The alpha 5 beta 1 integrin supports survival of cells on fibronectin and up-regulates Bcl-2 expression

Update on mast cell biology

Mast cells (MCs) are heterogeneous tissue-resident effector cells that are thought to play central roles in allergic inflammatory disease, yet the degree of heterogeneity and nature of these roles has remained elusive. In recent years, advances in tissue culture systems, preclinical mouse models, and the continued spread of single-cell RNA sequencing have greatly advanced our understanding of MC phenotypes in health and disease. These approaches have identified novel interactions of MC subsets with immune cells, neurons, and tissue structural cells, changing our understanding of how MCs both drive and help resolve tissue inflammation, reshape tissue microenvironments, and influence host behavior. This review addresses key studies from 2022 to 2024 that have advanced our understanding of MC biology in mice and humans.

Integrin-α5 expression and its role in non-small cell lung cancer progression

Integrins are transmembrane receptors that facilitate cell adhesion to the extracellular matrix and neighboring cells. Aberrant expression of integrins has been associated with tumor progression and metastasis in various cancer types. Integrin alpha-5 (ITGA5) is an integrin subtype that serves as a receptor for fibronectin, fibrinogen, and fibrillin-1. The purpose of this study was to elucidate how ITGA5 expression plays a role in human non-small cell lung cancer (NSCLC). Our clinical data, along with data retrieved from The Cancer Genome Database (TCGA), revealed that high ITGA5 expression in NSCLC patients was associated with a lower recurrence-free survival and overall survival. In our in vitro functional assays, ITGA5 overexpression in human NSCLC cell lines resulted in increased cell size, adhesion, and migration properties, while knockdown of ITGA5 restored the phenotypes. Correspondingly, knockdown and inhibition of ITGA5 in endogenously high-expressing NSCLC cell lines resulted in decreased cell size, adhesion, migration, and proliferation. The antiproliferative effect was also confirmed by a reduction in Ki-67 without discernible changes in apoptosis. Collectively, these findings reveal the significant role of ITGA5 in various functional behaviors in NSCLC, providing a potential therapeutic target for NSCLC patients with high ITGA5 expression.

Pllans-II: Unveiling the Action Mechanism of a Promising Chemotherapeutic Agent Targeting Cervical Cancer Cell Adhesion and Survival Pathways

Despite advances in chemotherapeutic drugs used against cervical cancer, available chemotherapy treatments adversely affect the patient's quality of life. For this reason, new molecules from natural sources with antitumor potential and few side effects are required. In previous research, Pllans-II, a phospholipase A2 type-Asp49 from Porthidium lansbergii lansbergii snake venom, has shown selective attack against the HeLa and Ca Ski cervical cancer cell lines. This work suggests that the cytotoxic effect generated by Pllans-II on HeLa cells is triggered without affecting the integrity of the cytoplasmic membrane or depolarizing the mitochondrial membranes. The results allow us to establish that cell death in HeLa is related to the junction blockage between α5β1 integrins and fibronectin of the extracellular matrix. Pllans-II reduces the cells' ability of adhesion and affects survival and proliferation pathways mediated by intracellular communication with the external environment. Our findings confirmed Pllans-II as a potential prototype for developing a selective chemotherapeutic drug against cervical cancer.

The characteristics and the multiple functions of integrin β1 in human cancers

Integrins, which consist of two non-covalently linked α and β subunits, play a crucial role in cell-cell adhesion and cell-extracellular matrix (ECM) interactions. Among them, integrin β1 is the most common subunit and has emerged as a key mediator in cancer, influencing various aspects of cancer progression, including cell motility, adhesion, migration, proliferation, differentiation and chemotherapy resistance. However, given the complexity and sometimes contradictory characteristics, targeting integrin β1 for therapeutics has been a challenge. The emerging understanding of the mechanisms regulating by integrin β1 may guide the development of new strategies for anti-cancer therapy. In this review, we summarize the multiple functions of integrin β1 and signaling pathways which underlie the involvement of integrin β1 in several malignant cancers. Our review suggests the possibility of using integrin β1 as a therapeutic target and highlights the need for patient stratification based on expression of different integrin receptors in future clinical studies.

A cell cycle centric view of tumour dormancy

Tumour dormancy and recurrent metastatic cancer remain the greatest clinical challenge for cancer patients. Dormant tumour cells can evade treatment and detection, while retaining proliferative potential, often for years, before relapsing to tumour outgrowth. Cellular quiescence is one mechanism that promotes and maintains tumour dormancy due to its central role in reducing proliferation, elevating cyto-protective mechanisms, and retaining proliferative potential. Quiescence/proliferation decisions are dictated by intrinsic and extrinsic signals, which regulate the activity of cyclin-dependent kinases (CDKs) to modulate cell cycle gene expression. By clarifying the pathways regulating CDK activity and the signals which activate them, we can better understand how cancer cells enter, maintain, and escape from quiescence throughout the progression of dormancy and metastatic disease. Here we review how CDK activity is regulated to modulate cellular quiescence in the context of tumour dormancy and highlight the therapeutic challenges and opportunities it presents.

Cancer metastasis: Molecular mechanisms and clinical perspectives

Metastatic progression combined with non-responsiveness towards systemic therapy often shapes the course of disease for cancer patients and commonly determines its lethal outcome. The complex molecular events that promote metastasis are a combination of both, the acquired pro-metastatic properties of cancer cells and a metastasis-permissive or -supportive tumor micro-environment (TME). Yet, dissemination is a challenging process for cancer cells that requires a series of events to enable cancer cell survival and growth. Metastatic cancer cells have to initially detach themselves from primary tumors, overcome the challenges of their intravasal journey and colonize distant sites that are suited for their metastases. The implicated obstacles including anoikis and immune surveillance, can be overcome by intricate intra- and extracellular signaling pathways, which we will summarize and discuss in this review. Further, emerging modulators of metastasis, like the immune-microenvironment, microbiome, sublethal cell death engagement, or the nervous system will be integrated into the existing working model of metastasis.

Slow integrin-dependent migration organizes networks of tissue-resident mast cells

Immune cell locomotion is associated with amoeboid migration, a flexible mode of movement, which depends on rapid cycles of actin polymerization and actomyosin contraction1. Many immune cells do not necessarily require integrins, the major family of adhesion receptors in mammals, to move productively through three-dimensional tissue spaces2,3. Instead, they can use alternative strategies to transmit their actin-driven forces to the substrate, explaining their migratory adaptation to changing external environments4-6. However, whether these generalized concepts apply to all immune cells is unclear. Here, we show that the movement of mast cells (immune cells with important roles during allergy and anaphylaxis) differs fundamentally from the widely applied paradigm of interstitial immune cell migration. We identify a crucial role for integrin-dependent adhesion in controlling mast cell movement and localization to anatomical niches rich in KIT ligand, the major mast cell growth and survival factor. Our findings show that substrate-dependent haptokinesis is an important mechanism for the tissue organization of resident immune cells.

