Correction: Identification of a New Epitope in uPAR as a Target for the Cancer Therapeutic Monoclonal Antibody ATN-658, a Structural Homolog of the uPAR Binding Integrin CD11b (αM)
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PROVIDER: S-EPMC4045972 | biostudies-literature | 2014 Jan
REPOSITORIES: biostudies-literature
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Project description:The urokinase plasminogen activator receptor (uPAR) plays a role in tumor progression and has been proposed as a target for the treatment of cancer. We recently described the development of a novel humanized monoclonal antibody that targets uPAR and has anti-tumor activity in multiple xenograft animal tumor models. This antibody, ATN-658, does not inhibit ligand binding (i.e. uPA and vitronectin) to uPAR and its mechanism of action remains unclear. As a first step in understanding the anti-tumor activity of ATN-658, we set out to identify the epitope on uPAR to which ATN-658 binds. Guided by comparisons between primate and human uPAR, epitope mapping studies were performed using several orthogonal techniques. Systematic site directed and alanine scanning mutagenesis identified the region of aa 268-275 of uPAR as the epitope for ATN-658. No known function has previously been attributed to this epitope Structural insights into epitope recognition were obtained from structural studies of the Fab fragment of ATN-658 bound to uPAR. The structure shows that the ATN-658 binds to the DIII domain of uPAR, close to the C-terminus of the receptor, corroborating the epitope mapping results. Intriguingly, when bound to uPAR, the complementarity determining region (CDR) regions of ATN-658 closely mimic the binding regions of the integrin CD11b (αM), a previously identified uPAR ligand thought to be involved in leukocyte rolling, migration and complement fixation with no known role in tumor progression of solid tumors. These studies reveal a new functional epitope on uPAR involved in tumor progression and demonstrate a previously unrecognized strategy for the therapeutic targeting of uPAR.
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Project description:Urokinase plasminogen activator receptor (uPAR) is implicated in tumor growth and metastasis due to its ability to activate latent growth factors, proteases, and different oncogenic signaling pathways upon binding to different ligands. Elevated uPAR expression is correlated with the increased aggressiveness of cancer cells, which led to its credentialing as an attractive diagnostic and therapeutic target in advanced solid cancer. Here, we examine the antitumor effects of a humanized anti-uPAR antibody (huATN-658) alone and in combination with the approved bisphosphonate Zometa (Zoledronic acid) on skeletal lesion through a series of studies in vitro and in vivo. Treatment with huATN-658 or Zometa alone significantly decreased human MDA-MB-231 cell proliferation and invasion in vitro, effects which were more pronounced when huATN-658 was combined with Zometa. In vivo studies demonstrated that huATN-658 treatment significantly reduced MDA-MB-231 primary tumor growth compared with controls. In a model of breast tumor-induced bone disease, huATN-658 and Zometa were equally effective in reducing skeletal lesions. The skeletal lesions were significantly reduced in animals receiving the combination of huATN-658 + Zometa compared with monotherapy treatment. These effects were due to a significant decrease in osteoclastic activity and tumor cell proliferation in the combination treatment group. Transcriptome analysis revealed that combination treatment significantly changes the expression of genes from signaling pathways implicated in tumor progression and bone remodeling. Results from these studies provide a rationale for the continued development of huATN-658 as a monotherapy and in combination with currently approved agents such as Zometa in patients with metastatic breast cancer.
| S-EPMC7165173 | biostudies-literature
Project description:Hyperuricemia is an essential risk factor in chronic kidney disease (CKD), while urate-lowering therapy to prevent or delay CKD is controversial. Alternatively activated macrophages in response to local microenvironment play diverse roles in kidney diseases. Here, we aim to investigate whether and how macrophage integrin αM (ITGAM) contributes to hyperuricemia-related CKD. In vivo, we explored dynamic characteristics of renal tissue in hyperuricemia-related CKD mice. By incorporating transcriptomics and phosphoproteomics data, we analyzed gene expression profile, hub genes and potential pathways. In vitro, we validated bioinformatic findings under different conditions with interventions corresponding to core nodes. We found that hyperuricemia-related CKD was characterized by elevated serum uric acid levels, impaired renal function, activation of macrophage alternative (M2) polarization, and kidney fibrosis. Integrated bioinformatic analyses revealed Itgam as the potential core gene, which was associated with focal adhesion signaling. Notably, we confirmed the upregulated expression of macrophage ITGAM, activated pathway, and macrophage M2 polarization in injured kidneys. In vitro, through silencing Itgam, inhibiting p-FAK or p-AKT1 phosphorylation, and concurrent inhibiting of p-FAK while activating p-AKT1 all contributed to the modulation of macrophage M2 polarization. Our results indicated targeting macrophage ITGAM might be a promising therapeutic approach for preventing CKD.
