Breast cancer invasion and subsequent metastasis to distant tissues occur when cancer cells lose cell–cell contact, develop a migrating phenotype, and invade the basement membrane (BM) and the extracellular matrix (ECM) to penetrate blood and lymphatic vessels. The identification of the mechanisms which induce the development from a ductal carcinoma in situ (DCIS) to a minimally invasive breast carcinoma (MIBC) is an emerging area of research in understanding tumor invasion and metastatic potential. To investigate the progression from DCIS to MIBC, we analyzed peritumoral collagen architecture using correlative scanning electron microscopy (SEM) on histological sections from human biopsies. In DCIS, the peritumoral collagen organizes into concentric lamellae (‘circular fibers’) parallel to the ducts. Within each lamella, type I collagen fibrils align in parallel, while neighboring lamellae show orthogonal fiber orientation. The concentric lamellar arrangement of collagen may physically constrain cancer cell migration, explaining the lack of visible tumor cell invasion into the peritumoral ECM in DCIS. A lamellar dissociation or the development of small inter fiber gaps allowed isolated breast cancer cell invasion and exosomes infiltration in the DCIS microenvironment. The radially arranged fibers observed in the peri-tumoral microenvironment of MIBC biopsies develop from a bending of the circular fibers of DCIS and drive a collective cancer cell invasion associated with an intense immune cell infiltrate. Type I collagen fibrils represent the peri-tumoral nano-environment which can play a mechanical role in regulating the development from DCIS to MIBC. Collectively, it is plausible to suggest that the ECM effectors implicated in breast cancer progression released by the interplay between cancer, stromal, and/or immune cells, and degrading inter fiber/fibril hydrophilic ECM components of the peritumoral ECM, may serve as key players in promoting the dissociation of the concentric collagen lamellae.

Breast cancer (BC) remains a leading cause of cancer-related mortality in women. Extracellular matrix (ECM) remodeling is a critical modulator of tumor invasion and metastasis. Three-dimensional (3D) cell culture models have been proposed as advanced systems better mimicking the tumor microenvironment (TME), potentially offering enhanced insights into underlying mechanisms compared to conventional two-dimensional (2D) cultures. This study highlights how BC cells develop metastatic potential and tumor progression independently from ECM contact using advanced 3D spheroid culture models compared to traditional 2D cultures in triple-negative breast cancer (TNBC) cell lines. Spheroids were formed using ultra-low adhesion plates, and their morphological and functional properties were assessed via phase-contrast and scanning electron microscopy (SEM), along with functional assays. Both cell lines formed compact spheroids exhibiting mesenchymal-to-epithelial transition (MET) characteristics. Functional assays showed enhanced cell migration and dissemination of spheroid-derived cancer cells. Gene expression profiling revealed increased expression of ECM remodeling enzymes, cell surface receptors, and adhesion molecules in 3D cultures compared to 2D. MicroRNA analysis highlighted distinct regulatory patterns specifically associated with metastasis and epithelial-to-mesenchymal transition (EMT). These findings demonstrate that 3D spheroid models effectively recapitulate the complexity of TNBC, providing valuable insights into ECM dynamics, epigenetic regulation, and metastatic behavior and potentially guiding improved therapeutic strategies.

