Integrin α11 cytoplasmic tail is required for FAK activation to initiate 3D cell invasion and ERK-mediated cell proliferation

An endometrial biomimetic extracellular matrix (ECM) for enhanced endometrial regeneration using hyaluronic acid hydrogel containing recombinant human type III collagen

Endometrial injury poses a significant challenge in tissue regeneration, with type III collagen (COL III) playing a pivotal role in maintaining endometrial integrity and facilitating repair. Our study explored the utility of recombinant human type III collagen (RHC) as an intervention for endometrial damage. To address the challenges associated with the inherent instability and rapid degradation of COL III in vivo, we developed an RHC-HA hydrogel by conjugating RHC with hyaluronic acid (HA), thus ensuring a more stable and sustained delivery. Our findings suggested that the RHC-HA hydrogel significantly promoted endometrial regeneration and restored fertility. The hydrogel facilitated prolonged retention of RHC in the uterus, leading to a substantial improvement in the repair process. The synergistic interaction between RHC and HA greatly enhances cell proliferation and adhesion, surpassing the efficacy of HA or RHC alone. Additionally, the RHC-HA hydrogel demonstrated notable anti-fibrotic effects, which are crucial for preventing abnormalities during endometrial healing. These findings suggested that the RHC-HA hydrogel presented a therapeutic strategy in the treatment of uterine endometrial injuries, which may improve female reproductive health.

siRNA treatment targeting integrin α11 overexpressed via EZH2-driven axis inhibits drug-resistant breast cancer progression

BACKGROUND

Breast cancer, the most prevalent cancer in women worldwide, faces treatment challenges due to drug resistance, posing a serious threat to patient survival. The present study aimed to identify the key molecules that drive drug resistance and aggressiveness in breast cancer cells and validate them as therapeutic targets.

METHODS

Transcriptome microarray and analysis using PANTHER pathway and StemChecker were performed to identify the most significantly expressed genes in tamoxifen-resistant and adriamycin-resistant MCF-7 breast cancer cells. Clinical relevance of the key genes was determined using Kaplan-Meier survival analyses on The Cancer Genome Atlas dataset of breast cancer patients. Gene overexpression/knockdown, spheroid formation, flow cytometric analysis, chromatin immunoprecipitation, immunocytochemistry, wound healing/transwell migration assays, and cancer stem cell transcription factor activation profiling array were used to elucidate the regulatory mechanism of integrin α11 expression. Tumour-bearing xenograft models were used to demonstrate integrin α11 is a potential therapeutic target.

RESULTS

Integrin α11 was consistently upregulated in drug-resistant breast cancer cells, and its silencing inhibited cancer stem cells (CSCs) and epithelial-mesenchymal transition (EMT) while restoring sensitivity to anticancer drugs. HIF1α, GLI-1, and EZH2 contributed the most to the regulation of integrin α11 and EZH2 expression, with EZH2 being more necessary for EZH2 autoinduction than HIF1α and GLI-1. Additionally, unlike HIF1α or EZH2, GLI-1 was the sole transcription factor activated by integrin-linked focal adhesion kinase, indicating GLI-1 as a key driver of the EZH2-integrin α11 axis operating for cancer stem cell survival and EMT. Kaplan-Meier survival analysis using The Cancer Genome Atlas (TCGA) dataset also revealed both EZH2 and integrin α11 could be strong prognostic factors of relapse-free and overall survival in breast cancer patients. However, the superior efficacy of integrin α11 siRNA therapy over EZH2 siRNA treatment was demonstrated by enhanced inhibition of tumour growth and prolonged survival in murine models bearing tumours.

CONCLUSION

Our findings elucidate that integrin α11 is upregulated by EZH2, forming a positive feedback circuit involving FAK-GLI-1 and contributing to drug resistance, cancer stem cell survival and EMT. Taken together, the results suggest integrin α11 as a promising prognostic marker and a powerful therapeutic target for drug-resistant breast cancer.

