Pro-inflammatory megakaryocyte gene expression in murine models of breast cancer

Day + 100 bone marrow megakaryocyte count predicts transplant outcome in patients with high-risk myelodysplastic syndrome and acute leukemia

Megakaryocytes (MKs), the precursor cells of platelets, have essential roles in a variety of pathophysiological processes in the bone marrow (BM) niche. Megakaryocytes maintain hematopoietic stem cell microenvironment through inflammatory and immunological responses. The primary objective of this research was to investigate the clinical impact of BM-MK counts in high-risk myelodysplastic syndrome and acute leukemia patients who underwent allogeneic hematopoietic stem cell transplantation (alloHSCT). Three hundred and forty-six patients (median age, 42 (15-71) years; male/female, 207/139) participated in the study. Based on the BM-MK counts on day + 100 of alloHSCT, the study population was classified into normal/high-MK+100 and low-MK+100 groups. The probabilities of progression-free survival (PFS) and overall survival (OS) were significantly better in the normal/high-MK+100 group (p < 0.001, p < 0.001). Nonrelapse mortality was found to be reduced in the same group of patients (p = 0.012). BM-MK+100 count, which was indicated to be a predictor for relapse after alloHSCT (p = 0.018), represented a considerable impact on PFS and OS (p = 0.017, p = 0.009). Megakaryocytes have regulatory roles in association with a comprehensive cytokine network in the BM microenvironment. Although the localization of MKs may be determinative for their spectrum of efficacy, distinct biological subgroups may also help to clarify the heterogeneity of their functional features. Prospective efforts in larger populations are required to illuminate the potential prognostic role of MKs in alloHSCT recipients.

IRAP Drives Ribosomal Degradation to Refuel Energy for Platelet Activation during Septic Thrombosis

Platelets play crucial roles in multiple pathophysiological processes after energy-dependent activation. It is puzzling how such a small cellular debris has abundant energy supply. In this study, it is shown that insulin-regulated aminopeptidase (IRAP), a type II transmembrane protein, is a key regulator for platelet activation by promoting energy regeneration during septic thrombosis. Through interaction with certain endosome membrane proteins, IRAP can not only promote granule release, but also facilitate lysosomal degradation of theoretically discarded ribosomes in an mTORC1- and S-acylation-dependent manner in activated platelets. Plentiful amino acids obtained from IRAP-mediated ribophagy are recruited to aerobic glycolysis and then promote energy metabolism reprogramming, thereby producing abundant energy for platelet life extension and prolonged activation. Consequently, targeted blocking IRAP can dramatically alleviate platelet hyperactivation and septic thrombosis.

Platelets and megakaryocytes in cancer

Platelets have important roles in hemostasis but also actively participate in cancer metastasis and inflammatory processes. They are produced by large precursor cells, the megakaryocytes, residing mainly in the bone marrow. Clinically, elevated platelet counts and/or increased platelet-to-lymphocyte ratio are being explored as biomarkers of metastatic disease and to predict survival or response to therapy in certain cancers. Multiple mechanisms have been put forward on how platelets promote hematogenous metastasis stemming mainly from murine experimental models. Research is now beginning to explore the potential roles of megakaryocytes in solid cancer, myeloma, and lymphoma. Here, we review mechanisms on how platelets and megakaryocytes contribute to cancer progression and metastasis but also discuss potential cancer-suppressing functions mainly related to the regulation of vascular intratumor integrity. Recent developments in cancer immune checkpoint therapy are reviewed with a focus on the potential roles of platelets. Moreover, we review studies exploring platelets for targeted drug delivery systems in cancer therapy.

