invasion, the effect of an MMP inhibitor (llomastat) on the ability of MDA-MB-231 cells to penetrate reconstituted extracellular matrix (Matrigel) was examined. Results showed that MMP inhibition significantly decreased the hypoxic upregulation of invasion by these cells. These findings indicate that the increased cellular invasiveness observed under reduced oxygen conditions may be due in part to a shift in the balance between MMPs and their inhibitors favoring increased MMP activity.     

Inhibition of invasiveness of human lung cancer cell line H1299 by over-expression of cofilin

The Rho-LIM-kinase (LIMK) signaling pathway, believed to be involved in the regulation of tumor invasion, specifically regulates the activity of cofilin. However, it is unclear whether cofilin plays a pivotal role in tumor invasiveness. In this paper we show using a tet-on gene expression system that over-expression of cofilin inhibits the invasiveness of human lung cancer H1299 cells. Over-expressed cofilin disrupts the actin cytoskeleton at the leading edge of the cell and up-regulates p27(kip1), which is known to be involved in regulating cell motility. Removal of cofilin over-expression normalizes the p27(kip1) level and concomitantly restores the invasiveness of the cultured cells. These findings suggest that excessive cofilin production might prevent cancer cell invasion.     

Expression of endothelins and their receptors promotes an invasive phenotype of breast tumor cells but is insufficient to induce invasion in benign cells

There is increased staining of endothelins (ET-1, -2, and -3) and receptors (ET-RA and -RB) in invasive breast tumors compared to nonneoplastic tissue, and ETs stimulate MCF-7 cell invasion in vitro. We analyzed ETstimulation of benign and transformed mammary epithelial cells, and whether expression of ETs is sufficient to induce invasiveness. In breast cancer patient serum, ET-1 was increased in those patients with lymph node metastases compared to those with no lymph node involvement; ETs, however, had no mitogenic effect on breast tumor cell lines in vitro. The benign mammary epithelial cell line, hTERT-HME1, and the poorly invasive breast tumor cell line MCF-7 secreted low levels of ET-1, while the invasive cell lines SKBR3 and MDAMB231 secreted high levels. Expression of the ETs and receptors by the cell lines broadly correlated with their in vitro invasiveness; overexpression of ETs in MCF-7 cells increased basal invasion. ET-mediated invasion involved both receptors and a calcium influx to induce a pertussis toxin-sensitive MAPK pathway. MMP-14 activity was induced via ET-RA in an autocrine manner. In contrast to transformed cells, ET stimulation or overexpression did not induce an invasive phenotype in benign cells. Benign cells do not respond to ETs, and ET expression is not sufficient to induce invasion; however, the level of ET production by tumor cells correlates with their invasiveness, and increasing expression of the ET axis promotes breast tumor cell invasion via both receptors, while MMP-14 is induced via ET-RA.     

Central European plant species from more productive habitats are more invasive at a global scale

Aim Accumulating evidence indicates that species may be pre‐adapted for invasion success in new ranges. In the light of increasing global nutrient accumulation, an important candidate pre‐adaptation for invasiveness is the ability to grow in nutrient‐rich habitats. Therefore we tested whether globally invasive species originating from Central Europe have come from more productive rather than less productive habitats. A further important candidate pre‐adaptation for invasiveness is large niche width. Therefore, we also tested whether species able to grow across habitats with a wider range of productivity are more invasive. Location Global with respect to invasiveness, and Central European with respect to origin of study species. Methods We examined whether average habitat productivity and its width across habitats are significant predictors of the success of Central European species as aliens and as weeds elsewhere in the world based on data in the Global Compendium of Weeds. The two habitat productivity measures were derived from nutrient indicator values (after Ellenberg) of accompanying species present in vegetation records of the comprehensive Czech National Phytosociological Database. In the analyses, we accounted for phylogenetic relatedness among species and for size of the native distribution ranges. Results Species from more productive habitats and with a wider native habitat‐productivity niche in Central Europe have higher alien success elsewhere in the world. Weediness of species increased with mean habitat productivity. Niche width was also an important determinant of weediness for species with their main occurrence in nutrient‐poor habitats, but not for those from nutrient‐rich habitats. Main conclusions Our results indicate that Central European plant species from productive habitats and those species from nutrient‐poor habitat with wide productivity‐niche are pre‐adapted to become invasive. These results suggest that the world‐wide invasion success of many Central European species is likely to have been promoted by the global increase of resource‐rich habitats.     