Increased Expression of the Pathological O-glycosylated Form of Oncofetal Fibronectin in the Multidrug Resistance Phenotype of Cancer Cells

Changes in protein glycosylation are a hallmark of transformed cells and modulate numerous phenomena associated with cancer progression, such as the acquisition of multidrug resistance (MDR) phenotype. Different families of glycosyltransferases and their products have already been described as possible modulators of the MDR phenotype. Among the glycosyltransferases intensively studied in cancer research, UDP-N-acetyl-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase-6 (pp-GalNAc-T6), which is widely expressed in many organs and tissues, stands out. Its influence in several events associated with kidney, oral, pancreatic, renal, lung, gastric and breast cancer progression has already been described. However, its participation in the MDR phenotype has never been studied. Here, we demonstrate that human breast adenocarcinoma MCF-7 MDR cell lines, generated by chronic exposure to doxorubicin, in addition to exhibiting increased expression of proteins belonging to the ABC superfamily (ABCC1 and ABCG2), and anti-apoptotic proteins (Blcl-2 and Bcl-xL), also present high expression of pp-GalNAc-T6, the enzyme currently proposed as the main responsible for the biosynthesis of oncofetal fibronectin (onf-FN), a major extracellular matrix component expressed by cancer cells and embryonic tissues, but absent in healthy cells. Our results show that onf-FN, which is generated by the addition of a GalNAc unit at a specific threonine residue inside the type III homology connective segment (IIICS) domain of FN, is strongly upregulated during the acquisition of the MDR phenotype. Also, the silencing of pp-GalNAc-T6, not only compromises the expression of the oncofetal glycoprotein, but also made the MDR cells more sensitive to all anticancer drugs tested, partially reversing the MDR phenotype. Taken together, our results demonstrate for the first time the upregulation of the O-glycosylated oncofetal fibronectin, as well as the direct participation of pp-GalNAc-T6 during the acquisition of a MDR phenotype in a breast cancer model, giving credence to the hypothesis that in transformed cells, glycosyltransferases and/or their products, such as unusual extracellular matrix glycoproteins can be used as potential therapeutic targets for the treatment of cancer.

Pllans-II Induces Cell Death in Cervical Cancer Squamous Epithelial Cells via Unfolded Protein Accumulation and Endoplasmic Reticulum Stress

Due to the lack of chemotherapeutic drugs that selectively affect cervical cancer cells, natural sources such as snake venom are currently being investigated for molecules with antitumor potential. Pllans–II, a phospholipase A₂ type–Asp49 from Porthidium lansbergii lansbergii snake venom, induced cell death in a cervical cancer cell line—Ca Ski—related to dysfunction in the ability to resolve endoplasmic reticulum stress, evidenced by sub–expression of genes such as PERK, ERO1 PDIs, HSP70, and CHOP. Western blot analysis validated the last two genes′ sub–expression at the protein level. In addition, Pllans–II presented a dose–dependent cytotoxic effect on cancer cells and an insignificant effect on healthy endothelial cells (HUVEC). Additionally, Pllans–II inhibited cancer cells′ adhesion and migration capacity, induced cell cycle arrest in the G2/M phase, and induced apoptosis stimulated possibly by the extrinsic route. These results demonstrate for the first time that Pllans–II has an antitumor effect on a squamous epithelial cervical cancer cell line and represents a possible biotechnological tool for designing a prominent antitumor agent.

Cancer Stem Cells in Tumor Microenvironment of Adenocarcinoma of the Stomach, Colon, and Rectum

Gastrointestinal adenocarcinomas are one of the world's deadliest cancers. Cancer stem cells and the tissue microenvironment are highly regulated by cell and molecular mechanisms. Cancer stem cells are essential for maintenance and progression and are associated with resistance to conventional treatments. This article reviews the current knowledge of the role of the microenvironment during the primary establishment of gastrointestinal adenocarcinomas in the stomach, colon, and rectum and its relationship with cancer stem cells. We also describe novel developments in cancer therapeutics, such as targeted therapy, and discuss the advantages and disadvantages of different treatments for improving gastrointestinal cancer prognosis.

Integrins as attractive targets for cancer therapeutics

Integrins are transmembrane receptors that have been implicated in the biology of various human physiological and pathological processes. These molecules facilitate cell–extracellular matrix and cell–cell interactions, and they have been implicated in fibrosis, inflammation, thrombosis, and tumor metastasis. The role of integrins in tumor progression makes them promising targets for cancer treatment, and certain integrin antagonists, such as antibodies and synthetic peptides, have been effectively utilized in the clinic for cancer therapy. Here, we discuss the evidence and knowledge on the contribution of integrins to cancer biology. Furthermore, we summarize the clinical attempts targeting this family in anti-cancer therapy development.

Discoidin Domain Receptor 2 Regulates AT1R Expression in Angiotensin II-Stimulated Cardiac Fibroblasts via Fibronectin-Dependent Integrin-β1 Signaling

This study probed the largely unexplored regulation and role of fibronectin in Angiotensin II-stimulated cardiac fibroblasts. Using gene knockdown and overexpression approaches, Western blotting, and promoter pull-down assay, we show that collagen type I-activated Discoidin Domain Receptor 2 (DDR2) mediates Angiotensin II-dependent transcriptional upregulation of fibronectin by Yes-activated Protein in cardiac fibroblasts. Furthermore, siRNA-mediated fibronectin knockdown attenuated Angiotensin II-stimulated expression of collagen type I and anti-apoptotic cIAP2, and enhanced cardiac fibroblast susceptibility to apoptosis. Importantly, an obligate role for fibronectin was observed in Angiotensin II-stimulated expression of AT1R, the Angiotensin II receptor, which would link extracellular matrix (ECM) signaling and Angiotensin II signaling in cardiac fibroblasts. The role of fibronectin in Angiotensin II-stimulated cIAP2, collagen type I, and AT1R expression was mediated by Integrin-β1-integrin-linked kinase signaling. In vivo, we observed modestly reduced basal levels of AT1R in DDR2-null mouse myocardium, which were associated with the previously reported reduction in myocardial Integrin-β1 levels. The role of fibronectin, downstream of DDR2, could be a critical determinant of cardiac fibroblast-mediated wound healing following myocardial injury. In summary, our findings suggest a complex mechanism of regulation of cardiac fibroblast function involving two major ECM proteins, collagen type I and fibronectin, and their receptors, DDR2 and Integrin-β1.

Characteristics of TIMP1, CD63, and β1-Integrin and the Functional Impact of Their Interaction in Cancer

Tissue Inhibitor of Metalloproteases 1, also known as TIMP-1, is named for its well-established function of inhibiting the proteolytic activity of matrix metalloproteases. Given this function, many studies were carried out to verify if TIMP-1 was able to interrupt processes such as tumor cell invasion and metastasis. In contrast, many studies have shown that TIMP-1 expression is increased in several types of tumors, and this increase was correlated with a poor prognosis and lower survival in cancer patients. Later, it was shown that TIMP-1 is also able to modulate cell behavior through the induction of signaling pathways involved in cell growth, proliferation, and survival. The mechanisms involved in the regulation of the pleiotropic functions of TIMP-1 are still poorly understood. Thus, this review aimed to present literature data that show its ability to form a membrane complex with CD63 and β1-integrin, and point to N-glycosylation as a potential regulatory mechanism of the functions exerted by TIMP-1. This article reviewed the characteristics and functions performed individually by TIMP1, CD63, and β1-integrin, the roles of the TIMP-1/CD63/β1-integrin complex, both in a physiological context and in cancer, and the regulatory mechanisms involved in its assembly.

