Integrin Cell Research Articles

Protein kinase C iota (PKCι) and pVHL are both needed for lysosomal degradation of α5 integrin in renal carcinoma cells

Backgroundvon Hippel-Lindau (VHL) hereditary cancer syndrome is caused by mutations in the VHL tumor suppressor gene and is characterized by a predisposition to form various types of tumors, including renal cell carcinomas, hemangioblastomas, and pheochromocytomas. The protein products of the VHL gene, pVHL, are part of an ubiquitin ligase complex that tags hypoxia inducible factor alpha (HIF-α) for proteosomal degradation. pVHL has also been reported to bind to atypical protein kinase C (aPKC).Methods and resultsTo better understand the relationship between pVHL and aPKC, the PKC iota (PKCι) isoform of aPKC was knocked out in renal carcinoma cells, both pVHL-negative and those with replaced pVHL. Cellular properties associated with pVHL function were assayed. Knockout of PKCι in pVHL-expressing cells led to greater downregulation of HIF-α than seen with pVHL alone, suggesting that the presence of PKCι opposes complete regulation of HIF-α by pVHL. In contrast, absence of either pVHL or PKCι disrupted tight junction formation and led to upregulated levels of α5 integrin, both of which were phenocopied by lysosomal inhibition. LAMP1 (lysosome associated membrane protein 1), a marker for lysosomes, showed dysregulated localization and altered electrophoretic gel migration in the absence of pVHL. While the upregulated α5 integrin seen in the absence of either pVHL or PKCι loss was associated with increased cell adhesion, loss of pVHL caused increased cell motility whereas loss of PKCι decreased motility.ConclusionsThese data are consistent with a known role of PKCι in endocytosis of α5 integrin and suggest a subsequent novel role of pVHL in targeting a pool of endocytosed α5 integrin for lysosomal degradation.

Fast-Relaxing Hydrogels Promote Pancreatic Adenocarcinoma Cell Aggressiveness through Integrin β1 Signaling.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a dense extracellular matrix (ECM) exhibiting high stiffness and fast stress relaxation. In this work, gelatin-based viscoelastic hydrogels were developed to mimic the compositions, stiffness, and fast stress relaxation of PDAC tissues. The hydrogels were cross-linked by gelatin-norbornene-boronic acid (GelNB-BA), thiolated macromers, and a 1,2-diol-containing linear synthetic polymer PHD. Controlling the thiol-norbornene cross-linking afforded tunable stiffness, whereas increasing PHD content led to hydrogels with PDAC-mimicking fast stress relaxation. In vitro studies, including proliferation, morphology, and mRNA-sequencing, showed that fast-relaxing hydrogels supported PDAC cell proliferation, epithelial-mesenchymal transition (EMT), and integrin β1 activation. Blocking integrin β1 in vitro led to upregulating EMT markers in both slow and fast-relaxing hydrogels. However, this strategy profoundly impacted tumor growth rate and reduced tumor size but did not alter metastasis patterns in an orthotopic mouse model. This suggests a need to further evaluate the antitumor effect of integrin β1 blockade.

P0068 Distribution of α4β7 integrin and MAdCAM-1 expression according to the location of intestinal inflammation in a murine model of spontaneous chronic enterocolitis

