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Cancer remains a significant global health concern. Breast cancer is a multifaceted and prevalent disease influenced by several factors, among which estrogen receptors (ERs) and the extracellular matrix (ECM) play pivotal roles. ERs, encompassing ERα and ERβ, exert significant diversity on tumor behavior, cell signaling, invasion, and metastatic potential, thus guiding breast cancer prognosis. Understanding the multifunctional connections between ERs and ECM that mediate the dynamics of tumor microenvironment is vital for unraveling the complexity of breast cancer pathobiology and identifying novel therapeutic targets. This critical review delves into the intricate nature of ERs, emphasizing their structural isoforms and the consequential impact on breast cancer outcomes. A detailed examination of ER-mediated cell signaling pathways reveals how differential expression of ERα and ERβ isoforms influence breast cancer cell behavior. The functional ERs-matrix interactions emerge as a pivotal factor in modulating epigenetic mechanisms of breast cancer cells, orchestrating changes in cellular phenotype and expression patterns of matrix modulators. Specifically, ERα isoforms are shown to regulate ECM signaling cascades, while the effects of ECM components on ERα activity highlight a bidirectional regulatory axis. The diversity of ERβ isoforms is also highlighted, illustrating their distinct contribution to ECM-mediated cellular responses. This review underscores the complex interplay between ERα/β isoforms and the ECM, shedding light onto the potential therapeutic strategies targeting these interactions to improve breast cancer management., (© 2024 The Author(s). The FEBS Journal published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

Mammalian glycosaminoglycans (GAGs), except hyaluronan (HA), are sulfated polysaccharides that are covalently attached to core proteins to form proteoglycans (PGs). This article summarizes key biological findings for the most widespread GAGs, namely HA, chondroitin sulfate/dermatan sulfate (CS/DS), keratan sulfate (KS), and heparan sulfate (HS). It focuses on the major processes that remain to be deciphered to get a comprehensive view of the mechanisms mediating GAG biological functions. They include the regulation of GAG biosynthesis and postsynthetic modifications in heparin (HP) and HS, the composition, heterogeneity, and function of the tetrasaccharide linkage region and its role in disease, the functional characterization of the new PGs recently identified by glycoproteomics, the selectivity of interactions mediated by GAG chains, the display of GAG chains and PGs at the cell surface and their impact on the availability and activity of soluble ligands, and on their move through the glycocalyx layer to reach their receptors, the human GAG profile in health and disease, the roles of GAGs and particular PGs (syndecans, decorin, and biglycan) involved in cancer, inflammation, and fibrosis, the possible use of GAGs and PGs as disease biomarkers, and the design of inhibitors targeting GAG biosynthetic enzymes and GAG-protein interactions to develop novel therapeutic approaches., (© 2024 The Authors. The FEBS Journal published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

Oral squamous cell carcinoma (OSCC) is a head and neck cancer (HNC) with a high mortality rate. OSCC is developed in the oral cavity and it is triggered by many etiologic factors and can metastasize both regionally and distantly. Recent research advances in OSCC improved our understanding on the molecular mechanisms involved in and the initiation of OSCC metastasis. The key roles of the extracellular matrix (ECM) in OSCC are an emerging area of intensive research as the ECM macromolecular network is actively involved in events that regulate cellular morphological and functional properties, transcription and cell signaling mechanisms in invasion and metastasis. The provisional matrix that is formed by cancer cells is profoundly different in composition and functions as compared with the matrix of normal tissue. Fibroblasts are mainly responsible for matrix production and remodeling, but in cancer, the tumor matrix in the tumor microenvironment (TME) also originates from cancer cells. Even though extensive research has been conducted on the role of ECM in regulating cancer pathogenesis, its role in modulating OSCC is less elucidated since there are several issues yet to be fully understood. This critical review is focused on recent research as to present and discuss on the involvement of ECM macromolecular effectors (i.e., proteoglycans, integrins, matrix metalloproteinases) in OSCC development and progression., (© 2024 The Authors. IUBMB Life published by Wiley Periodicals LLC on behalf of International Union of Biochemistry and Molecular Biology.)

The incidence of head and neck cancer (HNC), constituting approximately one in ten cancer cases worldwide, affects approximately 644,000 individuals annually. Managing this complex disease involves various treatment modalities such as systemic therapy, radiation, and surgery, particularly for patients with locally advanced disease. HNC treatment necessitates a multidisciplinary approach due to alterations in patients' genomes affecting their functionality. Predominantly, squamous cell carcinomas (SCCs), the majority of HNCs, arise from the upper aerodigestive tract epithelium. The epidemiology, staging, diagnosis, and management techniques of head and neck squamous cell carcinoma (HNSCC), encompassing clinical, image-based, histopathological and molecular profiling, have been extensively reviewed. Lymph node metastasis (LNM) is a well-known predictive factor for HNSCC that initiates metastasis and significantly impacts HNSCC prognosis. Distant metastasis (DM) in HNSCC has been correlated to aberrant expression of cancer cell-derived cytokines and growth factors triggering abnormal activation of several signaling pathways that boost cancer cell aggressiveness. Recent advances in genetic profiling, understanding tumor microenvironment, oligometastatic disease, and immunotherapy have revolutionized treatment strategies and disease control. Future research may leverage genomics and proteomics to identify biomarkers aiding individualized HNSCC treatment. Understanding the molecular basis, genetic landscape, atypical signaling pathways, and tumor microenvironment have enhanced the comprehension of HNSCC molecular etiology. This critical review sheds light on regional and distant metastases in HNSCC, presenting major clinical and laboratory features, predictive biomarkers, and available therapeutic approaches., (© 2024. The Author(s).)