Engineering of Bio-Adhesive Ligand Containing Recombinant RGD and PHSRN Fibronectin Cell-Binding Domains in Fusion with a Colored Multi Affinity Tag: Simple Approach for Fragment Study from Expression to Adsorption

Engineering of biomimetic motives have emerged as promising approaches to improving cells’ binding properties of biomaterials for tissue engineering and regenerative medicine. In this study, a bio-adhesive ligand including cell-binding domains of human fibronectin (FN) was engineered using recombinant protein technology, a major extracellular matrix (ECM) protein that interacts with a variety of integrins cell-surface’s receptors and other ECM proteins through specific binding domains. 9th and 10th fibronectin type III repeat containing Arginine-Glycine-Aspartic acid (RGD) and Pro-His-Ser-Arg-Asn (PHSRN) synergic site (FNIII9-10) were expressed in fusion with a Colored Multi Affinity Tag (CMAT) to develop a simplified production and characterization process. A recombinant fragment was produced in the bacterial system using E. coli with high yield purified protein by double affinity chromatography. Bio-adhesive surfaces were developed by passive coating of produced fragment onto non adhesive surfaces model. The recombinant fusion protein (CMAT-FNIII9/10) demonstrated an accurate monitoring capability during expression purification and adsorption assay. Finally, biological activity of recombinant FNIII9/10 was validated by cellular adhesion assay. Binding to α5β1 integrins were successfully validated using a produced fragment as a ligand. These results are robust supports to the rational development of bioactivation strategies for biomedical and biotechnological applications.

Comprehensive understanding of anchorage-independent survival and its implication in cancer metastasis

Detachment is the initial and critical step for cancer metastasis. Only the cells that survive from detachment can develop metastases. Following the disruption of cell-extracellular matrix (ECM) interactions, cells are exposed to a totally different chemical and mechanical environment. During which, cells inevitably suffer from multiple stresses, including loss of growth stimuli from ECM, altered mechanical force, cytoskeletal reorganization, reduced nutrient uptake, and increased reactive oxygen species generation. Here we review the impact of these stresses on the anchorage-independent survival and the underlying molecular signaling pathways. Furthermore, its implications in cancer metastasis and treatment are also discussed.

Targeting Airway Smooth Muscle Hypertrophy in Asthma: An Approach Whose Time Has Come

Airway smooth muscle (ASM) cell dysfunction is an important component of several obstructive pulmonary diseases, particularly asthma. External stimuli such as allergens, dust, air pollutants, and change in environmental temperatures provoke ASM cell hypertrophy, proliferation, and migration without adequate mechanistic controls. ASM cells can switch between quiescent, migratory, and proliferative phenotypes in response to extracellular matrix proteins, growth factors, and other soluble mediators. While some aspects of airway hypertrophy and remodeling could have beneficial effects, in many cases these contribute to a clinical phenotype of difficult to control asthma. In this review, we discuss the factors responsible for ASM hypertrophy and proliferation in asthma, focusing on cytokines, growth factors, and ion transporters, and discuss existing and potential approaches that specifically target ASM hypertrophy to reduce the ASM mass and improve asthma symptoms. The goal of this review is to highlight strategies that appear ready for translational investigations to improve asthma therapy.

Fibronectin regulates anoikis resistance via cell aggregate formation

The loss of cell-matrix interactions induces apoptosis, known as anoikis. For successful distant metastasis, circulating tumor cells (CTCs) that have lost matrix attachment need to acquire anoikis resistance in order to survive. Cell aggregate formation confers anoikis resistance, and CTC clusters are more highly metastatic compared to single cells; however, the molecular mechanisms underlying this aggregation are not well understood. In this study, we demonstrated that cell detachment increased cell aggregation and upregulated fibronectin (FN) levels in lung and breast cancer cells, but not in their normal counterparts. FN knockdown decreased cell aggregation and increased anoikis. In addition, cell detachment induced cell-cell adhesion proteins, including E-cadherin, desmoglein-2, desmocollin-2/3, and plakoglobin. Interestingly, FN knockdown decreased the levels of desmoglein-2, desmocollin-2/3, and plakoglobin, but not E-cadherin, suggesting the involvement of desmosomal junction in cell aggregation. Accordingly, knockdown of desmoglein-2, desmocollin-2, or plakoglobin reduced cell aggregation and increased cell sensitivity to anoikis. Previously, we reported that NADPH oxidase 4 (Nox4) upregulation is important for anoikis resistance. Nox4 inhibition by siRNA or apocynin decreased cell aggregation and increased anoikis with the downregulation of FN, and, consequently, decreased desmoglein-2, desmocollin-2/3, or plakoglobin. The coexpression of Nox4 and FN was found to be significant in lung and breast cancer patients, based on cBioPortal data. In vivo mouse lung metastasis model showed that FN knockdown suppressed lung metastasis and thus enhanced survival. FN staining of micro tissue array revealed that FN expression was positive for human lung cancer (61%) and breast cancer (58%) patients. Furthermore, the expression levels of FN, desmoglein-2, desmocollin-2, and plakoglobin were significantly correlated with the poor survival of lung and breast cancer patients, as per the Kaplan-Meier plotter analysis. Altogether, our data suggest that FN upregulation and enhanced desmosomal interactions are critical for cell aggregation and anoikis resistance upon cell detachment.

Autophagy, tissue repair, and fibrosis: a delicate balance

Tissue repair and fibrosis, an abnormal form of repair, occur in most human organs in response to injury or inflammation. Fibroblasts play a major role in the normal repair process by differentiating into myofibroblasts that synthesize extracellular matrix (ECM) components and favor tissue remodeling to reestablish normal function and integrity. However, their persistent accumulation at the site of injury is a hallmark of fibrosis. Autophagy is a catabolic process that occurs in eukaryotic cells as a stress response to allow cell survival and maintenance of cellular homeostasis by degrading and recycling intracellular components. Recent advances identify autophagy as an important regulator of myofibroblast differentiation, tissue remodeling, and fibrogenesis. In this mini-review, we provide an overview of the interactions between autophagy, ECM, and fibrosis, and emphasize the molecular mechanisms involved in myofibroblast differentiation. We also describe the emerging concept of secretory autophagy as a new avenue for intercellular communication at the site of tissue injury and repair.

Extracellular Matrix in Vascular Disease, Part 2/4: JACC Focus Seminar

Medium-sized and large arteries consist of 3 layers: the tunica intima, tunica media, and tunica adventitia. The tunica media accounts for the bulk of the vessel wall and is the chief determinant of mechanical compliance. It is primarily composed of circumferentially arranged layers of vascular smooth muscle cells that are separated by concentrically arranged elastic lamellae; a form of extracellular matrix (ECM). The tunica media is separated from the tunica intima and tunica adventitia, the innermost and outermost layers, respectively, by the internal and external elastic laminae. This second part of a 4-part JACC Focus Seminar discusses the contributions of the ECM to vascular homeostasis and pathology. Advances in genetics and proteomics approaches have fostered significant progress in our understanding of vascular ECM. This review highlights the important role of the ECM in vascular disease and the prospect of translating these discoveries into clinical disease biomarkers and potential future therapies.