Abstract Background The selective blockade of α4β7 integrin is a treatment for inflammatory bowel disease (IBD), with different efficacy according to the location of inflammation along the gastrointestinal tract. A more pronounced effect has been reported in patients with predominant colonic inflammation. It may be attributed to differences in the regional expression of adhesion molecules. This study aimed to investigate the expression of α4β7 integrin and mucosal addressin cell adhesion molecule-1 (MAdCAM-1) in colon, ileum, and mesentery, using IL-10 knockout (KO) mice as a model of spontaneous chronic enterocolitis. Methods At 20 weeks, the colon, ileum, and mesentery were extracted from IL-10KO and C57BL/6 wild-type (WT) mice. Protein levels of α4β7 integrin and MAdCAM-1 were determined by Western blot in the different tissues. Additionally, pro-inflammatory cytokines (TNF-α and IFN-γ) and epithelial adhesion molecules (Zonula Occludens-1, ZO-1; E-cadherin and Mucin 2, Muc2) expression in the ileum, as well as adiponectin expression in the mesentery, were analyzed using real-time PCR. Results Analysis demonstrated a significant increase in gene expression of the pro-inflammatory cytokines TNF-α and IFN-γ in the ileum of IL-10 KO mice compared with WT mice (p<0.01). In addition, IL-10KO mice exhibited reduced expression of ZO-1, E-cadherin, and Muc2 in the ileum relative to WT mice (p<0.001). IL-10 deficiency also led to a marked decrease in adiponectin expression in the mesentery (p<0.05). We then analyzed the protein level of MAdCAM-1 and α4β7 integrin according to anatomic region. Remarkably, the protein analysis revealed significantly higher levels of MAdCAM-1 (p<0.01) and α4β7 integrin (p<0.05) in the colon of IL-10 KO mice compared to WT. In the ileum, while MAdCAM-1 levels remained unchanged, α4β7 integrin expression was increased in IL-10KO mice (p<0.01). No significant differences in MAdCAM-1 or α4β7 integrin levels were observed in the mesentery between IL-10KO and WT mice Conclusion IL-10-deficient mice develop inflammation in the ileum, accompanied by a reduction in adiponectin production in the mesentery. In this setting, both α4β7 integrin and MAdCAM-1 showed increased expression in the colon, which was not observed in the ileum or mesentery, despite the inflammation. This differential regional expression pattern of adhesion molecules may explain the variation in the efficacy of anti-integrin therapies. Characterizing these patterns in patients with IBD could help identify those who would benefit most from these treatments.

β1 Integrin/FAK signaling regulates interleukin-8 production in human gingival epithelial Ca9-22 cells.

Interleukin-8 (IL-8), a proinflammatory factor in human tissues, plays an important role in inflammation. Type IV collagen, a key component of the basement membrane, interacts with integrins, which are primary receptors in the extracellular matrix (ECM). Integrins are essential for the regulation of various cellular behaviors and signal transduction pathways. However, the relationship between type IV collagen, β1 integrin, and gingival epithelial cells is poorly understood. The aim in this study was to elucidate the effect of the interaction between type IV collagen and β1 integrin on IL-8 secretion in human gingival epithelial cells (Ca9-22). Ca9-22 cells were treated with or without type IV collagen, and IL-8 production was assessed using an enzyme-linked immunosorbent assay (ELISA). The role of β1 integrin was investigated using a β1 integrin-neutralizing antibody. Western blotting was performed to measure the phosphorylation levels of the relevant proteins. The effects of the focal adhesion kinase (FAK) inhibitor Y15 and the MEK inhibitor U0126 on β1 integrin/FAK and Erk1/2 MAPK pathways in IL-8 production were evaluated to explore the involvement of these signaling pathways. β1 integrin induced IL-8 secretion in the Ca9-22 cells by regulating FAK, Erk1/2, and p130Cas proteins. p130Cas was independent of FAK, whereas Erk1/2 functioned downstream of FAK. Inhibition of FAK or Erk1/2 substantially reduced IL-8 secretion, highlighting their pivotal roles in this signaling pathway. β1 integrin promotes IL-8 secretion in Ca9-22 cells via the β1 integrin/FAK/Erk1/2 signaling pathway. These findings elucidate the pathogenesis of periodontitis and provide a foundation for the development of targeted therapeutic strategies.