Acute inflammation induces acute megakaryopoiesis with impaired platelet production during fetal hematopoiesis

Hematopoietic development is tightly regulated by various factors. The role of RNA m6A modification during fetal hematopoiesis, particularly in megakaryopoiesis, remains unclear. Here, we demonstrate that loss of m6A methyltransferase METTL3 induces formation of double-stranded RNAs (dsRNAs) and activates acute inflammation during fetal hematopoiesis in mouse. This dsRNA-mediated inflammation leads to acute megakaryopoiesis, which facilitates the generation of megakaryocyte progenitors but disrupts megakaryocyte maturation and platelet production. The inflammation and immune response activate the phosphorylation of STAT1 and IRF3, and upregulate downstream interferon-stimulated genes (ISGs). Inflammation inhibits the proliferation rate of hematopoietic progenitors and further skews the cell fate determination toward megakaryocytes rather than toward erythroid from megakaryocyte-erythroid progenitors (MEPs). Transcriptional-wide gene expression analysis identifies IGF1 as a major factor whose reduction is responsible for the inhibition of megakaryopoiesis and thrombopoiesis. Restoration of IGF1 with METTL3-deficient hematopoietic cells significantly increases megakaryocyte maturation. In summary, we elucidate that the loss of RNA m6A modification-induced acute inflammation activates acute megakaryopoiesis, but impairs its final maturation through the inhibition of IGF1 expression during fetal hematopoiesis.

Cathepsin G promotes arteriovenous fistula maturation by positively regulating the MMP2/MMP9 pathway

BACKGROUND

Arteriovenous fistula (AVF) is currently the preferred vascular access for hemodialysis patients. However, the low maturation rate of AVF severely affects its use in patients. A more comprehensive understanding and study of the mechanisms of AVF maturation is urgently needed.

METHODS AND RESULTS

In this study, we downloaded the publicly available datasets (GSE119296 and GSE220796) from the Gene Expression Omnibus (GEO) and merged them for subsequent analysis. We screened 84 differentially expressed genes (DEGs) and performed the functional enrichment analysis. Next, we integrated the results obtained from the degree algorithm provided by the Cytohubba plug-in, Molecular complex detection (MCODE) plug-in, weighted gene correlation network analysis (WGCNA), and Least absolute shrinkage and selection operator (LASSO) logistic regression. This integration allowed us to identify CTSG as a hub gene associated with AVF maturation. Through the literature search and Pearson's correlation analysis, the genes matrix metalloproteinase 2 (MMP2) and MMP9 were identified as potential downstream effectors of CTSG. We then collected three immature clinical AVF vein samples and three mature samples and validated the expression of CTSG using immunohistochemistry (IHC) and double-immunofluorescence staining. The IHC results demonstrated a significant decrease in CTSG expression levels in the immature AVF vein samples compared to the mature samples. The results of double-immunofluorescence staining revealed that CTSG was expressed in both the intima and media of AVF veins. Moreover, the expression of CTSG in vascular smooth muscle cells (VSMCs) was significantly higher in the mature samples compared to the immature samples. The results of Masson's trichrome and collagen I IHC staining demonstrated a higher extent of collagen deposition in the media of immature AVF veins compared to the mature. By constructing an in vitro CTSG overexpression model in VSMCs, we found that CTSG upregulated the expression of MMP2 and MMP9 while downregulating the expression of collagen I and collagen III. Furthermore, CTSG was found to inhibit VSMC migration.

CONCLUSIONS

CTSG may promote AVF maturation by stimulating the secretion of MMP2 and MMP9 from VSMCs and reducing the extent of medial fibrosis in AVF veins by inhibiting the secretion of collagen I and collagen III.

S100A9 promotes renal calcium oxalate stone formation via activating the TLR4-p38/MAPK-LCN2 signaling pathway

OBJECTIVES

To explore the role of S100A9 protein in renal calcium oxalate (CaOx) stone formation.

METHODS

CaOx nephrocalcinosis mice were established via intraperitoneal injection of glyoxylate. They were treated with S100A9 deficiency, Paquinimod, or p38 MAPK-IN-1. Vonkossa staining was conducted to observe the deposition of CaOx crystals. Renal expression of inflammation, macrophage polarization, and injury markers was detected using immunohistochemistry and qPCR. Effects of S100A9 on renal tubular epithelial cells (HK-2) were explored by transcriptome sequencing. The mechanism of how S100A9 regulated lipocalin 2 (LCN2) was studied through Western Blot. Flow cytometry was performed to detect the influence of LCN2 on macrophages polarization.