Background/Objectives: Conventional two-dimensional (2D) cell cultures offer valuable insights into cancer cell biology; however, they lack in replicating the complex interactions present in solid tumors. Therefore, research has shifted towards the development of three-dimensional (3D) cell models that recapitulate the dynamic cell–cell and cell–matrix interactions within the complex tumor microenvironment (TME), better resembling tumor growth and initial stages of dissemination. Extracellular matrix, a key component within the TME, regulates cell morphology and signaling, influencing key functional properties. Breast cancer remains the most frequently diagnosed cancer type in women and a leading cause of cancer-related mortality. Methods: The aim of the present study was the development of breast cancer cell-derived spheroids, utilizing two breast cancer cell lines with differential estrogen receptor (ER) expression profile, and their characterization in terms of morphology, functional properties, and expression of epithelial-to-mesenchymal transition (EMT) markers and matrix signatures implicated in breast cancer progression. To this end, the ERα-positive MCF-7, and ERβ-positive MDA-MB-231 breast cancer cell lines were utilized. Results: Our findings revealed notable phenotypic transitions between 2D and 3D cultures, which were further supported by differential EMT markers expression. Moreover, spheroids exhibited distinct expression profiles of key receptors [ERs, epidermal growth factor receptor (EGFR) and insulin-like growth factor receptor (IGF1R)] and matrix molecules (syndecans, and matrix metalloproteinases), accompanied by altered functional cell properties. Bioinformatic tools further emphasized the interplay between the studied matrix regulators and their prognostic relevance in breast cancer. Conclusions: Overall, this study introduces a simple yet informative 3D breast cancer model that captures key TME features to better predict cell behavior in vitro.

Cell-cell communication is essential for the regulated exchange of information between cells, coordinating critical cellular processes under physiological and pathological conditions. The extracellular matrix (ECM) is a complex three-dimensional (3D) intercellular macromolecular network that provides structural support to tissues, while actively modulating cellular functions and responses. ECM-mediated intercellular communication is a key player in both homeostasis and disease development. Particularly in cancer, ECM reorganization drives tumor development and progression, shaping dynamic interactions within the tumor microenvironment (TME). In this review, we present and discuss two principal mechanisms of matrix-mediated cell-cell communication in both physiological and cancerous contexts. First, we explore the impact of ECM biomechanical properties in mechanical sensing and communication, which govern key aspects of cell signaling, adhesion, and migration across normal and malignant tissues. Second, we discuss the role of the ECM in facilitating cell-cell communication through the controlled release and navigation of extracellular vesicles (EVs). EVs carry, among other constituents, proteins, enzymes, microRNAs (miRNAs), and signaling molecules that relay information to nearby or distant cells, modulating the initiation of metastasis and pre-metastatic niche formation. Conclusively, in this review, we highlight the critical role of targeting ECM dynamics in cell-cell communication under physiological processes and during cancer progression. Targeted therapies that modulate ECM components and interactions with cells hold promise for future treatment approaches.

Together with the ACE2 protein, heparan sulfate present at the level of the glycocalyx in the lung epithelia is considered a cellular “co-receptor” for the viral spike protein that allows severe acute respiratory syndrome coronavirus 2 (SARS-CoV) to infect cells. An increase in the amount and activity of heparanase-1 (HPSE), the only enzyme capable of degrading the heparan sulfate (HS) chains of the glycocalyx and of the extracellular matrix, has been described in the plasma of patients affected by coronavirus disease 2019 (Covid-19). Furthermore, the activity of matrix metalloproteases, or MMPs, has been related to matrix degradation, oxidative stress, and inflammation in Covid-19 patients. In this study, we enrolled 26 Covid-19 patients and 15 controls with diagnosis of non-SARS-CoV-2-related pneumonia. We evaluated the expression and activity of HPSE and the expression of MMPs in their serum together with other clinical markers of disease and inflammation. Results proved that HPSE expression and activity serum levels were significantly increased, whereas MMP2 and 9 were decreased in Covid-19 versus non-Covid-19 pneumonia patients. In addition, IL-6 levels were higher, whereas platelet and white blood cells were lower in Covid-19 with respect to non-Covid-19 pneumonia. Moreover, MMP9 but not HPSE (expression and activity) levels were increased in Covid-19 pneumonia patients with ongoing lung alteration over time. In summary, the present findings indicate that HPSE and MMPs are differentially regulated in Covid-19 and non-Covid-19 pneumonia.