Head and neck cancer (HNC) encompasses a number of malignancies originating in the head and neck area. In patients with HNC, cervical lymph nodes constitute metastatic sites for cancer cells that escape primary tumors. The premetastatic niche (PMN) is a crucial concept in understanding metastatic disease. PMN refers to the microenvironment resulting mainly from primary tumor cells to foster metastatic tumor cell growth at a distant organ. Tumor microenvironment (TME) plays an important part in the pathogenesis of PMN. A significant prognostic factor is the close association between metastases of lymph nodes and organ dissemination in many different malignancies. The nodal premetastatic niche (NPMN) is a particular type of PMN located within the lymph nodes. NPMN formation is specifically important in HNC as regional lymph node metastasis commonly occurs. The formation happens when tumor cells create a supportive microenvironment within lymph nodes, facilitating their survival, growth, spread, and invasion. This complex mechanism involves multiple steps and cellular interactions between the primary tumor and tumor microenvironment. Several extracellular matrix (ECM) macromolecules, cytokines, and growth factors are implicated in this process. The aim of this article is to present the most recent data on the regulation of the lymph node PMN at molecular and cellular levels in HNC, as well as insights with respect to the relationship between primary tumor cells and the microenvironment of lymph nodes, and the formation of NPMN. We also critically discuss on potential targets for preventing or disrupting nodal metastases and identify potential biomarkers for predicting HNC outcomes.

Cancer initiation and progression heavily rely on microenvironmental cues derived from various components of the niche including the extracellular matrix (ECM). ECM is a complex macromolecular network that governs cell functionality. Although the two-dimensional (2D) cell culture systems provide useful information at the molecular level and preclinical testing, they could not accurately represent the in vivo matrix microenvironmental architecture. Hence, it is no surprise that researchers in the last decade have focussed their efforts on establishing novel advanced in vitro culture models that mimic tumour and tissue-specific niches and interactions. These numerous three-dimensional (3D) culture systems that are now widely available, as well as those still under development, grant researchers with new, improved tools to study cancer progression and to explore innovative therapeutic options. Herein, we report on the emerging methods and cutting-edge technologies in 3D cell culture platforms and discuss their potential use in unveiling tumour microenvironmental cues, drug screening and personalized treatment., (© 2023 The Authors. The FEBS Journal published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

Background: Osteoarthritis (OA) is a common degenerative chronic disease accounting for physical pain, tissue stiffness and mobility restriction. Current therapeutic approaches fail to prevent the progression of the disease considering the limited knowledge on OA pathobiology. During OA progression, the extracellular matrix (ECM) of the cartilage is aberrantly remodeled by chondrocytes. Chondrocytes, being the main cell population of the cartilage, participate in cartilage regeneration process. To this end, modern tissue engineering strategies involve the recruitment of mesenchymal stem cells (MSCs) due to their regenerative capacity as to promote chondrocyte self-regeneration., Methods and Results: In the present study, we evaluated the role of type II collagen, as the main matrix macromolecule in the cartilage matrix, to promote chondrogenic differentiation in two MSC in vitro culture systems. The chondrogenic differentiation of human Wharton's jelly- and dental pulp-derived MSCs was investigated over a 24-day culture period on type II collagen coating to improve the binding affinity of MSCs. Functional assays, demonstrated that type II collagen promoted chondrogenic differentiation in both MSCs tested, which was confirmed through gene and protein analysis of major chondrogenic markers., Conclusions: Our data support that type II collagen contributes as a natural bioscaffold enhancing chondrogenesis in both MSC models, thus enhancing the commitment of MSC-based therapeutic approaches in regenerative medicine to target OA and bring therapy closer to the clinical use., (© 2023. The Author(s).)

A facile experimental protocol for the synthesis of poly(ethylene glycol)-modified (PEGylated) gold nanorods (AuNRs@PEG) is presented as well as an effective drug loading procedure using the non-steroidal anti-inflammatory drug (NSAID) naproxen (NAP). The interaction of AuNRs@PEG and drug-loaded AuNRs (AuNRs@PEG@NAP) with calf-thymus DNA was studied at a diverse temperature revealing different interaction modes; AuNRs@PEG may interact via groove-binding and AuNRs@PEG@NAP may intercalate to DNA-bases. The cleavage activity of the gold nanoparticles for supercoiled circular pBR322 plasmid DNA was studied by gel electrophoresis while their affinity for human and bovine serum albumins was also evaluated. Drug-release studies revealed a pH-sensitive behavior with a release up to a maximum of 24% and 33% NAP within the first 180 min at pH = 4.2 and 6.8, respectively. The cytotoxicity of AuNRs@PEG and AuNRs@PEG@NAP was evaluated against MCF-7 and MDA-MB-231 breast cancer cell lines. The development of AuNRs as an efficient non-steroidal anti-inflammatory drugs (NSAIDs) delivery system for chemotherapy is still in its infancy. The present work can shed light and inspire other research groups to work in this direction., Competing Interests: The authors declare no conflict of interest.