Increased perfluorooctanoic acid accumulation facilitates the migration and invasion of lung cancer cells via remodeling cell mechanics

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are widely used in industrial and household products, raising serious concerns due to their environmental persistence and mobility. Epidemiological studies have reported potential carcinogenic risks of PFAS based on their widespread occurrence and population exposure. In this study, we observed that perfluorooctanoic acid (PFOA), a common PFAS, functions as a mechanical regulator in lung cancer cells. PFOA exposure reduces cell stiffness, thereby decreasing cell adhesion and enhancing immune evasion, ultimately exacerbating tumor metastasis. In various lung cancer models, more aggressive tumor metastases have been observed in the PFOA exposure group. Additionally, serum PFOA levels in patients with advanced lung adenocarcinoma were significantly higher than those in patients with early-stage disease. Mechanistically, the interaction between PFOA and transmembrane integrins in cancer cells triggers changes in cellular mechanical properties, leading to the reorganization of the cytoskeleton, and activation of the intracellular FAK-PI3K-Akt signaling pathway. Our findings demonstrate that in individuals with lung adenocarcinoma, PFOA can increase the risk of cancer metastasis even at daily exposure levels.

Expression of αv Integrin in Feline Injection-Site Sarcoma (FISS): Preliminary Investigations.

Feline injection-site sarcomas (FISSs) are malignant skin tumors of mesenchymal origin arising at local post-vaccination (or injection) sites. In recent years, a fluorescence imaging technique based on probes targeting αvβ3 integrin has been effectively applied for the surgical complete resection of the tumor. In our study, we investigated the utility of a commercially available anti-αv integrin polyclonal antibody for the histopathological evaluation of FISS's surgical excision margins. We collected 10 formalin-fixed paraffin-embedded (FFPE) feline excisional biopsies with a histopathological diagnosis of FISS (7 fibrosarcomas and 3 pleomorphic sarcomas) and wide margin tissue, along with one subcutaneous injection-site granuloma and 6 osteosarcomas. Samples were processed for histology, and slides were stained for IHC with the anti-αv integrin antibody. Immunostained slides were evaluated for the cellular localization and intensity of the staining in different neoplastic and non-neoplastic cell populations. Neoplastic and non-neoplastic spindle cells had cytoplasmic positivity in all fibrosarcomas. Inflammatory cells, including macrophages of the injection-site granuloma, were negative. Multinucleated giant cells in the pleomorphic sarcomas had an intense membranous positivity. Although the anti-αv integrin antibody was ineffective for the histopathological evaluation of surgical excision margins, the membranous localization of αv integrin in multinucleated giant cells of pleomorphic sarcomas suggests that it plays a role in the oncogenesis of this FISS variant.

Deletion of α5 integrin in endothelial cells ameliorates age–associated cognitive decline and increases survival in mice

Deletion of α5 integrin in endothelial cells ameliorates age–associated cognitive decline and increases survival in mice

Integrin Subtypes and Lamellipodia Mediate Spatial Sensing of RGD Ligands during Cell Adhesion.

Understanding how the spatial distribution of adhesive ligands regulates cell behavior is crucial for designing biomaterials. This study investigates how precisely controlled ligand spacing affects cell spreading and integrin subtype engagement. Using engineered polyacrylamide hydrogels with gold nanoparticle arrays, we explored the impact of RGD ligand spacings (30 and 150 nm) on human mesenchymal stromal cells. Cells exhibited distinct morphological behaviors: smaller spacings promoted larger spreading areas, while larger spacings resulted in elongated shapes with reduced spreading. Mechanistically, we found that the α5β1 integrin, not the αvβ3 integrin, played a central role in mediating these responses, alongside lamellipodia formation. Our findings provide critical insights into the spatial sensing of ligands, highlighting the influence of ligand spacing on cellular mechanotransduction and integrin-specific responses. This work advances the understanding of cell-material interactions and offers potential strategies for designing biomaterials to guide cell behavior in tissue engineering.

Clotting Promotes Glioma Growth and Infiltration Through Activation of Focal Adhesion Kinase.

