The role of β3-integrins in tumor angiogenesis: context is everything

Treatment with αvβ3-integrin-specific 29P attenuates pressure-overload induced cardiac remodelling after transverse aortic constriction in mice

Heart failure remains one of the largest clinical burdens globally, with little to no improvement in the development of disease-eradicating therapeutics. Integrin targeting has been used in the treatment of ocular disease and cancer, but little is known about its utility in the treatment of heart failure. Here we sought to determine whether the second generation orally available, αvβ3-specific RGD-mimetic, 29P , was cardioprotective. Male mice were subjected to transverse aortic constriction (TAC) and treated with 50 μg/kg 29P or volume-matched saline as Vehicle control. At 3 weeks post-TAC, echocardiography showed that 29P treatment significantly restored cardiac function and structure indicating the protective effect of 29P treatment in this model of heart failure. Importantly, 29P treatment improved cardiac function giving improved fractional shortening, ejection fraction, heart weight and lung weight to tibia length fractions, together with partial restoration of Ace and Mme levels, as markers of the TAC insult. At a tissue level, 29P reduced cardiomyocyte hypertrophy and interstitial fibrosis, both of which are major clinical features of heart failure. RNA sequencing identified that, mechanistically, this occurred with concomitant alterations to genes involved molecular pathways associated with these processes such as metabolism, hypertrophy and basement membrane formation. Overall, targeting αvβ3 with 29P provides a novel strategy to attenuate pressure-overload induced cardiac hypertrophy and fibrosis, providing a possible new approach to heart failure treatment.

Integrin αVβ3 antagonist-c(RGDyk) peptide attenuates the progression of ossification of the posterior longitudinal ligament by inhibiting osteogenesis and angiogenesis

BACKGROUND

Ossification of the posterior longitudinal ligament (OPLL), an emerging heterotopic ossification disease, causes spinal cord compression, resulting in motor and sensory dysfunction. The etiology of OPLL remains unclear but may involve integrin αVβ3 regulating the process of osteogenesis and angiogenesis. In this study, we focused on the role of integrin αVβ3 in OPLL and explored the underlying mechanism by which the c(RGDyk) peptide acts as a potent and selective integrin αVβ3 inhibitor to inhibit osteogenesis and angiogenesis in OPLL.

METHODS

OPLL or control ligament samples were collected in surgery. For OPLL samples, RNA-sequencing results revealed activation of the integrin family, particularly integrin αVβ3. Integrin αVβ3 expression was detected by qPCR, Western blotting, and immunohistochemical analysis. Fluorescence microscopy was used to observe the targeted inhibition of integrin αVβ3 by the c(RGDyk) peptide on ligaments fibroblasts (LFs) derived from patients with OPLL and endothelial cells (ECs). The effect of c(RGDyk) peptide on the ossification of pathogenic LFs was detected using qPCR, Western blotting. Alkaline phosphatase staining or alizarin red staining were used to test the osteogenic capability. The effect of the c(RGDyk) peptide on angiogenesis was determined by EC migration and tube formation assays. The effects of the c(RGDyk) peptide on heterotopic bone formation were evaluated by micro-CT, histological, immunohistochemical, and immunofluorescence analysis in vivo.

RESULTS

The results indicated that after being treated with c(RGDyk), the osteogenic differentiation of LFs was significantly decreased. Moreover, the c(RGDyk) peptide inhibited the migration of ECs and thus prevented the nutritional support required for osteogenesis. Furthermore, the c(RGDyk) peptide inhibited ectopic bone formation in mice. Mechanistic analysis revealed that c(RGDyk) peptide could inhibit osteogenesis and angiogenesis in OPLL by targeting integrin αVβ3 and regulating the FAK/ERK pathway.

CONCLUSIONS

Therefore, the integrin αVβ3 appears to be an emerging therapeutic target for OPLL, and the c(RGDyk) peptide has dual inhibitory effects that may be valuable for the new therapeutic strategy of OPLL.

Dual targeting of DR5 and VEGFR2 molecular pathways by multivalent fusion protein significantly suppresses tumor growth and angiogenesis

Destroying tumor vasculature is a relevant therapeutic strategy due to its involvement in tumor progression. However, adaptive resistance to approved antiangiogenic drugs targeting VEGF/VEGFR pathway requires the recruitment of additional targets. In this aspect, targeting TRAIL pathway is promising as it is an important component of the immune system involved in tumor immunosurveillance. For dual targeting of malignant cells and tumor vascular microenvironment, we designed a multivalent fusion protein SRH-DR5-B-iRGD with antiangiogenic VEGFR2-specific peptide SRH at the N-terminus and a tumor-targeting and -penetrating peptide iRGD at the C-terminus of receptor-selective TRAIL variant DR5-B. SRH-DR5-B-iRGD obtained high affinity for DR5, VEGFR2 and αvβ3 integrin in nanomolar range. Fusion of DR5-B with effector peptides accelerated DR5 receptor internalization rate upon ligand binding. Antitumor efficacy was evaluated in vitro in human tumor cell lines and primary patient-derived glioblastoma neurospheres, and in vivo in xenograft mouse model of human glioblastoma. Multivalent binding of SRH-DR5-B-iRGD fusion efficiently stimulated DR5-mediated tumor cell death via caspase-dependent mechanism, suppressed xenograft tumor growth by >80 %, doubled the lifespan of xenograft animals, and inhibited tumor vascularization. Therefore, targeting DR5 and VEGFR2 molecular pathways with SRH-DR5-B-iRGD protein may provide a novel therapeutic approach for treatment of solid tumors.

Luteolin inhibits angiogenesis and enhances radiotherapy sensitivity of laryngeal cancer via downregulating Integrin β1

AIM

To demonstrate the role and mechanism of luteolin in radio-sensitization and angiogenesis of laryngeal cancer.

METHODS

Firstly, we analyzed the cytotoxicity of Luteolin and radiation sensitive cytotoxicity through CCK8, and selected subsequent radiation doses and Luteolin concentrations. Next, we further analyzed the effects of Luteolin on radiation sensitivity and neovascularization of laryngeal cancer, and conducted CCK8, plate cloning, and angiogenesis experiments, respectively. At the same time, the effects of individual treatment and combination treatment on the expression of Integrin β1 and VEGFA were analyzed through immunofluorescence analysis. We also analyzed the regulation of Integrin β1 protein expression by Luteolin through Western blot. To investigate the mechanism of Integrin β1, we transfected overexpressed and silenced Integrin β1 vectors and analyzed the role of Integrin β1 in Luteolin enhancing radiation sensitivity of laryngeal cancer by repeating the above experiments. We have also constructed an in vivo subcutaneous tumor transplantation model to further validate the cell experimental results. The expression of Integrin, KI67, VEGFA, and CD31 was analyzed through Western blot and immunohistochemistry experiments.

RESULTS

Radiation inhibited cell proliferation and decreased Integrin β1 expression, and increased the radiosensitivity through inhibiting cell proliferation, and inhibit angiogenesis during radiation. Overexpression of Integrin β1 weakened radiotherapy sensitivity on the basis of cells treated with combined administration. Integrin β1 is considered as the downstream molecule of luteolin, participating in radiosensitivity of luteolin to FaDu cells. Animal experiments also demonstrated that luteolin strengthened tumor suppression and anti-angiogenesis during radiation via Integrin β1.

