Coagulation and angiogenic gene expression profiles are defined by molecular subgroups of medulloblastoma: evidence for growth factor-thrombin cross-talk

Roles and interactions of tumor microenvironment components in medulloblastoma with implications for novel therapeutics

Medulloblastomas, the most common malignant pediatric brain tumors, can be classified into the wingless, sonic hedgehog (SHH), group 3, and group 4 subgroups. Among them, the SHH subgroup with the TP53 mutation and group 3 generally present with the worst patient outcomes due to their high rates of recurrence and metastasis. A novel and effective treatment for refractory medulloblastomas is urgently needed. To date, the tumor microenvironment (TME) has been shown to influence tumor growth, recurrence, and metastasis through immunosuppression, angiogenesis, and chronic inflammation. Treatments targeting TME components have emerged as promising approaches to the treatment of solid tumors. In this review, we summarize progress in research on medulloblastoma microenvironment components and their interactions. We also discuss challenges and future research directions for TME-targeting medulloblastoma therapy.

Oncogenes and cancer associated thrombosis: what can we learn from single cell genomics about risks and mechanisms?

Single cell analysis of cancer cell transcriptome may shed a completely new light on cancer-associated thrombosis (CAT). CAT causes morbid, and sometimes lethal complications in certain human cancers known to be associated with high risk of venous thromboembolism (VTE), pulmonary embolism (PE) or arterial thromboembolism (ATE), all of which worsen patients' prognosis. How active cancers drive these processes has long evaded scrutiny. While "unspecific" microenvironmental effects and consequences of patient care (e.g., chemotherapy) have been implicated in pathogenesis of CAT, it has also been suggested that oncogenic pathways driven by either genetic (mutations), or epigenetic (methylation) events may influence the coagulant phenotype of cancer cells and stroma, and thereby modulate the VTE/PE risk. Consequently, the spectrum of driver events and their downstream effector mechanisms may, to some extent, explain the heterogeneity of CAT manifestations between cancer types, molecular subtypes, and individual cases, with thrombosis-promoting, or -protective mutations. Understanding this molecular causation is important if rationally designed countermeasures were to be deployed to mitigate the clinical impact of CAT in individual cancer patients. In this regard, multi-omic analysis of human cancers, especially at a single cell level, has brought a new meaning to concepts of cellular heterogeneity, plasticity, and multicellular complexity of the tumour microenvironment, with profound and still relatively unexplored implications for the pathogenesis of CAT. Indeed, cancers may contain molecularly distinct cellular subpopulations, or dynamic epigenetic states associated with different profiles of coagulant activity. In this article we discuss some of the relevant lessons from the single cell "omics" and how they could unlock new potential mechanisms through which cancer driving oncogenic lesions may modulate CAT, with possible consequences for patient stratification, care, and outcomes.

The role of coagulome in the tumor immune microenvironment

The rising incidence and persistent thrombosis in multiple cancers including those that are immunosuppressive highlight the need for understanding the tumor coagulome system and its role beyond hemostatic complications. Immunotherapy has shown significant benefits in solid organ tumors but has been disappointing in the treatment of hypercoagulable cancers, such as glioblastoma and pancreatic ductal adenocarcinomas. Thus, targeting thrombosis to prevent immunosuppression seems a clinically viable approach in cancer treatment. Hypercoagulable tumors often develop fibrin clots within the tumor microenvironment (TME) that dictates the biophysical characteristics of the tumor tissue. The application of systems biology and single-cell approaches highlight the potential role of coagulome or thrombocytosis in shaping the tumor immune microenvironment (TIME). In-depth knowledge of the tumor coagulome would provide unprecedented opportunities to better predict the hemostatic complications, explore how thrombotic stroma modulates tumor immunity, reexamine the significance of clinical biomarkers, and enable steering the stromal versus systemic immune response for boosting the effectiveness of immune checkpoint inhibitors in cancer treatment. We focus on the role of coagulation factors in priming a suppressive TIME and the huge potential of existing anticoagulant drugs in the clinical settings of cancer immunotherapy.

Associations of CYP2C19 and F2R genetic polymorphisms with platelet reactivity in Chinese ischemic stroke patients receiving clopidogrel therapy

OBJECTIVES

Genetic variation has been considered a major contributor to the high variability in the response to dual antiplatelet therapy in patients with acute ischemic stroke or transient ischemic attack. Recently, incidences of ischemic stroke are increasing rapidly in China. We aimed to evaluate the influence of potential determinants on the response of antiplatelet therapy and adverse events in Chinese ischemic stroke patients receiving clopidogrel-aspirin treatment.