Exosomes are nanosized vesicles that are produced in normal and cancer cells, promoting intracellular communication. In head and neck cancer (HNC), exosomes are involved in many undesirable events of cancer development and progression, including angiogenesis, tumor microenvironment (TME) remodeling, invasion, epithelial-to-mesenchymal transition (EMT), metastasis, extracellular matrix (ECM) degradation, and drug resistance. Exosomes are involved in altering the signaling pathways in recipient cells by the cargoes they carry. Proteins, lipids, and nucleic acids such as DNA fragments and RNAs (i.e., mRNAs, miRNAs, and long non-coding RNAs) are carried in the exosomes to promote cell communication. EMT is a critical cellular process in which epithelial cells are forced to become mesenchymal cells by the actions of SNAIL/SLUG, TWIST, and ZEB family transcription factors carried in exosomes that facilitate metastasis. In this critical review, we focused on exosome biogenesis, their cargoes, and their involvement in EMT induction and metastasis during HNC. Insights into exosome isolation and characterization, as well as their key role in ECM remodeling and degradation, are also presented and critically discussed. More importantly, this article addresses the role of exosomes in HNC and drug resistance induced in drug-sensitive cancer cells. In addition, exosomes have a great potential to be used as diagnostic and therapeutic tools. A better understanding on exosome biogenesis, composition, and functions in HNC will aid in developing novel therapeutic strategies to treat HNC, overcome therapy resistance, and avoid metastasis, which is a significant cause of cancer death.

Extracellular matrixes (ECMs) are intricate 3-dimensional macromolecular networks of unique architectures with regulatory roles in cell morphology and functionality. As a dynamic native biomaterial, ECM undergoes constant but tightly controlled remodeling that is crucial for the maintenance of normal cellular behavior. Under pathological conditions like cancer, ECM remodeling ceases to be subjected to control resulting in disease initiation and progression. ECM is comprised of a staggering number of molecules that interact not only with one another, but also with neighboring cells via cell surface receptors. Such interactions, too many to tally, are of paramount importance for the identification of novel disease biomarkers and more personalized therapeutic intervention. Recent advances in big data analytics have allowed the development of online databases where researchers can take advantage of a stochastic evaluation of all the possible interactions and narrow them down to only those of interest for their study, respectively. This novel approach addresses the limitations that currently exist in studies, expands our understanding on ECM interactions, and has the potential to advance the development of targeted therapies. In this article we present the current trends in ECM biology research and highlight its importance in tissue integrity, the main interaction networks, ECM-mediated cell functional properties and issues related to pharmacological targeting., (© 2022. The Author(s).)

Circulating microRNAs (miRNAs) possess significant roles in normal homeostasis and disease conditions, including cardiovascular diseases, fibrosis, inflammatory response, and cancer. Secreted miRNAs, via the membrane vesicles, actively communicate with extracellular matrix (ECM) components to affect cell-cell and cell-matrix interactions, thereby affecting matrix remodeling and metabolic pathways in the recipient cells. Matrix macromolecules regulate the expression of miRNAs, and in turn miRNAs have been identified as emerging mediators of matrix constituents, serving as appealing biomarkers for many pathophysiological processes. Therefore, the expression profile of certain miRNAs highlights the importance of their targeting in several aspects of human pathologies. In this chapter, we report molecular biology protocols to determine the effects of selected miRNAs on the expression and activity of matrix biomolecules., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

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., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Extracellular matrix (ECM) critically regulates cancer cell behavior by governing cell signaling and properties. Hyaluronan (HA) acts as a structural and functional ECM component that mediates critical properties of cancer cells in a molecular size-dependent manner. HA fragments secreted by cancer-associated fibroblasts (CAFs) reveal the correlation of HA to CAF-mediated matrix remodeling, a key step for the initiation of metastasis. The main goal of this article is to highlight the vital functions of HA in cancer cell initiation and progression as well as HA-mediated paracrine interactions among cancer and stromal cells. Furthermore, the HA implication in mediating immune responses to cancer progression is also discussed. Novel data on the role of HA in the formation of pre-metastatic niche may contribute towards the improvement of current theranostic approaches that benefit cancer management., (© 2022 International Union of Biochemistry and Molecular Biology.)

Air pollution by pathogens has posed serious concern on global health during the last decades, especially since the breakout of the last pandemic. Therefore, advanced high-efficiency techniques for air purification are highly on demand. However, in air-filtering devices, the prevention of secondary pollution that may occur on the filters remains a challenge. Toward this goal, in the present work, we demonstrate a facile and eco-friendly process for the biocidal treatment of commercial high-efficiency particulate air filters. The antibacterial filters were successfully prepared through spray coating of aqueous solutions based on biocidal water-soluble polymers, poly(sodium 4-styrene sulfonate- co -cetyl trimethylammonium 4-styrene sulfonate- co -glycidyl methacrylate) [P(SSNa24- co -SSAmC 16 56- co -GMA20)] and poly(2-dimethylaminoethyl)methacrylate. Significantly, an optimized green route was developed for the synthesis of the used polymers in aqueous conditions and their stabilization through cross-linking reaction, leading to biocidal air filters with long-lasting activity. The developed coatings presented strong and rapid antibacterial activity against Staphylococcus aureus (in 5 min) and Escherichia coli (in 15 min). Moreover, the cytotoxicity test of the polymeric materials toward Α549 lung adenocarcinoma cells indicated very low toxicity as they did not affect either the cell growth or cell morphology. The above-mentioned results together with the scalable and easy-to-produce green methodology suggest that these materials can be promising candidates as filter coatings for use on air-purification devices., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Obesity is a remarkably important factor for breast carcinogenesis and aggressiveness. The implication of increased BMI in triple negative breast cancer (TNBC) development is also well established. A malignancy-promoting role of the adipose tissue has been supposed, where the adipocytes that constitute the majority of stromal cells release pro-inflammatory cytokines and growth factors. Alterations in adipokines and their receptors play significant roles in breast cancer initiation, progression, metastasis, and drug response. Classic adipokines, such as leptin, adiponectin, and resistin, have been extensively studied in breast cancer and connected with breast cancer risk and progression. Notably, new molecules are constantly being discovered and the list is continuously growing. Additionally, substantial progress has been made concerning their differential expression in association with clinical and pathological parameters of tumors and the prognostic and predictive value of their dysregulation in breast cancer carcinogenesis. However, evidence regarding the mechanisms by which adipose tissue is involved in the development of TNBC is lacking. In the present article we comment on current data on the suggested involvement of these mediators in breast cancer development and progression, with particular emphasis on TNBC, to draw attention to the design of novel targeted therapies and biomarkers.