CONCLUSION

In summary, our results manifested that radio-sensitivity effect of luteolin depended on downregulating Integrin β1 in laryngocarcinoma.

The challenges and opportunities of αvβ3-based therapeutics in cancer: From bench to clinical trials

Integrins are main cell adhesion receptors serving as linker attaching cells to extracellular matrix (ECM) and bidirectional hubs transmitting biochemical and mechanical signals between cells and their environment. Integrin αvβ3 is a critical family member of integrins and interacts with ECM proteins containing RGD tripeptide sequence. Accumulating evidence indicated that the abnormal expression of integrin αvβ3 was associated with various tumor progressions, including tumor initiation, sustained tumor growth, distant metastasis, drug resistance development, maintenance of stemness in cancer cells. Therefore, αvβ3 has been explored as a therapeutic target in various types of cancers, but there is no αvβ3 antagonist approved for human therapy. Targeting-integrin αvβ3 therapeutics has been a challenge, but lessons from the past are valuable to the development of innovative targeting approaches. This review systematically summarized the structure, signal transduction, regulatory role in cancer, and drug development history of integrin αvβ3, and also provided new insights into αvβ3-based therapeutics in cancer from bench to clinical trials, which would contribute to developing effective targeting αvβ3 agents for cancer treatment.

Peptidomimetics in cancer targeting

The low efficiency of treatment strategies is one of the main obstacles to developing cancer inhibitors. Up to now, various classes of therapeutics have been developed to inhibit cancer progression. Peptides due to their small size and easy production compared to proteins are highly regarded in designing cancer vaccines and oncogenic pathway inhibitors. Although peptides seem to be a suitable therapeutic option, their short lifespan, instability, and low binding affinity for their target have not been widely applicable against malignant tumors. Given the peptides' disadvantages, a new class of agents called peptidomimetic has been introduced. With advances in physical chemistry and biochemistry, as well as increased knowledge about biomolecule structures, it is now possible to chemically modify peptides to develop efficient peptidomimetics. In recent years, numerous studies have been performed to the evaluation of the effectiveness of peptidomimetics in inhibiting metastasis, angiogenesis, and cancerous cell growth. Here, we offer a comprehensive review of designed peptidomimetics to diagnose and treat cancer.

Structure-Based Discovery of a Novel Class of Small-Molecule Pure Antagonists of Integrin αVβ3

Inhibitors of integrin αVβ3 have therapeutic promise for a variety of diseases. Most αVβ3-targeting small molecules patterned after the RGD motif are partial agonists because they induce a high-affinity, ligand-binding conformation and prime the receptor to bind the ligand without an activating stimulus, in part via a charge-charge interaction between their aspartic acid carboxyl group and the metal ion in the metal-ion-dependent adhesion site (MIDAS). Building upon our previous studies on the related integrin αIIbβ3, we searched for pure αVβ3 antagonists that lack this typical aspartic acid carboxyl group and instead engage through direct binding to one of the coordinating residues of the MIDAS metal ion, specifically β3 E220. By in silico screening of two large chemical libraries for compounds interacting with β3 E220, we indeed discovered a novel molecule that does not contain an acidic carboxyl group and does not induce the high-affinity, ligand-binding state of the receptor. Functional and structural characterization of a chemically optimized version of this compound led to the discovery of a novel small-molecule pure αVβ3 antagonist that (i) does not prime the receptor to bind the ligand and does not induce hybrid domain swing-out or receptor extension as judged by antibody binding and negative-stain electron microscopy, (ii) binds at the RGD-binding site as predicted by metadynamics rescoring of induced-fit docking poses and confirmed by a cryo-electron microscopy structure of the compound-bound integrin, and (iii) coordinates the MIDAS metal ion via a quinoline moiety instead of an acidic carboxyl group.

Targeted Alpha Therapy of Glioma Using 211At-Labeled Heterodimeric Peptide Targeting Both VEGFR and Integrins

Targeted radionuclide therapy based on α-emitters plays an increasingly important role in cancer treatment. In this study, we proposed to apply a heterodimeric peptide (iRGD-C6-lys-C6-^DA7R) targeting both VEGFR and integrins as a new vector for ²¹¹At radiolabeling to obtain high-performance radiopharmaceuticals with potential in targeted alpha therapy (TAT). An astatinated peptide, iRGD-C6-lys(²¹¹At-ATE)-C6-^DA7R, was prepared with a radiochemical yield of ∼45% and high radiochemical purity of >95% via an electrophilic radioastatodestannylation reaction. iRGD-C6-lys(²¹¹At-ATE)-C6-^DA7R showed good stability in vitro and high binding ability to U87MG (glioma) cells. Systematic in vitro antitumor investigations involving cytotoxicity, apoptosis, distribution of the cell cycle, and reactive oxygen species (ROS) clearly demonstrated that ²¹¹At-labeled heterodimeric peptides could significantly inhibit cell viability, induce cell apoptosis, arrest the cell cycle in G2/M phase, and increase intracellular ROS levels in a dose-dependent manner. Biodistribution revealed that iRGD-C6-lys(²¹¹At-ATE)-C6-^DA7R had rapid tumor accumulation and fast normal tissue/organ clearance, which was mainly excreted through the kidneys. Moreover, in vivo therapeutic evaluation indicated that iRGD-C6-lys(²¹¹At-ATE)-C6-^DA7R was able to obviously inhibit tumor growth and prolong the survival of mice bearing glioma xenografts without notable toxicity to normal organs. All these results suggest that TAT mediated by iRGD-C6-lys(²¹¹At-ATE)-C6-^DA7R can provide an effective and promising strategy for the treatment of glioma and some other tumors.

Opposite roles of Kindlin orthologs in cell survival and proliferation

OBJECTIVE

It is unclear why adhesion-dependent cells such as epithelium undergo anoikis without anchorage, while adhesion-independent blood cells thrive in suspension. The adhesive machinery of these cells is similar, with the exception of Kindlin orthologs, Kindlin 2 (K2) and Kindlin 3 (K3). Here we address how Kindlins control cell survival and proliferation in anchorage-dependent and independent cells.

MATERIAL AND METHODS

To demonstrate the opposite roles of Kindlin's in cell survival we utilized in vivo and in vitro models and K3 and K2 knockdown and knockin cells. We used human lymphocytes from the K3 deficient patients in tumour model, K3 knockout and knockin macrophages and K2 knockout and knockin MEF cells for experiments in under conditions of adhesion and in suspension.

RESULTS

Depletion of K3 promotes cell proliferation and survival of anchorage-independent cells regardless of cell attachment. In contrast, the absence of K2 in anchorage-dependent cells accelerates apoptosis and limits proliferation. K3 deficiency promotes human lymphoma growth and survival in vivo. Kindlins' interaction with paxillin, is critical for their differential roles in cell anchorage. While disruption of K2-paxillin binding leads to increased apoptosis, the lack of K3-paxillin binding has an opposite effect in adhesion-independent cells.

CONCLUSION

Kindlin ortologs and their interaction to cytoskeletal protein paxillin define the mechanisms of anchorage dependence. Our study identifies the key elements of the cell adhesion machinery in cell survival and tumour metastasis, proposing possible targets for tumour treatment.