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Project description:An amendment to this paper has been published and can be accessed via a link at the top of the paper.
| S-EPMC7655800 | biostudies-literature
Project description:Integrin α(4)β(7) is a lymphocyte homing receptor that mediates both rolling and firm adhesion of lymphocytes on vascular endothelium, two of the critical steps in lymphocyte migration and tissue-specific homing. The rolling and firm adhesions of lymphocytes rely on the dynamic shift between the inactive and active states of integrin α(4)β(7), which is associated with the conformational rearrangement of integrin molecules. Activation-specific antibodies, which specifically recognize the activated integrins, have been used as powerful tools in integrin studies, whereas there is no well characterized activation-specific antibody to integrin α(4)β(7). Here, we report the identification, characterization, and epitope mapping of an activation-specific human mAb J19 against integrin α(4)β(7). J19 was discovered by screening a human single-chain variable fragment phage library using an activated α(4)β(7) mutant as target. J19 IgG specifically bound to the high affinity α(4)β(7) induced by Mn(2+), DTT, ADP, or CXCL12, but not to the low affinity integrin. Moreover, J19 IgG did not interfere with α(4)β(7)-MAdCAM-1 interaction. The epitope of J19 IgG was mapped to Ser-331, Ala-332, and Ala-333 of β(7) I domain and a seven-residue segment from 184 to 190 of α(4) β-propeller domain, which are buried in low affinity integrin with bent conformation and only exposed in the high affinity extended conformation. Taken together, J19 is a potentially powerful tool for both studies on α(4)β(7) activation mechanism and development of novel therapeutics targeting the activated lymphocyte expressing high affinity α(4)β(7).
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Project description:Myeloid cells are recruited to damaged tissues where they can resolve infections and tumor growth or stimulate wound healing and tumor progression. Recruitment of these cells is regulated by integrins, a family of adhesion receptors that includes integrin CD11b. Here we report that, unexpectedly, integrin CD11b does not regulate myeloid cell recruitment to tumors but instead controls myeloid cell polarization and tumor growth. CD11b activation promotes pro-inflammatory macrophage polarization by stimulating expression of microRNA Let7a. In contrast, inhibition of CD11b prevents Let7a expression and induces cMyc expression, leading to immune suppressive macrophage polarization, vascular maturation, and accelerated tumor growth. Pharmacological activation of CD11b with a small molecule agonist, Leukadherin 1 (LA1), promotes pro-inflammatory macrophage polarization and suppresses tumor growth in animal models of murine and human cancer. These studies identify CD11b as negative regulator of immune suppression and a target for cancer immune therapy.
| S-EPMC6300665 | biostudies-literature
Project description:Pharmacological activation of integrin CD11b/CD18 (αMβ2, Mac-1, and CR3) shows anti-inflammatory benefits in a variety of animal models of human disease, and it is a novel therapeutic strategy. Reasoning that genetic models can provide an orthogonal and direct system for the mechanistic study of CD11b agonism, we present in this study, to our knowledge, a novel knock-in model of constitutive active CD11b in mice. We genetically targeted the Itgam gene (which codes for CD11b) to introduce a point mutation that results in the I332G substitution in the protein. The I332G mutation in CD11b promotes an active, higher-affinity conformation of the ligand-binding I/A-domain (CD11b αA-domain). In vitro, this mutation increased adhesion of knock-in neutrophils to fibrinogen and decreased neutrophil chemotaxis to a formyl-Met-Leu-Phe gradient. In vivo, CD11bI332G animals showed a reduction in recruitment of neutrophils and macrophages in a model of sterile peritonitis. This genetic activation of CD11b also protected against development of atherosclerosis in the setting of hyperlipidemia via reduction of macrophage recruitment into atherosclerotic lesions. Thus, our animal model of constitutive genetic activation of CD11b can be a useful tool for the study of integrin activation and its potential contribution to modulating leukocyte recruitment and alleviating different inflammatory diseases.