Constitutive activation of integrin αvβ3 contributes to anoikis resistance of ovarian cancer cells

Epithelial ovarian cancer involves the shedding of single tumor cells or spheroids from the primary tumor into ascites, followed by their survival, and transit to the sites of metastatic colonization within the peritoneal cavity. During their flotation, anchorage-dependent epithelial-type tumor cells gain anoikis resistance, implicating integrins, including αvß3. In this study, we explored anoikis escape, cisplatin resistance, and prosurvival signaling as a function of the αvß3 transmembrane conformational activation state in cells suspended in ascites. A high-affinity and constitutively signaling-competent αvß3 variant, which harbored unclasped transmembrane domains, was found to confer delayed anoikis onset, enhanced cisplatin resistance, and reduced cell proliferation in ascites or 3D-hydrogels, involving p27^kip upregulation. Moreover, it promoted EGF-R expression and activation, prosurvival signaling, implicating FAK, src, and PKB/Akt. This led to the induction of the anti-apoptotic factors Bcl-2 and survivin suppressing caspase activation, compared to a signaling-incapable αvß3 variant displaying firmly associated transmembrane domains. Dissecting the mechanistic players for αvß3-dependent survival and peritoneal metastasis of ascitic ovarian cancer spheroids is of paramount importance to target their anchorage independence by reversing anoikis resistance and blocking αvß3-triggered prosurvival signaling.

Integrin-EGFR interaction regulates anoikis resistance in colon cancer cells

Anoikis resistance is an essential property of cancer cells that allow the extra-cellular matrix-detached cells to survive in a suspended state in body fluid in order to metastasize and invade to distant organs. It is known that integrins play an important role in anoikis resistance, but detailed mechanisms are not well understood. Here we report that highly metastatic colon cancer cells showed a higher degree of anoikis resistance than the normal intestinal epithelial cells. These anoikis-resistant cancer cells express high-levels of integrin-α2, β1, and activated EGFR in the anchorage-independent state than the anchorage-dependent state. In contrast, normal intestinal epithelial cells failed to elevate these proteins. Interestingly, a higher co-association of EGFR with integrin-α2β1/-α5β1 was observed on the surface of anoikis-resistant cells. Thus, in the absence of extra-cellular matrix, integrins in association with EGFR activates downstream effectors ERK and AKT and suppress Caspase-3 activation to induce anoikis resistance as was confirmed from the gene-ablation and pharmacological inhibitor studies. Interestingly, these anoikis-resistant cancer cells express high-level of cancer stem cell signatures (CD24, CD44, CD133, EpCAM) and pluripotent stem cell markers (OCT-4, SOX-2, Nanog) as well as drug-resistant pumps (ABCG2, MDR1, MRP1). Altogether, our findings unravel the interplay between integrin-α2β1/-α5β1 and EGFR in anoikis resistance and suggest that the resistant cells are cancer initiating or cancer stem cells, which may serve as a promising target to combat metastasis of cancer.

Loss of 4.1N in epithelial ovarian cancer results in EMT and matrix-detached cell death resistance

Epithelial ovarian cancer (EOC) is one of the leading causes of death from gynecologic cancers and peritoneal dissemination is the major cause of death in patients with EOC. Although the loss of 4.1N is associated with increased risk of malignancy, its association with EOC remains unclear. To explore the underlying mechanism of the loss of 4.1N in constitutive activation of epithelial-mesenchymal transition (EMT) and matrix-detached cell death resistance, we investigated samples from 268 formalin-fixed EOC tissues and performed various in vitro and in vivo assays. We report that the loss of 4.1N correlated with progress in clinical stage, as well as poor survival in EOC patients. The loss of 4.1N induces EMT in adherent EOC cells and its expression inhibits anoikis resistance and EMT by directly binding and accelerating the degradation of 14-3-3 in suspension EOC cells. Furthermore, the loss of 4.1N could increase the rate of entosis, which aggravates cell death resistance in suspension EOC cells. Moreover, xenograft tumors in nude mice also show that the loss of 4.1N can aggravate peritoneal dissemination of EOC cells. Single-agent and combination therapy with a ROCK inhibitor and a 14-3-3 antagonist can reduce tumor spread to varying degrees. Our results not only define the vital role of 4.1N loss in inducing EMT, anoikis resistance, and entosis-induced cell death resistance in EOC, but also suggest that individual or combined application of 4.1N, 14-3-3 antagonists, and entosis inhibitors may be a promising therapeutic approach for the treatment of EOC.

Integrin-Mediated Adhesion and Chemoresistance of Acute Lymphoblastic Leukemia Cells Residing in the Bone Marrow or the Central Nervous System

Acute Lymphoblastic Leukemia (ALL) is the most common cancer in childhood. Despite a significantly improved prognosis over the last decade with a 5-years survival rate of ~90%, treatment-related morbidity remains substantial and relapse occurs in 10–15% of patients (1). The most common site of relapse is the bone marrow, but early colonization and subsequent reoccurrence of the disease in the central nervous system (CNS) also occurs. Integrins are a family of cell surface molecules with a longstanding history in cancer cell adherence, migration and metastasis. In chronic lymphoblastic leukemia (CLL), the VLA-4 integrin has been acknowledged as a prognostic marker and mounting evidence indicates that this and other integrins may also play a role in acute leukemia, including ALL. Importantly, integrins engage in anti-apoptotic signaling when binding extracellular molecules that are enriched in the bone marrow and CNS microenvironments. Here, we review the current evidence for a role of integrins in the adherence of ALL cells within the bone marrow and their colonization of the CNS, with particular emphasis on mechanisms adding to cancer cell survival and chemoresistance.

The road best traveled: Neural crest migration upon the extracellular matrix

Neural crest cells have the extraordinary task of building much of the vertebrate body plan, including the craniofacial cartilage and skeleton, melanocytes, portions of the heart, and the peripheral nervous system. To execute these developmental programs, stationary premigratory neural crest cells first acquire the capacity to migrate through an extensive process known as the epithelial-to-mesenchymal transition. Once motile, neural crest cells must traverse a complex environment consisting of other cells and the protein-rich extracellular matrix in order to get to their final destinations. Herein, we will highlight some of the main molecular machinery that allow neural crest cells to first exit the neuroepithelium and then later successfully navigate this intricate in vivo milieu. Collectively, these extracellular and intracellular factors mediate the appropriate migration of neural crest cells and allow for the proper development of the vertebrate embryo.

Tumor cell-organized fibronectin maintenance of a dormant breast cancer population

Tumors can undergo long periods of dormancy, with cancer cells entering a largely quiescent, nonproliferative state before reactivation and outgrowth. To understand the role of the extracellular matrix (ECM) in regulating tumor dormancy, we created an in vitro cell culture system with carefully controlled ECM substrates to observe entrance into and exit from dormancy with live imaging. We saw that cell populations capable of surviving entrance into long-term dormancy were heterogeneous, containing quiescent, cell cycle-arrested, and actively proliferating cells. Cell populations capable of entering dormancy formed an organized, fibrillar fibronectin matrix via αvβ3 and α5β1 integrin adhesion, ROCK-generated tension, and TGFβ2 stimulation, and cancer cell outgrowth after dormancy required MMP-2-mediated fibronectin degradation. We propose this approach as a useful, in vitro method to study factors important in regulating dormancy, and we used it here to elucidate a role for fibronectin deposition and MMP activation.

