The Vascular Microenvironment in Glioblastoma: A Comprehensive Review

Tumors and their microenvironments: Learning from pediatric brain pathologies

Early clues to tumors and their microenvironments come from embryonic development. Here we review the literature and consider whether the embryonic brain and its pathologies can serve as a better model. Among embryonic organs, the brain is the most heterogenous and complex, with multiple lineages leading to wide spectrum of cell states and types. Its dysregulation promotes neurodevelopmental brain pathologies and pediatric tumors. Embryonic brain pathologies point to the crucial importance of spatial heterogeneity over time, akin to the tumor microenvironment. Tumors dedifferentiate through genetic mutations and epigenetic modulations; embryonic brains differentiate through epigenetic modulations. Our innovative review proposes learning developmental brain pathologies to target tumor evolution-and vice versa. We describe ways through which tumor pharmacology can learn from embryonic brains and their pathologies, and how learning tumor, and its microenvironment, can benefit targeting neurodevelopmental pathologies. Examples include pediatric low-grade versus high-grade brain tumors as in rhabdomyosarcomas and gliomas.

Closer proximity of pre-treatment CD4+ T cells to CD8+ T cells favor response to neoadjuvant immunotherapy in patients with PD-L1 low-expressing non-small cell lung cancer

Background

Neoadjuvant chemo-immunotherapy improves non-small cell lung cancer (NSCLC) outcomes, but remission rates vary, emphasizing the need for biomarkers. This study aimed to investigate the impact of the baseline intratumoral CD4+ T-cell-adjacent microenvironment on the efficacy of neoadjuvant immunotherapy in NSCLC and its correlation with hypoxia-inducible factor-1α (HIF-1α), microvessel density (MVD), and cancer-associated fibroblasts (CAFs).

Methods

Tumor samples from 49 NSCLC patients before neoadjuvant immunotherapy were retrospectively collected and subjected to multiplex immunohistochemistry staining (panel 1: DAPI/CK/CD4/CD8/CD68; Panel 2: DAPI/CK/CD4/HIF-1α/CD31/α-SMA) to characterize CD4+ T cells, CD8+ T cells CD68+ macrophages, HIF-1α+ cells, HIF-1α+CD4+ cells, MVD, and CAF. Mann-Whitney U test and receiver operating characteristic (ROC) curve were used to assess the relationship between the number and spatial distribution of each metric and the efficacy of the treatment, and Spearman's rank correlation was used to assess the correlation of each metric.

Results

In 49 NSCLC patients, responders (54.2%) and non-responders (45.8%). Single-indicator analysis revealed a positive correlation between high infiltration of CD8+ T cells in the stromal area and response to treatment in overall and programmed cell death-ligand 1 (PD-L1) low-expressing patients [CD8+ T (str) density: overall patient, 38 vs. 16, P=0.03; tumor proportion score (TPS) 1-49% subgroup, 37 vs. 14, P=0.04], with an area under curve (AUC) 0.684 and 0.746, respectively. CD4+ T cells combined with CD8+ T cells or CD68+ macrophages were analyzed and found to be more efficacious than CD4+ThiCD8+Thi compared to CD4+TloCD8+Tlo in patients with low expression of PD-L1 (P=0.03). Assessment of the nearest neighbor distance (NND) of CD4+ T cells and their adjacent cells revealed that the closer the CD4+ T cells and CD8+ T cells in the overall compartment, the better the efficacy in NSCLC patients, especially in patients with low PD-L1 expression [CD4+ T to CD8+ T (all) NND: overall patients, 34 vs. 47 μm, P=0.03; TPS 1-49% subgroup, 34 vs. 69 μm, P=0.006], and the AUC was 0.670 and 0.830, respectively. Notably, this favorable spatial interaction may not be dependent on direct contact between CD4+ T cells and CD8+ T cells within 10/20/30 μm (P>0.05). Furthermore, in overall and PD-L1 low-expressing patients, the closer the distance between CD4+ T cells and CD8+ T cells, the higher the MVD (overall patients, r=-0.39, P=0.008; TPS 1-49% subgroup, r=-0.49, P=0.01).

Conclusions

The baseline intratumoral CD4+ T-cell-adjacent microenvironment in NSCLC is associated with the efficacy of neoadjuvant immunotherapy for NSCLC, with the closer proximity of pre-treatment CD4+ T cells and CD8+ T cells, the better the treatment efficacy in NSCLC patients (even especially in the low-expressing PD-L1 population), and is associated with high MVD.