Extracellular matrices (ECMs) are dynamic 3D macromolecular networks that exhibit structural characteristics and composition specific to different tissues, serving various biomechanical and regulatory functions. The interactions between ECM macromolecules such as collagen, elastin, glycosaminoglycans (GAGs), proteoglycans (PGs), fibronectin, and laminin, along with matrix effectors and water, contribute to the unique cellular and tissue functional properties during organ development, tissue homoeostasis, remodeling, disease development, and progression. Cells adapt to environmental changes by adjusting the composition and array of ECM components. ECMs, forming the 3D bioscaffolds of our body, provide mechanical support for tissues and organs and respond to the environmental variables influencing growth and final adult body shape in mammals. Different cell types display distinct adaptations to the respective ECM environments. ECMs regulate biological processes by controlling the diffusion of infections and inflammations, sensing and adapting to external stimuli and gravity from the surrounding habitat, and, in the context of cancer, interplaying with and regulating cancer cell invasion and drug resistance. Alterations in the ECM composition in pathological conditions drive adaptive responses of cells and could therefore result in abnormal cell behavior and tissue dysfunction. Understanding the biomechanical functionality, adaptation, and roles of distinct ECMs is essential for research on various pathologies, including cancer progression and multidrug resistance, which is of crucial importance for developing targeted therapies. In this Viewpoint article, we critically present and discuss specific biomechanical functions of ECMs and regulatory adaptation mechanisms in both health and disease, with a particular focus on cancer progression.

Abstract Background and Aims Glucose remains the predominant osmotic agent in peritoneal dialysis (PD), yet its prolonged use is associated with an inevitable decline in peritoneal filtration capacity. Persistent contact with glucose during dialysis can induce significant morphological and functional changes in the peritoneum. In this study, we explore the morphological alterations in mesothelial cells exposed to both conventional glucose-based PD solutions and an innovative biocompatible PD solution (XyloCore) containing L-carnitine and Xylitol. Method Met5A mesothelial cells were seeded and cultured on a polyester filter (with a pore size of 0.4 micrometers, Transwell, 12 well type, Millipore) utilizing a full medium. The impact of PD solutions, differentiating between glucose-based and XyloCore, was assessed on cells cultivated on transwells. These cells were exposed to PD solutions on the apical side and to culture medium on the basal side. The cells were then employed for proteomic and metabolomic assessments and were also fixed and scrutinized through scanning electron microscopy (SEM). Results Through unsupervised hierarchical clustering analysis, discernable proteomic distinctions emerged between wild-type (WT) cells (control) and cells exposed to either glucose-based PD solution or XyloCore. In SEM analysis, control cells exhibited a distinct flat epithelial appearance. Contrastingly, subjecting WT cells to treatment with a glucose-based PD solution induced significant alterations in cellular morphology. Notably, cells displayed elongated shapes, loosening of cell-cell contacts, and a consistent denuding of the culture surface. In contrast, XyloCore maintained a better cellular morphology and mitigated cell detachment. Conclusion Preserving the integrity of the mesothelial barrier is crucial for maintaining peritoneal ultrafiltration capacity. The findings suggest that glucose-based PD solutions trigger early morphological changes in cell shape and cell-cell contacts, likely stemming from alterations in cytoskeleton or adhesion molecules. The exploration of new osmotic agents in clinical practice holds paramount significance for the future of peritoneal dialysis.