METHODS

Based on the clopidogrel drug response pathway and the coagulation and anticoagulation function, we systematically selected 34 genetic polymorphisms in 12 candidate genes. Three hundred and eight patients were divided into 2 groups according to their degree of inhibition of platelet aggregation. Multivariate analysis was then performed to assess the influence of demographic, clinical and genetic factors on platelet reactivity in Chinese ischemic stroke patients.

RESULTS

We found that polymorphisms in CYP2C19 and F2R genes were still significantly associated with platelet reactivity in Chinese ischemic stroke patients (P = 0.037 and 0.015). The newly identified rs168753 in F2R gene may influence the efficacy to clopidogrel-aspirin therapy for ischemic stroke patients. We also found that ischemic stroke patients with low level of inhibition of platelet aggregation had higher risk of recurrent ischemic events (P = 0.001).

CONCLUSIONS

Together, these results emphasized the necessity of genotype-directed antiplatelet therapy and facilitated to minimize adverse ischemic events.

Genetic and epigenetic regulation of cancer coagulome - lessons from heterogeneity of cancer cell populations

Cancer-associated thrombosis (CAT) is a morbid, potentially life threatening and biologically impactful paraneoplastic state. At least in part, CAT is likely driven by cancer-specific mechanisms the nature of which is still poorly understood, hampering diagnostic, prophylactic and therapeutic efforts. It is increasingly appreciated that cancer-specific drivers of CAT include a constellation of oncogenic mutations and their superimposed epigenetic states that shape the transcriptome, phenotype and secretome of cancer cell populations, including the repertoire of genes impacting the vascular and coagulation systems. High-grade brain tumours, such as glioblastoma multiforme (GBM) represent a paradigm of locally initiated haemostatic abnormalities that propagate systemically, likely through circulating mediators, such as extracellular vesicles and soluble factors. Reciprocally, CAT impacts the biology of cancer cells and may drive tumour evolution. The constituent, oncogene-transformed cancer cell populations form complex ecosystems, the intricate architecture of which has been recently revealed by single cell sequencing technologies. Amidst this phenotypic heterogeneity, several alternative pathways of CAT may exist both between and within individual tumours and their subtypes, including GBM. Indeed, different contributions of cells expressing key coagulant mediators, such as tissue factor, or podoplanin, have been identified in GBM subtypes driven by oncogenic mutations in EGFR, IDH1 and other transforming genes. Thus, a better understanding of cellular sources of CAT, including dominant cancer cell phenotypes and their dynamic shifts, may help design more personalised approaches to thrombosis in cancer patients to improve outcomes.

Syndecan-1 Promotes Angiogenesis in Triple-Negative Breast Cancer through the Prognostically Relevant Tissue Factor Pathway and Additional Angiogenic Routes

Simple Summary

Triple-negative breast cancer is an aggressive subtype of breast cancer characterized by tumor angiogenesis and poor patient survival. Here, we analyzed the function of the cell surface molecule Syndecan-1 in tumor angiogenesis in a 3D cell culture system. As a novel finding, we demonstrate that downregulation of Syndecan-1 reduces angiogenesis by decreasing the amount of angiogenesis factors of the tissue factor pathway. Furthermore, we show that the components of this pathway are associated with the prognosis of breast cancer patients. Our study identifies Syndecan-1 and the tissue factor pathway as novel potential therapeutic targets in the aggressive triple-negative subtype of breast cancer, for which no targeted therapies are currently available.

Abstract

Triple-negative breast cancer (TNBC) is characterized by increased angiogenesis, metastasis, and poor survival. Dysregulation of the cell surface heparan sulfate proteoglycan and signaling co-receptor Syndecan-1 is linked to poor prognosis. To study its role in angiogenesis, we silenced Syndecan-1 in TNBC cell lines using a 3D human umbilical vein endothelial cell (HUVEC) co-culture system. Syndecan-1 siRNA depletion in SUM-149, MDA-MB-468, and MDA-MB-231 cells decreased HUVEC tubule network formation. Angiogenesis array revealed reduced VEGF-A and tissue factor (TF) in the Syndecan-1-silenced secretome. qPCR independently confirmed altered expression of F3, F7, F2R/PAR1, F2RL1/PAR2, VEGF-A, EDN1, IGFBP1, and IGFBP2 in SUM-149, MDA-MB-231, and MDA-MB-468 cells. ELISA revealed reduced secreted endothelin-1 (SUM-149, MDA-MB-468) and TF (all cell lines) upon Syndecan-1 depletion, while TF pathway inhibitor treatment impaired angiogenesis. Survival analysis of 3951 patients demonstrated that high expression of F3 and F7 are associated with better relapse-free survival, whereas poor survival was observed in TNBC and p53 mutant basal breast cancer (F3) and in ER-negative and HER2-positive breast cancer (F2R, F2RL1). STRING protein network analysis revealed associations of Syndecan-1 with VEGF-A and IGFBP1, further associated with the TF and ET-1 pathways. Our study suggests that TNBC Syndecan-1 regulates angiogenesis via the TF and additional angiogenic pathways and marks its constituents as novel prognostic markers and therapeutic targets.