PET imaging of VEGFR and integrins in glioma tumor xenografts using 89Zr labelled heterodimeric peptide

Vascular endothelial growth factor receptor (VEGFR) and integrin αv are over-expressed in angiogenesis of variety malignant tumors with key roles in angiogenesis, and have been proven as valuable targets for cancer imaging and treatment. In this study, a heterodimeric peptide targeting VEGFR and integrin was designed, and radiolabeled with zirconium-89 (⁸⁹Zr) for PET imaging of glioma. ⁸⁹Zr-DFO-heterodimeric peptide, a the newly developed probe, was prepared with radiochemical yield of 88.7 ± 2.4%. Targeted binding capability of ⁸⁹Zr-DFO-heterodimeric peptide towards U87MG cells was investigated in murine glioma xenograft models, which shows that the designed probe has good binding ability to both targeting sites. Biodistribution indicated that kidney metabolism is the main pathway and tumor uptake of ⁸⁹Zr-DFO-heterodimeric peptide reached the peak of 0.62 ± 0.10% ID/g . U87MG xenograft could be clearly visualized by microPET/CT imaging through 1 to 3 h post-injection of ⁸⁹Zr-DFO-heterodimeric peptide. Importantly, the tumor radiouptake was significantly reduced after blocking, and the imaging effect of this radioactive compound was more obvious than that of monomeric peptide probes. ⁸⁹Zr-DFO-heterodimeric peptide has been demonstrated to show potential as a new radiopharmaceutical probe towards glioma, and multi-target probes do have advantages in tumor imaging.

Integrin-Mediated Tumorigenesis and Its Therapeutic Applications

Integrins, a family of adhesion molecules generally exist on the cell surface, are essential for regulating cell growth and its function. As a bi-directional signaling molecule, they mediate cell-cell and cell-extracellular matrix interaction. The recognitions of their key roles in many human pathologies, including autoimmunity, thrombosis and neoplasia, have revealed their great potential as a therapeutic target. This paper focuses on the activation of integrins, the role of integrins in tumorigenesis and progression, and advances of integrin-dependent tumor therapeutics in recent years. It is expected that understanding function and signaling transmission will fully exploit potentialities of integrin as a novel target for tumors.

CRISPR/Cas9 in cancer therapy: A review with a special focus on tumor angiogenesis

Tumor angiogenesis is a critical target for cancer treatment and its inhibition has become a common anticancer approach following chemotherapy. However, due to the simultaneous activation of different compensatory molecular mechanisms that enhance tumor angiogenesis, clinically authorized anti-angiogenic medicines are ineffective. Additionally, medications used to treat cancer have an effect on normal body cells; nonetheless, more research is needed to create new cancer therapeutic techniques. With advances in molecular biology, it is now possible to use gene-editing technology to alter the genome and study the functional changes resulting from genetic manipulation. With the development of CRISPR/Cas9 technology, it has become a very powerful tool for altering the genomes of many organisms. It was determined that CRISPR/Cas9, which first appeared in bacteria as a part of an adaptive immune system, could be used, in modified forms, to alter genomes and function. In conclusion, CRISPR/Cas9 could be a major step forward to cancer management by providing patients with an effective method for dealing with cancers by dissecting the carcinogenesis pathways, identifying new biologic targets, and perhaps arming cancer cells with drugs. Hence, this review will discuss the current applications of CRISPR/Cas9 technology in tumor angiogenesis research for the purpose of cancer treatment.

RGD engineered dendrimer nanotherapeutic as an emerging targeted approach in cancer therapy

A bird's eye view is now demanded in the area of cancer research to suppress the suffering of cancer patient and mediate the lack of treatment related to chemotherapy. Chemotherapy is always preferred over surgery or radiation therapy, but they never met the patient's demand of safe medication. Targeted therapy has now been in research that could hinder the unnecessary effect of drug on normal cells but could affect the tumor cells in much efficient manner. Angiogenesis is process involved in development of new blood vessel that nourishes tumor growth. Integrin receptors are over expressed on cancer cells that play vital role in angiogenesis for growth and metastasis of tumor cell. A delivery of RGD based peptide to integrin targeted site could help in its successful binding and liberation of drug in tumor vasculature. Dendrimers, in addition to its excellent pharmacokinetic properties also helps to carry targeting ligand to site of tumor by successfully conjugating with them. The aim of this review is to bring light upon the role of integrin in cancer progression, interaction of RGD to integrin receptor and more importantly the RGD-dendrimer based targeted therapy for the treatment of various cancers.

Expression Analysis of α5 Integrin Subunit Reveals Its Upregulation as a Negative Prognostic Biomarker for Glioblastoma

Integrin α5β1 was suggested to be involved in glioblastoma (GBM) aggressiveness and treatment resistance through preclinical studies and genomic analysis in patients. However, further protein expression data are still required to confirm this hypothesis. In the present study, we investigated by immunofluorescence the expression of integrin α5 and its prognostic impact in a glioblastoma series of patients scheduled to undergo the Stupp protocol as first-line treatment for GBM. The integrin α5 protein expression level was estimated in each tumor by the mean fluorescence intensity (MFI) and allowed us to identify two subpopulations showing either a high or low expression level. The distribution of patients in both subpopulations was not significantly different according to age, gender, recursive partitioning analysis (RPA) prognostic score, molecular markers or surgical and medical treatment. A high integrin α5 protein expression level was associated with a high risk of recurrence (HR = 1.696, 95% CI 1.031-2.792, p = 0.0377) and reduced overall survival (OS), even more significant in patients who completed the Stupp protocol (median OS: 15.6 vs. 22.8 months; HR = 2.324; 95% CI 1.168-4.621, p = 0.0162). In multivariate analysis, a high integrin α5 protein expression level was confirmed as an independent prognostic factor in the subpopulation of patients who completed the temozolomide-based first-line treatment for predicting OS over age, extent of surgery, RPA score and O-6-methylguanine-DNA methyltransferase (MGMT) promoter methylation (p = 0.029). In summary, for the first time, our study validates that a high integrin α5 protein expression level is associated with poor prognosis in GBM and confirms its potential as a therapeutic target implicated in the Stupp protocol resistance.

A Monotargeting Peptidic Network Antibody Inhibits More Receptors for Anti-Angiogenesis

The overexpression of growth factors and receptors on neovascular endothelial cells (ECs) and their binding may promote the abnormal growth of new blood vessels, leading to corneal neovascularization (CNV). Normally, monoclonal antibodies may bind and block only one growth factor or receptor, such as bevacizumab binding and blocking vascular endothelial growth factor (VEGF). Herein, we develop a monotargeting peptidic network antibody (pepnetibody) that blocks multiple receptors on the membrane of ECs through forming a fibrous network and ultimately achieves high-efficient treatment of CNV. The pepnetibody could bind to integrin α_vβ₃ in particulate formulation and in situ fibrillogenesis on ECs, mimicking the process of fibronectin fibrillogenesis on the cell membrane. The in situ formed peptidic network could firmly block integrin and cover other angiogenesis-related receptors, such as VEGF receptor-2 and neuropilin-1, exhibiting competitive efficacy of antiangiogenesis compared with traditional monoclonal antibody bevacizumab with 97.7 times lower dose.