We investigated how the extracellular matrix (ECM) affects LoVo colorectal cancer cells behavior during a spatiotemporal invasion. Epithelial-to-mesenchymal transition (EMT) markers, matrix-degrading enzymes, and morphological phenotypes expressed by LoVo-S (doxorubicin-sensitive) and higher aggressive LoVo-R (doxorubicin-resistant) were evaluated in cells cultured for 3 and 24 h on Millipore filters covered by Matrigel, mimicking the basement membrane, or type I Collagen reproducing a desmoplastic lamina propria. EMT and invasiveness were investigated with RT-qPCR, Western blot, and scanning electron microscopy. As time went by, most gene expressions decreased, but in type I Collagen samples, a strong reduction and high increase in MMP-2 expression in LoVo-S and -R cells occurred, respectively. These data were confirmed by the development of an epithelial morphological phenotype in LoVo-S and invading phenotypes with invadopodia in LoVo-R cells as well as by protein-level analysis. We suggest that the duration of culturing and type of substrate influence the morphological phenotype and aggressiveness of both these cell types differently. In particular, the type I collagen meshwork, consisting of large fibrils confining inter fibrillar micropores, affects the two cell types differently. It attenuates drug-sensitive LoVo-S cell aggressiveness but improves a proteolytic invasion in drug-resistant LoVo-R cells as time goes by. Experimental studies on CRC cells should examine the peri-tumoral ECM components, as well as the dynamic physical conditions of TME, which affect the behavior and aggressiveness of both drug-sensitive and drug-resistant LoVo cells differently.

Glycosaminoglycans, the building blocks of proteoglycans, play a central role in the extracellular matrix and regulate a number of cellular processes. Therefore, any imbalance in their levels can lead to significant changes in cell behavior and phenotype. Additionally, glycosaminoglycans and their derivatives can be deployed as therapeutic agents in pathological conditions. Since cell morphology is a critical indicator of specialized cellular functions, its study can provide valuable insight. Scanning electron microscopy is a high-resolution imaging technique that makes for an ideal tool to observe the cellular appearance in 2D and 3D cultures under different conditions and/or substrates. In this chapter we provide a step-by-step protocol to study the influence of exogenously added glycosaminoglycans in the morphology of cells using scanning electron microscopy.

The surface of all animal cells is coated with a layer of carbohydrates linked in various ways to the outer side of the plasma membrane. These carbohydrates are mainly bound to proteins in the form of glycoproteins and proteoglycans and together with the glycolipids constitute the so-called glycocalyx. In particular, the endothelial glycocalyx that covers the luminal layer of the endothelium is composed of glycosaminoglycans (heparan sulphate -HS and hyaluronic acid -HA), proteoglycans (syndecans and glypicans) and adsorbed plasma proteins. Thanks to its ability to absorb water, this structure contributes to making the surface of the vessels slippery but at the same time acts by modulating the mechano-transduction of the vessels, the vascular permeability and the adhesion of leukocytes in thus regulating several physiological and pathological events. Among the various enzymes involved in the degradation of the glycocalyx, heparanase (HPSE) has been shown to be particularly involved. This enzyme is responsible for the cutting of heparan sulfate (HS) chains at the level of the proteoglycans of the endothelial glycocalyx whose dysfunction appears to have a role in organ fibrosis, sepsis and viral infection. In this mini-review, we describe the mechanisms by which HPSE contributes to glycocalyx remodeling and then examine the role of glycocalyx degradation in the development of pathological conditions and pharmacological strategies to preserve glycocalyx during disease pathogenesis.

Cancer cell invasion is regulated by extracellular matrix (ECM) chemical signaling and gene expression but it also consists in a mechanical process controlled by ECM’s array. Scanning electron microscope analysis, invasion test, and real-time PCR demonstrated that Matrigel mimicking basement membrane (BM) doesn’t promote epithelial–mesenchymal transition (EMT) in both low and very aggressive breast cancer cells (MCF-7 and MDA-MB-231). A loose network of type I collagen mimicking the sub-BM favors EMT in MCF-7 cells but physically limits their invasion ability vs. Matrigel, as collagen does not induce an increase of metalloproteases (MMPs) in cells following ameboid-invasion mode. Collagen doesn’t change MDA-MB-231 phenotypes but further improves their invasion capability vs. Matrigel, by stimulating MMPs production. Concentrated type I collagen mimicking deeper ECM induces cells adhesion, further development of microvesicles, microvilli, long filopodia, and tunneling nanotubes (TNTs). Nonaligned fibronectin favors breast cancer cells adhesion, microvesicles, and TNTs development. Densely packed and parallel collagen fibers mimicking a collagen array in mammary tumor progression oppose invasion. In colon cancer, LoVo-R cells, resistant to doxorubicin, concentrated collagen favors development of invaginating phenotypes with invadopodia. We suggest that collagen acts as a physical factor inducing EMT in breast cancer cells and drug resistance in LoVo-R cells.