High-grade gliomas are associated with intratumoral thrombosis, tumor cell necrosis, and hemorrhage. The resulting blood clot serves as an adhesive matrix for glioma cell integrins that activate FAK. Knocking down FAK with CRISPR cas9, on the other hand, is highly effective at halting GBM growth in mice.

Identification of CD44 as a key engager to hyaluronic acid-rich extracellular matrices for cell traction force generation and tumor invasion in 3D

Mechanical properties of the extracellular matrix (ECM) critically regulate a number of important cell functions including growth, differentiation and migration. Type I collagen and glycosaminoglycans (GAGs) are two primary components of ECMs that contribute to mammalian tissue mechanics, with the collagen fiber network sustaining tension, and GAGs withstanding compression. The architecture and stiffness of the collagen network are known to be important for cell-ECM mechanical interactions via cell surface adhesion receptor integrin. In contrast, studies of GAGs in modulating cell-ECM interactions are limited. Here, we present experimental studies on the roles of hyaluronic acid (HA) in single tumor cell traction force generation using a recently developed 3D cell traction force microscopy method. Our work reveals that CD44, a cell surface receptor to HA, is engaged in cell traction force generation in conjunction with β1-integrin. We find that HA significantly modifies the architecture and mechanics of the collagen fiber network, decreasing tumor cells’ propensity to remodel the collagen network, attenuating traction force generation, transmission distance, and tumor invasion. Our findings point to a novel role for CD44 in traction force generation, which can be a potential therapeutic target for diseases involving HA rich ECMs such as breast cancer and glioblastoma.

Monocyte-derived extracellular vesicles, stimulated by Trypanosoma cruzi, enhance cellular invasion invitro via activated TGF-β1.

During cell invasion, large Extracellular Vesicle (lEV) release from host cells was dose-dependently triggered by Trypanosoma cruzi metacyclic trypomastigotes (Mtr). This lEV release was inhibited when IP3-mediated Ca2+ exit from the ER and further Ca2+ entry from plasma membrane channels was blocked, but whilst any store-independent Ca2+ entry (SICE) could continue unabated. That lEV release was equally inhibited if all entry from external sources was blocked by chelation of external Ca2+ points to the major contributor to Mtr-triggered host cell lEV release being IP3/store-mediated Ca2+ release, SICE playing a minor role. Host cell lEVs were released through Mtr interaction with host cell lipid raft domains, integrins, and mechanosensitive ion channels, whereupon [Ca2+]cyt increased (50 to 750nM) within 15 s. lEV release and cell entry of T. cruzi, which increased up to 30 and 60 mpi, respectively, as well as raised actin depolymerization at 60 mpi, were all reduced by TRPC inhibitor, GsMTx-4. Vesicle release and infection was also reduced with RGD peptide, methyl-β-cyclodextrin, knockdown of calpain and with the calpain inhibitor, calpeptin. Restoration of lEV levels, whether with lEVs from infected or uninfected epithelial cells, did not restore invasion, but supplementation with lEVs from infected monocytes, did. We provide evidence of THP-1 monocyte-derived lEV interaction with Mtr (lipid mixing by R18-dequenching; flow cytometry showing transfer to Mtr of R18 from R18-lEVs and of LAP(TGF-β1). Active, mature TGF-β1 (at 175 pg/×105 in THP-1 lEVs) was detected in concentrated lEV-/cell-free supernatant by western blotting, only after THP-1 lEVs had interacted with Mtr. The TGF-β1 receptor (TβRI) inhibitor, SB-431542, reduced the enhanced cellular invasion due to monocyte-lEVs.