| S-EPMC7577938 | biostudies-literature
Project description:General mechanisms of adhesion in the immune response are coordinated by the leukocyte integrins CD11/CD18. The possible participation of these differentiation molecules in early events of transmembrane signalling was investigated. Monoclonal antibody (mAb) cross-linking of CD18, the integrin beta subunit ubiquitously expressed by all leukocytes, increased the cytosolic free Ca2+ concentration ([Ca2+]i) by 2-3-fold in monocyte THP-1 cells. Digitalized imaging in single adherent cells showed that this Ca2+ response is temporally biphasic, involves both release of Ca2+ from the intracellular stores as well as Ca2+ influx from the external compartment, and is dramatically down-modulated by terminal differentiation of THP-1 cells to a mature monocyte phenotype. Similarly, only a minor subset of 20-30% of peripheral blood monocytes heterogeneously maintain the CD18-mediated Ca(2+)-signalling properties. Cross-linking of CD18 also increased cytosolic free [Ca2+]i in a subset of approx. 15-20% of resting T lymphocytes, in a Ca2+ response that was completely abrogated during T-cell mitogenic activation with lectins or alloreactive antigen. While cross-linking of CD11a or CD11c was without effect, occupancy of CD11b increased cytosolic free [Ca2+]i in monocytic cells. This response was functionally coupled with a transient activation state of CD11b/CD18, which was reflected in its increased avidity to bind the complementary ligand fibrinogen. These results suggest that occupancy of CD18 transduces a stimulatory Ca2+ signal that is critically regulated by the state of cell activation/differentiation and by the association with the unique alpha-subunit CD11b. These intrinsic signalling properties may directly participate in regulating the oligospecific ligand recognition of leukocyte integrins.
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Project description:Fibrosis is involved in 45% of deaths in the United States, and no treatment exists to reverse the progression of lung or kidney fibrosis. Myofibroblasts are key to the progression and maintenance of fibrosis. We investigated features of cell adhesion necessary for monocytes to differentiate into myofibroblasts, seeking to identify pathways key to myofibroblast differentiation. Blocking antibodies against integrins α3, αM, and αMβ2 de-differentiate myofibroblasts in vitro, lower the pro-fibrotic secretome of myofibroblasts, and treat lung fibrosis and inhibit kidney fibrosis in vivo. Decorin's collagen-binding peptide can be used to direct functionalized blocking antibodies (against integrins-α3, -αM, -αMβ2) to both fibrotic lungs and fibrotic kidneys, reducing the dose of antibody necessary to treat fibrosis. This targeted immunotherapy blocking key integrins may be an effective therapeutic for the treatment of fibrosis.
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Project description:Hyperuricemia is an essential risk factor in chronic kidney disease (CKD), while urate-lowering therapy to prevent or delay CKD is controversial. Alternatively activated macrophages in response to local microenvironment play diverse roles in kidney diseases. Here, we aim to investigate whether and how macrophage integrin αM (ITGAM) contributes to hyperuricemia-related CKD. In vivo, we explored dynamic characteristics of renal tissue in C57BL/6J mice with hyperuricemia-related CKD. By incorporating transcriptomics and phosphoproteomics data, we analyzed gene expression profile, hub genes and potential pathways. In vitro, we validated bioinformatic findings under different conditions with interventions corresponding to core nodes. We found that hyperuricemia-related CKD was characterized by elevated serum uric acid levels, impaired renal function, activation of macrophage alternative (M2) polarization, and kidney fibrosis. Integrated bioinformatic analyses revealed Itgam as the potential core gene and was associated with focal adhesion signaling. Notably, we confirmed the upregulated expression of macrophage ITGAM, activated pathway, and macrophage M2 polarization in injured kidneys. In vitro, through silencing Itgam, inhibiting p-FAK or p-AKT1 phosphorylation, and concurrent inhibiting of p-FAK while activating p-AKT1 all contributed to the modulation of macrophage M2 polarization. Our results indicated targeting macrophage ITGAM might be a promising therapeutic approach for preventing CKD.
2024-06-26 | GSE262687 | GEO