RESULTS

S100A9 deficiency inhibited the renal deposition of CaOx crystals in nephrocalcinosis mice. S100A9 upregulated the expression of LCN2 in HK-2 cells via activating the TLR4-p38/MAPK pathway. LCN2 promoted the migration and M1 polarization of macrophages. S100A9 deficiency downregulated the renal expression of LCN2, IL1-β, Kim-1, F4/80, and CD80 in nephrocalcinosis mice. Paquinimod and p38 MAPK-IN-1 both inhibited the renal deposition of CaOx crystals and downregulated the expression of LCN2, IL1-β, Kim-1, F4/80, iNOS, and CD68 in nephrocalcinosis mice.

CONCLUSIONS

S100A9 promotes renal inflammatory injury by activating the TLR4-p38/MAPK-LCN2 pathway and then contributes to CaOx stone formation.

Platelet Angiopoietin-1 Protects Against Murine Models of Tumor Metastasis

BACKGROUND

In addition to their fundamental roles in preserving vascular integrity, platelets also contribute to tumor angiogenesis and metastasis. However, despite being a reservoir for angiogenic and metastatic cytokines, platelets also harbor negative regulators of tumor progression. Angpt1 (angiopoietin-1) is a cytokine essential for developmental angiogenesis that also protects against tumor cell metastasis through an undefined mechanism. Although activated platelets release Angpt1 from α-granules into circulation, the contributions of platelet Angpt1 to tumor growth, angiogenesis, and metastasis have not been investigated.

METHODS

Using cytokine arrays and ELISAs, we first compared platelet Angpt1 levels in breast and melanoma mouse tumor models to tumor-free controls. We then assessed tumor growth and metastasis in mice lacking megakaryocyte and platelet Angpt1 (Angpt1Plt KO). The spontaneous metastasis of mammary-injected tumor cells to the lungs was quantified using RT-PCR (reverse transcription-polymerase chain reaction). The lung colonization of intravenously injected tumor cells and tumor cell extravasation were determined using fluorescent microscopy and flow cytometry.

RESULTS

Platelet Angpt1 is selectively upregulated in the PyMT (polyoma middle tumor antigen) breast cancer mouse model, and platelets are the principal source of Angpt1 in blood circulation. While primary tumor growth and angiogenesis were unaffected, Angpt1Plt KO mice had both increased spontaneous lung metastasis and tumor cell lung colonization following mammary or intravenous injection, respectively. Although platelet Angpt1 did not affect initial tumor cell entrapment in the lungs, Angpt1Plt KO mice had increased tumor cell retention and extravasation. Serum from Angpt1Plt KO mice increased endothelial permeability and reduced VE (vascular endothelial)-cadherin expression at endothelial junctions compared with serum from control mice (Angpt1WT).

CONCLUSIONS

Platelets provide an intravascular source of Angpt1 that restrains tumor metastasis by preserving the lung microvasculature to limit tumor cell extravasation.

Procoagulant platelets promote immune evasion in triple-negative breast cancer

ABSTRACT

Triple-negative breast cancer (TNBC) is an aggressive tumor entity in which immune checkpoint (IC) molecules are primarily synthesized in the tumor environment. Here, we report that procoagulant platelets bear large amounts of such immunomodulatory factors and that the presence of these cellular blood components in TNBC relates to protumorigenic immune-cell activity and impaired survival. Mechanistically, tumor-released nucleic acids attract platelets to the aberrant tumor microvasculature, where they undergo procoagulant activation, thus delivering specific stimulatory and inhibitory IC molecules. This concomitantly promotes protumorigenic myeloid leukocyte responses and compromises antitumorigenic lymphocyte activity, ultimately supporting tumor growth. Interference with platelet-leukocyte interactions prevented immune cell misguidance and suppressed tumor progression, nearly as effective as systemic IC inhibition. Hence, our data uncover a self-sustaining mechanism of TNBC by using platelets to misdirect immune-cell responses. Targeting this irregular multicellular interplay may represent a novel immunotherapeutic strategy for TNBC without the adverse effects of systemic IC inhibition.