Estrogen receptors (ERs) have pivotal roles in the development and progression of triple-negative breast cancer (TNBC). Interactions among cancer cells and tumor microenvironment are orchestrated by the extracellular matrix that is rapidly emerging as prominent contributor of fundamental processes of breast cancer progression. Early studies have correlated ERβ expression in tumor sites with a more aggressive clinical outcome, however ERβ exact role in the progression of TNBC remains to be elucidated. Herein, we introduce the functional role of ERβ suppression following isolation of monoclonal cell populations of MDA-MB-231 breast cancer cells transfected with shRNA against human ESR2 that permanently resulted in 90% reduction of ERβ mRNA and protein levels. Further, we demonstrate that clone selection results in strongly reduced levels of the aggressive functional properties of MDA-MB-231 cells, by transforming their morphological characteristics, eliminating the mesenchymal-like traits of triple-negative breast cancer cells. Monoclonal populations of shERβ MDA-MB-231 cells undergo universal matrix reorganization and pass on a mesenchymal-to-epithelial transition state. These striking changes are encompassed by the total prevention of tumorigenesis in vivo following ERβ maximum suppression and isolation of monoclonal cell populations in TNBC cells. We propose that these novel findings highlight the promising role of ERβ targeting in future pharmaceutical approaches for managing the metastatic dynamics of TNBC breast cancer.

Consolidated data indicate that tumor bulk is not only made up of a heterogeneous set of neoplastic cells but also of a variety of resident and infiltrating host cells, soluble factors, and components of the extracellular matrix which as a whole is defined as the tumor microenvironment. In this context, the extracellular matrix plays a fundamental role in tumor progression as it acts as a repository for various biomolecules such as growth factors, cytokines, enzymes, and inhibitors which are mainly linked to heparan sulfate proteoglycans (HSPG) and whose release can regulate the response or not of cancer cells. Among the various enzymes involved in the degradation of the ECM, heparanase (HPSE) has been shown to be particularly involved in tumor progression and metastatic invasion. This enzyme, capable of cutting heparan sulfate (HS) chains, is overexpressed in practically all solid tumors, clearly demonstrating that it has pro-invasive and pro-angiogenic characteristics for neoplastic cells. Furthermore, considering that heparanase is released not only by tumor cells but also by platelets, endothelial cells, and immune cells, we can admit that its enzymatic activity has a strong impact on the tumor microenvironment. Here, we discuss the recent development in the study of heparanase in cancer progression as well as on novel mechanisms by which heparanase regulates the nature of the tumor microenvironment.

Aim of the study was to understand the behavior of colon cancer LoVo-R cells (doxorubicin-resistant) vs. LoVo-S (doxorubicin sensitive) in the initial steps of extracellular matrix (ECM) invasion. We investigated how the matrix substrates Matrigel and type I collagen-mimicking the basement membrane (BM) and the normal or desmoplastic lamina propria, respectively-could affect the expression of epithelial-to-mesenchymal transition (EMT) markers, matrix-degrading enzymes, and phenotypes. Gene expression with RT-qPCR, E-cadherin protein expression using Western blot, and phenotypes using scanning electron microscopy (SEM) were analyzed. The type and different concentrations of matrix substrates differently affected colon cancer cells. In LoVo-S cells, the higher concentrated collagen, mimicking the desmoplastic lamina propria, strongly induced EMT, as also confirmed by the expression of Snail, metalloproteases (MMPs)-2, -9, -14 and heparanase (HPSE), as well as mesenchymal phenotypes. Stimulation in E-cadherin expression in LoVo-S groups suggests that these cells develop a hybrid EMT phenotype. Differently, LoVo-R cells did not increase their aggressiveness: no changes in EMT markers, matrix effectors, and phenotypes were evident. The low influence of ECM components in LoVo-R cells might be related to their intrinsic aggressiveness related to chemoresistance. These results improve understanding of the critical role of tumor microenvironment in colon cancer cell invasion, driving the development of new therapeutic approaches.

