Platelet glycoprotein VI promotes metastasis through interaction with cancer cell-derived galectin-3.

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, because its inhibition is protective in models of arterial thrombosis, with only minor effects on hemostasis. In this study, the genetic deficiency of platelet GPVI in mice decreased 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 supported that mouse, as well as human GPVI, had platelet adhesion to colon and breast cancer cells. Using a CRISPR/Cas9-based gene knockout approach, we identified galectin-3 as the major counterreceptor of GPVI on tumor cells. In vivo studies demonstrated that the interplay between platelet GPVI and tumor cell-expressed galectin-3 uses 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 revealed 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.

Inhibition of platelet GPVI induces intratumor hemorrhage and increases efficacy of chemotherapy in mice.

Maintenance of tumor vasculature integrity is indispensable for tumor growth and thus affects tumor progression. Previous studies have identified platelets as major regulators of tumor vascular integrity, as their depletion selectively rendered tumor vessels highly permeable and caused massive intratumoral hemorrhage. While these results established platelets as potential targets for antitumor therapy, their depletion is not a treatment option due to their essential role in hemostasis. Thus, a detailed understanding of how platelets safeguard vascular integrity in tumors is urgently demanded. Here, we show for the first time that functional inhibition of glycoprotein VI (GPVI) on the platelet surface with an antibody (JAQ1) F(ab)2 fragment rapidly induces tumor hemorrhage and diminishes tumor growth similar to complete platelet depletion while not inducing systemic bleeding complications. The intratumor bleeding and tumor growth arrest could be reverted by depletion of Ly6G+ cells, confirming them to be responsible for the induction of bleeding and necrosis within the tumor. In addition, JAQ1 F(ab)2-mediated GPVI inhibition increased intratumoral accumulation of coadministered chemotherapeutic agents, such as Doxil and paclitaxel, thereby resulting in a profound antitumor effect. In summary, our findings identify platelet GPVI as a key regulator of vascular integrity specifically in growing tumors and could serve as a basis for the development of antitumor strategies based on the interference with platelet function.

MiSet RFC Standards: Defining a Universal Minimum Set of Standards Required for Reproducibility and Rigor in Research Flow Cytometry Experiments.

Poor adherence to best practices, insufficient training, and pressure to produce data quickly may lead to publications of suboptimal biomedical research flow cytometry data, which contributes to the body of irreproducible research findings. In addition, documentation of compliance with best flow cytometry practices for submission, visualization, and publication of flow cytometry data is currently endorsed by very few scientific journals, which is particularly concerning as numerous peer-reviewed flow cytometry publications emphasize instrumentation, experimental design, and data analysis as important sources of variability. Guidelines and resources for adequate reporting, annotation and deposition of flow cytometry experiments are provided by MIFlowCyt and the FlowRepository database, and comprehensive expert recommendations covering principles and techniques of field-specific flow cytometry applications have been published. To facilitate the integration of quality-defining parameters into manuscript and grant submission and publication requirements across biomedical fields that rely on the use of flow-cytometry-based techniques, a single comprehensive yet easily and universally applicable document is needed. To produce such a list of gold-standard parameters that assess whether a research flow cytometry experiment has been planned, conducted, interpreted, and reported at the highest standard, a new initiative defining the minimum set of standards a robust and rigorous research flow experiment must fulfill (MiSet RFC Standards) was proposed at CYTO 2019. MiSet RFC Standards will integrate and simplify existing resources to provide a universal benchmark a flow cytometry experiment can easily be measured against. The goal of MiSET RFC Standards is its integration into peer-review and publication procedures through partnership with stakeholders, journals and publishers in biomedical and translational research. This article introduces the aims and anticipated timeline and discusses strategies for interdisciplinary consensus and implementation. A single-resource broadly applicable guideline will harmonize standards across different fields of biomedical research and lead to publication of more robust research findings. © 2019 International Society for Advancement of Cytometry.

Cutting Edge: Imbalanced Cation Homeostasis in MAGT1-Deficient B Cells Dysregulates B Cell Development and Signaling in Mice.

Cation homeostasis, in relation to various immune-suppressive diseases, is a novel field of investigation. Recently, patients with a loss-of-function mutation in magnesium transporter 1 (MAGT1) were reported to present a dysregulated Mg2+ homeostasis in T lymphocytes. Using Magt1-knockout mice (Magt1-/y ), we show that Mg2+ homeostasis was impaired in Magt1-/y B cells and Ca2+ influx was increased after BCR stimulation, whereas T and NK cell function was unaffected. Consequently, mutant B cells displayed an increased phosphorylation of BCR-related proteins differentially affecting protein kinase C activation. These in vitro findings translated into increased frequencies of CD19+ B cells and marginal zone B cells and decreased frequencies of plasma cells among CD45+ splenocytes in vivo. Altogether, our study demonstrates for the first time, to our knowledge, that abolished MAGT1 function causes imbalanced cation homeostasis and developmental responses in B cells. Therefore, this study might contribute to a further understanding of B cell-related pathologies.

Interleukin-23 receptor expressing γδ T cells locally promote early atherosclerotic lesion formation and plaque necrosis in mice.