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., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Piperigkou, Koutsandreas, Franchi, Zolota, Kletsas, Passi and Karamanos.)

Proteoglycans consist one of the major extracellular matrix class of biomolecules that demonstrate nodal roles in cancer progression. Modern diagnostic and therapeutic approaches include proteoglycan detection and pharmacological targeting in various cancer types. Proteoglycans orchestrate critical signaling pathways for cancer development and progression through dynamic interactions with matrix components. It is well established that the epigenetic signatures of cancer cells play critical role in guiding their functional properties and metastatic potential. Secreted microRNAs (miRNAs) reside in a complex network with matrix proteoglycans, thus affecting cell-cell and cell-matrix communication. This mini-review aims to highlight current knowledge on the cell-surface proteoglycan-mediated signaling cascades that regulate miRNA biogenesis in cancer. Moreover, the miRNA-mediated proteoglycan regulation during cancer progression and mechanistic aspects on the way that proteoglycans affect miRNA expression are presented. Recent advances on the role of cell surface proteoglycans in exosome biogenesis and miRNA packaging and expression are also discussed.

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., (© 2021 Federation of European Biochemical Societies.)

Exosomes are a subtype of extracellular vesicles (EVs) composed of a lipid bilayer, which carry various cargoes such as nucleic acids, proteins, and bioactive lipids. Cancer cells release exosomes to promote cell communication and interaction with the extracellular matrix (ECM). ECM regulates the secretion and uptake of exosomes. Moreover, the cargo of exosomes can control ECM remodeling, thus affecting cancer progression. Aside from the rearrangement of ECM, exosomal cargo also modulates different signaling pathways that maintain homeostasis and play a major role in tumor growth and immune evasion in the tumor microenvironment (TME). Exosomes are now widely recognized as circulating biomarkers for diagnosis and prognosis. Their role in cancer initiation, progression, and chemoresistance is becoming increasingly clear from preclinical and clinical investigations, thereby gaining interest for their potential use as cancer diagnostics tools, but also for the development of future innovative cancer therapeutics. In this mini review we outline and discuss the correlation between exosomes, TME and cancer progression, while focusing on the potential role of exosomes as diagnostic and prognostic biomarkers, as well as therapeutic vehicles for drug delivery.

Hyaluronan (HA) is an extracellular matrix glycosaminoglycan (GAG) that plays a pivotal role in breast cancer. While HA is the only GAG not normally substituted with sulfate groups, sulfated hyaluronan (sHA) has previously been used in studies with promising antitumor results. The aim of the present study was to evaluate the effects sHA fragments have on breast cancer cells with different estrogen receptor (ER) status. To this end, ERα-positive MCF-7, and ERβ-positive MDA-MB-231 cells were treated with non-sulfated HA or sHA fragments of 50 kDa. The functional properties of the breast cancer cells and the expression of key matrix effectors were investigated. According to the results, sHA attenuates cell proliferation, migration, and invasion, while increasing adhesion on collagen type I. Furthermore, sHA modulates the expression of epithelial-to-mesenchymal transition (EMT) markers, such as e-cadherin and snail2/slug. Additionally, sHA downregulates matrix remodeling enzymes such as the matrix metalloproteinases MT1-MMP, MMP2, and MMP9. Notably, sHA exhibits a stronger effect on the breast cancer cell properties compared to the non-sulfated counterpart, dependent also on the type of cancer cell type. Consequently, a deeper understanding of the mechanism by which sHA facilitate these processes could contribute to the development of novel therapeutic strategies.

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., (© 2021 Federation of European Biochemical Societies.)

Tumor extracellular matrix (ECM) operates in a coordinated mode with cancer and stroma cells to evoke the multistep process of metastatic potential. The remodeled tumor-associated matrix provides a point for direct or complementary therapeutic targeting. Here, we cover and critically address the importance of ECM networks and their macromolecules in cancer. We focus on the roles of key structural and functional ECM components, and their degradation enzymes and extracellular vesicles, aiming at improving our understanding of the mechanisms contributing to tumor initiation, growth, and dissemination, and discuss potential new approaches for ECM-based therapeutic targeting and diagnosis., Competing Interests: Declaration of interests The authors declare no potential conflicts of interest., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

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., (© 2021 Federation of European Biochemical Societies.)

Tissue functionality and integrity demand continuous changes in distribution of major components in the extracellular matrices (ECMs) under normal conditions aiming tissue homeostasis. Major matrix degrading proteolytic enzymes are matrix metalloproteinases (MMPs), plasminogen activators, atypical proteases such as intracellular cathepsins and glycolytic enzymes including heparanase and hyaluronidases. Matrix proteases evoke epithelial-to-mesenchymal transition (EMT) and regulate ECM turnover under normal procedures as well as cancer cell phenotype, motility, invasion, autophagy, angiogenesis and exosome formation through vital signaling cascades. ECM remodeling is also achieved by glycolytic enzymes that are essential for cancer cell survival, proliferation and tumor progression. In this article, the types of major matrix remodeling enzymes, their effects in cancer initiation, propagation and progression as well as their pharmacological targeting and ongoing clinical trials are presented and critically discussed.