MicroRNA-142 Is Critical for the Homeostasis and Function of Type 1 Innate Lymphoid Cells

Natural killer (NK) cells are cytotoxic type 1 innate lymphoid cells (ILCs) that defend against viruses and mediate anti-tumor responses, yet mechanisms controlling their development and function remain incompletely understood. We hypothesized that the abundantly expressed microRNA-142 (miR-142) is a critical regulator of type 1 ILC biology. Interleukin-15 (IL-15) signaling induced miR-142 expression, whereas global and ILC-specific miR-142-deficient mice exhibited a cell-intrinsic loss of NK cells. Death of NK cells resulted from diminished IL-15 receptor signaling within miR-142-deficient mice, likely via reduced suppressor of cytokine signaling-1 (Socs1) regulation by miR-142-5p. ILCs persisting in Mir142-/- mice demonstrated increased expression of the miR-142-3p target αV integrin, which supported their survival. Global miR-142-deficient mice exhibited an expansion of ILC1-like cells concurrent with increased transforming growth factor-β (TGF-β) signaling. Further, miR-142-deficient mice had reduced NK-cell-dependent function and increased susceptibility to murine cytomegalovirus (MCMV) infection. Thus, miR-142 critically integrates environmental cues for proper type 1 ILC homeostasis and defense against viral infection.

Modulation of αvβ3 Integrin via Transactivation of β3 Integrin Gene on Murine Bone Marrow Macrophages by 1,25(OH)2D3, Retinoic Acid and Interleukin-4

The interleukin (IL)-4, 1,25(OH)₂D₃ and retinoic acid, increase surface expression of functional integrin α_vβ₃ on murine osteoclast precursors. All three agonists stimulate transcription of the β₃ gene, leading to increased steady-state levels of mRNA this protein. By contrast, mRNA levels of α_v remain unchanged. In each instance, the increase in the surface expression of the integrin results in increased migration of the cells onto an α_vβ₃ substrate. Because β₃ subunit, except platelet where β₃ subunit conform a dimer with α_IIb, associates solely with α_v subunit monogamously, while promiscuous α_v subunit combines with various subunit, our present data support the idea that the β₃ subunit governs the surface-expressed functional integrin complex.

Aiding and Abetting: How the Tumor Microenvironment Protects Cancer from Chemotherapy

Disease recurrence following cancer therapy remains an intractable clinical problem and represents a major impediment to reducing the mortality attributable to malignant tumors. While research has traditionally focused on the cell-intrinsic mechanisms and mutations that render tumors refractory to both classical chemotherapeutics and targeted therapies, recent studies have begun to uncover myriad roles for the tumor microenvironment (TME) in modulating therapeutic efficacy. This work suggests that drug resistance is as much ecological as it is evolutionary. Specifically, cancers resident in organs throughout the body do not develop in isolation. Instead, tumor cells arise in the context of nonmalignant cellular components of a tissue. While the roles of these cell-extrinsic factors in cancer initiation and progression are well established, our understanding of the TME's influence on therapeutic outcome is in its infancy. Here, we focus on mechanisms by which neoplastic cells co-opt preexisting or treatment-induced signaling networks to survive chemotherapy.

Recent Developments in Breast Muscle Myopathies Associated with Growth in Poultry

The functional unit in skeletal muscle is the multinucleated myofiber, which is composed of parallel arrays of microfibrils. The myofiber and sarco-mere structure of skeletal muscle are established during embryogenesis, when mononuclear myoblast cells fuse to form multinucleated myotubes and develop into muscle fibers. With the myoblasts permanently unable to enter a proliferative state again after they fuse to form the multinucleated myotube, postnatal myofiber growth, muscle homeostasis, and myofiber regeneration are dependent on a myogenic stem cell, the satellite cell. Because the satellite cell is a partially differentiated stem cell controlling the state of skeletal muscle structure throughout the life of the bird, it can impact muscle development and structure, growth, and regeneration and, subsequently, meat quality. When myofibers are damaged, muscle repair is dependent on the satellite cells. Regenerated myofibers after the repair process should be similar to the original muscle fiber. Despite significant improvements in meat-type birds, degenerative myopathies have arisen. In many of these degenerative breast muscle myopathies, like Wooden Breast, satellite cell–mediated regeneration of muscle is suppressed. Thus, the biological function of avian myogenic satellite cells and their influence on cellular mechanisms affecting breast muscle development and growth, function during degenerative myopathies, and meat quality are discussed.

Alpha-5 Integrin Mediates Simvastatin-Induced Osteogenesis of Bone Marrow Mesenchymal Stem Cells

Simvastatin (SVS) promotes the osteogenic differentiation of mesenchymal stem cells (MSCs) and has been studied for MSC-based bone regeneration. However, the mechanism underlying SVS-induced osteogenesis is not well understood. We hypothesize that α5 integrin mediates SVS-induced osteogenic differentiation. Bone marrow MSCs (BMSCs) derived from BALB/C mice, referred to as D1 cells, were used. Alizarin red S (calcium deposition) and alkaline phosphatase (ALP) staining were used to evaluate SVS-induced osteogenesis of D1 cells. The mRNA expression levels of α5 integrin and osteogenic marker genes (bone morphogenetic protein-2 (BMP-2), runt-related transcription factor 2 (Runx2), collagen type I, ALP and osteocalcin (OC)) were detected using quantitative real-time PCR. Surface-expressed α5 integrin was detected using flow cytometry analysis. Protein expression levels of α5 integrin and phosphorylated focal adhesion kinase (p-FAK), which is downstream of α5 integrin, were detected using Western blotting. siRNA was used to deplete the expression of α5 integrin in D1 cells. The results showed that SVS dose-dependently enhanced the gene expression levels of osteogenic marker genes as well as subsequent ALP activity and calcium deposition in D1 cells. Upregulated p-FAK was accompanied by an increased protein expression level of α5 integrin after SVS treatment. Surface-expressed α5 integrin was also upregulated after SVS treatment. Depletion of α5 integrin expression significantly suppressed SVS-induced osteogenic gene expression levels, ALP activity, and calcium deposition in D1 cells. These results identify a critical role of α5 integrin in SVS-induced osteogenic differentiation of BMSCs, which may suggest a therapeutic strategy to modulate α5 integrin/FAK signaling to promote MSC-based bone regeneration.

The EBV-Encoded Oncoprotein, LMP1, Induces an Epithelial-to-Mesenchymal Transition (EMT) via Its CTAR1 Domain through Integrin-Mediated ERK-MAPK Signalling

The Epstein–Barr virus (EBV)-encoded latent membrane protein 1 (LMP1) oncogene can induce profound effects on epithelial growth and differentiation including many of the features of the epithelial-to-mesenchymal transition (EMT). To better characterise these effects, we used the well-defined Madin Darby Canine Kidney (MDCK) epithelial cell model and found that LMP1 expression in these cells induces EMT as defined by characteristic morphological changes accompanied by loss of E-cadherin, desmosomal cadherin and tight junction protein expression. The induction of the EMT phenotype required a functional CTAR1 domain of LMP1 and studies using pharmacological inhibitors revealed contributions from signalling pathways commonly induced by integrin–ligand interactions: extracellular signal-regulated kinases/mitogen-activated protein kinases (ERK-MAPK), PI3-Kinase and tyrosine kinases, but not transforming growth factor beta (TGFβ). More detailed analysis implicated the CTAR1-mediated induction of Slug and Twist in LMP1-induced EMT. A key role for β1 integrin signalling in LMP1-mediated ERK-MAPK and focal adhesion kianse (FAK) phosphorylation was observed, and β1 integrin activation was found to enhance LMP1-induced cell viability and survival. These findings support an important role for LMP1 in disease pathogenesis through transcriptional reprogramming that enhances tumour cell survival and leads to a more invasive, metastatic phenotype.