Prostate cancer displays a certain phenotypic plasticity that allows for the transition of cells from the epithelial to the mesenchymal state. This process, known as epithelial–mesenchymal transition (EMT), is one of the factors that give the tumor cells greater invasive and migratory capacity with subsequent formation of metastases. In addition, many cancers, including prostate cancer, are derived from a cell population that shows the properties of stem cells. These cells, called cancer stem cells (CSCs) or tumor-initiating cells, not only initiate the tumor process and growth but are also able to mediate metastasis and drug resistance. However, the impact of EMT and CSCs in prostate cancer progression and patient survival is still far from fully understood. Heparanase (HPSE), the sole mammalian endoglycosidase capable of degrading heparan sulfate (HS), is also involved in prostate cancer progression. We had previously proved that HPSE regulates EMT in non-cancerous pathologies. Two prostate cancer cell lines (DU145 and PC3) were silenced and overexpressed for HPSE. Expression of EMT and stemness markers was evaluated. Results showed that the expression of several EMT markers are modified by HPSE expression in both the prostate cancer cell lines analyzed. In the same way, the stemness markers and features are also modulated by HPSE expression. Taken together, the present findings seem to prove a new mechanism of action of HPSE in sustaining prostate cancer growth and diffusion. As for other tumors, these results highlight the importance of HPSE as a potential pharmacological target in prostate cancer treatment.

Triple-negative breast cancer (TNBC) is defined by aggressive behavior, limited response to chemotherapy and lower overall survival rates. The increased metastatic potential of TNBC is a combined result of extensive extracellular matrix (ECM) remodeling that leads to cytoskeleton rearrangement and activation of epithelial-to-mesenchymal transition (EMT). The overexpression of epidermal growth factor receptor (EGFR) in TNBC tumors has been linked to induced expression of EMT-related molecules. EMT activation has often been associated with increased metastasis and stemness. Recently, we described the crucial role of EGFR/estrogen receptor beta (ERβ) interplay in the regulation of invasion and cell-matrix interactions. In this study, we report on the EGFR-ERβ functional relationship in connection to the aggressiveness and cancer stem cell (CSC)-like characteristics of TNBC cells. ERβ-suppressed and MDA-MB-231 cells were subjected to downstream EGFR inhibition and/or estradiol stimulation to assess alterations in functional parameters as well as in morphological characteristics, studied by scanning electron, atomic force, and immunofluorescence microscopies. Moreover, the expression and localization of key EMT and CSC-related markers were also evaluated by real-time qPCR, immunofluorescence microscopy, and flow cytometry. EGFR inhibition resulted in an overall suppression of aggressive functional characteristics, which occurred in an ERβ-mediated manner. These changes could be attributed to a reduction, at the molecular level, of EMT and stemness-linked markers, most notably reduced expression of Notch signaling constituents and the cell surface proteoglycan, syndecan-1. Collectively, our study highlights the importance of EGFR signaling as a key effector of aggressiveness, EMT, and stemness in an ERβ-dependent way in TNBC.