Interaction between cancer cells and their microenvironment is central in defining the fate of cancer development. Tumour cells secrete signals (cytokines, chemokines, growth factors) that modify the surrounding area, while the niche supplies structures and activities necessary for tumour maintenance and growth. Hyaluronan (HA) is a glycosaminoglycan that constitute cancer cell niche and is known to influence tumour functions such as proliferation, migration and neoangiogenesis. The knowledge of the factors regulating HA synthesis and size is crucial in understanding the mechanisms sustaining tumour development. Here we show that a yet uncharacterized protein secreted by breast tumour cell lines, named c10orf118 (accession number NM&#95;018017 in NCBI/BLAST, and Q7z3E2 according to the Uniprot identifier), with a predicted length of 898 amino acids, can induce the secretion of HA by stromal fibroblasts through the up-regulation of the hyaluronan synthase 2 gene (HAS2). Intracellularly, this protein is localized in the Golgi apparatus with a possible role in vesicle maturation and transport. The expression of c10orf118 was verified in breast cancer patient specimens and was found to be associated with the presence of estrogen receptor that characterizes a good patient survival. We suggest c10orf118 as a new player that influences the HA amount in breast cancer microenvironment and is associated with low aggressiveness of cancer.

Triple-negative breast cancer (TNBC) is an aggressive subgroup of breast cancer characterized by genomic complexity and therapeutic options limited to only standard chemotherapy. Although it has been suggested that stratifying TNBC patients by pathway-specific molecular alterations may predict benefit from specific therapeutic agents, application in routine clinical practice has not yet been established. There is a growing body of the literature supporting that epigenetic modifications comprised by DNA methylation, chromatin remodeling and non-coding RNAs play a fundamental role in TNBC pathogenesis. Extracellular matrix (ECM) is a highly dynamic 3D network of macromolecules with structural and cellular regulatory roles. Alterations in the expression of ECM components result in uncontrolled matrix remodeling, thus affecting its ability to regulate vital functions of cancer cells, including proliferation, migration, adhesion, invasion and epithelial-to-mesenchymal transition (EMT). Recent molecular data highlight the major role of tumor microenvironment and ECM alterations in TNBC and approaches for targeting tumor microenvironment have recently been recognized as potential therapeutic strategies. Notably, many of the ECM/EMT modifications in cancer are largely driven by epigenetic events, highlighting the pleiotropic effects of the epigenetic network in TNBC. This article presents and critically discusses the current knowledge on the epigenetic alterations correlated with TNBC pathogenesis, with emphasis on those associated with ECM/EMT modifications, their prognostic and predictive value and their use as therapeutic targets., Competing Interests: The authors declare no conflict of interest.

Βradykinin stimulation of B2 receptor is known to activate the oncogenic ERK pathway and overexpression of bradykinin receptors B1 and B2 has been reported to occur in glioma, colorectal and cervical cancers. B1R and B2R antagonists have been shown to reverse tumor proliferation and invasion. Paradoxically, B1R and B2R agonism has also been reported to elicit antiproliferative benefits. In order to complement the data accumulated to date with the natural substrate bradykinin and peptidic B2R antagonists, we decided to examine for the first time the response elicited by B2R stimulation in breast cancer lines with a non-peptidic small molecule B2R agonist. We synthesized and assessed the highly selective and potent B2R partial agonist FR-190997 in MCF-7 and MDA-MBA-231 breast cancer lines and found it possessed significant antiproliferative activity (IC 50 2.14 and 0.08 μΜ, respectively). The modular nature of FR-190997 allowed us to conduct a focused SAR study and discover compound 10 which exhibits subnanomolar antiproliferative activity (IC 50 0.06 nΜ) in the TNBC MDA-MBA-231 cell line. This performance surpasses, in most cases by several orders of magnitude, those of established anticancer agents and FDA-approved breast cancer drugs. In line with the established literature we suggest that this remarkable activity precipitates from a dual mode of action involving agonist-induced receptor internalization/degradation combined with sequestration of functional intracellular B2 receptors and inhibition of the associated endosomal signaling. The latter mode may be realized by appropriate ligands regardless of B2R agonist/antagonist designation which only relates to membrane residing GCPRs. Under this prism the controversy over the antiproliferative effects of B2 agonists and antagonists is potentially neutralized., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Breast cancer accounts for almost one in four cancer diagnoses in women. Studies in breast cancer patients have identified several molecular markers, indicators of aggressiveness, which help toward more individual therapeutic approaches. In triple-negative breast cancer (TNBC), epidermal growth factor receptor (EGFR) overexpression is associated with increased metastatic potential and worst survival rates. Specifically, abnormal EGFR activation leads to altered matrix metalloproteinases' (MMPs) expression and, hence, extracellular matrix (ECM) degradation, resulting in induced migration and invasion. The use of matrix substrates for cell culture gives the opportunity to mimic the natural growth conditions of the cells and their microenvironment, as well as cell-cell and cell-matrix interactions. The aim of this study was to evaluate the impact of EGFR inhibition, estrogen receptor beta (ERβ) and different matrix substrates [type I collagen and fibronectin (FN)] on the functional properties, expression of MMPs and cell morphology of ERβ-positive TNBC cells and shERβ ones. Our results highlight EGFR as a crucial regulator of the expression and activity levels of MMPs, while ERβ emerges as a mediator of MMP7 and MT1-MMP expression. In addition, the EGFR/ERβ axis impacts the adhesion and invasion potential of breast cancer cells on collagen type I. Images obtained by scanning electron microscope (SEM) from cultures on the different matrix substrates revealed novel observations regarding various structures of breast cancer cells (filopodia, extravesicles, tunneling nanotubes, etc.). Moreover, the significant contribution of EGFR and ERβ in the morphological characteristics of these cells is also demonstrated, hence highlighting the possibility of dual pharmacological targeting.