Selective Suppression of Integrin-Ligand Binding by Single Molecular Tension Probes Mediates Directional Cell Migration

Cell migration interacting with continuously changing microenvironment, is one of the most essential cellular functions, participating in embryonic development, wound repair, immune response, and cancer metastasis. The migration process is finely tuned by integrin-mediated binding to ligand molecules. Although numerous biochemical pathways orchestrating cell adhesion and motility are identified, how subcellular forces between the cell and extracellular matrix regulate intracellular signaling for cell migration remains unclear. Here, it is showed that a molecular binding force across integrin subunits determines directional migration by regulating tension-dependent focal contact formation and focal adhesion kinase phosphorylation. Molecular binding strength between integrin αvβ3 and fibronectin is precisely manipulated by developing molecular tension probes that control the mechanical tolerance applied to cell-substrate interfaces. This data reveals that integrin-mediated molecular binding force reduction suppresses cell spreading and focal adhesion formation, attenuating the focal adhesion kinase (FAK) phosphorylation that regulates the persistence of cell migration. These results further demonstrate that manipulating subcellular binding forces at the molecular level can recapitulate differential cell migration in response to changes of substrate rigidity that determines the physical condition of extracellular microenvironment. Novel insights is provided into the subcellular mechanics behind global mechanical adaptation of the cell to surrounding tissue environments featuring distinct biophysical signatures.

The Interplay between Integrins and Immune Cells as a Regulator in Cancer Immunology

Integrins are a group of heterodimers consisting of α and β subunits that mediate a variety of physiological activities of immune cells, including cell migration, adhesion, proliferation, survival, and immunotolerance. Multiple types of integrins act differently on the same immune cells, while the same integrin may exert various effects on different immune cells. In the development of cancer, integrins are involved in the regulation of cancer cell proliferation, invasion, migration, and angiogenesis; conversely, integrins promote immune cell aggregation to mediate the elimination of tumors. The important roles of integrins in cancer progression have provided valuable clues for the diagnosis and targeted treatment of cancer. Furthermore, many integrin inhibitors have been investigated in clinical trials to explore effective regimens and reduce side effects. Due to the complexity of the mechanism of integrin-mediated cancer progression, challenges remain in the research and development of cancer immunotherapies (CITs). This review enumerates the effects of integrins on four types of immune cells and the potential mechanisms involved in the progression of cancer, which will provide ideas for more optimal CIT in the future.

Targeting integrin pathways: mechanisms and advances in therapy

Integrins are considered the main cell-adhesion transmembrane receptors that play multifaceted roles as extracellular matrix (ECM)-cytoskeletal linkers and transducers in biochemical and mechanical signals between cells and their environment in a wide range of states in health and diseases. Integrin functions are dependable on a delicate balance between active and inactive status via multiple mechanisms, including protein-protein interactions, conformational changes, and trafficking. Due to their exposure on the cell surface and sensitivity to the molecular blockade, integrins have been investigated as pharmacological targets for nearly 40 years, but given the complexity of integrins and sometimes opposite characteristics, targeting integrin therapeutics has been a challenge. To date, only seven drugs targeting integrins have been successfully marketed, including abciximab, eptifibatide, tirofiban, natalizumab, vedolizumab, lifitegrast, and carotegrast. Currently, there are approximately 90 kinds of integrin-based therapeutic drugs or imaging agents in clinical studies, including small molecules, antibodies, synthetic mimic peptides, antibody-drug conjugates (ADCs), chimeric antigen receptor (CAR) T-cell therapy, imaging agents, etc. A serious lesson from past integrin drug discovery and research efforts is that successes rely on both a deep understanding of integrin-regulatory mechanisms and unmet clinical needs. Herein, we provide a systematic and complete review of all integrin family members and integrin-mediated downstream signal transduction to highlight ongoing efforts to develop new therapies/diagnoses from bench to clinic. In addition, we further discuss the trend of drug development, how to improve the success rate of clinical trials targeting integrin therapies, and the key points for clinical research, basic research, and translational research.

Characterization of recombinant humanized collagen type III and its influence on cell behavior and phenotype

Collagen made a tremendous impact in the field of regenerative medicine as a bioactive material. For decades, collagen has been used not only as a scaffolding material but also as an active component in regulating cells' biological behavior and phenotype. However, animal-derived collagen as a major source suffered from problems of immunogenicity, risk of viral infection, and the unclear relationship between bioactive sequence and function. Recombinant humanized collagen (rhCol) provided alternatives for regenerative medicine with more controllable risks. However, the characterization of rhCol and the interaction between rhCol and cells still need further investigation, including cell behavior and phenotype. The current study preliminarily demonstrated that recombinant humanized collagen type III (rhCol III) conformed to the theoretical amino acid sequence and had an advanced structure resembling bovine collagen. Furthermore, rhCol III could facilitate basal biological behaviors of human skin fibroblasts, such as adhesion, proliferation and migration. rhCol III was beneficial for some extracellular matrix-expressing cell phenotypes. The study would shed light on the mechanism research of rhCol and cell interactions and further understanding of effectiveness in tissue regeneration.