Longitudinal tracking of circulating rare events in the liquid biopsy of stage III-IV non-small cell lung cancer patients

In the United States, lung cancer is the second most common type of cancer with non-small cell lung cancer (NSCLC) encompassing around 85% of total lung cancer cases. Late-stage patients with metastatic disease have worsening prognosis, highlighting the importance of longitudinal disease monitoring. Liquid biopsy (LBx) represents a way for physicians to non-invasively track tumor analytes, such as circulating tumor cells (CTCs), and understand tumor progression in real-time through analyzing longitudinal blood samples. CTCs have been shown to be effective predictive biomarkers in measuring treatment efficacy and survival outcomes. We used the third-generation High-Definition Single Cell Assay (HDSCA3.0) workflow to analyze circulating rare events longitudinally during treatment in a cohort of 10 late-stage NSCLC patients, identifying rare events including circulating cancer cells (i.e., CTCs), and oncosomes. Here, we show (1) that there is a cancer specific LBx profile, (2) there is considerable heterogeneity of rare cells and oncosomes, and (3) that LBx data elements correlated with patient survival outcomes. Additional studies are warranted to understand the biological significance of the rare events detected, and the clinical potential of the LBx to monitor and predict response to treatment in NSCLC patient care.

Platelet Contributions to the (Pre)metastatic Tumor Microenvironment

Alongside their conventional roles in thrombosis and hemostasis, platelets have long been associated with nonhemostatic pathologies, including tumor cell metastasis. Numerous mechanistic studies have since demonstrated that the direct binding of platelets to intravascular tumor cells promotes key hallmarks of metastasis, including survival in circulation and tumor cell arrest at secondary sites. However, platelets also interact with nonmalignant cells that make up the stromal and immune compartments within both primary and metastatic tumors. This review will first provide a brief historical perspective on platelet contributions to metastatic disease before discussing the emerging roles that platelets play in creating microenvironments that likely support successful tumor cell metastasis.

Revealing profile of cancer-educated platelets and their factors to foster immunotherapy development

Among multiple hemostasis components, platelets hyperactivity plays major roles in cancer progression by providing surface and internal components for intercellular crosstalk as well as by behaving like immune cells. Since platelets participate and regulate immunity in homeostatic and disease states, we assumed that revealing platelets profile might help in conceiving novel anti-cancer immune-based strategies. The goal of this review is to compile and discuss the most recent reports on the nature of cancer-associated platelets and their interference with immunotherapy. An increasing number of studies have emphasized active communication between cancer cells and platelets, with platelets promoting cancer cell survival, growth, and metastasis. The anti-cancer potential of platelet-directed therapy has been intensively investigated, and anti-platelet agents may prevent cancer progression and improve the survival of cancer patients. Platelets can (i) reduce antitumor activity; (ii) support immunoregulatory cells and factors generation; (iii) underpin metastasis and, (iv) interfere with immunotherapy by expressing ligands of immune checkpoint receptors. Mediators produced by tumor cell-induced platelet activation support vein thrombosis, constrain anti-tumor T- and natural killer cell response, while contributing to extravasation of tumor cells, metastatic potential, and neovascularization within the tumor. Recent studies showed that attenuation of immunothrombosis, modulation of platelets and their factors have a good perspective in immunotherapy optimization. Particularly, blockade of intra-tumoral platelet-associated programmed death-ligand 1 might promote anti-tumor T cell-induced cytotoxicity. Collectively, these findings suggest that platelets might represent the source of relevant cancer staging biomarkers, as well as promising targets and carriers in immunotherapeutic approaches for combating cancer.

The dynamic role of platelets in cancer progression and their therapeutic implications

Systemic antiplatelet treatment represents a promising option to improve the therapeutic outcomes and therapeutic efficacy of chemotherapy and immunotherapy due to the critical contribution of platelets to tumour progression. However, until recently, targeting platelets as a cancer therapeutic has been hampered by the elevated risk of haemorrhagic and thrombocytopenic (low platelet count) complications owing to the lack of specificity for tumour-associated platelets. Recent work has advanced our understanding of the molecular mechanisms responsible for the contribution of platelets to tumour progression and metastasis. This has led to the identification of the biological changes in platelets in the presence of tumours, the complex interactions between platelets and tumour cells during tumour progression, and the effects of platelets on antitumour therapeutic response. In this Review, we present a detailed picture of the dynamic roles of platelets in tumour development and progression as well as their use in diagnosis, prognosis and monitoring response to therapy. We also provide our view on how to overcome challenges faced by the development of precise antiplatelet strategies for safe and efficient clinical cancer therapy.