Pericytes cross-talks within the tumor microenvironment

Cancer cells are embedded within the tumor microenvironment and interact dynamically with its components during tumor progression. Understanding the molecular mechanisms by which the tumor microenvironment components communicate is crucial for the success of therapeutic applications. Recent studies show, by using state-of-the-art technologies, including sophisticated in vivo inducible Cre/loxP mediated systems and CRISPR-Cas9 gene editing, that pericytes communicate with cancer cells. The arising knowledge on cross-talks within the tumor microenvironment will be essential for the development of new therapies against cancer. Here, we review recent progress in our understanding of pericytes roles within tumors.

Endothelial neuropilin-2 influences angiogenesis by regulating actin pattern development and α5-integrin-p-FAK complex recruitment to assembling adhesion sites

The ability to form a variety of cell-matrix connections is crucial for angiogenesis to take place. Without stable anchorage to the extracellular matrix (ECM), endothelial cells (ECs) are unable to sense, integrate and disseminate growth factor stimulated responses that drive growth of a vascular bed. Neuropilin-2 (NRP2) is a widely expressed membrane-bound multifunctional non-tyrosine kinase receptor, which has previously been implicated in influencing cell adhesion and migration by interacting with α5-integrin and regulating adhesion turnover. α5-integrin, and its ECM ligand fibronectin (FN) are both known to be upregulated during the formation of neo-vasculature. Despite being descriptively annotated as a candidate biomarker for aggressive cancer phenotypes, the EC-specific roles for NRP2 during developmental and pathological angiogenesis remain unexplored. The data reported here support a model whereby NRP2 actively promotes EC adhesion and migration by regulating dynamic cytoskeletal remodeling and by stimulating Rab11-dependent recycling of α5-integrin-p-FAK complexes to newly assembling adhesion sites. Furthermore, temporal depletion of EC-NRP2 in vivo impairs primary tumor growth by disrupting vessel formation. We also demonstrate that EC-NRP2 is required for normal postnatal retinal vascular development, specifically by regulating cell-matrix adhesion. Upon loss of endothelial NRP2, vascular outgrowth from the optic nerve during superficial plexus formation is disrupted, likely due to reduced FAK phosphorylation within sprouting tip cells.

THE MAIN CYTOTOXIC EFFECTS OF METHYLSELENINIC ACID ON VARIOUS CANCER CELLS

Studies of recent decades have repeatedly demonstrated the cytotoxic effect of selenium-containing compounds on cancer cells of various origins. Particular attention in these studies is paid to methylseleninic acid, a widespread selenium-containing compound of organic nature, for several reasons: it has a selective cytotoxic effect on cancer cells, it is cytotoxic in small doses, it is able to generate methylselenol, excluding the action of the enzyme β-lyase. All these qualities make methylseleninic acid an attractive substrate for the production of anticancer drugs on its basis with a well-pronounced selective effect. However, the studies available to date indicate that there is no strictly specific molecular mechanism of its cytotoxic effect in relation to different cancer cell lines and cancer models. This review contains generalized information on the dose- and time-dependent regulation of the toxic effect of methylseleninic acid on the proliferative properties of a number of cancer cell lines. In addition, special attention in this review is paid to the influence of this selenium-containing compound on the regulation of endoplasmic reticulum stress and on the expression of seven selenoproteins, which are localized in the endoplasmic reticulum.

Imaging Inflammation with Positron Emission Tomography

The impact of inflammation on the outcome of many medical conditions such as cardiovascular diseases, neurological disorders, infections, cancer, and autoimmune diseases has been widely acknowledged. However, in contrast to neurological, oncologic, and cardiovascular disorders, imaging plays a minor role in research and management of inflammation. Imaging can provide insights into individual and temporospatial biology and grade of inflammation which can be of diagnostic, therapeutic, and prognostic value. There is therefore an urgent need to evaluate and understand current approaches and potential applications for imaging of inflammation. This review discusses radiotracers for positron emission tomography (PET) that have been used to image inflammation in cardiovascular diseases and other inflammatory conditions with a special emphasis on radiotracers that have already been successfully applied in clinical settings.

Effects of microRNA regulation on antiangiogenic therapy resistance in non-small cell lung cancer

Antiangiogenic drugs have become a standard therapeutic regimen for advanced non-small cell lung cancer (NSCLC); however, many issues remain to be solved. Identifying specific markers to predict patient response to antiangiogenic drugs to ensure therapeutic efficacy would increase their clinical benefit. MicroRNAs (miRNAs) are involved in the process of resistance to antiangiogenic therapy, as they regulate various key signaling pathways. Therefore, miRNAs may be used as targets for reversing tumor resistance to antiangiogenic therapy. This article reviews the molecular mechanisms of antiangiogenic therapy resistance and the specific mechanisms of miRNA regulation of resistance. Signal transducer and activator of transcription 3 (STAT3) is one of multiple target genes of miRNAs, and is closely related to antiangiogenic research. Thus, it is described separately in this review article.

Exosomes-Mediated Transfer of Itga2 Promotes Migration and Invasion of Prostate Cancer Cells by Inducing Epithelial-Mesenchymal Transition

Although integrin alpha 2 subunit (ITGA2) mediates cancer progression and metastasis, its transfer by exosomes has not been investigated in prostate cancer (PCa). We aimed to determine the role of exosomal ITGA2 derived from castration-resistant PCa (CRPC) cells in promoting aggressive phenotypes in androgen receptor (AR)-positive cells. Exosomes were co-incubated with recipient cells and tested for different cellular assays. ITGA2 was enriched in exosomes derived from CRPC cells. Co-culture of AR-positive cells with CRPC-derived exosomes increased their proliferation, migration, and invasion by promoting epithelial-mesenchymal transition, which was reversed via ITGA2 knockdown or inhibition of exosomal uptake by methyl-β-cyclodextrin (MβCD). Ectopic expression of ITGA2 reproduced the effect of exosomal ITGA2 in PCa cells. ITGA2 transferred by exosomes exerted its effect within a shorter time compared to that triggered by its endogenous expression. The difference of ITGA2 protein expression in localized tumors and those with lymph node metastatic tissues was indistinguishable. Nevertheless, its abundance was higher in circulating exosomes collected from PCa patients when compared with normal subjects. Our findings indicate the possible role of the exosomal-ITGA2 transfer in altering the phenotype of AR-positive cells towards more aggressive phenotype. Thus, interfering with exosomal cargo transfer may inhibit the development of aggressive phenotype in PCa cells.

Antiangiogenic Targets for Glioblastoma Therapy from a Pre-Clinical Approach, Using Nanoformulations

Glioblastoma (GBM) is the most aggressive tumor type whose resistance to conventional treatment is mediated, in part, by the angiogenic process. New treatments involving the application of nanoformulations composed of encapsulated drugs coupled to peptide motifs that direct drugs to specific targets triggered in angiogenesis have been developed to reach and modulate different phases of this process. We performed a systematic review with the search criterion (Glioblastoma OR Glioma) AND (Therapy OR Therapeutic) AND (Nanoparticle) AND (Antiangiogenic OR Angiogenesis OR Anti-angiogenic) in Pubmed, Scopus, and Cochrane databases, in which 312 articles were identified; of these, only 27 articles were included after selection and analysis of eligibility according to the inclusion and exclusion criteria. The data of the articles were analyzed in five contexts: the characteristics of the tumor cells; the animal models used to induce GBM for antiangiogenic treatment; the composition of nanoformulations and their physical and chemical characteristics; the therapeutic anti-angiogenic process; and methods for assessing the effects on antiangiogenic markers caused by therapies. The articles included in the review were heterogeneous and varied in practically all aspects related to nanoformulations and models. However, there was slight variance in the antiangiogenic effect analysis. CD31 was extensively used as a marker, which does not provide a view of the effects on the most diverse aspects involved in angiogenesis. Therefore, the present review highlighted the need for standardization between the different approaches of antiangiogenic therapy for the GBM model that allows a more effective meta-analysis and that helps in future translational studies.