Macrophage-expressed coagulation factor 7 promotes adverse cardiac remodeling

Abstract Background Excess fibrotic remodeling leads to cardiac dysfunction in ischemic heart disease and is driven by MAP kinase-dependent transforming growth factor-ß1 (TGF-ß1) activation by coagulation signaling of myeloid cells. How coagulation-inflammatory circuits can be specifically targeted to achieve beneficial macrophage reprogramming after myocardial infarction (MI) is incompletely understood. Methods Mice with permanent ligation of the proximal left anterior descending artery (LAD) were used to model ischemic heart disease and analyzed by single cell RNA sequencing, protein expression changes, confocal microscopy, and longitudinal monitoring of recovery. We probed the role of the tissue factor (TF)-factor 7 (F7)-integrin ß1-protease activated receptor (PAR) 2 signaling complex by utilizing genetic mouse models and pharmacological intervention. Results Cleavage-insensitive PAR2R38E and myeloid cell integrin ß1-deficient mice had improved cardiac function after MI compared to controls. Proximity ligation assays of monocytic cells in the infarcted myocardium demonstrated that colocalization of F7 with integrin ß1 was diminished in monocyte/macrophage F7-deficient mice. F7fl/fl CX3CR1Cre relative to littermate control mice showed reduced TGF-ß1 and MAP kinase activation, as well as cardiac dysfunction after MI, despite unaltered overall recruitment of myeloid cells into the infarct zone. Single cell mRNA sequencing of CD45+ cells 3 and 7 days after MI uncovered a trajectory from ischemic myocardium-recruited monocytes to inflammatory TF+/F7+/TREM1+ macrophages. As early as 7 days after MI, macrophage F7-deletion led to an expansion of Olfml3+ macrophages with a reparative phenotype and, conversely, to a reduction of TF+/F7+/TREM1+ macrophages, which were also attenuated in activation-resistant PAR2R38E mice. To demonstrate the therapeutic potential of inhibiting the TF-F7-PAR2 signaling complex, we injected a specific monoclonal anti-TF antibody that lacks anticoagulant activity. Short-term treatment from day 1-5 after non-reperfused MI improved cardiac dysfunction, decreased excess fibrosis, attenuated vascular endothelial dysfunction, and increased survival 28 days after MI. Conclusion Extravascular TF-F7-PAR2 complex signaling drives inflammatory macrophage polarization in ischemic heart disease. Targeting this signaling complex for specific therapeutic macrophage reprogramming following MI attenuates cardiac fibrosis and improves cardiovascular function.

Force-mediated recruitment and reprogramming of healthy endothelial cells drive vascular lesion growth

Force-driven cellular interactions are crucial for cancer cell invasion but remain underexplored in vascular abnormalities. Cerebral cavernous malformations (CCM), a vascular abnormality characterized by leaky vessels, involves CCM mutant cells recruiting wild-type endothelial cells to form and expand mosaic lesions. The mechanisms behind this recruitment remain poorly understood. Here, we use an in-vitro model of angiogenic invasion with traction force microscopy to reveal that hyper-angiogenic Ccm2-silenced endothelial cells enhance angiogenic invasion of neighboring wild-type cells through force and extracellular matrix-guided mechanisms. We demonstrate that mechanically hyperactive CCM2-silenced tips guide wild-type cells by transmitting pulling forces and by creating paths in the matrix, in a ROCKs-dependent manner. This is associated with reinforcement of β1 integrin and actin cytoskeleton in wild-type cells. Further, wild-type cells are reprogrammed into stalk cells and activate matrisome and DNA replication programs, thereby initiating proliferation. Our findings reveal how CCM2 mutants hijack wild-type cell functions to fuel lesion growth, providing insight into the etiology of vascular malformations. By integrating biophysical and molecular techniques, we offer tools for studying cell mechanics in tissue heterogeneity and disease progression.

Macrophage-Expressed Coagulation Factor VII Promotes Adverse Cardiac Remodeling.