Novel neutrophil targeting platforms in treating Glioblastoma: Latest evidence and therapeutic approaches

Glioblastoma (GBM) is the most aggressive and lethal type of primary brain tumor, characterized by its rapid growth, resistance to conventional therapies, and a highly immunosuppressive tumor microenvironment (TME). Recent studies have highlighted the critical role of neutrophils in the progression of GBM, where they contribute to tumor growth, invasion, and treatment resistance. As a result, neutrophils have emerged as a promising target for therapeutic intervention in GBM. Various strategies are being investigated to specifically target neutrophils within the GBM environment, including using small molecules, antibodies, and nanoparticle-based methods. These approaches aim to regulate neutrophils' recruitment, activation, and functions. This study reviews the latest findings regarding the involvement of neutrophils in GBM, explores potential techniques targeting neutrophils for therapeutic purposes, and discusses current clinical studies and prospects in this rapidly evolving field. By studying the diverse functions of neutrophils in GBM, these innovative therapeutic strategies can help address some of the most significant challenges in treating this malignancy.

Understanding Neovascularization in Glioblastoma: Insights from the Current Literature

Glioblastomas (GBMs), among the most aggressive and resilient brain tumors, characteristically exhibit high angiogenic potential, leading to the formation of a dense yet aberrant vasculature, both morphologically and functionally. With these premises, numerous expectations were initially placed on anti-angiogenic therapies, soon dashed by their limited efficacy in concretely improving patient outcomes. Neovascularization in GBM soon emerged as a complex, dynamic, and heterogeneous process, hard to manage with the classical standard of care. Growing evidence has revealed the existence of numerous non-canonical strategies of angiogenesis, variously exploited by GBM to meet its ever-increasing metabolic demand and differently involved in tumor progression, recurrence, and escape from treatments. In this review, we provide an accurate description of each neovascularization mode encountered in GBM tumors to date, highlighting the molecular players and signaling cascades primarily involved. We also detail the key architectural and functional aspects characteristic of the GBM vascular compartment because of an intricate crosstalk between the different angiogenic networks. Additionally, we explore the repertoire of emerging therapies against GBM that are currently under study, concluding with a question: faced with such a challenging scenario, could combined therapies, tailored to the patient's genetic signatures, represent an effective game changer?

Towards Effective Treatment of Glioblastoma: The Role of Combination Therapies and the Potential of Phytotherapy and Micotherapy

Glioblastoma multiforme (GBM) is one of the most aggressive and difficult-to-treat brain tumors, with a poor prognosis due to its high resistance to conventional therapies. Current treatment options, including surgical resection, radiotherapy, and chemotherapy, have limited effectiveness in improving long-term survival. Despite the emergence of new therapies, monotherapy approaches have not shown significant improvements, highlighting the need for innovative therapeutic strategies. Combination therapies appear to be the most promising solution, as they target multiple molecular pathways involved in GBM progression. One area of growing interest is the incorporation of phytotherapy and micotherapy as complementary treatments, which offer potential benefits due to their anti-tumor, anti-inflammatory, and immunomodulatory properties. This review examines the current challenges in GBM treatment, discusses the potential of combination therapies, and highlights the promising role of phytotherapy and micotherapy as integrative therapeutic options for GBM management.

Clinical research framework proposal for ketogenic metabolic therapy in glioblastoma

Glioblastoma (GBM) is the most aggressive primary brain tumor in adults, with a universally lethal prognosis despite maximal standard therapies. Here, we present a consensus treatment protocol based on the metabolic requirements of GBM cells for the two major fermentable fuels: glucose and glutamine. Glucose is a source of carbon and ATP synthesis for tumor growth through glycolysis, while glutamine provides nitrogen, carbon, and ATP synthesis through glutaminolysis. As no tumor can grow without anabolic substrates or energy, the simultaneous targeting of glycolysis and glutaminolysis is expected to reduce the proliferation of most if not all GBM cells. Ketogenic metabolic therapy (KMT) leverages diet-drug combinations that inhibit glycolysis, glutaminolysis, and growth signaling while shifting energy metabolism to therapeutic ketosis. The glucose-ketone index (GKI) is a standardized biomarker for assessing biological compliance, ideally via real-time monitoring. KMT aims to increase substrate competition and normalize the tumor microenvironment through GKI-adjusted ketogenic diets, calorie restriction, and fasting, while also targeting glycolytic and glutaminolytic flux using specific metabolic inhibitors. Non-fermentable fuels, such as ketone bodies, fatty acids, or lactate, are comparatively less efficient in supporting the long-term bioenergetic and biosynthetic demands of cancer cell proliferation. The proposed strategy may be implemented as a synergistic metabolic priming baseline in GBM as well as other tumors driven by glycolysis and glutaminolysis, regardless of their residual mitochondrial function. Suggested best practices are provided to guide future KMT research in metabolic oncology, offering a shared, evidence-driven framework for observational and interventional studies.