AIMS: Atherosclerosis is a chronic inflammatory disease of the vessel wall controlled by local and systemic immune responses. The role of interleukin-23 receptor (IL-23R), expressed in adaptive immune cells (mainly T-helper 17 cells) and γδ T cells, in atherosclerosis is only incompletely understood. Here, we investigated the vascular cell types expressing IL-23R and addressed the function of IL-23R and γδ T cells in atherosclerosis. METHODS AND RESULTS: IL-23R+ cells were frequently found in the aortic root in contrast to the aorta in low-density lipoprotein receptor deficient IL-23R reporter mice (Ldlr-/-Il23rgfp/+), and mostly identified as γδ T cells that express IL-17 and GM-CSF. scRNA-seq confirmed γδ T cells as the main cell type expressing Il23r and Il17a in the aorta. Ldlr-/-Il23rgfp/gfp mice deficient in IL-23R showed a loss of IL-23R+ cells in the vasculature, and had reduced atherosclerotic lesion formation in the aortic root compared to Ldlr-/- controls after 6 weeks of high-fat diet feeding. In contrast, Ldlr-/-Tcrδ-/- mice lacking all γδ T cells displayed unaltered early atherosclerotic lesion formation compared to Ldlr-/- mice. In both HFD-fed Ldlr-/-Il23rgfp/gfp and Ldlr-/-Tcrδ-/- mice a reduction in the plaque necrotic core area was noted as well as an expansion of splenic regulatory T cells. In vitro, exposure of bone marrow-derived macrophages to both IL-17A and GM-CSF induced cell necrosis, and necroptotic RIP3K and MLKL expression, as well as inflammatory mediators. CONCLUSIONS: IL-23R+ γδ T cells are predominantly found in the aortic root rather than the aorta and promote early atherosclerotic lesion formation, plaque necrosis, and inflammation at this site. Targeting IL-23R may thus be explored as a therapeutic approach to mitigate atherosclerotic lesion development.

Actin cytoskeleton deregulation confers midostaurin resistance in FLT3-mutant acute myeloid leukemia.

The presence of FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) is one of the most frequent mutations in acute myeloid leukemia (AML) and is associated with an unfavorable prognosis. FLT3 inhibitors, such as midostaurin, are used clinically but fail to entirely eradicate FLT3-ITD + AML. This study introduces a new perspective and highlights the impact of RAC1-dependent actin cytoskeleton remodeling on resistance to midostaurin in AML. RAC1 hyperactivation leads resistance via hyperphosphorylation of the positive regulator of actin polymerization N-WASP and antiapoptotic BCL-2. RAC1/N-WASP, through ARP2/3 complex activation, increases the number of actin filaments, cell stiffness and adhesion forces to mesenchymal stromal cells (MSCs) being identified as a biomarker of resistance. Midostaurin resistance can be overcome by a combination of midostaruin, the BCL-2 inhibitor venetoclax and the RAC1 inhibitor Eht1864 in midostaurin-resistant AML cell lines and primary samples, providing the first evidence of a potential new treatment approach to eradicate FLT3-ITD + AML.

Antigen-presenting dendritic cells in atherosclerosis.

Atherosclerosis is characterized by lipid accumulation and chronic inflammation of the arterial wall, involving both innate and adaptive immune responses. Accumulation of lipid-laden macrophages is a key event in atherosclerosis. However, also other immune cells, such as dendritic cells (DC) and T cells, are found within lesions. DCs are classified as a separate lineage of mononuclear phagocytes that arise from progenitors distinct from precursors of monocytes/macrophages. Although a clear attribution of the effects of antigen-presenting cells (APCs) to monocytes/macrophages and DCs is hampered by the use of promiscuous surface markers, recent research has approached to resolve the contribution of bona fide DCs and their subsets, and of plasmacytoidDCs (pDCs) to atherosclerosis. We here discuss the pathogenic and protective mechanisms engaged by APCs in atherosclerosis and highlight current concepts to further address their role in atherosclerosis.

Deletion of Batf3-dependent antigen-presenting cells does not affect atherosclerotic lesion formation in mice.

Atherosclerosis is the main underlying cause for cardiovascular events such as myocardial infarction and stroke and its development might be influenced by immune cells. Dendritic cells (DCs) bridge innate and adaptive immune responses by presenting antigens to T cells and releasing a variety of cytokines. Several subsets of DCs can be discriminated that engage specific transcriptional pathways for their development. Basic leucine zipper transcription factor ATF-like 3 (Batf3) is required for the development of classical CD8α+ and CD103+ DCs. By crossing mice deficient in Batf3 with atherosclerosis-prone low density lipoprotein receptor (Ldlr-/-)-deficient mice we here aimed to further address the contribution of Batf3-dependent CD8α+ and CD103+ antigen-presenting cells to atherosclerosis. We demonstrate that deficiency in Batf3 entailed mild effects on the immune response in the spleen but did not alter atherosclerotic lesion formation in the aorta or aortic root, nor affected plaque phenotype in low density lipoprotein receptor-deficient mice fed a high fat diet. We thus provide evidence that Batf3-dependent antigen-presenting cells do not have a prominent role in atherosclerosis.

Gripe y sistema inmunitario (II): pasado, presente y futuro de la vacuna contra la gripe / No disponible

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¿Cómo pueden las células del sistema inmunitario contribuir a los infartos e ictus? / No disponible

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Artritis reumatoide: tus articulaciones como escenario de batalla entre tú y tus guerreros / No disponible

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¿Por qué cada año hay que vacunarse frente a la gripe? / No disponible

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Enfermedad inflamatoria intestinal: el intestino como campo de batalla / No disponible

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Psoriasis: cuando la piel se descontrola / No disponible

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¿Es siempre beneficioso para nuestro sistema inmunitario hacer ejercicio? / No disponible

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Acorralando al Lupus Sistémico Eritomatoso / No disponible

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