An atom-economical design of PET tracer for imaging αvβ3 integrin via utilizing the three-in-one function of 64Copper

In this study, α_vβ₃ integrin in U87 tumor cells was imaged with a ⁶⁴Cu-peptidic probe, in which the linear peptide GHRGDHG is used as a pre-ligand, while ⁶⁴Cu bears three functional roles that include generation of the PET signal, coordination with two GH moieties of the pre-ligand, and cyclizing the linear pre-ligand into an active cyclic-RGD form (termed as ⁶⁴Cu-Cyclo-RGD) for α_vβ₃ integrin.

Endothelial MT1-MMP targeting limits intussusceptive angiogenesis and colitis via TSP1/nitric oxide axis

Pathological angiogenesis contributes to cancer progression and chronic inflammatory diseases. In inflammatory bowel disease, the microvasculature expands by intussusceptive angiogenesis (IA), a poorly characterized mechanism involving increased blood flow and splitting of pre-existing capillaries. In this report, mice lacking the protease MT1-MMP in endothelial cells (MT1iΔEC ) presented limited IA in the capillary plexus of the colon mucosa assessed by 3D imaging during 1% DSS-induced colitis. This resulted in better tissue perfusion, preserved intestinal morphology, and milder disease activity index. Combined in vivo intravital microscopy and lentiviral rescue experiments with in vitro cell culture demonstrated that MT1-MMP activity in endothelial cells is required for vasodilation and IA, as well as for nitric oxide production via binding of the C-terminal fragment of MT1-MMP substrate thrombospondin-1 (TSP1) to CD47/αvβ3 integrin. Moreover, TSP1 levels were significantly higher in serum from IBD patients and in vivo administration of an anti-MT1-MMP inhibitory antibody or a nonamer peptide spanning the αvβ3 integrin binding site in TSP1 reduced IA during mouse colitis. Our results identify MT1-MMP as a new actor in inflammatory IA and a promising therapeutic target for inflammatory bowel disease.

"Splitting the matrix": intussusceptive angiogenesis meets MT1-MMP

Pathological angiogenesis contributes to tumour progression as well as to chronic inflammatory diseases. In this issue of EMBO Molecular Medicine, Esteban and co-workers identify endothelial cell MT1-MMP as a key regulator of intussusceptive angiogenesis (IA) in inflammatory colitis. Thrombospondin 1 (TSP1) cleavage by MT1-MMP results in the binding of the c-terminal fragment of TSP1 to αvβ3 integrin, which induces nitric oxide (NO) production, vasodilation and further initiation of IA. This novel control mechanism of inflammatory IA points towards promising new therapeutic targets for inflammatory bowel disease.

MFGE8 attenuates Ang-II-induced atrial fibrosis and vulnerability to atrial fibrillation through inhibition of TGF-β1/Smad2/3 pathway

Atrial fibrillation (AF) is characterized by potentiated growth of atrial fibroblasts and excessive deposition of the extracellular matrix. Atrial fibrosis has emerged as a hallmark of atrial structural remodeling linked to AF. Nonetheless, the specific mechanism underlying the progression of atrial fibrosis to AF is still largely unknown. MFGE8 (milk fat globule-EGF factor 8) is a soluble glycoprotein associated with many human diseases. Recently, a number of studies revealed that MFGE8 plays a crucial role in heart disease. Yet, MFGE8 regulation and function in the process of atrial fibrosis and vulnerability to AF remain unexplored. In this study, we found that the expression of MFGE8 was downregulated in the atriums of patients with AF compared with individuals without AF. In addition, the expression of MFGE8 was lower in atriums of angiotensin II (Ang-II)-stimulated rats as compared with the sham group. In vitro, silencing of MFGE8 by small interfering RNA significantly increased Ang-II-induced atrial fibrosis, whereas administration of recombinant human MFGE8 (rhMFGE8) attenuated the atrial fibrosis. Moreover, we found that the activated TGF-β1/Smad2/3 pathway after Ang-II treatment was significantly potentiated by the MFGE8 knockdown but inhibited by rhMFGE8 in vitro. Inhibition of integrin β3 which is the receptor for MFGE8, suppressed the TGF-β1/Smad2/3 activating effects of the MFGE8 knockdown in Ang-II-treated rat atrial fibroblasts. Finally, we administered rhMFGE8 to rats; it attenuated atrial fibrosis and remodeling and further reduced AF vulnerability induced by Ang-II, indicating that MFGE8 might have the potential both as a novel biomarker and as a therapeutic target in atrial fibrosis and AF.

Repurposing an anti-cancer agent for the treatment of hypertrophic heart disease

Coronary microvascular dysfunction combined with maladaptive cardiomyocyte morphology and energetics is a major contributor to heart failure advancement. Thus, dually enhancing cardiac angiogenesis and targeting cardiomyocyte function to slow, or reverse, the development of heart failure is a logical step towards improved therapy. We present evidence for the potential to repurpose a former anti-cancer Arg-Gly-Asp (RGD)-mimetic pentapeptide, cilengitide, here used at low doses. Cilengitide targets αvβ3 integrin and this protein is upregulated in human dilated and ischaemic cardiomyopathies. Treatment of mice after abdominal aortic constriction (AAC) surgery with low-dose cilengitide (ldCil) enhances coronary angiogenesis and directly affects cardiomyocyte hypertrophy with an associated reduction in disease severity. At a molecular level, ldCil treatment has a direct effect on cardiac endothelial cell transcriptomic profiles, with a significant enhancement of pro-angiogenic signalling pathways, corroborating the enhanced angiogenic phenotype after ldCil treatment. Moreover, ldCil treatment of Angiotensin II-stimulated AngII-stimulated cardiomyocytes significantly restores transcriptomic profiles similar to those found in normal human heart. The significance of this finding is enhanced by transcriptional similarities between AngII-treated cardiomyocytes and failing human hearts. Taken together, our data provide evidence supporting a possible new strategy for improved heart failure treatment using low-dose RGD-mimetics with relevance to human disease. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Synergistic Antitumorigenic Activity of Calcitriol with Curcumin or Resveratrol is Mediated by Angiogenesis Inhibition in Triple Negative Breast Cancer Xenografts

Calcitriol is a multitarget anticancer hormone; however, its effects on angiogenesis remain contradictory. Herein, we tested whether the antiangiogenic phytochemicals curcumin or resveratrol improved calcitriol antitumorigenic effects in vivo. Triple-negative breast cancer tumoral cells (MBCDF-T) were xenografted in nude mice, maintaining treatments for 3 weeks. Tumor onset, volume and microvessel density were significantly reduced in mice coadministered with calcitriol and curcumin (Cal+Cur). Vessel count was also reduced in mice simultaneously treated with calcitriol and resveratrol (Cal+Rsv). Cal+Cur and Cal+Rsv treatments resulted in less tumor activated endothelium, as demonstrated by decreased tumor uptake of integrin-targeted biosensors in vivo. The renal gene expression of Cyp24a1 and Cyp27b1 suggested increased calcitriol bioactivity in the combined regimens. In vitro, the phytochemicals inhibited both MBCDF-T and endothelial cells proliferation, while potentiated calcitriol’s ability to reduce MBCDF-T cell-growth and endothelial cells migration. Resveratrol induced endothelial cell death, as deduced by increased sub-G1 cells accumulation, explaining the reduced tumor vessel number in resveratrol-treated mice, which further diminished when combined with calcitriol. In conclusion, the concomitant administration of calcitriol with curcumin or resveratrol synergistically promoted anticancer effects in vitro and in vivo in human mammary tumor cells. Whereas the results suggest different mechanisms of action of the phytochemicals when coadministered with calcitriol, the converging biological effect was inhibition of tumor neoangiogenesis.