Excess fibrotic remodeling causes cardiac dysfunction in ischemic heart disease, driven by MAP (mitogen-activated protein) kinase-dependent TGF-ß1 (transforming growth factor-ß1) activation by coagulation signaling of myeloid cells. How coagulation-inflammatory circuits can be specifically targeted to achieve beneficial macrophage reprogramming after myocardial infarction (MI) is not completely understood. Mice with permanent ligation of the left anterior descending artery were used to model nonreperfused MI and analyzed by single-cell RNA sequencing, protein expression changes, confocal microscopy, and longitudinal monitoring of recovery. We probed the role of the tissue factor (TF)-FVIIa (activated factor VII)-integrin ß1-PAR2 (protease-activated receptor 2) signaling complex by utilizing genetic mouse models and pharmacological intervention. Cleavage-insensitive PAR2R38E and myeloid cell integrin ß1-deficient mice had improved cardiac function after MI compared with controls. Proximity ligation assays of monocytic cells demonstrated that colocalization of FVIIa with integrin ß1 was diminished in monocyte/macrophage FVII-deficient mice after MI. Compared with controls, F7fl/fl CX3CR1 (CX3C motif chemokine receptor 1)Cre mice showed reduced TGF-ß1 and MAP kinase activation, as well as cardiac dysfunction after MI, despite unaltered overall recruitment of myeloid cells. Single-cell mRNA sequencing of CD45 (cluster of differentiation 45)+ cells 3 and 7 days after MI uncovered a trajectory from recruited monocytes to inflammatory TF+/TREM (triggered receptor expressed on myeloid cells) 1+ macrophages requiring F7. As early as 7 days after MI, macrophage F7 deletion led to an expansion of reparative Olfml 3 (olfactomedin-like protein 3)+ macrophages and, conversely, to a reduction of TF+/TREM1+ macrophages, which were also reduced in PAR2R38E mice. Short-term treatment from days 1 to 5 after nonreperfused MI with a monoclonal antibody inhibiting the macrophage TF-FVIIa-PAR2 signaling complex without anticoagulant activity improved cardiac dysfunction, decreased excess fibrosis, attenuated vascular endothelial dysfunction, and increased survival 28 days after MI. Extravascular TF-FVIIa-PAR2 complex signaling drives inflammatory macrophage polarization in ischemic heart disease. Targeting this signaling complex for specific therapeutic macrophage reprogramming following MI attenuates cardiac fibrosis and improves cardiovascular function.

An interpretable deep learning framework identifies proteomic drivers of Alzheimer's disease.

Alzheimer's disease (AD) is the leading neurodegenerative pathology in aged individuals, but many questions remain on its pathogenesis, and a cure is still not available. Recent research efforts have generated measurements of multiple omics in individuals that were healthy or diagnosed with AD. Although machine learning approaches are well-suited to handle the complexity of omics data, the models typically lack interpretability. Additionally, while the genetic landscape of AD is somewhat more established, the proteomic landscape of the diseased brain is less well-understood. Here, we establish a deep learning method that takes advantage of an ensemble of autoencoders (AEs) - EnsembleOmicsAE-to reduce the complexity of proteomics data into a reduced space containing a small number of latent features. We combine brain proteomic data from 559 individuals across three AD cohorts and demonstrate that the ensemble autoencoder models generate stable latent features which are well-suited for downstream biological interpretation. We present an algorithm to calculate feature importance scores based on the iterative scrambling of individual input features (i.e., proteins) and show that the algorithm identifies signaling modules (AE signaling modules) that are significantly enriched in protein-protein interactions. The molecular drivers of AD identified within the AE signaling modules derived with EnsembleOmicsAE were missed by linear methods, including integrin signaling and cell adhesion. Finally, we characterize the relationship between the AE signaling modules and the age of death of the patients and identify a differential regulation of vimentin and MAPK signaling in younger compared with older AD patients.

Bone sialoprotein stimulates cancer cell adhesion through the RGD motif and the αvβ3 and αvβ5 integrin receptors.