Extracellular Vesicle Mediated Vascular Pathology in Glioblastoma

Glioblastoma (GBM) is an incurable, infiltrative high-grade brain tumour associated with dramatic vascular responses observed both locally (angiogenesis, vascular cooption, angiocrine effects, microthrombosis) and systemically (venous thromboembolism). GBM-associated vascular pathology is diagnostically relevant and constitutes a source of morbidity, mortality and progressive changes in tumour biology. Extracellular vesicles (EVs) have emerged as unique mediators of vascular effects in brain tumours acting as vehicles for intercellular transfer of oncoproteins (e.g. EGFRvIII), RNA, DNA and molecular effectors of angiogenesis and thrombosis. Vascular effects of GBM EVs are regulated by cancer cell genome, epigenome and microenvironment and differ between subtypes of cancer cells and stem cells. Understanding and targeting EV-driven vascular processes in GBM may offer new approaches to diagnose and treat these intractable tumours.

Recent advances in SHH medulloblastoma progression: tumor suppressor mechanisms and the tumor microenvironment

Medulloblastoma, the most common of the malignant pediatric brain tumors, is a group of four molecularly and clinically distinct cancers with different cells of origin. One of these medulloblastoma groups displays activation of Sonic hedgehog (SHH) signaling and originates from granule cell precursors of the developing cerebellum. Ongoing basic and clinical research efforts are tailored to discover targeted and safer therapies, which rely on the identification of the basic mechanisms regulating tumor initiation, progression, and metastasis. In SHH medulloblastoma, the mechanisms regulating neural progenitor transformation and progression to advanced tumors have been studied in some detail. The present review discusses recent advances on medulloblastoma progression derived from studies using mouse models of SHH medulloblastoma. We focus on mechanisms that regulate progression from precancerous lesions to medulloblastoma, describing novel roles played by tumor suppressor mechanisms and the tumor microenvironment.

Oncogenic Regulation of Extracellular Vesicle Proteome and Heterogeneity

Mutational and epigenetic driver events profoundly alter intercellular communication pathways in cancer. This effect includes deregulated release, molecular composition, and biological activity of extracellular vesicles (EVs), membranous cellular fragments ranging from a few microns to less than 100 nm in diameter and filled with bioactive molecular cargo (proteins, lipids, and nucleic acids). While EVs are usually classified on the basis of their physical properties and biogenetic mechanisms, recent analyses of their proteome suggest a larger than expected molecular diversity, a notion that is also supported by multicolour nano-flow cytometry and other emerging technology platforms designed to analyze single EVs. Both protein composition and EV diversity are markedly altered by oncogenic transformation, epithelial to mesenchymal transition, and differentiation of cancer stem cells. Interestingly, only a subset of EVs released from mutant cells may carry oncogenic proteins (e.g., EGFRvIII), hence, these EVs are often referred to as "oncosomes". Indeed, oncogenic transformation alters the repertoire of EV-associated proteins, increases the presence of pro-invasive cargo, and alters the composition of distinct EV populations. Molecular profiling of single EVs may reveal a more intricate effect of transforming events on the architecture of EV populations in cancer and shed new light on their biological role and diagnostic utility.

Single cell coagulomes as constituents of the oncogene-driven coagulant phenotype in brain tumours

Molecular profiling of human cancers revealed a startling diversity in disease-causing mechanisms superseding histological and anatomical commonalities. The emerging molecular subtypes and disease entities are often driven by distinct oncogenic pathways and their effectors, including those acting extracellularly on the vascular and coagulation systems. Indeed, several oncogenic mutations such as those affecting protein-coding genes (RAS, EGFR, PTEN, TP53) and non-coding RNA (microRNA) regulate multiple effectors of the coagulation system (coagulome), including tissue factor, protease activated receptors, clotting factors, mediators of platelet function and fibrinolysis. This is exemplified by differential coagulome profiles in the molecular subtypes of glioblastoma, medulloblastoma and other human tumours. There is mounting clinical evidence that the mutational status of cancer driver genes such as KRAS or IDH1 may influence the risk of venous thromboembolism in patients with colorectal, lung or brain cancers. Notably, single cell sequencing in glioblastoma revealed a remarkable intra-tumoural heterogeneity of cancer cell populations with regard to their individual coagulomes, suggesting a combinatorial and dynamic nature of the global pro-thrombotic phenotype. We suggest that the cellular complexity of specific cancers may define their mechanisms of interactions with the coagulation system, and the risks of thrombosis. Thus, more biologically- based, disease-specific and personalized approaches may be needed to diagnose and manage cancer-related thrombosis.