Effect of αvβ3 Integrin Expression and Activity on Intraocular Pressure

Purpose

To determine the effects of αvβ3 integrin expression and activation on intraocular pressure (IOP).

Methods

Cre^+/−β3^flox/flox mice were treated with topical tamoxifen eye drops for 5 days to activate Cre and excise the β3 integrin gene from the anterior segment. IOP was measured weekly for 11 weeks using rebound tonometry. Mice were then killed and changes in expression of the β3 integrin subunit in Cre^+/− β3^flox/flox mice were determined using Western blotting analysis and immunofluorescence microscopy. To determine the effect of αvβ3 integrin activation on outflow facility, porcine organ culture anterior segments (POCAS) were perfused with the αvβ3 integrin-activating antibody AP5 or an isotype IgG control for 21 hours. The effect of αvβ3 integrin activation on IOP was measured over 7 days in C57BL/6J mice intracamerally infused with AP5, AP3, IgG, or PBS.

Results

Deletion of the β3 integrin subunit using the tamoxifen-inducible Cre-loxP system resulted in a decrease in expression of the β3 integrin subunit in the trabecular meshwork and ciliary muscle. Morphologically no gross changes in the anterior segment were detected. Deletion of the β3 integrin subunit resulted in a significantly (P < 0.05) lower IOP in mice within 2 weeks following the tamoxifen treatment and persisted for 11 weeks. Activating the αvβ3 integrin with the AP5 antibody resulted in a significant (P < 0.05) increase in IOP in C57BL/6J mice and a decrease in outflow facility in 42% of the POCAS.

Conclusions

These studies demonstrate a role for αvβ3 integrin signaling in the regulation of IOP.

Novel Pure αVβ3 Integrin Antagonists That Do Not Induce Receptor Extension, Prime the Receptor, or Enhance Angiogenesis at Low Concentrations

The integrin αVβ3 receptor has been implicated in several important diseases, but no antagonists are approved for human therapy. One possible limitation of current small-molecule antagonists is their ability to induce a major conformational change in the receptor that induces it to adopt a high-affinity ligand-binding state. In response, we used structural inferences from a pure peptide antagonist to design the small-molecule pure antagonists TDI-4161 and TDI-3761. Both compounds inhibit αVβ3-mediated cell adhesion to αVβ3 ligands, but do not induce the conformational change as judged by antibody binding, electron microscopy, X-ray crystallography, and receptor priming studies. Both compounds demonstrated the favorable property of inhibiting bone resorption in vitro, supporting potential value in treating osteoporosis. Neither, however, had the unfavorable property of the αVβ3 antagonist cilengitide of paradoxically enhancing aortic sprout angiogenesis at concentrations below its IC₅₀, which correlates with cilengitide's enhancement of tumor growth in vivo.

Palmitate up-regulates laminin expression via ROS/integrin αvβ3 pathway in HLSECs

Aims/Introduction

To investigate the roles of reactive oxygen species (ROS) and integrin αvβ3 in palmitate-induced laminin expression of human liver sinusoidal endothelial cells (HLSECs).

Results

The protein expression of integrin αv, integrin β3 and laminin are increased by palmitate in HLSECs in a time- and dose-dependent manner. NAC, the ROS inhibitor, significantly inhibited the up-regulation of protein expression of integrin αv, integrin β3 and laminin by palmitate (P < 0.05). Palmitate markedly enhanced ROS formation (P < 0.05), which was not inhibited by LM609, the antibody of integrin αvβ3. Palmitate significantly increased laminin synthesis (P < 0.05), which was attenuated by LM609 and NAC (P < 0.05).

Materials and Methods

HLSECs were treated with palmitate in the presence or absence of LM609 (10 μg/ml) or N-acetylcysteine (NAC) (2 mM). Expression of integrin αv, integrin β3 and laminin were measured by RT-PCR and Western blot. Immunocytochemistry were used for examining laminin expression. The generation of ROS was measured using the fluorescent signal 2',7' dichloro-fluorescein diacetate (DCFH-DA).

Conclusions

The results suggested that palmitate increases laminin expression through ROS/integrin αv/β3 pathway.

Culture surfaces induce hypoxia-regulated genes in human mesenchymal stromal cells

Culturing human Mesenchymal stromal cells (hMSCs) in vitro in hypoxic conditions resulted in reduced senescence, enhanced pluripotency and altered proliferation rate. It has been known that in vitro hypoxia affects expression of cell surface proteins. However, the impact of culture surfaces on the hypoxia-regulated genes (HRG) have not yet been reported. This study utilized Next-Generation sequencing to analyse the changes in the gene expression levels of HRG for hMSCs cultured on different culture surfaces. The samples, which were cultured on four different synthesized surfaces (treatments) and tissue culture plate (control), resulted in a difference in growth rate. The sequencing results revealed that the transcription of a number of key genes involved in regulating hypoxic functions were significantly altered, including HIF2A, a marker for potency, differentiation, and various cellular functions. Significant alternations in the expression levels of previously reported oxygen-sensitive surface proteins were detected in this study, some of which closely correlate with the expression levels of HIF2A. Our analysis of the hMSCs transcriptome and HRG mapped out a list of genes encoding surface proteins which may directly regulate or be regulated by HIF2A. The findings from this study showed that culture surfaces have an impact on regulating the expression profile of HRG. Therefore, novel culture surfaces may be designed to selectively activate HIF2A and other HRG and pathways under in vitro normoxia. The understanding of the crosstalk between the regulating genes of hypoxia and culture surfaces may be utilized to strengthen desired hypoxic functions.

Integrin Signaling in Cancer: Mechanotransduction, Stemness, Epithelial Plasticity, and Therapeutic Resistance

Integrins mediate cell adhesion and transmit mechanical and chemical signals to the cell interior. Various mechanisms deregulate integrin signaling in cancer, empowering tumor cells with the ability to proliferate without restraint, to invade through tissue boundaries, and to survive in foreign microenvironments. Recent studies have revealed that integrin signaling drives multiple stem cell functions, including tumor initiation, epithelial plasticity, metastatic reactivation, and resistance to oncogene- and immune-targeted therapies. Here, we discuss the mechanisms leading to the deregulation of integrin signaling in cancer and its various consequences. We place emphasis on novel functions, determinants of context dependency, and mechanism-based therapeutic opportunities.