The extracellular matrix is engaged in an ever-evolving and elegant ballet of dynamic reciprocity that directly and bi-directionally regulates cell behavior. Homeostatic and pathophysiological changes in cell-matrix signaling cascades manifest as complex matrix phenotypes. Indeed, the extracellular matrix can be implicated in virtually every known human disease, thus, making it the most critical and dynamic "organ" in the human body. The overall goal of this Special Issue is to provide an accurate and inclusive functional definition that addresses the inherent complexity of matrix phenotypes. This goal is summarily achieved via a corpus of expertly written articles, reviews and original research, focused at answering this question empirically and fundamentally via state-of-the-art methods and research strategies., Competing Interests: The authors declare no conflicts of interest., (© 2020 The Author(s).)

Numerous studies point out serglycin as an important regulator of tumorigenesis in a variety of malignancies. Serglycin expression correlates with the aggressive phenotype of tumor cells and serves as a poor prognostic indicator for disease progression. Although serglycin is considered as an intracellular proteoglycan, it is also secreted in the extracellular matrix by tumor cells affecting cell properties, oncogenic signaling and exosomes cargo. Serglycin directly interacts with CD44 and possibly other cell surface receptors including integrins, evoking cell adhesion and signaling. Serglycin also creates a pro-inflammatory and pro-angiogenic tumor microenvironment by regulating the secretion of proteolytic enzymes, IL-8, TGFβ2, CCL2, VEGF and HGF. Hence, serglycin activates multiple signaling cascades that drive angiogenesis, tumor cell growth, epithelial to mesenchymal transition, cancer cell stemness and metastasis. The interference with the tumorigenic functions of serglycin emerges as an attractive prospect to target malignancies., (Copyright © 2019. Published by Elsevier Ltd.)

The biological functions of estrogens are regulated by estrogen receptors (ERα and ERβ), which contribute in the progression of several hormone-responsive cancer types via estrogen signaling mechanisms. The coordinated actions of ERs and extracellular matrix (ECM) macromolecules are principal mediators of ECM remodeling in the tumor and the adjacent stroma. In breast cancer, ERs are critical biomarkers as their expression in breast tumor determines the disease-free survival, yet guiding treatment decisions and predicting prognosis as well as response to endocrine therapy. In this article, we critically survey the current knowledge on dynamic interactions among ERs and major ECM macromolecules and effectors, such as growth factor receptors, proteoglycans and matrix metalloproteinases, in respect to their key effects in cancer progression, cancer cell functional properties, epithelial-to-mesenchymal transition and epigenetics. Understanding the ERs-mediated ECM reorganization during cancer progression may pave way in identifying novel targets for diagnosis and novel therapeutic approaches for cancer management., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Despite the functional role of serglycin as an intracellular proteoglycan, a variety of malignant cells depends on its expression and constitutive secretion to advance their aggressive behavior. Serglycin arose to be a biomarker for glioblastoma, which is the deadliest and most treatment-resistant form of brain tumor, but its role in this disease is not fully elucidated. In our study we suppressed the endogenous levels of serglycin in LN-18 glioblastoma cells to decipher its involvement in their malignant phenotype. Serglycin suppressed LN-18 (LN-18 shSRGN ) glioblastoma cells underwent astrocytic differentiation characterized by induced expression of GFAP, SPARCL-1 and SNAIL, with simultaneous loss of their stemness capacity. In particular, LN-18 shSRGN cells presented decreased expression of glioma stem cell-related genes and ALDH1 activity, accompanied by reduced colony formation ability. Moreover, the suppression of serglycin in LN-18 shSRGN cells retarded the proliferative and migratory rate, the invasive potential in vitro and the tumor burden in vivo. The lack of serglycin in LN-18 shSRGN cells was followed by G2 arrest, with subsequent reduction of the expression of cell-cycle regulators. LN-18 shSRGN cells also exhibited impaired expression and activity of proteolytic enzymes such as MMPs, TIMPs and uPA, both in vitro and in vivo. Moreover, suppression of serglycin in LN-18 shSRGN cells eliminated the activation of pro-tumorigenic signal transduction. Of note, LN-18 shSRGN cells displayed lower expression and secretion levels of IL-6, IL-8 and CXCR-2. Concomitant, serglycin suppressed LN-18 shSRGN cells demonstrated repressed phosphorylation of ERK1/2, p38, SRC and STAT-3, which together with PI3K/AKT and IL-8/CXCR-2 signaling control LN-18 glioblastoma cell aggressiveness. Collectively, the absence of serglycin favors an astrocytic fate switch and a less aggressive phenotype, characterized by loss of pluripotency, block of the cell cycle, reduced ability for ECM proteolysis and pro-tumorigenic signaling attenuation., Competing Interests: The authors declare that no conflict of interest exists., (© 2020 The Authors.)