Clinicopathological Parameters and Immunohistochemical Profiles in Correlation with MRI Characteristics in Glioblastomas

Glioblastoma is considered the most aggressive tumor of the central nervous system. The tumor microenvironment includes several components, such as endothelial cells, immune cells, and extracellular matrix components like matrix metalloproteinase-9 (MMP-9), which facilitates the proliferation of endothelial cells with pro-angiogenic roles. The MRI characteristics of glioblastomas can contribute to determining the prognosis. The aim of this study was to analyze the relationship between tumor angiogenesis in glioblastomas in association with MMP-9 immunoexpression. The results were correlated with the Ki-67 proliferation index, p53 immunoexpression, and the mutational status of IDH1 and ATRX, as well as MRI imaging data. This retrospective study included forty-four patients diagnosed with glioblastoma at the Department of Pathology, Târgu Mureș County Emergency Clinical Hospital. MMP-9 immunoexpression was observed in approximately half of the cases, more frequently in patients over 65 years old. Comparing the imaging data with the immunohistochemical results, we observed that the median tumor volume was higher in glioblastomas with IDH1 and p53 mutations, ATRX wild-type status, negative MMP-9 expression, and high Ki-67 proliferation indexes. The median values of MVD-CD34 and MVD-CD105 were higher in cases with extensive peritumoral edema in the contralateral hemisphere. Additionally, ATRX mutations were frequently associated with a more pronounced deviation of the median structures. To statistically validate the associations between MRI and the histopathological features of glioblastomas, further studies with larger cohorts are required.

The neglected burden of chronic hypoxia on the resistance of glioblastoma multiforme to first-line therapies

Glioblastoma multiforme (GBM) is the most common adult primary brain tumor. The standard of care involves maximal surgery followed by radiotherapy and concomitant chemotherapy with temozolomide (TMZ), in addition to adjuvant TMZ. However, the recurrence rate of GBM within 1-2 years post-diagnosis is still elevated and has been attributed to the accumulation of multiple factors including the heterogeneity of GBM, genomic instability, angiogenesis, and chronic tumor hypoxia. Tumor hypoxia activates downstream signaling pathways involved in the adaptation of GBM to the newly oxygen-deprived environment, thereby contributing to the resistance and recurrence phenomena, despite the multimodal therapeutic approach used to eradicate the tumor. Therefore, in this review, we will focus on the development and implication of chronic or limited-diffusion hypoxia in tumor persistence through genetic and epigenetic modifications. Then, we will detail the hypoxia-induced activation of vital biological pathways and mechanisms that contribute to GBM resistance. Finally, we will discuss a proteomics-based approach to encourage the implication of personalized GBM treatments based on a hypoxia signature.

PYGL regulation of glycolysis and apoptosis in glioma cells under hypoxic conditions via HIF1α-dependent mechanisms

Background

Gliomas are highly aggressive brain tumors with complex metabolic and molecular alterations. The role of glycolysis in glioma progression and its regulation by hypoxia remain poorly understood. This study investigated the function of glycogen phosphorylase L (PYGL) in glioma and its interaction with glycolytic pathways under hypoxic conditions.

Methods

Differential expression analysis was conducted using The Cancer Genome Atlas (TCGA) glioma and GSE67089 datasets, revealing significant changes in the expression of genes. A prognostic risk model incorporating PYGL was built by univariate and multivariate Cox regression analyses. The impacts of PYGL on glioma cell proliferation, glycolysis, apoptosis, and metabolic activities were evaluated by in vitro assays. Additionally, the influences of hypoxia and hypoxia-inducible factor 1-alpha (HIF1α) on PYGL expression were evaluated.

Results

Our prognostic prediction model showed a C-index of 0.76 [95% confidence interval (CI): 0.70-0.82], indicating a good predictive accuracy of the model. In addition, genetic predictors included in the nomogram included PYGL, HIF1α, and other genes associated with the glycolytic pathway. Differential expression analysis identified PYGL as a key gene associated with glioma survival. PYGL expression was significantly upregulated in glioma cells. PYGL knockdown inhibited cell invasion, proliferation, migration, and colony formation and enhanced apoptosis via modulation of Bcl-2, caspase-3, and Bax. Glycolysis was impaired in PYGL-knockdown cells, as indicated by increased glycogen levels and a reduced extracellular acidification rate (ECAR), adenosine triphosphate (ATP) levels, lactate levels, and PKM2 and LDHA expression. PYGL overexpression promoted glycolysis and cell viability, which was counteracted by 2-deoxy-D-glucose (2-DG). Hypoxia-induced PYGL expression was regulated by HIF1α, underscoring the interplay between the hypoxia and glycolysis pathways.

Conclusions

PYGL is a crucial regulator of glycolysis in gliomas and contributes to tumor progression under hypoxic conditions. Targeting PYGL and its associated metabolic pathways may offer new therapeutic strategies for glioma treatment.