Graphical abstract

The Sall2 transcription factor promotes cell migration regulating focal adhesion turnover and integrin β1 expression

SALL2/Sall2 is a transcription factor associated with development, neuronal differentiation, and cancer. Interestingly, SALL2/Sall2 deficiency leads to failure of the optic fissure closure and neurite outgrowth, suggesting a positive role for SALL2/Sall2 in cell migration. However, in some cancer cells, SALL2 deficiency is associated with increased cell migration. To further investigate the role of Sall2 in the cell migration process, we used immortalized Sall2 knockout (Sall2−/−) and Sall2 wild-type (Sall2+/+) mouse embryonic fibroblasts (iMEFs). Our results indicated that Sall2 positively regulates cell migration, promoting cell detachment and focal adhesions turnover. Sall2 deficiency decreased cell motility and altered focal adhesion dynamics. Accordingly, restoring Sall2 expression in the Sall2−/− iMEFs by using a doxycycline-inducible Tet-On system recovered cell migratory capabilities and focal adhesion dynamics. In addition, Sall2 promoted the autophosphorylation of Focal Adhesion Kinase (FAK) at Y397 and increased integrin β1 mRNA and its protein expression at the cell surface. We demonstrated that SALL2 increases ITGB1 promoter activity and binds to conserved SALL2-binding sites at the proximal region of the ITGB1 promoter, validated by ChIP experiments. Furthermore, the overexpression of integrin β1 or its blockade generates a cell migration phenotype similar to that of Sall2+/+ or Sall2−/− cells, respectively. Altogether, our data showed that Sall2 promotes cell migration by modulating focal adhesion dynamics, and this phenotype is associated with SALL2/Sall2-transcriptional regulation of integrin β1 expression and FAK autophosphorylation. Since deregulation of cell migration promotes congenital abnormalities, tumor formation, and spread to other tissues, our findings suggest that the SALL2/Sall2-integrin β1 axis could be relevant for those processes.

Depletion of ALMS1 affects TGF-β signalling pathway and downstream processes such as cell migration and adhesion capacity

Background: ALMS1 is a ubiquitous gene associated with Alström syndrome (ALMS). The main symptoms of ALMS affect multiple organs and tissues, generating at last, multi-organic fibrosis in the lungs, kidneys and liver. TGF-β is one of the main pathways implicated in fibrosis, controlling the cell cycle, apoptosis, cell migration, cell adhesion and epithelial-mesenchymal transition (EMT). Nevertheless, the role of ALMS1 gene in fibrosis generation and other implicated processes such as cell migration or cell adhesion via the TGF- β pathway has not been elucidated yet. Methods: Initially, we evaluated how depletion of ALMS1 affects different processes like apoptosis, cell cycle and mitochondrial activity in HeLa cells. Then, we performed proteomic profiling with TGF-β stimuli in HeLa ALMS1 -/- cells and validated the results by examining different EMT biomarkers using qPCR. The expression of these EMT biomarkers were also studied in hTERT-BJ-5ta ALMS1 -/-. Finally, we evaluated the SMAD3 and SMAD2 phosphorylation and cell migration capacity in both models. Results: Depletion of ALMS1 generated apoptosis resistance to thapsigargin (THAP) and C2-Ceramide (C2-C), and G2/M cell cycle arrest in HeLa cells. For mitochondrial activity, results did not show significant differences between ALMS1 +/+ and ALMS1 -/-. Proteomic results showed inhibition of downstream pathways regulated by TGF-β. The protein-coding genes (PCG) were associated with processes like focal adhesion or cell-substrate adherens junction in HeLa. SNAI1 showed an opposite pattern to what would be expected when activating the EMT in HeLa and BJ-5ta. Finally, in BJ-5ta model a reduced activation of SMAD3 but not SMAD2 were also observed. In HeLa model no alterations in the canonical TGF-β pathway were observed but both cell lines showed a reduction in migration capacity. Conclusion: ALMS1 has a role in controlling the cell cycle and the apoptosis processes. Moreover, the depletion of ALMS1 affects the signal transduction through the TGF-β and other processes like the cell migration and adhesion capacity.