Being implicated in bone metastasis development, bone sialoprotein (BSP) expression is upregulated in patients with cancer. While BSP regulates cancer cell adhesion to the extracellular matrix, to the best of our knowledge, the specific adhesive molecular interactions in metastatic bone disease remain unclear. The present study aimed to improve the understanding of the arginine-glycine-aspartic acid (RGD) sequence of BSP and the integrin receptors αvβ3 and αvβ5 in BSP-mediated cancer cell adhesion. Human breast cancer (MDA-MB-231), prostate cancer (PC-3) and non-small cell lung cancer (NSCLC; NCI-H460) cell lines were cultured on BSP-coated plates. Adhesion assays with varying BSP concentrations were performed to evaluate the effect of exogenous glycine-arginine-glycine-aspartic acid-serine-proline (GRGDSP) peptide and anti-integrin antibodies on the attachment of cancer cells to BSP. Cell attachment was assessed using the alamarBlue® assay. The present results indicated that BSP supported the adhesion of cancer cells. The RGD counterpart GRGDSP peptide reduced the attachment of all tested cancer cell lines to BSP by ≤98.4%. Experiments with anti-integrin antibodies demonstrated differences among integrin receptors and cancer cell types. The αvβ5 antibody decreased NSCLC cell adhesion to BSP by 84.3%, while the αvβ3 antibody decreased adhesion by 14%. The αvβ3 antibody decreased PC-3 cell adhesion to BSP by 46.4%, while the αvβ5 antibody decreased adhesion by 9.5%. Adhesion of MDA-MB-231 cells to BSP was inhibited by 54.7% with αvβ5 antibody. The present results demonstrated that BSP-induced cancer cell adhesion occurs through the binding of the RGD sequence of BSP to the cell integrin receptors αvβ3 and αvβ5. Differences between cancer types were found regarding the mediation via αvβ3 or αvβ5 receptors. The present findings may explain why certain cancer cells preferentially spread to the bone tissue, suggesting that targeting the RGD-integrin binding interaction could be a promising novel cancer treatment option.

Hypoxia-driven heterogeneous expression of α5 integrin in glioblastoma stem cells is linked to HIF-2α

Despite numerous molecular targeted therapies tested in glioblastoma (GBM), no significant progress in patient survival has been achieved in the last 20 years in the overall population of GBM patients except with TTfield setup associated with the standard of care chemoradiotherapy. Therapy resistance is associated with target expression heterogeneity and plasticity between tumors and in tumor niches. We focused on α5 integrin implicated in aggressive GBM in preclinical and clinical samples. To address the characteristics of α5 integrin heterogeneity we started with patient data indicating that elevated levels of its mRNA are related to hypoxia pathways. We turned on glioma stem cells which are considered at the apex of tumor formation and recurrence but also as they localize in hypoxic niches. We demonstrated that α5 integrin expression is stem cell line dependent and is modulated positively by hypoxia in vitro. Importantly, heterogeneity of expression is conserved in in vivo stem cell-derived mice xenografts. In hypoxic niches, HIF-2α is preferentially implicated in α5 integrin expression which confers migratory capacity to GBM stem cells. Hence combining HIF-2α and α5 integrin inhibitors resulted in proliferation and migration impairment of α5 integrin expressing cells. Stabilization of HIF-2α is however not sufficient to control integrin α5 expression. Our results show that AHR (aryl hydrocarbon receptor) expression is inversely related to HIF-2α and α5 integrin expressions suggesting a functional competition between the two transcription factors. Collectively, data confirm the high heterogeneity of a GBM therapeutic target, its induction in hypoxic niches by HIF-2α and suggest a new way to attack molecularly defined GBM stem cells.

Integrin αV Inhibition by GMI, a Ganoderma Microsporum Immunomodulatory Protein, Abolish Stemness and Migration in EGFR-Mutated Lung Cancer Cells Resistant to Osimertinib.