The role of postoperative blood pressure management in early postoperative hemorrhage in awake craniotomy glioma patients

Postoperative hemorrhage can severely affect the patients' neurological outcome after awake craniotomy. Higher postoperative blood pressure can increase the risk of postoperative hemorrhage. The aim of this study was to investigate the role of postoperative blood pressure and other common radiological and epidemiological features with the incidence of postoperative hemorrhage. In this retrospective analysis, we included patients who underwent awake surgery at our institution. We assessed the blood pressure both intra- and postoperatively as well as the heart rate for the first 12 h. We compared a cohort with postoperative hemorrhage, who required further treatment (surgical revision or intravenous antihypertensive therapy), with a cohort with no postoperative hemorrhage. We included 48 patients with a median age of 39 years. 9 patients (19%) required further treatment due to postoperative hemorrhage, which was surgery in 2 cases and intensive blood pressure measurements in 7 cases. However, with early treatment, no significant difference in Performance scores at follow-up could be found. Patients with postoperative hemorrhage showed significantly higher postoperative systolic blood pressure during the hours 3-12 (p < 0.05) as well as intraoperatively throughout the procedure (p < 0.05). In ROC and Youden Test, a strong impact of systolic blood pressure over 140mmHg during the early postoperative course could be shown. Postoperative hemorrhage is a rare but possible complication in awake surgery glioma patients. To avoid postoperative hemorrhage, treating physicians should aim strictly on systolic blood pressure of under 140mmHg for the postoperative course.

Neuroinflammation in Glioblastoma: Progress and Perspectives

Glioblastoma is the most common and malignant primary brain tumor, with high morbidity and mortality. Despite an aggressive, multimodal treatment regimen, including surgical resection followed by chemotherapy and radiotherapy, the prognosis of glioblastoma patients remains poor. One formidable challenge to advancing glioblastoma therapy is the complexity of the tumor microenvironment. The tumor microenvironment of glioblastoma is a highly dynamic and heterogeneous system that consists of not only cancerous cells but also various resident or infiltrating inflammatory cells. These inflammatory cells not only provide a unique tumor environment for glioblastoma cells to develop and grow but also play important roles in regulating tumor aggressiveness and treatment resistance. Targeting the tumor microenvironment, especially neuroinflammation, has increasingly been recognized as a novel therapeutic approach in glioblastoma. In this review, we discuss the components of the tumor microenvironment in glioblastoma, focusing on neuroinflammation. We discuss the interactions between different tumor microenvironment components as well as their functions in regulating glioblastoma pathogenesis and progression. We will also discuss the anti-tumor microenvironment interventions that can be employed as potential therapeutic targets.

Survival strategies: How tumor hypoxia microenvironment orchestrates angiogenesis

During tumor development, the tumor itself must continuously generate new blood vessels to meet their growth needs while also allowing for tumor invasion and metastasis. One of the most common features of tumors is hypoxia, which drives the process of tumor angiogenesis by regulating the tumor microenvironment, thus adversely affecting the prognosis of patients. In addition, to overcome unsuitable environments for growth, such as hypoxia, nutrient deficiency, hyperacidity, and immunosuppression, the tumor microenvironment (TME) coordinates angiogenesis in several ways to restore the supply of oxygen and nutrients and to remove metabolic wastes. A growing body of research suggests that tumor angiogenesis and hypoxia interact through a complex interplay of crosstalk, which is inextricably linked to the TME. Here, we review the TME's positive contribution to angiogenesis from an angiogenesis-centric perspective while considering the objective impact of hypoxic phenotypes and the status and limitations of current angiogenic therapies.

Evaluation of Microvascular Density in Glioblastomas in Relation to p53 and Ki67 Immunoexpression

Glioblastoma is the most aggressive tumor in the central nervous system, with a survival rate of less than 15 months despite multimodal therapy. Tumor recurrence frequently occurs after removal. Tumoral angiogenesis, the formation of neovessels, has a positive impact on tumor progression and invasion, although there are controversial results in the specialized literature regarding its impact on survival. This study aims to correlate the immunoexpression of angiogenesis markers (CD34, CD105) with the proliferation index Ki67 and p53 in primary and secondary glioblastomas. This retrospective study included 54 patients diagnosed with glioblastoma at the Pathology Department of County Emergency Clinical Hospital Târgu Mureș. Microvascular density was determined using CD34 and CD105 antibodies, and the results were correlated with the immunoexpression of p53, IDH1, ATRX and Ki67. The number of neoformed blood vessels varied among cases, characterized by different shapes and calibers, with endothelial cells showing modified morphology and moderate to marked pleomorphism. Neovessels with a glomeruloid aspect, associated with intense positivity for CD34 or CD105 in endothelial cells, were observed, characteristic of glioblastomas. Mean microvascular density values were higher for the CD34 marker in all cases, though there were no statistically significant differences compared to CD105. Mutant IDH1 and ATRX glioblastomas, wild-type p53 glioblastomas, and those with a Ki67 index above 20% showed a more abundant microvascular density, with statistical correlations not reaching significance. This study highlighted a variety of percentage intervals of microvascular density in primary and secondary glioblastomas using immunohistochemical markers CD34 and CD105, respectively, with no statistically significant correlation between evaluated microvascular density and p53 or Ki67.

