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  • 1
    Publication Date: 2020-02-07
    Description: Increasing evidence suggests that platelets play a predominant role in colon and breast cancer metastasis but the underlying molecular mechanisms remain elusive. Glycoprotein VI (GPVI) is a platelet-specific receptor for collagen and fibrin that triggers platelet activation through immunoreceptor tyrosine-based activation motif (ITAM)-signaling and thereby regulates diverse functions including platelet adhesion, aggregation and procoagulant activity. GPVI has been proposed as a safe antithrombotic target as its inhibition is protective in models of arterial thrombosis with only minor effects on hemostasis. Here, we demonstrate that genetic deficiency of platelet GPVI in mice decreases experimental and spontaneous metastasis of colon and breast cancer cells. Similar results were obtained with mice lacking the spleen-tyrosine kinase Syk in platelets, an essential component of the ITAM-signaling cascade. In vitro and in vivo analyses show that mouse, as well as human GPVI, supports platelet adhesion to colon and breast cancer cells. Using a CRISPR/Cas9-based gene knock-out approach, we identified Galectin-3 as the major counter-receptor of GPVI on tumor cells. In vivo studies demonstrated that the interplay between platelet GPVI and tumor cell-expressed Galectin-3 utilizes ITAM-signaling components in platelets and favors the extravasation of tumor cells. Finally, we showed that JAQ1 F(ab)2-mediated inhibition of GPVI efficiently impairs platelet-tumor cell interaction and tumor metastasis. Our study reveals a new mechanism by which platelets promote the metastasis of colon and breast cancer cells and suggests that GPVI represents a promising target for antimetastatic therapies.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 2
    Publication Date: 1992-08-15
    Description: Cultured endothelial cells can be induced by tumor necrosis factor/cachectin (TNF) and other cytokines to synthesize the procoagulant cofactor tissue factor (TF). Intact monolayers of TNF- treated endothelial cells showed only minimal TF activity. In contrast, after permeabilization of these monolayers with detergent (saponin, 0.02%), there was approximately 10- to 20-fold increase in TF-mediated, factor VIIa-dependent factor Xa formation. Extracellular matrix derived from TNF-treated endothelium, prepared after removing the cells by hypotonic lysis or ammonium hydroxide (0.1 N), also had similarly enhanced TF activity. Incubation with a blocking monoclonal antibody to TF inhibited the procoagulant activity of both TNF-stimulated endothelial cells, whether they were intact or permeabilized, and of their matrices. However, when the apical cell surface was pretreated with anti-TF antibody, washed, and then cells were lysed with water or permeabilized with saponin, similar augmentation of TF activity was still observed, suggesting the presence of a pool of TF to which the antibody did not initially gain access. Consistent with this concept, the presence of TF in the matrix of TNF-treated endothelial cells was shown by immunoblotting and morphologic studies; cultured endothelial monolayers and the native endothelium of aortic segments after exposure to TNF showed TF in extracellular matrix, associated with vesicles. In contrast, TF was virtually undetectable on the apical endothelial surface. Taken together, these findings suggest that endothelial TF can be present in a cryptic pool that only gains access to the blood after alteration in the integrity of the endothelial monolayer.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 3
    Publication Date: 1993-07-15
    Description: The acute inflammatory response is frequently accompanied by serious thrombotic events. We show that C-reactive protein (CRP), an acute- phase reactant that markedly increases its serum concentration in response to inflammatory stimuli, induced monocytes to express tissue factor (TF), a potent procoagulant. Purified human CRP in concentrations commonly achieved in vivo during inflammation (10 to 100 micrograms/mL) induced a 75-fold increase in TF procoagulant activity (PCA) of human peripheral blood mononuclear cells (PBM), with a parallel increase in TF antigen levels. CRP-induced PCA was completely blocked by a monoclonal antibody against human TF but not by irrelevant murine IgG. Dot blot analysis showed a significant increase of TF mRNA after 4 hours of incubation with CRP, followed by a peak of PCA within 6 and 8 hours. Actinomycin D and cycloheximide blocked CRP-stimulated PCA, suggesting that de novo TF protein synthesis was required. Endotoxin (LPS) contamination of CRP was excluded as the mediator of TF synthesis because: (1) CRP was Limulus assay negative; (2) induction of TF PCA by CRP was not blocked by Polymyxin B, in contrast to LPS- induced PCA; (3) antihuman CRP IgG inhibited CRP-induced PCA, but not LPS-induced PCA; (4) CRP was able to stimulate TF production in LPS- pretreated PBM refractory to additional LPS stimulation; and, (5) unlike LPS, CRP was incapable of inducing TF in human umbilical vein endothelial cells. We suggest that CRP-mediated TF production in monocytes may contribute to the development of disseminated intravascular coagulation and thrombosis in inflammatory states.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 4