Integrins, the receptors of the extracellular matrix, are critical in the proliferation and metastasis of cancer cells. GMI, a Ganoderma microsporum immunomodulatory protein, possesses anticancer and antivirus abilities. The object of this study is to investigate the role of GMI in the integrins signaling pathway in lung cancer cells that harbor the EGFR L858R/T790M double mutation and osimertinib-resistance. Liquid chromatography-mass spectrometry and western blot assay were used to investigate the effect of GMI on inhibiting the protein expressions of integrins in H1975 cells. The migration ability and xenograft tumor growth of H1975 were suppressed by GMI. To elucidate the role of the integrin family in lung cancer resistant to osimertinib (AZD-9291, Tagrisso), H1975 cells were used to establish the osimertinib-resistant cells, named H1975/TR cells. The expressions of Integrin αV and stemness markers were much higher in H1975/TR cells than in H1975 cells. GMI suppressed cell viability, tumor spheroid growth, and the expressions of integrin αV and β1 in H1975/TR cells. Furthermore, GMI suppressed the expressions of stemness markers and formation of tumor spheres via blocking integrin αV signaling cascade. This is the first study to reveal the novel function of GMI in constraining cancer stem cells and migration by abolishing the integrin αV-related signaling pathway in EGFR-mutated and osimertinib-resistant lung cancer cells.

The Proangiogenic Effects of Melanoma-Derived Ectosomes Are Mediated by αvβ5 Integrin Rather than αvβ3 Integrin.

Ectosomes are carriers of proangiogenic factors during cancer progression. This study investigated whether the proangiogenic effect exerted by melanoma-derived ectosomes on recipient endothelial cells is mediated by ectosomal αvβ3 and αvβ5 integrins. Ectosomes were isolated from the conditioned culture media of four melanoma cell lines and melanocytes. Changes in gene and protein expression of αvβ3 and αvβ5 integrins, as well as VEGF and TNF-α were assessed in ectosome-treated endothelial cells. To confirm the functional involvement of ectosomal integrins in functional tests (Alamar Blue, wound healing and tube formation assays), ectosomes were also pretreated with anti-integrin antibodies and integrin-blocking peptides echistatin and cilengitide. Melanoma-derived ectosomes induced changes in the expression of αvβ3 and αvβ5 integrins in recipient endothelial cells, leading to increased viability, migratory properties, and tube formation potential. The extent of proangiogenic stimulation varied depending on the types of cells releasing ectosomes and the recipient cells. The use of anti-integrin antibodies and integrin-blocking peptides revealed a more significant role for the αvβ5 integrin/VEGF than the αvβ3 integrin/TNF-α pathway in the interactions between ectosomes and endothelial cells. The study demonstrated the functional role of ectosomal αvβ3 and αvβ5 integrins. It also provided a baseline understanding of ectosome-mediated αvβ3 integrin/TNF-α and αvβ5 integrin/VEGF signaling in angiogenesis.

Recruitment of Vitronectin by Bacterial Pathogens: A Comprehensive Overview.

The key factor that enables pathogenic bacteria to establish successful infections lies largely in their ability to escape the host's immune response and adhere to host surfaces. Vitronectin (Vn) is a multidomain glycoprotein ubiquitously present in blood and the extracellular matrix of several tissues, where it plays important roles as a regulator of membrane attack complex (MAC) formation and as a mediator of cell adhesion. Vn has emerged as an intriguing target for several microorganisms. Vn binding by bacterial receptors confers protection from lysis resulting from MAC deposition. Furthermore, through its Arg-Gly-Asp (RGD) motif, Vn can bind several host cell integrins. Therefore, Vn recruited to the bacterial cell functions as a molecular bridge between bacteria and host surfaces, where it triggers several host signaling events that could promote bacterial internalization. Each bacterium uses different receptors that recognize specific Vn domains. In this review, we update the current knowledge of Vn receptors of major bacterial pathogens, emphasizing the role they may play in the host upon Vn binding. Focusing on the structural properties of bacterial proteins, we provide details on the residues involved in their interaction with Vn. Furthermore, we discuss the possible involvement of Vn adsorption on biomaterials in promoting bacterial adhesion on abiotic surfaces and infection.