Breast cancer constitutes a heterogeneous disease. The expression profiles of estrogen receptors (ERs), as well as the expression patterns of extracellular matrix (ECM) macromolecules, determine its development and progression. Hyaluronan (HA) is an ECM molecule that regulates breast cancer cells' properties in a molecular size‐dependent way. Previous studies have shown that 200‐kDa HA fragments modulate the functional properties, morphology, and expression of several matrix mediators of the highly metastatic ERα−/ERβ+ MDA‐MB‐231 cells. In order to evaluate the effects of HA fragments (< 10, 30 and 200‐kDa) in ERβ‐suppressed breast cancer cells, the shERβ MDA‐MB‐231 cells were used. These cells are less aggressive when compared with MDA‐MB‐231 cells. To this end, the functional properties, the morphology, and the expression of the molecules associated with breast cancer cells metastatic potential were studied. Notably, both cell proliferation and invasion were significantly reduced after treatment with 200‐kDa HA. Moreover, as assessed by scanning electron microscopy, 200‐kDa HA affected cellular morphology, and as assessed by qPCR, upregulated the epithelial marker Ε‐cadherin. The expression profiles of ECM mediators, such as HAS2, CD44, and MMP7, were also altered. On the other hand, cellular migration and the expression levels of syndecan‐4 (SDC‐4) were not significantly affected in contrast to our observations regarding MDA‐MB‐231 cells. These novel data demonstrate that the molecular size of the HA determines its effects on ERβ‐suppressed breast cancer cells and that 200‐kDa HA exhibits antiproliferative effects on these cells. A deeper understanding of this mechanism may contribute to the development of therapeutic strategies against breast cancer.

Extracellular matrix (ECM) is a dynamic 3‐dimensional network of macromolecules that provides structural support for the cells and tissues. Accumulated knowledge clearly demonstrated over the last decade that ECM plays key regulatory roles since it orchestrates cell signaling, functions, properties and morphology. Extracellularly secreted as well as cell‐bound factors are among the major members of the ECM family. Proteins/glycoproteins, such as collagens, elastin, laminins and tenascins, proteoglycans and glycosaminoglycans, hyaluronan, and their cell receptors such as CD44 and integrins, responsible for cell adhesion, comprise a well‐organized functional network with significant roles in health and disease. On the other hand, enzymes such as matrix metalloproteinases and specific glycosidases including heparanase and hyaluronidases contribute to matrix remodeling and affect human health. Several cell processes and functions, among them cell proliferation and survival, migration, differentiation, autophagy, angiogenesis, and immunity regulation are affected by certain matrix components. Structural alterations have been also well associated with disease progression. This guide on the composition and functions of the ECM gives a broad overview of the matrisome, the major ECM macromolecules, and their interaction networks within the ECM and with the cell surface, summarizes their main structural features and their roles in tissue organization and cell functions, and emphasizes the importance of specific ECM constituents in disease development and progression as well as the advances in molecular targeting of ECM to design new therapeutic strategies.

It was reported that lumican inhibits the activity of metalloproteinase MMP-14 and melanoma cell migration in vitro and in vivo. Moreover, Snail triggers epithelial-to-mesenchymal transition and the metastatic potential of cancer cells. Therefore, the aim of this study was to examine the effect of lumican on Mock and Snail overexpressing melanoma B16F1 cells in vivo. Lung metastasis was analyzed after intravenous injections of Mock-B16F1 and Snail-B16F1 cells in Lum+/+ and Lum−/− mice. At day 14, mice were sacrificed, and lungs were collected. The number of lung metastatic nodules was significantly higher in mice injected with Snail-B16F1 cells as compared to mice injected with Mock-B16F1 cells confirming the pro-metastatic effect of Snail. This effect was stronger in Lum−/− mice as compared to Lum+/+, suggesting that endogenous lumican of wild-type mice significantly inhibits metastasis to lungs. Scanning electron and confocal microscopy investigations demonstrated that lumican inhibits the development of elongated cancer cell phenotypes which are known to develop invadopodia releasing MMPs. Moreover, lumican was shown to affect the expression of cyclin D1, cortactin, vinculin, hyaluronan synthase 2, heparanase, MMP-14 and the phosphorylation of FAK, AKT, p130 Cas and GSK3α/β. Altogether, these data demonstrated that lumican significantly inhibits lung metastasis in vivo, as well as cell invasion in vitro, suggesting that a lumican-based strategy targeting Snail-induced metastasis could be useful for melanoma treatment.