Development of Diagnostic and Therapeutic Probes with Controlled Pharmacokinetics for Use in Radiotheranostics

The word "theranostics," a portmanteau word made by combining "therapeutics" and "diagnostics," refers to a personalized medicine concept. Recently, the word, "radiotheranostics," has also been used in nuclear medicine as a term that refer to the use of radioisotopes for combined imaging and therapy. For radiotheranostics, a diagnostic probe and a corresponding therapeutic probe can be prepared by introducing diagnostic and therapeutic radioisotopes into the same precursor. These diagnostic and therapeutic probes can be designed to show equivalent pharmacokinetics, which is important for radiotheranostics. As imaging can predict the absorbed radiation dose and thus the therapeutic and side effects, radiotheranostics can help achieve the goal of personalized medicine. In this review, I discuss the use of radiolabeled probes targeting bone metastases, sigma-1 receptor, and αVβ3 integrin for radiotheranostics.

Tension enhances cell proliferation and collagen synthesis by upregulating expressions of integrin αvβ3 in human keloid-derived mesenchymal stem cells

AIMS

Keloids are a dermal fibrotic disease whose etiology remains totally unknown and for which there is no successful treatment. Mechanical tension, in addition, is closely associated with the germination and development of keloids. In this study, we investigated the influence of human keloid-derived mesenchymal stem cells (KD-MSCs) on cell proliferation, collagen synthesis, and expressions of integrin αvβ3 under tension.

MAIN METHODS

KD-MSCs and human normal skin-derived mesenchymal stem cells (NS-MSCs) were isolated and cultured in stem cell medium with a gradual increase in the serum concentration. Cell proliferation and collagen synthesis were detected by Cell Counting Kit-8 (CCK-8) assay and hydroxyproline content analysis under tension respectively. We investigated the messenger RNA expressions of nine integrin subunits, including integrin units α2, α3, α5, αv, α8, α10, α11, β1, and β3, in KD-MSCs stimulated with tension. Identification of differentially expressed genes was performed by Western blot analysis and immunocytochemistry staining.

KEY FINDINGS

We obtained high-purity KD-MSCs and NS-MSCs using the culture method of decreasing serum concentration gradient gradually. Furthermore, we found that tension enhances cell proliferation and collagen synthesis and promotes expressions of integrin αvβ3 in KD-MSCs. In addition, blocking experiments showed that increased integrin αvβ3 expression affects cell proliferation and collagen synthesis of KD-MSCs under tension.

SIGNIFICANCE

Our results suggest that integrin αvβ3 receptor may be sensitive molecules of mechanical tension and could contribute to the occurrence and development of keloids. It could lead to novel targets for therapeutic intervention, treatment, and prevention of recurrence for keloid disorders.

The HU177 Collagen Epitope Controls Melanoma Cell Migration and Experimental Metastasis by a CDK5/YAP-Dependent Mechanism

Stromal components not only help form the structure of neoplasms such as melanomas, but they also functionally contribute to their malignant phenotype. Thus, uncovering signaling pathways that integrate the behavior of both tumor and stromal cells may provide unique opportunities for the development of more effective strategies to control tumor progression. In this regard, extracellular matrix-mediated signaling plays a role in coordinating the behavior of both tumor and stromal cells. Here, evidence is provided that targeting a cryptic region of the extracellular matrix protein collagen (HU177 epitope) inhibits melanoma tumor growth and metastasis and reduces angiogenesis and the accumulation of α-SMA-expressing stromal cell in these tumors. The current study suggests that the ability of the HU177 epitope to control melanoma cell migration and metastasis depends on the transcriptional coactivator Yes-associated protein (YAP). Melanoma cell interactions with the HU177 epitope promoted nuclear accumulation of YAP by a cyclin-dependent kinase-5-associated mechanism. These findings provide new insights into the mechanism by which the anti-HU177 antibody inhibits metastasis, and uncovers an unknown signaling pathway by which the HU177 epitope selectively reprograms melanoma cells by regulating nuclear localization of YAP. This study helps to define a potential new therapeutic strategy to control melanoma tumor growth and metastasis that might be used alone or in combination with other therapeutics.

Multifaced Roles of the αvβ3 Integrin in Ehlers-Danlos and Arterial Tortuosity Syndromes' Dermal Fibroblasts

The αvβ3 integrin, an endothelial cells’ receptor-binding fibronectin (FN) in the extracellular matrix (ECM) of blood vessels, regulates ECM remodeling during migration, invasion, angiogenesis, wound healing and inflammation, and is also involved in the epithelial mesenchymal transition. In vitro-grown human control fibroblasts organize a fibrillar network of FN, which is preferentially bound on the entire cell surface to its canonical α5β1 integrin receptor, whereas the αvβ3 integrin is present only in rare patches in focal contacts. We report on the preferential recruitment of the αvβ3 integrin, due to the lack of FN–ECM and its canonical integrin receptor, in dermal fibroblasts from Ehlers–Danlos syndromes (EDS) and arterial tortuosity syndrome (ATS), which are rare multisystem connective tissue disorders. We review our previous findings that unraveled different biological mechanisms elicited by the αvβ3 integrin in fibroblasts derived from patients affected with classical (cEDS), vascular (vEDS), hypermobile EDS (hEDS), hypermobility spectrum disorders (HSD), and ATS. In cEDS and vEDS, respectively, due to defective type V and type III collagens, αvβ3 rescues patients’ fibroblasts from anoikis through a paxillin-p60Src-mediated cross-talk with the EGF receptor. In hEDS and HSD, without a defined molecular basis, the αvβ3 integrin transduces to the ILK-Snail1-axis inducing a fibroblast-to-myofibroblast-transition. In ATS cells, the deficiency of the dehydroascorbic acid transporter GLUT10 leads to redox imbalance, ECM disarray together with the activation of a non-canonical αvβ3 integrin-TGFBRII signaling, involving p125FAK/p60Src/p38MAPK. The characterization of these different biological functions triggered by αvβ3 provides insights into the multifaced nature of this integrin, at least in cultured dermal fibroblasts, offering future perspectives for research in this field.

β1 and β3 integrins in breast, prostate and pancreatic cancer: A novel implication

Integrins are transmembrane glycoproteins that consist of an α and a β subunit. Specific integrin heterodimers preferentially bind to distinct extracellular matrix (ECM) proteins to affect the characteristics of cells or the components of the ECM. Among the different integrins, β1 and β3 integrins serve essential roles in the progression of different cancer-associated processes, including the initiation, proliferation, survival, migration and invasion. Furthermore, previous studies have revealed a ratio between these two integrins in cancer cells, which also demonstrated that the functions of these two integrins are paradoxical. This indicated that the proliferation and metastasis of cancer cells are not always parallel and may be considered independently maintained. Additionally, the present review may assist in understanding certain aspects of cancer, and in making clinical decisions in a novel and more comprehensive manner.