Mitochondrial DNA 3243A>G heteroplasmy is associated with changes in cytoskeletal protein expression and cell mechanics

Mitochondrial and mechanical alterations in cells have both been shown to be hallmarks of human disease. However, little research has endeavoured to establish connections between these two essential features of cells in both functional and dysfunctional situations. In this work, we hypothesized that a specific genetic alteration in mitochondrial function known to cause human disease would trigger changes in cell mechanics. Using a previously characterized set of mitochondrial cybrid cell lines, we examined the relationship between heteroplasmy for the mitochondrial DNA (mtDNA) 3243A>G mutation, the cell cytoskeleton, and resulting cellular mechanical properties. We found that cells with increasing mitochondrial dysfunction markedly differed from one another in gene expression and protein production of various co-regulated cytoskeletal elements. The intracellular positioning and organization of actin also differed across cell lines. To explore the relationship between these changes and cell mechanics, we then measured cellular mechanical properties using atomic force microscopy and found that cell stiffness correlated with gene expression data for known determinants of cell mechanics, γ-actin, α-actinin and filamin A. This work points towards a mechanism linking mitochondrial genetics to single-cell mechanical properties. The transcriptional and structural regulation of cytoskeletal components by mitochondrial function may explain why energetic and mechanical alterations often coexist in clinical conditions.

Biomaterials-Based Approaches to Tumor Spheroid and Organoid Modeling

Evolving understanding of structural and biological complexity of tumors has stimulated development of physiologically relevant tumor models for cancer research and drug discovery. A major motivation for developing new tumor models is to recreate the 3D environment of tumors and context-mediated functional regulation of cancer cells. Such models overcome many limitations of standard monolayer cancer cell cultures. Under defined culture conditions, cancer cells self-assemble into 3D constructs known as spheroids. Additionally, cancer cells may recapitulate steps in embryonic development to self-organize into 3D cultures known as organoids. Importantly, spheroids and organoids reproduce morphology and biologic properties of tumors, providing valuable new tools for research, drug discovery, and precision medicine in cancer. This Progress Report discusses uses of both natural and synthetic biomaterials to culture cancer cells as spheroids or organoids, specifically highlighting studies that demonstrate how these models recapitulate key properties of native tumors. The report concludes with the perspectives on the utility of these models and areas of need for future developments to more closely mimic pathologic events in tumors.

Microenvironment drug resistance in multiple myeloma: emerging new players

Multiple myeloma (MM) drug resistance (DR) is a multistep transformation process based on a powerful interplay between bone marrow stromal cells and MM cells that allows the latter to escape anti-myeloma therapies. Here we present an overview of the role of the bone marrow microenvironment in both soluble factors-mediated drug resistance (SFM-DR) and cell adhesion-mediated drug resistance (CAM-DR), focusing on the role of new players, namely miRNAs, exosomes and cancer-associated fibroblasts.

Synthetic Light-Curable Polymeric Materials Provide a Supportive Niche for Dental Pulp Stem Cells

Dental disease annually affects billions of patients, and while regenerative dentistry aims to heal dental tissue after injury, existing polymeric restorative materials, or fillings, do not directly participate in the healing process in a bioinstructive manner. There is a need for restorative materials that can support native functions of dental pulp stem cells (DPSCs), which are capable of regenerating dentin. A polymer microarray formed from commercially available monomers to rapidly identify materials that support DPSC adhesion is used. Based on these findings, thiol-ene chemistry is employed to achieve rapid light-curing and minimize residual monomer of the lead materials. Several triacrylate bulk polymers support DPSC adhesion, proliferation, and differentiation in vitro, and exhibit stiffness and tensile strength similar to existing dental materials. Conversely, materials composed of a trimethacrylate monomer or bisphenol A glycidyl methacrylate, which is a monomer standard in dental materials, do not support stem cell adhesion and negatively impact matrix and signaling pathways. Furthermore, thiol-ene polymerized triacrylates are used as permanent filling materials at the dentin-pulp interface in direct contact with irreversibly injured pulp tissue. These novel triacrylate-based biomaterials have potential to enable novel regenerative dental therapies in the clinic by both restoring teeth and providing a supportive niche for DPSCs.

Cardiosphere-Derived Cells Demonstrate Metabolic Flexibility That Is Influenced by Adhesion Status

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Cell adhesion status regulates energy metabolism in adult stem cells

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Adherent adult stem cells (CDCs, MSCs, ASCs) utilize glycolysis to generate majority (70% to 85%) of their cellular ATP needs

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Akt phosphorylation transduces adhesion-mediated regulation of energy metabolism by regulating membrane translocation of glucose transporters (GLUT1) and thus, cellular glucose uptake and glycolysis

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Cell dissociation/suspension leads to Akt de-phosphorylation, >3-fold reduction in the number of cell surface GLUT1 receptors, downregulation of cellular glucose uptake, glycolysis, cellular ATP levels, and loss of cell viability

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Encapsulation of dissociated cells in hydrogels that provide cell adhesion motifs, promotes Akt phosphorylation, rapidly restores glycolysis, and cellular ATP levels

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^99mTc-pertechnetate uptake (by cells genetically engineered to express the Na-Iodide symporter) reflects cellular ATP levels, thus permitting in vivo monitoring of energetics of transplanted cells by SPECT imaging.

Adult stem cells demonstrate metabolic flexibility that is regulated by cell adhesion status. The authors demonstrate that adherent cells primarily utilize glycolysis, whereas suspended cells rely on oxidative phosphorylation for their ATP needs. Akt phosphorylation transduces adhesion-mediated regulation of energy metabolism, by regulating translocation of glucose transporters (GLUT1) to the cell membrane and thus, cellular glucose uptake and glycolysis. Cell dissociation, a pre-requisite for cell transplantation, leads to energetic stress, which is mediated by Akt dephosphorylation, downregulation of glucose uptake, and glycolysis. They designed hydrogels that promote rapid cell adhesion of encapsulated cells, Akt phosphorylation, restore glycolysis, and cellular ATP levels.

JAM-A as a prognostic factor and new therapeutic target in multiple myeloma

Cell adhesion in the multiple myeloma (MM) microenvironment has been recognized as a major mechanism of MM cell survival and the development of drug resistance. Here we addressed the hypothesis that the protein junctional adhesion molecule-A (JAM-A) may represent a novel target and a clinical biomarker in MM. We evaluated JAM-A expression in MM cell lines and in 147 MM patient bone marrow aspirates and biopsies at different disease stages. Elevated JAM-A levels in patient-derived plasma cells were correlated with poor prognosis. Moreover, circulating soluble JAM-A (sJAM-A) levels were significantly increased in MM patients as compared with controls. Notably, in vitro JAM-A inhibition impaired MM migration, colony formation, chemotaxis, proliferation and viability. In vivo treatment with an anti-JAM-A monoclonal antibody (αJAM-A moAb) impaired tumor progression in a murine xenograft MM model. These results demonstrate that therapeutic targeting of JAM-A has the potential to prevent MM progression, and lead us to propose JAM-A as a biomarker in MM, and sJAM-A as a serum-based marker for clinical stratification.