PLX038A, a long-acting SN-38, penetrates the blood-tumor-brain-barrier, accumulates and releases SN-38 in brain tumors to increase survival of tumor bearing mice

Central nervous system tumors have resisted effective chemotherapy because most therapeutics do not penetrate the blood-tumor-brain-barrier. Nanomedicines between  ~ 10 and 100 nm accumulate in many solid tumors by the enhanced permeability and retention effect, but it is controversial whether the effect can be exploited for treatment of brain tumors. PLX038A is a long-acting prodrug of the topoisomerase 1 inhibitor SN-38. It is composed of a 15 nm 4-arm 40 kDa PEG tethered to four SN-38 moieties by linkers that slowly cleave to release the SN-38. The prodrug was remarkably effective at suppressing growth of intracranial breast cancer and glioblastoma (GBM), significantly increasing the life span of mice harboring them. We addressed the important issue of whether the prodrug releases SN-38 systemically and then penetrates the brain to exert anti-tumor effects, or whether it directly penetrates the blood-tumor-brain-barrier and releases the SN-38 cargo within the tumor. We argue that the amount of SN-38 formed systemically is insufficient to inhibit the tumors, and show by PET imaging that a close surrogate of the 40 kDa PEG carrier in PLX038A accumulates and is retained in the GBM. We conclude that the prodrug penetrates the blood-tumor-brain-barrier, accumulates in the tumor microenvironment and releases its SN-38 cargo from within. Based on our results, we pose the provocative question as to whether the 40 kDa nanomolecule PEG carrier might serve as a "Trojan horse" to carry other drugs past the blood-tumor-brain-barrier and release them into brain tumors.

Long-term Intravital Investigation of an Orthotopic Glioma Mouse Model via Optical Coherence Tomography Angiography

BACKGROUND/AIM

Probing brain tumor microvasculature holds significant importance in both basic cancer research and medical practice for tracking tumor development and assessing treatment outcomes. However, few imaging methods commonly used in clinics can noninvasively monitor the brain microvascular network at high precision and without exogenous contrast agents in vivo. The present study aimed to investigate the characteristics of microvasculature during brain tumor development in an orthotopic glioma mouse model.

MATERIALS AND METHODS

An orthotopic glioma mouse model was established by surgical orthotopic implantation of U87-MG-luc cells into the mouse brain. Then, optical coherence tomography angiography (OCTA) was utilized to characterize the microvasculature progression within 14 days.

RESULTS

The orthotopic glioma mouse model evaluated by bioluminescence imaging and MRI was successfully generated. As the tumor grew, the microvessels within the tumor area slowly decreased, progressing from the center to the periphery for 14 days.

CONCLUSION

This study highlights the potential of OCTA as a useful tool to noninvasively visualize the brain microvascular network at high precision and without any exogenous contrast agents in vivo.

Glioma Stem Cells-Features for New Therapy Design

On a molecular level, glioma is very diverse and presents a whole spectrum of specific genetic and epigenetic alterations. The tumors are unfortunately resistant to available therapies and the survival rate is low. The explanation of significant intra- and inter-tumor heterogeneity and the infiltrative capability of gliomas, as well as its resistance to therapy, recurrence and aggressive behavior, lies in a small subset of tumor-initiating cells that behave like stem cells and are known as glioma cancer stem cells (GCSCs). They are responsible for tumor plasticity and are influenced by genetic drivers. Additionally, GCSCs also display greater migratory abilities. A great effort is under way in order to find ways to eliminate or neutralize GCSCs. Many different treatment strategies are currently being explored, including modulation of the tumor microenvironment, posttranscriptional regulation, epigenetic modulation and immunotherapy.

Understanding the glioblastoma tumor microenvironment: leveraging the extracellular matrix to increase immunotherapy efficacy

Glioblastoma (GBM) accounts for approximately half of all malignant brain tumors, and it remains lethal with a five-year survival of less than 10%. Despite the immense advancements in the field, it has managed to evade even the most promising therapeutics: immunotherapies. The main reason is the highly spatiotemporally heterogeneous and immunosuppressive GBM tumor microenvironment (TME). Accounting for this complex interplay of TME-driven immunosuppression is key to developing effective therapeutics. This review will explore the immunomodulatory role of the extracellular matrix (ECM) by establishing its contribution to the TME as a key mediator of immune responses in GBM. This relationship will help us elucidate therapeutic targets that can be leveraged to develop and deliver more effective immunotherapies.