Leukocytes as a reservoir of circulating oncogenic DNA and regulatory targets of tumor-derived extracellular vesicles

Essentials Tumor-bearing mice were employed to follow oncogenic HRAS sequences in plasma, and blood cells. Cancer DNA accumulated in leukocytes above levels detected in exosomes, platelets and plasma. Extracellular vesicles and nucleosomes are required for uptake of tumor DNA by leukocytes. Uptake of tumor-derived extracellular vesicles by leukocytes triggers coagulant phenotype.

SUMMARY

Background Tumor-derived extracellular vesicles (EVs) and free nucleosomes (NSs) carry into the circulation a wealth of cancer-specific, bioactive and poorly understood molecular cargoes, including genomic DNA (gDNA). Objective Here we investigated the distribution of extracellular oncogenic gDNA sequences (HRAS and HER2) in the circulation of tumor-bearing mice. Methods and Results Surprisingly, circulating leukocytes (WBCs), especially neutrophils, contained the highest levels of mutant gDNA, which exceeded the amount of this material recovered from soluble fractions of plasma, circulating EVs, platelets, red blood cells (RBCs) and peripheral organs, as quantified by digital droplet PCR (ddPCR). Tumor excision resulted in disappearance of the WBC-associated gDNA signal within 2-9 days, which is in line with the expected half-life of these cells. EVs and nucleosomes were essential for the uptake of tumor-derived extracellular DNA by neutrophil-like cells and impacted their phenotype. Indeed, the exposure of granulocytic HL-60 cells to EVs from HRAS-driven cancer cells resulted in a selective increase in tissue factor (TF) procoagulant activity and interleukin 8 (IL-8) production. The levels of circulating thrombin-antithrombin complexes (TAT) were markedly elevated in mice harboring HRAS-driven xenografts. Conclusions Myeloid cells may represent a hitherto unrecognized reservoir of cancer-derived, EV/NS-associated oncogenic gDNA in the circulation, and a possible novel platform for liquid biopsy in cancer. In addition, uptake of this material alters the phenotype of myeloid cells, induces procoagulant and proinflammatory activity and may contribute to systemic effects associated with cancer.

The role of angiogenesis in Group 3 medulloblastoma pathogenesis and survival

Background

Of the 4 medulloblastoma subgroups, Group 3 is the most aggressive but the importance of angiogenesis is unknown. This study sought to determine the role of angiogenesis and identify clinically relevant biomarkers of tumor vascularity and survival in Group 3 medulloblastoma.

Methods

VEGFA mRNA expression and survival from several patient cohorts were analyzed. Group 3 xenografts were implanted intracranially in nude rats. Dynamic susceptibility weighted (DSC) MRI and susceptibility weighted imaging (SWI) were obtained. DSC MRI was used to calculate relative cerebral blood volume (rCBV) and flow (rCBF). Tumor vessel density and rat vascular endothelial growth factor alpha (VEGFA) expression were determined.

Results

Patient VEGFA mRNA levels were significantly elevated in Group 3 compared with the other subgroups (P < 0.001) and associated with survival. Xenografts D283, D341, and D425 were identified as Group 3 by RNA hierarchical clustering and MYC amplification. The D283 group had the lowest rCBV and rCBF, followed by D341 and D425 (P < 0.05). These values corresponded to histological vessel density (P < 0.05), rat VEGFA expression (P < 0.05), and survival (P = 0.002). Gene set enrichment analysis identified 5 putative genes with expression profiles corresponding with these findings: RNH1, SCG2, VEGFA, AGGF1, and PROK2. SWI identified 3 xenograft-independent categories of intratumoral vascular architecture with distinct survival (P = 0.004): organized, diffuse microvascular, and heterogeneous.

Conclusions

Angiogenesis plays an important role in Group 3 medulloblastoma pathogenesis and survival. DSC MRI and SWI are clinically relevant biomarkers for tumor vascularity and overall survival and can be used to direct the use of antivascular therapies for patients with Group 3 medulloblastoma.