The cancer cell adhesion resistome: mechanisms, targeting and translational approaches

Cell adhesion-mediated resistance limits the success of cancer therapies and is a great obstacle to overcome in the clinic. Since the 1990s, where it became clear that adhesion of tumor cells to the extracellular matrix is an important mediator of therapy resistance, a lot of work has been conducted to understand the fundamental underlying mechanisms and two paradigms were deduced: cell adhesion-mediated radioresistance (CAM-RR) and cell adhesion-mediated drug resistance (CAM-DR). Preclinical work has evidently demonstrated that targeting of integrins, adapter proteins and associated kinases comprising the cell adhesion resistome is a promising strategy to sensitize cancer cells to both radiotherapy and chemotherapy. Moreover, the cell adhesion resistome fundamentally contributes to adaptation mechanisms induced by radiochemotherapy as well as molecular drugs to secure a balanced homeostasis of cancer cells for survival and growth. Intriguingly, this phenomenon provides a basis for synthetic lethal targeted therapies simultaneously administered to standard radiochemotherapy. In this review, we summarize current knowledge about the cell adhesion resistome and highlight targeting strategies to override CAM-RR and CAM-DR.

Deletion of β1-integrin in collecting duct principal cells leads to tubular injury and renal medullary fibrosis

The renal collecting duct (CD) contains two major cell types, intercalated (ICs) and principal cells (PCs). A previous report showed that deletion of β1-integrin in the entire renal CD causes defective CD morphogenesis resulting in kidney dysfunction. However, subsequent deletion of β1-integrin specifically in ICs and PCs, respectively, did not cause any morphological defects in the CDs. The discrepancy between these studies prompts us to reinvestigate the role of β1-integrin in CD cells, specifically in the PCs. We conditionally deleted β1-integrin in mouse CD PCs using a specific aquaporin-2 (AQP2) promoter Cre-LoxP system. The resulting mutant mice, β-1^f/fAQP2-Cre+, had lower body weight, failed to thrive, and died around 8-12 wk. Their CD tubules were dilated, and some of them contained cellular debris. Increased apoptosis and proliferation of PCs were observed in the dilated CDs. Trichrome staining and electron microscopy revealed the presence of peritubular and interstitial fibrosis that is associated with increased production of extracellular matrix proteins including collagen type IV and fibronectin, as detected by immunoblotting. Further analysis revealed a significantly increased expression of transforming growth factor-β (TGF-β)-induced protein, fibronectin, and TGF-β receptor-1 mRNAs and concomitantly increased phosphorylation of SMAD-2 that indicates the activation of the TGF-β signaling pathway. Therefore, our data reveal that normal expression of β1-integrin in PCs is a critical determinant of CD structural and functional integrity and further support the previously reported critical role of β1-integrin in the development and/or maintenance of the CD structure and function.

Improvement of paracellular transport in the Caco-2 drug screening model using protein-engineered substrates

The Caco-2 assay has achieved wide popularity among pharmaceutical companies in the past two decades as an in vitro method for estimation of in vivo oral bioavailability of pharmaceutical compounds during preclinical characterization. Despite its popularity, this assay suffers from a severe underprediction of the transport of drugs which are absorbed paracellularly, that is, which pass through the cell-cell tight junctions of the absorptive cells of the small intestine. Here, we propose that simply replacing the collagen I matrix employed in the standard Caco-2 assay with an engineered matrix, we can control cell morphology and hence regulate the cell-cell junctions that dictate paracellular transport. Specifically, we use a biomimetic engineered extracellular matrix (eECM) that contains modular protein domains derived from two ECM proteins found in the small intestine, fibronectin and elastin. This eECM allows us to independently tune the density of cell-adhesive RGD ligands presented to Caco-2 cells as well as the mechanical stiffness of the eECM. We observe that lower amounts of RGD ligand presentation as well as decreased matrix stiffness results in Caco-2 morphologies that more closely resemble primary small intestinal epithelial cells than Caco-2 cells cultured on collagen. Additionally, these matrices result in Caco-2 monolayers with decreased recruitment of actin to the apical junctional complex and increased expression of claudin-2, a tight junction protein associated with higher paracellular permeability that is highly expressed throughout the small intestine. Consistent with these morphological differences, drugs known to be paracellularly transported in vivo exhibited significantly improved transport rates in this modified Caco-2 model. As expected, permeability of transcellularly transported drugs remained unaffected. Thus, we have demonstrated a method of improving the physiological accuracy of the Caco-2 assay that could be readily adopted by pharmaceutical companies without major changes to their current testing protocols.

Stathmin decreases cholangiocarcinoma cell line sensitivity to staurosporine-triggered apoptosis via the induction of ERK and Akt signaling

Cholangiocarcinoma is a rare, but highly fatal malignancy. However, the intrinsic mechanism involved in its tumorigenesis remains obscure. An urgent need remains for a promising target for cholangiocarcinoma biological therapies. Based on comparative proteomical technologies, we found 253 and 231 different spots in gallbladder tumor cell lines and cholangiocarcinoma cell lines, respectively, relative to non-malignant cells. Using Mass Spectrometry (MS) and database searching, we chose seven differentially expressed proteins. High Stathmin expression was found in both cholangiocarcinoma and gallbladder carcinoma cells. Stathmin expression was validated using immunohistochemistry and western blot in cholangiocarcinoma tissue samples and peritumoral tissue. It was further revealed that high Stathmin expression was associated with the repression of staurosporine-induced apoptosis in the cholangiocarcinoma cell. Moreover, we found that Stathmin promoted cancer cell proliferation and inhibited its apoptosis through protein kinase B (Akt) and extracellular signal-regulated kinase (ERK) signaling. Integrin, β1 appears to serve as a partner of Stathmin induction of ERK and Akt signaling by inhibiting apoptosis in the cholangiocarcinoma cell. Understanding the regulation of anti-apoptosis effect by Stathmin might provide new insight into how to overcome therapeutic resistance in cholangiocarcinoma.

Full-Length Fibronectin Drives Fibroblast Accumulation at the Surface of Collagen Microtissues during Cell-Induced Tissue Morphogenesis

Generating and maintaining gradients of cell density and extracellular matrix (ECM) components is a prerequisite for the development of functionality of healthy tissue. Therefore, gaining insights into the drivers of spatial organization of cells and the role of ECM during tissue morphogenesis is vital. In a 3D model system of tissue morphogenesis, a fibronectin-FRET sensor recently revealed the existence of two separate fibronectin populations with different conformations in microtissues, i.e. 'compact and adsorbed to collagen' versus 'extended and fibrillar' fibronectin that does not colocalize with the collagen scaffold. Here we asked how the presence of fibronectin might drive this cell-induced tissue morphogenesis, more specifically the formation of gradients in cell density and ECM composition. Microtissues were engineered in a high-throughput model system containing rectangular microarrays of 12 posts, which constrained fibroblast-populated collagen gels, remodeled by the contractile cells into trampoline-shaped microtissues. Fibronectin's contribution during the tissue maturation process was assessed using fibronectin-knockout mouse embryonic fibroblasts (Fn-/- MEFs) and floxed equivalents (Fnf/f MEFs), in fibronectin-depleted growth medium with and without exogenously added plasma fibronectin (full-length, or various fragments). In the absence of full-length fibronectin, Fn-/- MEFs remained homogenously distributed throughout the cell-contracted collagen gels. In contrast, in the presence of full-length fibronectin, both cell types produced shell-like tissues with a predominantly cell-free compacted collagen core and a peripheral surface layer rich in cells. Single cell assays then revealed that Fn-/- MEFs applied lower total strain energy on nanopillar arrays coated with either fibronectin or vitronectin when compared to Fnf/f MEFs, but that the presence of exogenously added plasma fibronectin rescued their contractility. While collagen decoration of single fibronectin fibers enhanced the non-persistent migration of both Fnf/f and Fn-/- MEFs, the migration speed was increased for Fn-/- MEFs on plasma fibronectin fibers compared to Fnf/f MEFs. In contrast, the average speed was the same for all cells on collagen-coated Fn fibers. A Fn-FRET sensor revealed that fibronectin on average was more extended on the microtissue surface compared to fibronectin in the core. Gradients of collagen-to-fibronectin ratios and of the fraction of collagen-adsorbed to stretched fibrillar fibronectin conformations might thereby provide critical cell migration cues. This study highlights a dominant role for fibronectin in tissue morphogenesis and the development of tissue heterogeneities.