Collagen Type XI Inhibits Lung Cancer-Associated Fibroblast Functions and Restrains the Integrin Binding Site Availability on Collagen Type I Matrix

The tumor microenvironment, including cancer-associated fibroblast (CAF), plays an active role in non-small cell lung cancer (NSCLC) development and progression. We previously reported that collagen type XI and integrin α11, a collagen receptor, were upregulated in NSCLC; the latter promotes tumor growth and metastasis. We here explored the role of collagen type XI in NSCLC stroma. We showed that the presence of collagen type XI in collagen type I matrices inhibits CAF-mediated collagen remodeling and cell migration. This resulted in the inhibition of CAF-dependent lung-tumor cell invasion. Among the collagen receptors expressed on CAF, we determined that DDR2 and integrin α2β1, but not integrin α11β1, mediated the high-affinity binding to collagen type XI. We further demonstrated that collagen type XI restrained the integrin binding site availability on collagen type I matrices, thus limiting cell interaction with collagen type I. As a consequence, CAFs failed to activate FAK, p38 and Akt one hour after they interacted with collagen type I/XI. We concluded that collagen type XI may have a competitive negative feedback role on the binding of collagen type I to its receptors.

Integrin α11β1 and syndecan-4 dual receptor ablation attenuates cardiac hypertrophy in the pressure overloaded heart

Pathological myocardial hypertrophy in response to an increase in left ventricular (LV) afterload may ultimately lead to heart failure. Cell surface receptors bridge the interface between the cell and the ECM in cardiac myocytes and cardiac fibroblasts, and have been suggested to be important mediators of pathological myocardial hypertrophy. We identify for the first time that integrin α11 (α11) is preferentially upregulated amongst integrin beta 1 heterodimer-forming α subunits in response to increased afterload induced by aortic banding (AB) in wild type mice (WT). Mice were anesthetized in a chamber with 4% isoflurane and 95% oxygen before being intubated and ventilated with 2.5% isoflurane and 97% oxygen. For pre- and post-operative analgesia, animals were administered 0.02 mL buprenorphine (0.3 mg/mL) subcutaneously. Surprisingly, mice lacking α11 develop myocardial hypertrophy following AB comparable to WT. In the mice lacking α11, we further show a compensatory increase in the expression of another mechanoreceptor, syndecan-4, following AB compared to WT AB mice, indicating that syndecan-4 compensated for lack of α11. Intriguingly, mice lacking mechanoreceptors α11 and syndecan-4 show ablated myocardial hypertrophy following AB compared to WT mice. Expression of the main cardiac collagen isoforms col1a2 and col3a1 was significantly reduced in AB mice lacking mechanoreceptors α11 and syndecan-4 compared to WT AB.

Asiatic acid inhibits angiogenesis and vascular permeability through the VEGF/VEGFR2 signaling pathway to inhibit the growth and metastasis of breast cancer in mice

Anti-angiogenic medicines have been evaluated as anticancer therapies, however, their use remains limited in clinical practice due to associated adverse effects. Asiatic acid (AA) is known to have broad-spectrum anticancer properties, however, its effects on angiogenesis in breast cancer remain to be fully established. In this study, we analyzed the inhibitory effects of AA on angiogenesis using human umbilical vein endothelial cells (HUVECs) cultured in vitro and on the growth and metastasis of a subcutaneous breast cancer 4T1 tumor model and a lung metastasis model in vivo. AA significantly inhibited HUVECs proliferation, migration, and tube formation in vitro. In vivo, AA significantly reduced the microvascular density and blood vascular permeability in breast cancer tumors and inhibited growth and lung metastasis. AA inhibited the expression of vascular endothelial growth factor (VEGF) in HUVECs and subsequently downregulated the phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2) and its downstream target proteins including ERK1/2, Src, and FAK. These results indicate that AA significantly inhibits angiogenesis and blood vessel permeability through the VEGF/VEGFR2 signal axis to inhibit the growth and metastasis of breast cancer. Our data strongly demonstrate the potential applications of AA in the treatment of breast cancer.