Immune Escape in Glioblastoma: Mechanisms of Action and Implications for Immune Checkpoint Inhibitors and CAR T-Cell Therapy

Glioblastoma, the most common primary brain cancer in adults, is characterized by a poor prognosis and resistance to standard treatments. The advent of immunotherapy has revolutionized the treatment of several cancers in recent years but has failed to demonstrate benefit in patients with glioblastoma. Understanding the mechanisms by which glioblastoma exerts tumor-mediated immune suppression in both the tumor microenvironment and the systemic immune landscape is a critical step towards developing effective immunotherapeutic strategies. In this review, we discuss the current understanding of immune escape mechanisms in glioblastoma that compromise the efficacy of immunotherapies, with an emphasis on immune checkpoint inhibitors and chimeric antigen receptor T-cell therapy. In parallel, we review data from preclinical studies that have identified additional therapeutic targets that may enhance overall treatment efficacy in glioblastoma when administered alongside existing immunotherapies.

Novel Function of Cancer Stem Cell Marker ALDH1A3 in Glioblastoma: Pro-Angiogenesis through Paracrine PAI-1 and IL-8

Hyper-angiogenesis is a typical feature of glioblastoma (GBM), the most aggressive brain tumor. We have reported the expression of aldehyde dehydrogenase 1A3 (ALDH1A3) in proliferating vasculature in GBM patients. We hypothesized that ALDH1A3 may act as an angiogenesis promoter in GBM. Two GBM cell lines were lentivirally transduced with either ALDH1A3 (ox) or an empty vector (ev). The angiogenesis phenotype was studied in indirect and direct co-culture of endothelial cells (ECs) with oxGBM cells (oxGBMs) and in an angiogenesis model in vivo. Angiogenesis array was performed in oxGBMs. RT2-PCR, Western blot, and double-immunofluorescence staining were performed to confirm the expression of targets identified from the array. A significantly activated angiogenesis phenotype was observed in ECs indirectly and directly co-cultured with oxGBMs and in vivo. Overexpression of ALDH1A3 (oxALDH1A3) led to a marked upregulation of PAI-1 and IL-8 mRNA and protein and a consequential increased release of both proteins. Moreover, oxALDH1A3-induced angiogenesis was abolished by the treatment of the specific inhibitors, respectively, of PAI-1 and IL-8 receptors, CXCR1/2. This study defined ALDH1A3 as a novel angiogenesis promoter. oxALDH1A3 in GBM cells stimulated EC angiogenesis via paracrine upregulation of PAI-1 and IL-8, suggesting ALDH1A3-PAI-1/IL-8 as a novel signaling for future anti-angiogenesis therapy in GBM.

Multi-ligand functionalized blood-to-tumor sequential targeting strategies in the field of glioblastoma nanomedicine

Glioblastoma (GBM) is an unmet clinical need characterized by a standard of care (SOC) 5-year survival rate of only 5%, and a treatment mostly palliative. Significant hurdles in GBM therapies include an effective penetration of therapeutics through the brain protective barrier, namely the blood-brain barrier (BBB), and a successful therapeutic delivery to brain-invading tumor cells post-BBB crossing. These hurdles, along with the poor prognosis and critical heterogeneity of the disease, have shifted attention to treatment modalities with capacity to precisely and sequentially target (i) BBB cells, inducing blood-to-brain transport, and (ii) GBM cells, leading to a higher therapeutic accumulation at the tumor site. This sequential targeting allows therapeutic molecules to reach the brain parenchyma and compromise molecular processes that support tumor cell invasion. Besides improving formulation and pharmacokinetics constraints of drugs, nanomedicines offer the possibility of being surface functionalized with multiple possibilities of targeting ligands, while delivering the desired therapeutic cargos to the biological sites of interest. Targeting ligands exploit the site-specific expression or overexpression of specific molecules on BBB and GBM cells, triggering brain plus tumor transport. Since the efficacy of single-ligand functionalized nanomedicines is limited due to the GBM anatomical site (brain) and disease complexity, this review presents an overview of multi-ligand functionalized, BBB and GBM sequentially- and dual-targeted nanomedicines reported in literature over the last 10 years. The role of the BBB in GBM progression, treatment options, and the multiple possibilities of currently available targeting ligands will be summarized. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Shaping the brain vasculature in development and disease in the single-cell era