Coronary-Heart-Disease-Associated Genetic Variant at the COL4A1/COL4A2 Locus Affects COL4A1/COL4A2 Expression, Vascular Cell Survival, Atherosclerotic Plaque Stability and Risk of Myocardial Infarction

Genome-wide association studies have revealed an association between coronary heart disease (CHD) and genetic variation on chromosome 13q34, with the lead single nucleotide polymorphism rs4773144 residing in the COL4A2 gene in this genomic region. We investigated the functional effects of this genetic variant. Analyses of primary cultures of vascular smooth muscle cells (SMCs) and endothelial cells (ECs) from different individuals showed a difference between rs4773144 genotypes in COL4A2 and COL4A1 expression levels, being lowest in the G/G genotype, intermediate in A/G and highest in A/A. Chromatin immunoprecipitation followed by allelic imbalance assays of primary cultures of SMCs and ECs that were of the A/G genotype revealed that the G allele had lower transcriptional activity than the A allele. Electrophoretic mobility shift assays and luciferase reporter gene assays showed that a short DNA sequence encompassing the rs4773144 site interacted with a nuclear protein, with lower efficiency for the G allele, and that the G allele sequence had lower activity in driving reporter gene expression. Analyses of cultured SMCs from different individuals demonstrated that cells of the G/G genotype had higher apoptosis rates. Immunohistochemical and histological examinations of ex vivo atherosclerotic coronary arteries from different individuals disclosed that atherosclerotic plaques with the G/G genotype had lower collagen IV abundance and thinner fibrous cap, a hallmark of unstable, rupture-prone plaques. A study of a cohort of patients with angiographically documented coronary artery disease showed that patients of the G/G genotype had higher rates of myocardial infarction, a phenotype often caused by plaque rupture. These results indicate that the CHD-related genetic variant at the COL4A2 locus affects COL4A2/COL4A1 expression, SMC survival, and atherosclerotic plaque stability, providing a mechanistic explanation for the association between the genetic variant and CHD risk.

Proteomic Changes in the Plasma of Broiler Chickens with Femoral Head Necrosis

Femoral head necrosis (FHN) is a skeletal problem in broiler chickens, where the proximal femoral head cartilage shows susceptibility to separation from its growth plate. The selected birds with FHN showed higher body weights and reduced plasma cholesterol. The proteomic differences in the plasma of healthy and FHN-affected chickens were explored using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) and liquid chromatography/electrospray ionization-tandem mass spectrometry (LC-MS/MS) to prospect for protein biomarkers. We isolated two differentially expressed low molecular weight proteins and identified them by MALDI peptide mass fingerprinting as fibrinogen- and fetuin-derived peptides, respectively. These peptides were reduced in birds susceptible to femoral head problems. Quantitation of LC-MS/MS spectra showed elevated levels of gallinacin-9, apolipoprotein A1, and hemoglobin and reduced levels of alpha-1-acid glycoprotein, albumin, and SPINK7 proteins in FHN. These results suggest that the bodyweight and the lipid profiles along with the above proteins can be useful as noninvasive biomarkers of FHN.

17β-Estradiol Protects Rat Annulus Fibrosus Cells Against Apoptosis via α1 Integrin-Mediated Adhesion to Type I Collagen: An In-vitro Study

Background

17β-Estradiol (E2) has been reported to protect annulus fibrosus (AF) cells in vitro against interleukin-1β (IL-1β)-induced apoptosis in a concentration-dependent manner. However, its time-response effect remains unexplored. In addition, integrin α₂/collagen II interaction has been reported to influence the apoptosis of nucleus pulposus cells in vitro. Thus, we hypothesized that integrin α₁/collagen II might play a role in exerting the anti-apoptosis effect by E2. The aim of the current study was to further investigate the anti-apoptotic effect of E2 and determine the role of integrin α₁/collagen II interaction.

Material/Methods

Rat AF cells were primary cultured and used for the following experiments. AF cells were identified by immunocytochemistry of type I collagen. Cell apoptosis was detected by fluorescence-activated cell sorter (FACS) analysis. The activity of active caspase-3 was determined by use of a caspase-3 detection kit. AF cell adhesion to type I collagen was determined by cell adhesion assay. Protein level of integrin subunit α₁ was quantified by Western blot and mRNA expression was determined by real-time qPCR.

Results

The immunocytochemistry of type I collagen revealed that cell purity was eligible for the following experiments with 98% of purity. FACS analysis indicated time-dependent anti-apoptosis effect of E2 at time points of 6 h, 12 h, and 24 h, which was confirmed by Caspase-3 activity. Furthermore, cell adhesion assay showed that E2 significantly increased cell binding to 95% of control, and qPCR and Western blot analysis showed that E2 effectively upregulated integrin α₁. However, estrogen receptor antagonist ICI182780 prohibited the effect of E2.

Conclusions

This study shows that E2 protects against apoptosis in a time-dependent manner, and α₁ integrin-mediated adhesion to collagen II is essential for estrogen-dependent anti-apoptosis in rat annulus fibrosus cells in vitro.

Endostatin's emerging roles in angiogenesis, lymphangiogenesis, disease, and clinical applications

BACKGROUND

Angiogenesis is the process of neovascularization from pre-existing vasculature and is involved in various physiological and pathological processes. Inhibitors of angiogenesis, administered either as individual drugs or in combination with other chemotherapy, have been shown to benefit patients with various cancers. Endostatin, a 20-kDa C-terminal fragment of type XVIII collagen, is one of the most potent inhibitors of angiogenesis.

SCOPE OF REVIEW

We discuss the biology behind endostatin in the context of its endogenous production, the various receptors to which it binds, and the mechanisms by which it acts. We focus on its inhibitory role in angiogenesis, lymphangiogenesis, and cancer metastasis. We also present emerging clinical applications for endostatin and its potential as a therapeutic agent in the form a short peptide.

MAJOR CONCLUSIONS

The delicate balance between pro- and anti-angiogenic factors can be modulated to result in physiological wound healing or pathological tumor metastasis. Research in the last decade has emphasized an emerging clinical potential for endostatin as a biomarker and as a therapeutic short peptide. Moreover, elevated or depressed endostatin levels in diseased states may help explain the pathophysiological mechanisms of the particular disease.

GENERAL SIGNIFICANCE

Endostatin was once sought after as the 'be all and end all' for cancer treatment; however, research throughout the last decade has made it apparent that endostatin's effects are complex and involve multiple mechanisms. A better understanding of newly discovered mechanisms and clinical applications still has the potential to lead to future advances in the use of endostatin in the clinic.