Platelets and cancer angiogenesis nexus

There has been remarkable insight into the importance of platelets in a wide range of pathophysiologic events, including inflammation and cancer progression. Thrombocytosis in cancer patients is a common finding. Tumor cells induce platelet activation and subsequent aggregation through direct and indirect mechanisms. Platelets are recognized to contribute to metastatic dissemination. There is plenty of evidence that components of the hemostatic system contribute to the process of angiogenesis. Furthermore, there are accumulated data on the substantial influence of blood platelets in the process of blood vessel formation during malignancy. Platelets appear to be the main physiologic transporters of proangiogenic and antiangiogenic factors. Moreover, they influence the process of angiogenesis through platelet-derived microparticles, microRNA, lipids, and variety of surface receptors. Platelets contribute to early and late stages of angiogenesis. Available data support the overall stimulatory effect of platelets on tumor angiogenesis. It raises the possibility that interfering with platelet function may be an effective antineoplastic treatment strategy.

Thrombin-unique coagulation system protein with multifaceted impacts on cancer and metastasis

The association between blood coagulation and cancer development is well recognized. Thrombin, the pleiotropic enzyme best known for its contribution to fibrin formation and platelet aggregation during vascular hemostasis, may also trigger cellular events through protease-activated receptors, PAR-1 and PAR-4, leading to cancer progression. Our pioneering findings provided evidence that thrombin contributes to cancer metastasis by increasing adhesive potential of malignant cells. However, there is evidence that thrombin regulates every step of cancer dissemination: (1) cancer cell invasion, detachment from primary tumor, migration; (2) entering the blood vessel; (3) surviving in vasculature; (4) extravasation; (5) implantation in host organs. Recent studies have provided new molecular data about thrombin generation in cancer patients and the mechanisms by which thrombin contributes to transendothelial migration, platelet/tumor cell interactions, angiogenesis, and other processes. Though a great deal is known regarding the role of thrombin in cancer dissemination, there are new data for multiple thrombin-mediated events that justify devoting focus to this topic with a comprehensive approach.

Biological basis of personalized anticoagulation in cancer: oncogene and oncomir networks as putative regulators of coagulopathy

Activation of stromal response pathways in cancer is increasingly viewed as both a local and systemic extension of molecular alterations driving malignant transformation. Rather than reflecting passive and unspecific responses to anatomical abnormalities, the coagulation system is a target of oncogenic deregulation, impacting the role of clotting and fibrinolytic proteins, and integrating hemostasis, inflammation, angiogenesis and cellular growth effects in cancer. These processes signify, but do not depend on, the clinically manifest coagulopathy and thrombosis. In this regard, the role of driver mutations affecting oncoprotein coding genes such as RAS, EGFR or MET and tumour suppressors (PTEN, TP53) are well described as regulators of tissue factor (TF), protease activated receptors (PAR-1/2) and ectopic coagulation factors (FVII). Indeed, in both adult and pediatric brain tumours the expression patterns of coagulation and angiogenesis regulators (coagulome and angiome, respectively) reflect the molecular subtypes of the underlying diseases (glioblastoma or medulloblastoma) as defined by their oncogenic classifiers and clinical course. This emerging understanding is still poorly established in relation to the transforming effects of non-coding genes, including those responsible for the expression of microRNA (miR). Indeed, several miRs have been recently found to regulate TF and other effectors. We recently documented that in the context of the aggressive embryonal tumour with multilayered rosettes (ETMR) the oncogenic driver miR (miR-520g) suppresses the expression of TF and correlates with hypocoagulant tumour characteristics. Unlike in adult cancers, the growth of pediatric embryonal brain tumour cells as spheres (to maintain stem cell properties) results in upregulation of miR-520g and downregulation of TF expression and activity. We postulate that oncogenic protein and miR coding genes form alternative pathways of coagulation system regulation in different tumour settings, a property necessitating more personalised and biologically-based approaches to anticoagulation.