The CNS critically relies on the formation and proper function of its vasculature during development, adult homeostasis and disease. Angiogenesis - the formation of new blood vessels - is highly active during brain development, enters almost complete quiescence in the healthy adult brain and is reactivated in vascular-dependent brain pathologies such as brain vascular malformations and brain tumours. Despite major advances in the understanding of the cellular and molecular mechanisms driving angiogenesis in peripheral tissues, developmental signalling pathways orchestrating angiogenic processes in the healthy and the diseased CNS remain incompletely understood. Molecular signalling pathways of the 'neurovascular link' defining common mechanisms of nerve and vessel wiring have emerged as crucial regulators of peripheral vascular growth, but their relevance for angiogenesis in brain development and disease remains largely unexplored. Here we review the current knowledge of general and CNS-specific mechanisms of angiogenesis during brain development and in brain vascular malformations and brain tumours, including how key molecular signalling pathways are reactivated in vascular-dependent diseases. We also discuss how these topics can be studied in the single-cell multi-omics era.

Markedly divergent effects of Ouabain on a Temozolomide-resistant (T98G) vs. a Temozolomide-sensitive (LN229) Glioblastoma cell line

BACKGROUND

Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor with poor prognosis. GMB are highly recurrent mainly because of radio- and chemoresistance. Radiotherapy with Temozolomide (TMZ) is until today the golden standard adjuvant therapy, however, the optimal treatment of recurrent glioblastoma remains controversial. Ouabain belongs to the Cardiotonic Steroids (CTS) the natural ligands of the Na/K-ATPase (NKA). It is established that the NKA represents a signal transducer with either stimulating or inhibiting cell growth, apoptosis, migration and angiogenesis. Over the last decade evidence grew that CTS have anti-tumor properties especially in GBM.

AIM

Proceeding from recent studies we wanted to further demonstrate a divergent effect of Ouabain on a TMZ-resistant (T98G) as compared to a TMZ-sensitive (LN229) GBM cell line.

METHODS

We analyzed the effect of Ouabain on cell migration and plasma cell membrane potential (PCMP) in the LN229 and T98G GBM cell line as well as underlying mechanisms (Bcl-2 and p-Akt/pan-Akt expression). Moreover, we analyzed the anti-angiogenic effect of Ouabain on human umbilical vein endothelial cells (HUVECs).

RESULTS

T98G cells showed a significant inhibition of cell migration and a significant depolarization of the PCMP at similar Ouabain concentrations (IC50 = 1.67 × 10^-7 M) resp. (IC50 = 2.72 × 10^-7 M) with a strong inverse correlation (R² = 0.95). In contrast, LN229 cells did not respond to Ouabain in these assays at all. Similarly, only T98G but not LN229 cells revealed Bcl-2 down-regulation at nanomolar Ouabain concentrations. This unique response to Ouabain is associated with a down-regulation of pan-Akt in T98G cells 24 h after Ouabain (1.0 × 10^-6 M) treatment. For the first time, the anti-angiogenic effect of Ouabain on HUVEC cells (IC50 = 5.49 × 10^-8 M) was demonstrated which correlated strongly with the anti-migratory effect (R² = 0.85).

CONCLUSION

The TMZ-resistant T98G cell line as compared to the TMZ-sensitive LN229 cell line shows a high sensitivity towards Ouabain. We consider it as a promising new compound especially in recurrent GBM to overcome the resistance to TMZ and irradiation.

Pleiotropic effects of the COX-2/PGE2 axis in the glioblastoma tumor microenvironment

Glioblastoma (GBM) is the most common and aggressive form of malignant glioma. The GBM tumor microenvironment (TME) is a complex ecosystem of heterogeneous cells and signaling factors. Glioma associated macrophages and microglia (GAMs) constitute a significant portion of the TME, suggesting that their functional attributes play a crucial role in cancer homeostasis. In GBM, an elevated GAM population is associated with poor prognosis and therapeutic resistance. Neoplastic cells recruit these myeloid populations through release of chemoattractant factors and dysregulate their induction of inflammatory programs. GAMs become protumoral advocates through production a variety of cytokines, inflammatory mediators, and growth factors that can drive cancer proliferation, invasion, immune evasion, and angiogenesis. Among these inflammatory factors, cyclooxygenase-2 (COX-2) and its downstream product, prostaglandin E2 (PGE2), are highly enriched in GBM and their overexpression is positively correlated with poor prognosis in patients. Both tumor cells and GAMs have the ability to signal through the COX-2 PGE2 axis and respond in an autocrine/paracrine manner. In the GBM TME, enhanced signaling through the COX-2/PGE2 axis leads to pleotropic effects that impact GAM dynamics and drive tumor progression.