Invasive clonal plant species have a greater root-foraging plasticity than non-invasive ones

Clonality is frequently positively correlated with plant invasiveness, but which aspects of clonality make some clonal species more invasive than others is not known. Due to their spreading growth form, clonal plants are likely to experience spatial heterogeneity in nutrient availability. Plasticity in allocation of biomass to clonal growth organs and roots may allow these plants to forage for high-nutrient patches. We investigated whether this foraging response is stronger in species that have become invasive than in species that have not. We used six confamilial pairs of native European clonal plant species differing in invasion success in the USA. We grew all species in large pots under homogeneous or heterogeneous nutrient conditions in a greenhouse, and compared their nutrient-foraging response and performance. Neither invasive nor non-invasive species showed significant foraging responses to heterogeneity in clonal growth organ biomass or in aboveground biomass of clonal offspring. Invasive species had, however, a greater positive foraging response in terms of root and belowground biomass than non-invasive species. Invasive species also produced more total biomass. Our results suggest that the ability for strong root foraging is among the characteristics promoting invasiveness in clonal plants.     

MUC1 induced by Epstein-Barr virus latent membrane protein 1 causes dissociation of the cell-matrix interaction and cellular invasiveness via STAT signaling

Disruption of cellular adhesion is an essential pathobiologic step leading to tumor dissemination. Mucin 1 (MUC1) is a mucinous glycoprotein expressed at the surfaces of epithelial cells in many tissues and their carcinomas. MUC1 plays crucial roles in tumor invasion and metastasis, especially in opposing cell adhesion. We have shown that virus infection, specifically by the human tumor virus Epstein-Barr virus (EBV) induces a spectrum of cellular invasiveness and metastasis factors. Here we show that expression of MUC1 is increased in diverse latently EBV-infected cell lines that express latent membrane protein 1 (LMP1), the main viral oncoprotein, and that the level of MUC1 was suppressed by expression of a dominant-negative mutant of LMP1. Expression of LMP1 in EBV-negative nasopharyngeal cell lines induces expression of MUC1 through activation of the MUC1 promoter via binding of STAT1 and STAT3. Finally, LMP1 reduces cell adhesion ability, which is restored by inhibition of MUC1 expression with MUC1 small interfering RNA (siRNA). In addition, LMP1 increases cell invasiveness, which is suppressed by MUC1 siRNA. Thus, LMP1 induces MUC1, a factor important in an early step of detachment and release of tumor cells, which along with induction of other invasiveness and angiogenic factors may combine to act in a complex sequential process that culminates in metastasis of EBV-infected tumor cells.     

Ectopic expression of L-plastin in human tumor cells: Diagnostic and therapeutic implications

Modulation of the actin cytoskeleton is critical for tumor cell migration and invasion. Therefore, actin-binding proteins which regulate this modulation may be valuable targets to inhibit the metastatic properties of tumor cells. Changes in the actin cytoskeleton are accomplished by a variety of actin-binding proteins such as cofilin, α-actinin, filamin, fascin and the plastins. Interestingly, the hematopoetic isoform of the plastins, L-plastin, is not only expressed by hematopoetic cells, but also by most human cancer cell lines. Yet, data regarding the functional importance of L-plastin expression in tumor tissues are controversial: in colon carcinomas, the expression level of L-plastin correlated with tumor progression, whereas no such correlation could be seen in breast carcinomas. We therefore systematically investigated whether expression of L-plastin influences the adhesiveness, the motility and invasiveness of human tumor cells. An siRNA mediated knock-down of L-plastin in an L-plastin positive melanoma cell line inhibited migration of these cells. Accordingly, expression of L-plastin in L-plastin negative melanoma cells led to enhanced cell migration towards extracellular matrix components. However, mere expression of L-plastin did not promote tumor cell invasion into basement membranes. Only, if L-plastin was phosphorylated, tumor cell invasion was promoted. Therefore, in clinical studies, not only the expression of L-plastin but also the phosphorylation status of L-plastin should be compared with regard to tumor progression.Besides the potential prognostic relevance of L-plastin expression and phosphorylation in human cancer cells, L-plastin may represent a novel target for cancer therapy. Moreover, the constitutive activity of the L-plastin promotor in non-hematopoetic tumors opens up novel perspectives for gene therapy of cancer using L-plastin-promotor driven viral vectors.     