Extracellular vesicle communication pathways as regulatory targets of oncogenic transformation

Pathogenesis of human cancers bridges intracellular oncogenic driver events and their impact on intercellular communication. Among multiple mediators of this 'pathological connectivity' the role of extracellular vesicles (EVs) and their subsets (exosomes, ectosomes, oncosomes) is of particular interest for several reasons. The release of EVs from cancer cells represents a unique mechanism of regulated expulsion of bioactive molecules, a process that also mediates cell-to-cell transfer of lipids, proteins, and nucleic acids. Biological effects of these processes have been implicated in several aspects of cancer-related pathology, including tumour growth, invasion, angiogenesis, metastasis, immunity and thrombosis. Notably, the emerging evidence suggests that oncogenic mutations may impact several aspects of EV-mediated cell-cell communication including: (i) EV release rate and protein content; (ii) molecular composition of cancer EVs; (iii) the inclusion of oncogenic and mutant macromolecules in the EV cargo; (iv) EV-mediated release of genomic DNA; (v) deregulation of mechanisms responsible for EV biogenesis (vesiculome) and (vi) mechanisms of EV uptake by cancer cells. Intriguingly, EV-mediated intercellular transfer of mutant and oncogenic molecules between subpopulations of cancer cells, their indolent counterparts and stroma may exert profound biological effects that often resemble (but are not tantamount to) oncogenic transformation, including changes in cell growth, clonogenicity and angiogenic phenotype, or cause cell stress and death. However, several biological barriers likely curtail a permanent horizontal transformation of normal cells through EV-mediated mechanisms. The ongoing analysis and targeting of EV-mediated intercellular communication pathways can be viewed as a new therapeutic paradigm in cancer, while the analysis of oncogenic cargo contained in EVs released from cancer cells into biofluids is being developed for clinical use as a biomarker and companion diagnostics. Indeed, studies are underway to further explore the multiple links between molecular causality in cancer and various aspects of cellular vesiculation.

Protease-activated receptors (PARs)--biology and role in cancer invasion and metastasis

Although many studies have demonstrated that components of the hemostatic system may be involved in signaling leading to cancer progression, the potential mechanisms by which they contribute to cancer dissemination are not yet precisely understood. Among known coagulant factors, tissue factor (TF) and thrombin play a pivotal role in cancer invasion. They may be generated in the tumor microenvironment independently of blood coagulation and can induce cell signaling through activation of protease-activated receptors (PARs). PARs are transmembrane G-protein-coupled receptors (GPCRs) that are activated by a unique proteolytic mechanism. They play important roles in vascular physiology, neural tube closure, hemostasis, and inflammation. All of these agents (TF, thrombin, PARs—mainly PAR-1 and PAR-2) are thought to promote cancer invasion and metastasis at least in part by facilitating tumor cell migration, angiogenesis, and interactions with host vascular cells, including platelets, fibroblasts, and endothelial cells lining blood vessels. Here, we discuss the role of PARs and their activators in cancer progression, focusing on TF- and thrombin-mediated actions. Therapeutic options tailored specifically to inhibit PAR-induced signaling in cancer patients are presented as well.

Anomalous vascularization in a Wnt medulloblastoma: a case report

BACKGROUND

Medulloblastoma is the most common malignant brain tumor in children. To date only few cases of medulloblastoma with hemorrhages have been reported in the literature. Although some studies speculate on the pathogenesis of this anomalous increased vascularization in medulloblastoma, the specific mechanism is still far from clearly understood. A correlation between molecular medulloblastoma subgroups and hemorrhagic features has not been reported, although recent preliminary studies described that WNT-subtype tumors display increased vascularization and hemorrhaging.

CASE PRESENTATION

Herein, we describe a child with a Wnt-medulloblastoma presenting as cerebellar-vermian hemorrhagic lesion. Brain magnetic resonance imaging (MRI) showed the presence of a midline posterior fossa mass with a cystic hemorrhagic component. The differential diagnosis based on imaging included cavernous hemangioma, arteriovenous malformation and traumatic lesion. At surgery, the tumor appeared richly vascularized as documented by the preoperative angiography.

CONCLUSIONS

The case we present showed that Wnt medulloblastoma may be associated with anomalous vascularization. Further studies are needed to elucidate if there is a link between the hypervascularization and the Wnt/β-catenin signaling activation and if this abnormal vasculature might influence drug penetration contributing to good prognosis of this medulloblastoma subgroup.

A Novel Prioritization Method in Identifying Recurrent Venous Thromboembolism-Related Genes

Identifying the genes involved in venous thromboembolism (VTE) recurrence is important not only for understanding the pathogenesis but also for discovering the therapeutic targets. We proposed a novel prioritization method called Function-Interaction-Pearson (FIP) by creating gene-disease similarity scores to prioritize candidate genes underling VTE. The scores were calculated by integrating and optimizing three types of resources including gene expression, gene ontology and protein-protein interaction. As a result, 124 out of top 200 prioritized candidate genes had been confirmed in literature, among which there were 34 antithrombotic drug targets. Compared with two well-known gene prioritization tools Endeavour and ToppNet, FIP was shown to have better performance. The approach provides a valuable alternative for drug targets discovery and disease therapy.