Implications of Cellular Immaturity in Necrosis and Microvascularization in Glioblastomas IDH-Wild-Type

Necrosis and increased microvascular density in glioblastoma IDH-wild-type are the consequence of both hypoxia and cellular immaturity. Our study aimed to identify the main clinical-imaging and morphogenetic risk factors associated with tumor necrosis and microvascular in the prognosis of patient survival. We performed a retrospective study (10 years) in which we identified 39 cases. We used IDH1, Ki-67 and Nestin immunomarkers, as well as CDKN2A by FISH. The data were analyzed using SPSS Statistics. The clinical characterization identified only age over 50 years as a risk factor (HR = 3.127). The presence of the tumor residue, as well as the absence of any therapeutic element from the trimodal treatment, were predictive factors of mortality (HR = 1.024, respectively HR = 7.460). Cellular immaturity quantified by Nestin was associated with reduced overall survival (p = 0.007). Increased microvascular density was associated with an increased proliferative index (p = 0.009) as well as alterations of the CDKN2A gene (p < 0.001). CDKN2A deletions and cellular immaturity were associated with an increased percentage of necrosis (p < 0.001, respectively, p = 0.017). The main risk factors involved in the unfavorable prognosis are moderate and increased Nestin immunointensity, as well as the association of increased microvascular density with age over 50 years. Necrosis was not a risk factor.

Distribution, Function, and Expression of the Apelinergic System in the Healthy and Diseased Mammalian Brain

Apelin, a peptide initially isolated from bovine stomach extract, is an endogenous ligand for the Apelin Receptor (APLNR). Subsequently, a second peptide, ELABELA, that can bind to the receptor has been identified. The Apelin receptor and its endogenous ligands are widely distributed in mammalian organs. A growing body of evidence suggests that this system participates in various signaling cascades that can regulate cell proliferation, blood pressure, fluid homeostasis, feeding behavior, and pituitary hormone release. Additional research has been done to elucidate the system's potential role in neurogenesis, the pathophysiology of Glioblastoma multiforme, and the protective effects of apelin peptides on some neurological and psychiatric disorders-ischemic stroke, epilepsy, Parkinson's, and Alzheimer's disease. This review discusses the current knowledge on the apelinergic system's involvement in brain physiology in health and disease.

Glioblastoma-Specific Strategies of Vascularization: Implications in Anti-Angiogenic Therapy Resistance

Angiogenesis has long been implicated as a crucial process in GBM growth and progression. GBM can adopt several strategies to build up its abundant and aberrant vasculature. Targeting GBM angiogenesis has gained more and more attention in anti-cancer therapy, and many strategies have been developed to interfere with this hallmark. However, recent findings reveal that the effects of anti-angiogenic treatments are temporally limited and that tumors become refractory to therapy and more aggressive. In this review, we summarize the GBM-associated neovascularization processes and their implication in drug resistance mechanisms underlying the transient efficacy of current anti-angiogenic therapies. Moreover, we describe potential strategies and perspectives to overcome the mechanisms adopted by GBM to develop resistance to anti-angiogenic therapy as new potential therapeutic approaches.

CD93 is Associated with Glioma-related Malignant Processes and Immunosuppressive Cell Infiltration as an Inspiring Biomarker of Survivance

Previous reports have confirmed the significance of CD93 in the progression of multiple tumors; however, there are few studies examining its immune properties for gliomas. Here, we methodically investigated the pathophysiological characteristics and clinical manifestations of gliomas. Six hundred ninety-nine glioma patients in TCGA along with 325 glioma patients in CGGA were correspondingly collected for training and validating. We analyzed and visualized total statistics using RStudio. One-way ANOVA and Student's t-test were used to assess groups' differences. All differences were considered statistically significant at the level of P < 0.05. CD93 markedly upregulated among HGG, MGMT promoter unmethylated subforms, IDH wild forms, 1p19q non-codeletion subforms, and mesenchyme type gliomas. ROC analysis illustrated the favorable applicability of CD93 in estimating mesenchyme subform. Kaplan-Meier curves together with multivariable Cox analyses upon survivance identified high-expression CD93 as a distinct prognostic variable for glioma patients. GO analysis of CD93 documented its predominant part in glioma-related immunobiological processes and inflammation responses. We examined the associations of CD93 with immune-related meta-genes, and CD93 positively correlated with HCK, LCK, MHC I, MHC II, STAT1 and IFN, while adverse with IgG. Association analyses between CD93 and gliomas-infiltrating immunocytes indicated that the infiltrating degrees of most immunocytes exhibited positive correlations with CD93, particularly these immunosuppressive subsets such as TAM, Treg, and MDSCs. CD93 is markedly associated with adverse pathology types, unfavorable survival, and immunosuppressive immunocytes infiltration among gliomas, thus identifying CD93 as a practicable marker and a promising target for glioma-based precise diagnosis and therapeutic strategies.