Understanding collagen interactions and their targeted regulation by novel drugs

Introduction: Among protein and fibers in the extracellular matrix (ECM), collagen is the most copious and widely employed in cosmetic, food, pharmaceutical, and biomedical industries due to its extensive biocompatible and versatile properties. In the last years, the knowledge about functions of collagens increased and expanded dramatically. Once considered only crucial for the ECM scaffolding and mechanotransduction, additional functional roles have now been ascribed to the collagen superfamily which are defined by other recently discovered domains, supramolecular assembly and receptors.Areas covered: Given the importance of each step in the collagen biosynthesis, folding and signaling, medicinal chemists have explored small molecules, peptides, and monoclonal antibodies to modulate enzymes, receptors and interactions with the physiological ligands of collagen. These compounds were also explored toward diseases and pathological conditions. The authors discuss this providing their expert perspectives on the subject area.Expert opinion: Understanding collagen protein properties and its interactome is beneficial for therapeutic drug design. Nevertheless, compounds targeting collagen-based interactome suffered from the presence of different isoforms for each target and the lack of specific 3D crystal structures able to guide properly drug design.

Visualization of integrin molecules by fluorescence imaging and techniques

Integrin molecules are transmembrane αβ heterodimers involved in cell adhesion, trafficking, and signaling. Upon activation, integrins undergo dynamic conformational changes that regulate their affinity to ligands. The physiological functions and activation mechanisms of integrins have been heavily discussed in previous studies and reviews, but the fluorescence imaging techniques -which are powerful tools for biological studies- have not. Here we review the fluorescence labeling methods, imaging techniques, as well as Förster resonance energy transfer assays used to study integrin expression, localization, activation, and functions.

Integrin α11β1 is a receptor for collagen XIII

Collagen XIII is a conserved transmembrane collagen mainly expressed in mesenchymal tissues. Previously, we have shown that collagen XIII modulates tissue development and homeostasis. Integrins are a family of receptors that mediate signals from the environment into the cells and vice versa. Integrin α11β1 is a collagen receptor known to recognize the GFOGER (O=hydroxyproline) sequence in collagens. Interestingly, collagen XIII and integrin α11β1 both have a role in the regulation of bone homeostasis. To study whether α11β1 is a receptor for collagen XIII, we utilized C2C12 cells transfected to express α11β1 as their only collagen receptor. The interaction between collagen XIII and integrin α11β1 was also confirmed by surface plasmon resonance and pull-down assays. We discovered that integrin α11β1 mediates cell adhesion to two collagenous motifs, namely GPKGER and GF(S)QGEK, that were shown to act as the recognition sites for the integrin α11-I domain. Furthermore, we studied the in vivo significance of the α11β1-collagen XIII interaction by crossbreeding α11 null mice (Itga11^−/−) with mice overexpressing Col13a1 (Col13a1^oe). When we evaluated the bone morphology by microcomputed tomography, Col13a1^oe mice had a drastic bone overgrowth followed by severe osteoporosis, whereas the double mutant mouse line showed a much milder bone phenotype. To conclude, our data identifies integrin α11β1 as a new collagen XIII receptor and demonstrates that this ligand-receptor pair has a role in the maintenance of bone homeostasis.

Reciprocal Interplay Between Fibrillar Collagens and Collagen-Binding Integrins: Implications in Cancer Progression and Metastasis

Cancers are complex ecosystems composed of malignant cells embedded in an intricate microenvironment made of different non-transformed cell types and extracellular matrix (ECM) components. The tumor microenvironment is governed by constantly evolving cell-cell and cell-ECM interactions, which are now recognized as key actors in the genesis, progression and treatment of cancer lesions. The ECM is composed of a multitude of fibrous proteins, matricellular-associated proteins, and proteoglycans. This complex structure plays critical roles in cancer progression: it functions as the scaffold for tissues organization and provides biochemical and biomechanical signals that regulate key cancer hallmarks including cell growth, survival, migration, differentiation, angiogenesis, and immune response. Cells sense the biochemical and mechanical properties of the ECM through specialized transmembrane receptors that include integrins, discoidin domain receptors, and syndecans. Advanced stages of several carcinomas are characterized by a desmoplastic reaction characterized by an extensive deposition of fibrillar collagens in the microenvironment. This compact network of fibrillar collagens promotes cancer progression and metastasis, and is associated with low survival rates for cancer patients. In this review, we highlight how fibrillar collagens and their corresponding integrin receptors are modulated during cancer progression. We describe how the deposition and alignment of collagen fibers influence the tumor microenvironment and how fibrillar collagen-binding integrins expressed by cancer and stromal cells critically contribute in cancer hallmarks.