The oncogenic role of hyaluronan in several aspects of tumor biology has been well established. Recent studies by us and others suggest that inhibition of hyaluronan synthesis could represent an emerging therapeutic approach with significant clinical relevance in controlling different breast cancer subtypes, including triple-negative breast cancer. Epidemiological and preclinical studies have revealed the therapeutic potential of aspirin (acetyl salicylate), a classical anti-inflammatory drug, in patients with cancer. However, the underlying molecular mechanisms remain unknown. The present study demonstrates that salicylate, a break down product of aspirin in vivo, alters the organization of hyaluronan matrices by affecting the expression levels of hyaluronan synthesizing (HAS1, 2, 3) and degrading (HYAL-1, -2) enzymes, and that of hyaluronan receptor CD44. In particular, salicylate was found to potently activate AMPK, a kinase known to inhibit HAS2 activity, and caused a dose-dependent decrease of cell associated (intracellular and membrane-bound) as well as secreted hyaluronan, followed by the down-regulation of HAS2 and the induction of HYAL-2 and CD44 in metastatic breast cancer cells. These salicylate-mediated effects were associated with the redistribution of CD44 and actin cytoskeleton that resulted in a less motile cell phenotype. Interestingly, salicylate inhibited metastatic breast cancer cell proliferation and growth by inducing cell growth arrest without signs of apoptosis as evidenced by the substantial decrease of cyclin D1 protein and the absence of cleaved caspase-3, respectively. Collectively, our study offers a possible direction for the development of new matrix-based targeted treatments of metastatic breast cancer subtypes via inhibition of hyaluronan, a pro-angiogenic, pro-inflammatory and tumor promoting glycosaminoglycan., (© 2020 The Authors.)

Cancer cell invasion into the surrounding extracellular matrix (ECM) takes place when cell-cell junctions are disrupted upon epithelial-to-mesenchymal transition (EMT). Both cancer cell-stroma and cell-cell crosstalk are essential to support the continuous tumor invasion. Cancer cells release microvesicles and exosomes containing bioactive molecules and signal peptides, which are recruited by neighboring cells or carried to distant sites, thus supporting intercellular communication and cargo transfer. Besides this indirect communication mode, cancer cells can develop cytoplasmic intercellular protrusions or tunneling nanotubes (TNTs), which allow the direct communication and molecular exchange between connected distinct cells. Using scanning electron microscopy (SEM) we show for the first time that MDA-MB-231 (high metastatic potential) and shERβ MDA-MB-231 (low metastatic potential) breast cancer cells cultured on fibronectin and collagen type I or 17β-estradiol (E2) develop TNTs and very long flexible filopodia. Interestingly, the less aggressive shERβ MDA-MB-231 cells treated with E2 in 3D collagen matrix showed the highest development of TNTs and filopodia. TNTs were often associated to adhering exosomes and microvesicles surfing from one cell to another, but no filopodia exhibited vesicle-like cytoplasmic structures on their surface. Moreover, E2 affected the expression of matrix macromolecules and cell effectors mostly in the presence of ERβ. Our novel data highlights the significance of matrix substrates and the presence of E2 and ERβ in the formation of cellular protrusion and the production of surface structures, defining novel phenotypes that unravel nodal reports for breast cancer progression., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2020 The Authors.)

Secreted microRNAs (miRNAs) reside in a complex regulatory network with extracellular matrix (ECM) macromolecules, which affect cell-cell communication, therefore miRNA expression highlights its significance in several aspects of human diseases, including cancer. miRNA-mediated regulation of breast cancer has received considerable attention due to evidence that shows miRNAs to mediate estrogen receptor (ER) status, metastasis, chemoresistance and epithelial-to-mesenchymal transition (EMT). miR-200b is a pluripotent miRNA, which is inversely regulated by ERα and ERβ in mammary cancer. It has been identified as tumor suppressor and EMT inhibitor serving as a critical biomarker, as its expression in breast tumor determines the disease-free survival, thus highlighting its roles in breast cancer invasion and metastasis. The main goal of this study was to investigate the role of miR-200b in modulating the behavior of breast cancer cells with different ER status. We demonstrate that estrogen signaling through ERs reduces miR-200b expression levels in ERα-positive breast cancer cells. Moreover, miR-200b upregulation reduces the aggressive phenotype of ERβ-positive breast cancer cells by inhibiting cell invasiveness and motility, followed by ECM reorganization as well as cytoskeletal and morphological changes concluded from deep inspection of cell topography. Future investigation towards the mechanistic perspective of miR-200b effects in the behavior of aggressive mammary cancer cells appears rewarding in order to expand our understanding of miR-200b as a novel mediator beyond breast cancer diagnosis and pharmaceutical targeting., Competing Interests: C.R. is an employee of Serend-ip GmbH; the other authors declare no conflict of interest., (© 2020 The Authors.)

Expression of miRNAs is critical for the regulation of several cell functions including proliferation, migration, differentiation, and survival, as well as extracellular matrix (ECM) remodeling. The dynamic interplay between miRNAs, ECM macromolecules, and the tumor microenvironment plays critical roles in many aspects of human diseases such as metabolic disorders and cancers. Circulating and secreted miRNAs, via membrane vesicles, affect cell-cell communication and cellular metabolic pathways, underscoring their significance in tumor progression. The primary goal of this article is to highlight the importance of epigenetic regulatory factors, focusing on miRNA-mediated ECM reorganization and their functional relationships, and how matrix-mediated miRNAs affect tumor progression., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The prominent role of CD44 in tumor cell signaling together with its establishment as a cancer stem cell (CSC) marker for various tumor entities imply a key role for CD44 in CSC functional properties. Hyaluronan, the main ligand of CD44, is a major constituent of CSC niche and, therefore, the hyaluronan-CD44 signaling axis is of functional importance in this special microenvironment. This review aims to provide recent advances in the importance of hyaluronan-CD44 interactions in the acquisition and maintenance of a CSC phenotype. Hyaluronan-CD44 axis has a substantial impact on stemness properties of CSCs and drug resistance through induction of EMT program, oxidative stress resistance, secretion of extracellular vesicles/exosomes and epigenetic control. Potential therapeutic approaches targeting CSCs based on the hyaluronan-CD44 axis are also presented., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Extracellular matrices (ECMs) are highly specialized and dynamic three-dimensional (3D) scaffolds into which cells reside in tissues. ECM is composed of a variety of fibrillar components, such as collagens, fibronectin, and elastin, and non-fibrillar molecules as proteoglycans, hyaluronan, and glycoproteins including matricellular proteins. These macromolecular components are interconnected forming complex networks that actively communicate with cells through binding to cell surface receptors and/or matrix effectors. ECMs exert diverse roles, either providing tissues with structural integrity and mechanical properties essential for tissue functions or regulating cell phenotype and functions to maintain tissue homeostasis. ECM molecular composition and structure vary among tissues, and is markedly modified during normal tissue repair as well as during the progression of various diseases. Actually, abnormal ECM remodeling occurring in pathologic circumstances drives disease progression by regulating cell-matrix interactions. The importance of matrix molecules to normal tissue functions is also highlighted by mutations in matrix genes that give rise to genetic disorders with diverse clinical phenotypes. In this review, we present critical and emerging issues related to matrix assembly in tissues and the multitasking roles for ECM in diseases such as osteoarthritis, fibrosis, cancer, and genetic diseases. The mechanisms underlying the various matrix-based diseases are also discussed. Research focused on the highly dynamic 3D ECM networks will help to discover matrix-related causative abnormalities of diseases as well as novel diagnostic tools and therapeutic targets., (© 2019 Federation of European Biochemical Societies.)