Extracellular Vesicles in Brain Tumor Progression

Brain tumors can be viewed as multicellular 'ecosystems' with increasingly recognized cellular complexity and systemic impact. While the emerging diversity of malignant disease entities affecting brain tissues is often described in reference to their signature alterations within the cellular genome and epigenome, arguably these cell-intrinsic changes can be regarded as hardwired adaptations to a variety of cell-extrinsic microenvironmental circumstances. Conversely, oncogenic events influence the microenvironment through their impact on the cellular secretome, including emission of membranous structures known as extracellular vesicles (EVs). EVs serve as unique carriers of bioactive lipids, secretable and non-secretable proteins, mRNA, non-coding RNA, and DNA and constitute pathway(s) of extracellular exit of molecules into the intercellular space, biofluids, and blood. EVs are also highly heterogeneous as reflected in their nomenclature (exosomes, microvesicles, microparticles) attempting to capture their diverse origin, as well as structural, molecular, and functional properties. While EVs may act as a mechanism of molecular expulsion, their non-random uptake by heterologous cellular recipients defines their unique roles in the intercellular communication, horizontal molecular transfer, and biological activity. In the central nervous system, EVs have been implicated as mediators of homeostasis and repair, while in cancer they may act as regulators of cell growth, clonogenicity, angiogenesis, thrombosis, and reciprocal tumor-stromal interactions. EVs produced by specific brain tumor cell types may contain the corresponding oncogenic drivers, such as epidermal growth factor receptor variant III (EGFRvIII) in glioblastoma (and hence are often referred to as 'oncosomes'). Through this mechanism, mutant oncoproteins and nucleic acids may be transferred horizontally between cellular populations altering their individual and collective phenotypes. Oncogenic pathways also impact the emission rates, types, cargo, and biogenesis of EVs, as reflected by preliminary analyses pointing to differences in profiles of EV-regulating genes (vesiculome) between molecular subtypes of glioblastoma, and in other brain tumors. Molecular regulators of vesiculation can also act as oncogenes. These intimate connections suggest the context-specific roles of different EV subsets in the progression of specific brain tumors. Advanced efforts are underway to capture these events through the use of EVs circulating in biofluids as biomarker reservoirs and to guide diagnostic and therapeutic decisions.

Studies on the Tumor Vasculature and Coagulant Microenvironment

Angiogenesis represents one aspect in the complex process that leads to the generation of the vascular tumor stroma. The related functional constituents include responses of endothelial, mural, bone marrow-derived, and resident inflammatory cells as well as activation of coagulation and fibrinolytic systems in blood. Multiple molecular and cellular effectors participate in these events, often in a tumor-specific manner and with changes enforced through the microenvironment, genetic evolution, and responses to anticancer therapies. To capture various elements of these interactions several surrogate assays have been devised, which can be mechanistically useful and are amenable to quantification, but are individually insufficient to describe the underlying complexity and are best used in a targeted and combinatorial manner. Below, we present a survey of angiogenesis assays and experimental approaches to analyze vascular events in cancer. We also provided specific examples of validated protocols, which are less described, but enable the straightforward analysis of vascular structures and coagulant properties of cancer cells in vivo and in vitro.

Tissue Factor Regulation by miR-520g in Primitive Neuronal Brain Tumor Cells: A Possible Link between Oncomirs and the Vascular Tumor Microenvironment

Pediatric embryonal brain tumors with multilayered rosettes demonstrate a unique oncogenic amplification of the chromosome 19 miRNA cluster, C19MC. Because oncogenic lesions often cause deregulation of vascular effectors, including procoagulant tissue factor (TF), this study explores whether there is a link between C19MC oncogenic miRNAs (oncomirs) and the coagulant properties of cancer cells, a question previously not studied. In a pediatric embryonal brain tumor tissue microarray, we observed an association between C19MC amplification and reduced fibrin content and TF expression, indicative of reduced procoagulant activity. In medulloblastoma cell lines (DAOY and UW228) engineered to express miR-520g, a biologically active constituent of the C19MC cluster, we observed reduced TF expression, procoagulant and TF signaling activities (responses to factor VIIa stimulation), and diminished TF emission as cargo of extracellular vesicles. Antimir and luciferase reporter assays revealed a specific and direct effect of miR-520g on the TF 3' untranslated region. Although the endogenous MIR520G locus is methylated in differentiated cells, exposure of DAOY cells to 5-aza-2'-deoxycytidine or their growth as stem cell-like spheres up-regulated endogenous miR-520g with a coincident reduction in TF expression. We propose that the properties of tumors harboring oncomirs may include unique alterations of the vascular microenvironment, including deregulation of TF, with a possible impact on the biology, therapy, and hemostatic adverse effects of both disease progression and treatment.