Generation of a novel mouse strain with fibroblast-specific expression of Cre recombinase

Cell-specific expression of genes offers the possibility to use their promoters to drive expression of Cre-recombinase, thereby allowing for detailed expression analysis using reporter gene systems, cell lineage tracing, conditional gene deletion, and cell ablation. In this context, current data suggest that the integrin α11 subunit has the potential to serve as a fibroblast biomarker in tissue regeneration and pathology, in particular in wound healing and in tissue- and tumor fibrosis. The mesenchyme-restricted expression pattern of integrin α11 thus prompted us to generate a novel ITGA11-driver Cre mouse strain using a ϕC31 integrase-mediated knock-in approach. In this transgenic mouse, the Cre recombinase is driven by regulatory promoter elements within the 3 kb segment of the human ITGA11 gene. β-Galactosidase staining of embryonic tissues obtained from a transgenic ITGA11-Cre mouse line crossed with Rosa 26R reporter mice (ITGA11-Cre;R26R) revealed ITGA11-driven Cre expression and activity in mesenchymal cells in a variety of mesenchymal tissues in a pattern reminiscent of endogenous α11 protein expression in mouse embryos. Interestingly, X-gal staining of mouse embryonic fibroblasts (MEFs) isolated from the ITGA11-Cre;R26R mice indicated heterogeneity in the MEF population. ITGA11-driven Cre activity was shown in approximately 60% of the MEFs, suggesting that the expression of integrin α11 could be exploited for isolation of different fibroblast populations. ITGA11-driven Cre expression was found to be low in adult mouse tissues but was induced in granulation tissue of excisional wounds and in fibrotic hearts following aortic banding. We predict that the ITGA11-Cre transgenic mouse strain described in this report will be a useful tool in matrix research for the deletion of genes in subsets of fibroblasts in the developing mouse and for determining the function of subsets of pro-fibrotic fibroblasts in tissue fibrosis and in different subsets of cancer-associated fibroblasts in the tumor microenvironment.

•

A mouse strain with Cre-recombinase driven by the human integrin α11 promoter has been generated.

•

Cre-recombinase expression in this strain has been characterized using the Rosa26R reporter mouse.

•

ITGA11-Cre is restricted to fibroblast subsets in mouse embryos, skin wounds and fibrotic hearts.

•

This Cre-driver strain will be a useful tool to study role fibroblasts in fibrosis and tumors.

Integrin α11β1 is expressed in breast cancer stroma and associates with aggressive tumor phenotypes

Cancer‐associated fibroblasts are essential modifiers of the tumor microenvironment. The collagen‐binding integrin α11β1 has been proposed to be upregulated in a pro‐tumorigenic subtype of cancer‐associated fibroblasts. Here, we analyzed the expression and clinical relevance of integrin α11β1 in a large breast cancer series using a novel antibody against the human integrin α11 chain. Several novel monoclonal antibodies against the integrin α11 subunit were tested for use on formalin‐fixed paraffin‐embedded tissues, and Ab 210F4B6A4 was eventually selected to investigate the immunohistochemical expression in 392 breast cancers using whole sections. mRNA data from METABRIC and co‐expression patterns of integrin α11 in relation to αSMA and cytokeratin‐14 were also investigated. Integrin α11 was expressed to varying degrees in spindle‐shaped cells in the stroma of 99% of invasive breast carcinomas. Integrin α11 co‐localized with αSMA in stromal cells, and with αSMA and cytokeratin‐14 in breast myoepithelium. High stromal integrin α11 expression (66% of cases) was associated with aggressive breast cancer features such as high histologic grade, increased tumor cell proliferation, ER negativity, HER2 positivity, and triple‐negative phenotype, but was not associated with breast cancer specific survival at protein or mRNA levels. In conclusion, high stromal integrin α11 expression was associated with aggressive breast cancer phenotypes.