The extracellular matrix (ECM) is a multifunctional 3D network of interconnected macromolecules that mediate cellular responses in normal and pathological conditions, including wound healing, tissue homeostasis, skeletal and cardiovascular disease, cancer and drug resistance. The potential of targeting ECM components, such as proteoglycans and glycosaminoglycans, matrix-degrading enzymes and miRNAs will serve as a novel tool for innovative diagnostic methods and therapeutic strategies. With this Special Issue on Extracellular Matrix in Health and Disease, The FEBS Journal offers an updated overview of the functional properties and biological roles of several ECM components, highlighting the significance of ECM targeting in disease management., (© 2019 Federation of European Biochemical Societies.)

High levels of hyaluronan (ΗΑ), a major extracellular matrix (ECM) glycosaminoglycan, have been correlated with poor clinical outcome in several malignancies, including breast cancer. The high and low molecular weight HΑ forms exert diverse biological functions. Depending on their molecular size, ΗΑ forms either promote or attenuate signaling cascades that regulate cancer progression. In order to evaluate the effects of different ΗΑ forms on breast cancer cells' behavior, ΗΑ fragments of defined molecular size were synthesized. Breast cancer cells of different estrogen receptor (ER) status - the low metastatic, ERα-positive MCF-7 epithelial cells and the highly aggressive, ERβ-positive MDA-MB-231 mesenchymal cells - were evaluated following treatment with HA fragments. Scanning electron microscopy revealed that HA fragments critically affect the morphology of breast cancer cells in a molecular-size dependent mode. Moreover, the ΗΑ fragments affect cell functional properties, the expression of major ECM mediators and epithelial-to-mesenchymal transition (ΕΜΤ) markers. Notably, treatment with 200 kDa ΗΑ increased the expression levels of the epithelial marker Ε-cadherin and reduced the expression levels of HA synthase 2 and mesenchymal markers, like fibronectin and snail2/slug. These novel data suggest that the effects of HA in breast cancer cells depend on the molecular size and the ER status. An in-depth understanding on the mechanistic basis of these effects may contribute on the development of novel therapeutic strategies for the pharmacological targeting of aggressive breast cancer., Competing Interests: Carlo Barbera, Mauro Pavan and Devis Galesso were, at the time of the study, full-time employees at Fidia Farmaceutici S.p.A., (© 2019 Published by Elsevier B.V.)

The malignant phenotype of various cancers is linked to enhanced expression of hyaluronan, a pro-angiogenic glycosaminoglycan whose expression is suppressed by 4-methylumbelliferone (4-MU), a non-toxic oral agent used as a dietary supplement to improve health and combat prostate cancer. In this study, we investigated the role of 4-MU in mammary carcinoma cells with distinct malignant phenotypes and estrogen receptor (ER) status, a major prognostic factor in the clinical management of breast cancers. We focused on two breast cancer cell lines, the low metastatic and ERα+ MCF-7 cells, and the highly-aggressive and ERα- MDA-MB-231 cells. Treatment with 4-MU caused a dose-dependent decrease of hyaluronan accumulation in the extracellular matrix as well as within the breast cancer cells, most prevalent in cells lacking ERα. This decrease in hyaluronan was accompanied by suppression of Hyaluronan Synthase 2 (HAS2), the major enzyme responsible for the synthesis of hyaluronan, and by induction of hyaluronidases (HYALs) -1 and -2. Moreover, 4-MU induced intense phenotypic changes and substantial loss of CD44, a major hyaluronan receptor, from cell protrusions. Importantly, 4-MU evoked differential effects depending on the absence or presence of ERα. Only the ERα+ cells showed signs of apoptosis, as determined by cleaved PARP-1, and anoikis as shown by concurrent loss of E-cadherin and β-catenin. Interestingly, 4-MU significantly reduced migration, adhesion and invasion of ERα- breast cancer cells, and concurrently reduced the expression and activity of several matrix degrading enzymes and pro-inflammatory molecules with tumor-promoting functions. Collectively, our findings suggest that 4-MU could represent a novel therapeutic for specific breast cancer subtypes with regard to their ER status via suppression of hyaluronan synthesis and regulation of HAS2, CD44, matrix-degrading enzymes and inflammatory mediators., (Copyright © 2018 Elsevier B.V. All rights reserved.)