Inhibition of oncogenic epidermal growth factor receptor kinase triggers release of exosome-like extracellular vesicles and impacts their phosphoprotein and DNA content

Cancer cells emit extracellular vesicles (EVs) containing unique molecular signatures. Here, we report that the oncogenic EGF receptor (EGFR) and its inhibitors reprogram phosphoproteomes and cargo of tumor cell-derived EVs. Thus, phosphorylated EGFR (P-EGFR) and several other receptor tyrosine kinases can be detected in EVs purified from plasma of tumor-bearing mice and from conditioned media of cultured cancer cells. Treatment of EGFR-driven tumor cells with second generation EGFR kinase inhibitors (EKIs), including CI-1033 and PF-00299804 but not with anti-EGFR antibody (Cetuximab) or etoposide, triggers a burst in emission of exosome-like EVs containing EGFR, P-EGFR, and genomic DNA (exo-gDNA). The EV release can be attenuated by treatment with inhibitors of exosome biogenesis (GW4869) and caspase pathways (ZVAD). The content of P-EGFR isoforms (Tyr-845, Tyr-1068, and Tyr-1173), ERK, and AKT varies between cells and their corresponding EVs and as a function of EKI treatment. Immunocapture experiments reveal the presence of EGFR and exo-gDNA within the same EV population following EKI treatment. These findings suggest that targeted agents may induce cancer cells to change the EV emission profiles reflective of drug-related therapeutic stress. We suggest that EV-based assays may serve as companion diagnostics for targeted anticancer agents.

The contribution of tumor and host tissue factor expression to oncogene-driven gliomagenesis

Glioblastoma multiforme (GBM) is an aggressive form of glial brain tumors, associated with angiogenesis, thrombosis, and upregulation of tissue factor (TF), the key cellular trigger of coagulation and signaling. Since TF is upregulated by oncogenic mutations occurring in different subsets of human brain tumors we investigated whether TF contributes to tumourigenesis driven by oncogenic activation of EGFR (EGFRvIII) and RAS pathways in the brain. Here we show that TF expression correlates with poor prognosis in glioma, but not in GBM. In situ, the TF protein expression is heterogeneously expressed in adult and pediatric gliomas. GBM cells harboring EGFRvIII (U373vIII) grow aggressively as xenografts in SCID mice and their progression is delayed by administration of monoclonal antibodies blocking coagulant (CNTO 859) and signaling (10H10) effects of TF in vivo. Mice in which TF gene is disrupted in the neuroectodermal lineage exhibit delayed progression of spontaneous brain tumors driven by oncogenic N-ras and SV40 large T antigen (SV40LT) expressed under the control of sleeping beauty transposase. Reduced host TF levels in low-TF/SCID hypomorphic mice mitigated growth of glioma subcutaneously but not in the brain. Thus, we suggest that tumor-associated TF may serve as therapeutic target in the context of oncogene-driven disease progression in a subset of glioma.

Brain neoplasms and coagulation-lessons from heterogeneity

The coagulation system constitutes an important facet of the unique vascular microenvironment in which primary and metastatic brain tumors evolve and progress. While brain tumor cells express tissue factor (TF) and other effectors of the coagulation system (coagulome), their propensity to induce local and peripheral thrombosis is highly diverse, most dramatic in the case of glioblastoma multiforme (GBM), and less obvious in pediatric tumors. While the immediate medical needs often frame the discussion on current clinical challenges, the coagulation pathway may contribute to brain tumor progression through subtle, context-dependent, and non-coagulant effects, such as induction of inflammation, angiogenesis, or by responding to iatrogenic insults (e.g. surgery). In this regard, the emerging molecular diversity of brain tumor suptypes (e.g. in glioma and medulloblastoma) highlights the link between oncogenic pathways and the tumor repertoire of coagulation system regulators (coagulome). This relationship may influence the mechanisms of spontaneous and therapeutically provoked tumor cell interactions with the coagulation system as a whole. Indeed, oncogenes (EGFR, MET) and tumor suppressors (PTEN, TP53) may alter the expression, activity, and vesicular release of tissue factor (TF), and cause other changes. Conversely, the coagulant microenvironment may also influence the molecular evolution of brain tumor cells through selective and instructive cues. We suggest that effective targeting of the coagulation system in brain tumors should be explored through molecular stratification, stage-specific analysis, and more personalized approaches including thromboprophylaxis and adjuvant treatment aimed at improvement of patient survival.