Heteromultivalent targeting of integrin αvβ3 and neuropilin 1 promotes cell survival via the activation of the IGF-1/insulin receptors

Angiogenesis strongly depends on the activation of integrins, especially integrin α_vβ₃, and of neuropilin-1 (NRP-1), a co-receptor of VEGFR2. Dual-targeted molecules that simultaneously block both of them are expected have increased anti-angiogenic and antitumor activity. Toward this goal, we generated bifunctional 40 nm-sized silica nanoparticles (NPs) coated with controlled amounts of cRGD and ATWLPPR peptides and studied their affinity, selectivity and biological activity in HUVECs. Sub-nanomolar concentrations of NPs grafted either with ATWLPPR alone or in combination with cRGD exhibit potent and specific antagonist activity against VEGFR2/AKT signaling. However, a 1 nM concentration of the cRGD/ATWLPPR-heteromultivalent particles (RGD/ATW-NPs) also blocks the phosphorylation of VEGFR2 while co-inducing an unexpected long-lasting activation of AKT via IGF-1R/IR-AKT/GSK3β/eNOS signaling that stimulates cell survival and abrogates the intrinsic toxicity of silica-NPs to serum-starved HUVECs. We also showed that their repeated intravenous administration was associated with the proliferation of human U87MG tumor cells engrafted in nude mice and a dilatation of the tumor blood vessels. We present biochemical evidence for the complex cross-talk generated by the binding of the heteromultivalent NPs with α_vβ₃-integrin and with NRP1. In particular, we show for the first time that such heteromultivalent NPs can trans-activate IGF-1/insulin receptors and exert dose-dependent pro-survival activity. This study demonstrates the difficulties in designing targeted silica-based NPs for antiangiogenic therapies and the possible risks posed by undesirable side effects.

Counterbalancing anti-adhesive effects of Tenascin-C through fibronectin expression in endothelial cells

Cellular fibronectin (FN) and tenascin-C (TNC) are prominent development- and disease-associated matrix components with pro- and anti-adhesive activity, respectively. Whereas both are present in the tumour vasculature, their functional interplay on vascular endothelial cells remains unclear. We have previously shown that basally-oriented deposition of a FN matrix restricts motility and promotes junctional stability in cultured endothelial cells and that this effect is tightly coupled to expression of FN. Here we report that TNC induces FN expression in endothelial cells. This effect counteracts the potent anti-adhesive activity of TNC and leads to the assembly of a dense highly-branched subendothelial matrix that enhances tubulogenic activity. These findings suggest that pro-angiogenic remodelling of the perivascular matrix may involve TNC-induced upregulation of FN in endothelial cells.

Optogenetic interrogation of integrin αVβ3 function in endothelial cells

The integrin αVβ3 is reported to promote angiogenesis in some model systems but not in others. Here, we used optogenetics to study the effects of αVβ3 interaction with the intracellular adapter kindlin-2 (Fermt2) on endothelial cell functions potentially relevant to angiogenesis. Because interaction of kindlin-2 with αVβ3 requires the C-terminal three residues of the β3 cytoplasmic tail (Arg-Gly-Thr; RGT), optogenetic probes LOVpep and ePDZ1 were fused to β3ΔRGT-GFP and mCherry-kindlin-2, respectively, and expressed in β3 integrin-null microvascular endothelial cells. Exposure of the cells to 450 nm (blue) light caused rapid and specific interaction of kindlin-2 with αVβ3 as assessed by immunofluorescence and total internal reflection fluorescence (TIRF) microscopy, and it led to increased endothelial cell migration, podosome formation and angiogenic sprouting. Analyses of kindlin-2 mutants indicated that interaction of kindlin-2 with other kindlin-2 binding partners, including c-Src, actin, integrin-linked kinase and phosphoinositides, were also likely necessary for these endothelial cell responses. Thus, kindlin-2 promotes αVβ3-dependent angiogenic functions of endothelial cells through its simultaneous interactions with β3 integrin and several other binding partners. Optogenetic approaches should find further use in clarifying spatiotemporal aspects of vascular cell biology.

Methylseleninic Acid Provided at Nutritional Selenium Levels Inhibits Angiogenesis by Down-regulating Integrin β3 Signaling

Targeting angiogenesis has emerged as a promising strategy for cancer treatment. Methylseleninic acid (MSA) is a metabolite of selenium (Se) in animal cells that exhibits anti-oxidative and anti-cancer activities at levels exceeding Se nutritional requirements. However, it remains unclear whether MSA exerts its effects on cancer prevention by influencing angiogenesis within Se nutritional levels. Herein, we demonstrate that MSA inhibited angiogenesis at 2 µM, which falls in the range of moderate Se nutritional status. We found that MSA treatments at 2 µM increased cell adherence, while inhibiting cell migration and tube formation of HUVECs in vitro. Moreover, MSA effectively inhibited the sprouts of mouse aortic rings and neoangiogenesis in chick embryo chorioallantoic membrane. We also found that MSA down-regulated integrin β3 at the levels of mRNA and protein, and disrupted clustering of integrin β3 on the cell surface. Additionally, results showed that MSA inhibited the phosphorylation of AKT, IκBα, and NFκB. Overall, our results suggest that exogenous MSA inhibited angiogenesis at nutritional Se levels not only by down-regulating the expression of integrin β3 but also by disorganizing the clustering of integrin β3, which further inhibited the phosphorylation involving AKT, IκBα, NFκB. These findings provide novel mechanistic insight into the function of MSA for regulating angiogenesis and suggest that MSA could be a potential candidate or adjuvant for anti-tumor therapy in clinical settings.

Inter-heterogeneity and intra-heterogeneity of αvβ3 in non-small cell lung cancer and small cell lung cancer patients as revealed by 68Ga-RGD2 PET imaging

PURPOSE

Integrin α_vβ₃ is the therapeutic target of the anti-angiogenic drug cilengitide. The objective of this study was to compare α_vβ₃ levels in non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) patients, by using the positron emission tomography (PET) tracer ⁶⁸Ga-labeled dimerized-RGD (⁶⁸Ga-RGD₂).

METHODS

Thirty-one patients with pathologically confirmed lung cancer were enrolled (21 were NSCLC and 10 were SCLC). PET/CT images were acquired using ⁶⁸Ga-RGD₂.¹⁸F-FDG PET/CT images were also acquired on the consecutive day as reference. The standard uptake values (SUV) and the tumor/nontarget (T/NT) values were quantitatively compared. Expression of the angiogenesis marker α_vβ₃ in NSCLC and SCLC lesions was analyzed by immunohistochemistry.

RESULTS

The ¹⁸F-FDG SUVmax and the SUVmean were not significantly different between NSCLC and SCLC patients. The ⁶⁸Ga-RGD₂ uptake of SCLC patients was at background levels in both SUV and T/NT measurements and was significantly lower than that of NSCLC patients. The range value of ⁶⁸Ga-RGD₂ SUVmean was 4.5 in the NSCLC group and 2.2 in the SCLC group, while the variation coefficient was 36.2% and 39.3% in NSCLC and SCLC primary lesions, respectively. Heterogeneity between primary lesions and putative distant metastases was also observed in some NSCLC cases. Immunostaining showed that α_vβ₃ integrin was expressed in the cells and neovasculature of NSCLC lesions, while SCLC samples had negative expression.

CONCLUSIONS

The uptake of ⁶⁸Ga-RGD₂ in SCLC patients is significantly lower than that in NSCLC patients, indicating a lower α_vβ₃ target level for cilengitide in SCLC. Apparent intra-tumor heterogeneities of α_vβ₃ also exist in both NSCLC and SCLC. Such inter- and intra-heterogeneity of α_vβ₃ may potentially improve current applications of α_vβ₃-targeted therapy and diagnostic imaging in lung cancer.