    Publication Date: 1993-07-15
    Description: The acute inflammatory response is frequently accompanied by serious thrombotic events. We show that C-reactive protein (CRP), an acute- phase reactant that markedly increases its serum concentration in response to inflammatory stimuli, induced monocytes to express tissue factor (TF), a potent procoagulant. Purified human CRP in concentrations commonly achieved in vivo during inflammation (10 to 100 micrograms/mL) induced a 75-fold increase in TF procoagulant activity (PCA) of human peripheral blood mononuclear cells (PBM), with a parallel increase in TF antigen levels. CRP-induced PCA was completely blocked by a monoclonal antibody against human TF but not by irrelevant murine IgG. Dot blot analysis showed a significant increase of TF mRNA after 4 hours of incubation with CRP, followed by a peak of PCA within 6 and 8 hours. Actinomycin D and cycloheximide blocked CRP-stimulated PCA, suggesting that de novo TF protein synthesis was required. Endotoxin (LPS) contamination of CRP was excluded as the mediator of TF synthesis because: (1) CRP was Limulus assay negative; (2) induction of TF PCA by CRP was not blocked by Polymyxin B, in contrast to LPS- induced PCA; (3) antihuman CRP IgG inhibited CRP-induced PCA, but not LPS-induced PCA; (4) CRP was able to stimulate TF production in LPS- pretreated PBM refractory to additional LPS stimulation; and, (5) unlike LPS, CRP was incapable of inducing TF in human umbilical vein endothelial cells. We suggest that CRP-mediated TF production in monocytes may contribute to the development of disseminated intravascular coagulation and thrombosis in inflammatory states.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 5
    Publication Date: 1992-08-15
    Description: Cultured endothelial cells can be induced by tumor necrosis factor/cachectin (TNF) and other cytokines to synthesize the procoagulant cofactor tissue factor (TF). Intact monolayers of TNF- treated endothelial cells showed only minimal TF activity. In contrast, after permeabilization of these monolayers with detergent (saponin, 0.02%), there was approximately 10- to 20-fold increase in TF-mediated, factor VIIa-dependent factor Xa formation. Extracellular matrix derived from TNF-treated endothelium, prepared after removing the cells by hypotonic lysis or ammonium hydroxide (0.1 N), also had similarly enhanced TF activity. Incubation with a blocking monoclonal antibody to TF inhibited the procoagulant activity of both TNF-stimulated endothelial cells, whether they were intact or permeabilized, and of their matrices. However, when the apical cell surface was pretreated with anti-TF antibody, washed, and then cells were lysed with water or permeabilized with saponin, similar augmentation of TF activity was still observed, suggesting the presence of a pool of TF to which the antibody did not initially gain access. Consistent with this concept, the presence of TF in the matrix of TNF-treated endothelial cells was shown by immunoblotting and morphologic studies; cultured endothelial monolayers and the native endothelium of aortic segments after exposure to TNF showed TF in extracellular matrix, associated with vesicles. In contrast, TF was virtually undetectable on the apical endothelial surface. Taken together, these findings suggest that endothelial TF can be present in a cryptic pool that only gains access to the blood after alteration in the integrity of the endothelial monolayer.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 6
    Publication Date: 2020-12-23
    Description: Inborn errors of immunity (IEI) are a genetically heterogeneous group of disorders with a broad clinical spectrum. Identification of molecular and functional bases of these disorders is important for diagnosis, treatment and an understanding of the human immune response. We identified six unrelated males with neutropenia, infections, lymphoproliferation, humoral immune defects, and in some cases bone marrow failure associated with three different variants in the X-linked gene TLR8, encoding the endosomal Toll-like receptor 8 (TLR8). Interestingly, five patients had somatic variants in TLR8 with less than 30% mosaicism, suggesting a dominant mechanism responsible for the clinical phenotype. Mosaicism was also detected in skin-derived fibroblasts in three patients, demonstrating that mutations were not limited to the hematopoietic compartment. All patients had refractory chronic neutropenia, and three patients underwent allogeneic hematopoietic cell transplantation. All variants conferred gain-of-function to TLR8 protein, and immune phenotyping demonstrated a pro-inflammatory phenotype with activated T cells and elevated serum cytokines associated with impaired B cell maturation. Differentiation of myeloid cells from patient-derived induce pluripotent stem cells demonstrated increased responsiveness to TLR8. Together these findings demonstrate that gain-of-function variants in TLR8 lead to a novel childhood-onset IEI with lymphoproliferation, neutropenia, infectious susceptibility, B and T cell defects, and in some cases bone marrow failure. Somatic mosaicism is a prominent molecular mechanism of this new disease.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 7
    Publication Date: 2021-04-01
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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