Glucose-limiting conditions induce an invasive population of MDA-MB-231 breast cancer cells with increased connexin 43 expression and membrane localization

Gap junctional intercellular communication (GJIC) is a homeostatic process mediated by membrane channels composed of a protein family known as connexins. Alterations to channel activity can modulate suppression or facilitation of cancer progression. These varying roles are influenced by the cancer cell genetic profile and the context-dependent mechanisms of a dynamic extracellular environment that encompasses fluctuations to nutrient availability. To better explore the effects of altered cellular metabolism on GJIC in breast cancer, we generated a derivative of the triple-negative breast cancer cell line MDA-MB-231 optimized for growth in low-glucose. Reduced availability of glucose is commonly encountered during tumor development and leads to metabolic reprogramming in cancer cells. MDA-MB-231 low-glucose adapted cells exhibited a larger size with improved cell–cell contact and upregulation of cadherin-11. Additionally, increased protein levels of connexin 43 and greater plasma membrane localization were observed with a corresponding improvement in GJIC activity compared to the parental cell line. Since GJIC has been shown to affect cellular invasion in multiple cancer cell types, we evaluated the invasive qualities of these cells using multiple three-dimensional Matrigel growth models. Results of these experiments demonstrated a significantly more invasive phenotype. Moreover, a decrease in invasion was noted when GJIC was inhibited. Our results indicate a potential response of triple-negative breast cancer cells to reduced glucose availability that results in changes to GJIC and invasiveness. Delineation of this relationship may help elucidate mechanisms by which altered cancer cell metabolism affects GJIC and how cancer cells respond to nutrient availability in this regard. Supplementary materialThe online version of this article (10.1007/s12079-020-00601-3) contains supplementary material, which is available to authorized users.     

Emergence of Spatial Structure in Cell Groups and the Evolution of Cooperation

On its own, a single cell cannot exert more than a microscopic influence on its immediate surroundings. However, via strength in numbers and the expression of cooperative phenotypes, such cells can enormously impact their environments. Simple cooperative phenotypes appear to abound in the microbial world, but explaining their evolution is challenging because they are often subject to exploitation by rapidly growing, non-cooperative cell lines. Population spatial structure may be critical for this problem because it influences the extent of interaction between cooperative and non-cooperative individuals. It is difficult for cooperative cells to succeed in competition if they become mixed with non-cooperative cells, which can exploit the public good without themselves paying a cost. However, if cooperative cells are segregated in space and preferentially interact with each other, they may prevail. Here we use a multi-agent computational model to study the origin of spatial structure within growing cell groups. Our simulations reveal that the spatial distribution of genetic lineages within these groups is linked to a small number of physical and biological parameters, including cell growth rate, nutrient availability, and nutrient diffusivity. Realistic changes in these parameters qualitatively alter the emergent structure of cell groups, and thereby determine whether cells with cooperative phenotypes can locally and globally outcompete exploitative cells. We argue that cooperative and exploitative cell lineages will spontaneously segregate in space under a wide range of conditions and, therefore, that cellular cooperation may evolve more readily than naively expected.     

Tumor-associated microglia/macrophages enhance the invasion of glioma stem-like cells via TGF-β1 signaling pathway

The invasion of malignant glioma cells into the surrounding normal brain tissues is crucial for causing the poor outcome of this tumor type. Recent studies suggest that glioma stem-like cells (GSLCs) mediate tumor invasion. However, it is not clear whether microenvironment factors, such as tumor-associated microglia/macrophages (TAM/Ms), also play important roles in promoting GSLC invasion. In this study, we found that in primary human gliomas and orthotopical transplanted syngeneic glioma, the number of TAM/Ms at the invasive front was correlated with the presence of CD133(+) GSLCs, and these TAM/Ms produced high levels of TGF-β1. CD133(+) GSLCs isolated from murine transplanted gliomas exhibited higher invasive potential after being cocultured with TAM/Ms, and the invasiveness was inhibited by neutralization of TGF-β1. We also found that human glioma-derived CD133(+) GSLCs became more invasive upon treatment with TGF-β1. In addition, compared with CD133(-) committed tumor cells, CD133(+) GSLCs expressed higher levels of type II TGF-β receptor (TGFBR2) mRNA and protein, and downregulation of TGFBR2 with short hairpin RNA inhibited the invasiveness of GSLCs. Mechanism studies revealed that TGF-β1 released by TAM/Ms promoted the expression of MMP-9 by GSLCs, and TGFBR2 knockdown reduced the invasiveness of these cells in vivo. These results demonstrate that TAM/Ms enhance the invasiveness of CD133(+) GSLCs via the release of TGF-β1, which increases the production of MMP-9 by GSLCs. Therefore, the TGF-β1 signaling pathway is a potential therapeutic target for limiting the invasiveness of GSLCs.     

BMP2 accelerates the motility and invasiveness of gastric cancer cells via activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway

Up-regulation of bone morphogenetic proteins (BMPs) and their receptors by tumor is an important hallmark in cancer progression, as it contributes through autocrine and paracrine mechanisms to tumor development, invasion, and metastasis. Generally, increased motility and invasion are positively correlated with the epithelial-mesenchymal transition (EMT). The purpose of the present study was to determine whether BMP-2 signaling to induce gastric cancer cells to undergo EMT-mediated invasion might pass through the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. Herein we showed that gastric cancer cell lines express all the components of BMP-2 signaling, albeit to different extents. Moreover, an increased concentration of BMP-2 strongly enhanced motility and invasiveness in gastric cancer cells, whereas no increase was observed in cells treated with either Noggin (a BMP-2 inhibitor) or BMP-2 blocking antibodies. The stimulation of BMP-2 in gastric cancer cells induces a full EMT characterized by Snail induction, E-cadherin delocalization and down-regulation, and up-regulation of mesenchymal and invasiveness markers. Furthermore, blockade of BMP-2 signaling by Noggin or BMP-2 blocking antibodies also restored these changes in EMT markers. In addition, phosphorylation of Akt was also enhanced by treatment with BMP-2, but not Noggin or BMP-2 blocking antibodies. Pretreatment of gastric cancer cells with PI-3 kinase/Akt kinase inhibitor (kinase-dead Akt [DN-Akt], Akt siRNA, or LY294002) significantly inhibited BMP-2-induced EMT and invasiveness. Overall, our studies suggest that BMP-2 promotes motility and invasion of gastric cancer cells by activating PI-3 kinase/Akt and that targeting of this signaling pathway may provide therapeutic opportunities in preventing metastasis mediated by BMP-2.     

p120 catenin is essential for mesenchymal cadherin-mediated regulation of cell motility and invasiveness

During epithelial tumor progression, the loss of E-cadherin expression and inappropriate expression of mesenchymal cadherins coincide with increased invasiveness. Reexpression experiments have established E-cadherin as an invasion suppressor. However, the mechanism by which E-cadherin suppresses invasiveness and the role of mesenchymal cadherins are poorly understood. We show that both p120 catenin and mesenchymal cadherins are required for the invasiveness of E-cadherin-deficient cells. p120 binding promotes the up-regulation of mesenchymal cadherins and the activation of Rac1, which are essential for cell migration and invasiveness. p120 also promotes invasiveness by inhibiting RhoA activity, independently of cadherin association. Furthermore, association of endogenous p120 with E-cadherin is required for E-cadherin-mediated suppression of invasiveness and is accompanied by a reduction in mesenchymal cadherin levels. The data indicate that p120 acts as a rheostat, promoting a sessile cellular phenotype when associated with E-cadherin or a motile phenotype when associated with mesenchymal cadherins.     

Macrophages induce invasiveness of epithelial cancer cells via NF-kappa B and JNK

Tumor-associated macrophages may influence tumor progression, angiogenesis and invasion. To investigate mechanisms by which macrophages interact with tumor cells, we developed an in vitro coculture model. Previously we reported that coculture enhanced invasiveness of the tumor cells in a TNF-alpha- and matrix metalloprotease-dependent manner. In this report, we studied intracellular signaling pathways and induction of inflammatory genes in malignant cells under the influence of macrophage coculture. We report that coculture of macrophages with ovarian or breast cancer cell lines led to TNF-alpha-dependent activation of JNK and NF-kappaB pathways in tumor cells, but not in benign immortalized epithelial cells. Tumor cells with increased JNK and NF-kappaB activity exhibited enhanced invasiveness. Inhibition of the NF-kappaB pathway by TNF-alpha neutralizing Abs, an NF-kappaB inhibitor, RNAi to RelA, or overexpression of IkappaB inhibited tumor cell invasiveness. Blockade of JNK also significantly reduced invasiveness, but blockade of p38 MAPK or p42 MAPK had no effect. Cocultured tumor cells were screened for the expression of 22 genes associated with inflammation and invasion that also contained an AP-1 and NF-kappaB binding site. EMMPRIN and MIF were up-regulated in cocultured tumor cells in a JNK- and NF-kappaB-dependent manner. Knocking down either MIF or EMMPRIN by RNAi in the tumor cells significantly reduced tumor cell invasiveness and matrix metalloprotease activity in the coculture supernatant. We conclude that TNF-alpha, via NF-kappaB, and JNK induces MIF and EMMPRIN in macrophage to tumor cell cocultures and this leads to increased invasive capacity of the tumor cells.