Implications of a granulocyte-high glioblastoma microenvironment in immune suppression and therapy resistance†

Insights of immune cell heterogeneity, tumor-initiated subtype transformation, drug resistance, treatment and detecting technologies in glioma microenvironment

BACKGROUND

With the gradual understanding of glioma development and the immune microenvironment, many immune cells have been discovered. Despite the growing comprehension of immune cell functions and the clinical application of immunotherapy, the precise roles and characteristics of immune cell subtypes, how glioma induces subtype transformation of immune cells and its impact on glioma progression have yet to be understood.

AIM OF THE REVIEW

In this review, we comprehensively center on the four major immune cells within the glioma microenvironment, particularly neutrophils, macrophages, lymphocytes, myeloid-derived suppressor cells (MDSCs), and other significant immune cells. We discuss (1) immune cell subtype markers, (2) glioma-induced immune cell subtype transformation, (3) the mechanisms of each subtype influencing chemotherapy resistance, (4) therapies targeting immune cells, and (5) immune cell-associated single-cell sequencing. Eventually, we identified the characteristics of immune cell subtypes in glioma, comprehensively summarized the exact mechanism of glioma-induced immune cell subtype transformation, and concluded the progress of single-cell sequencing in exploring immune cell subtypes in glioma.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In conclusion, we have analyzed the mechanism of chemotherapy resistance detailly, and have discovered prospective immunotherapy targets, excavating the potential of novel immunotherapies approach that synergistically combines radiotherapy, chemotherapy, and surgery, thereby paving the way for improved immunotherapeutic strategies against glioma and enhanced patient outcomes.

Causal Association Between Sleep Deprivation and Glioblastoma Risk: Insights from Multi-Omics Analysis

Emerging evidence suggests that sleep deprivation may contribute to cancer risk. However, the genetic association between sleep deprivation and glioblastoma (GBM) remains unexplored. This study aimed to investigate the causal relationship between sleep traits and GBM using genome-wide association study (GWAS) data of sleep duration, sleeplessness, GBM, and immune cell traits from the UK Biobank and FinnGen databases. Mendelian randomization (MR) analyses were conducted to assess potential causal links between sleep traits and GBM risk. Mediation analysis was performed to identify immune mediators affected by sleep duration that might influence GBM development. Single-nucleus RNA sequencing (snRNA-seq) was utilized to examine cellular subpopulation changes in brain tissue from sleep-deprived (SD) and ad libitum sleep mice. Additionally, a mouse model of sleep deprivation was established for transcriptomic analysis. We found a significant causal association between reduced sleep duration and increased GBM risk (IVW OR = 6.000 × 10-5, P = 0.003, Bonferroni P = 0.025). Sleeplessness also emerged as a potential risk factor for GBM (OR-IVW = 20.221, P = 0.038). Mediation analysis identified CD80 expression on plasmacytoid dendritic cells (pDCs) as a mediator in the association between sleep duration and GBM, with a mediation effect of 0.256. SnRNA-seq confirmed significant alterations in CD80 + pDCs in sleep-deprived mice. Transcriptomic analysis of SD mice demonstrated upregulation of GBM-related markers (Egfr, Tert, and Mgmt) and associated signaling pathways. These findings suggest a potential causal link between insufficient sleep and increased GBM risk, highlighting the importance of sleep management for GBM patients.

Angiogenesis in Glioblastoma-Treatment Approaches

Glioblastoma, the most common primary malignant brain tumor in adults, carries a poor prognosis, with a median survival of just 15 months, significantly impacting patients' quality of life. The aggressive growth of these highly vascularized tumors relies heavily on angiogenesis, driven primarily by vascular endothelial growth factor-A. Therefore, VEGF signaling pathway has become a prime therapeutic target in GBM treatment over the past decade. While anti-angiogenic treatment showed promise, agents like bevacizumab have ultimately failed to improve overall survival. This highlights the presence of compensatory angiogenic mechanisms that bypass VEGF inhibition, necessitating further investigation into resistance mechanisms and the development of more effective therapeutic strategies. This review examined the current landscape of anti-angiogenic agents for GBM, analyzed the mechanisms driving resistance to these therapies, and explored potential strategies for enhancing their effectiveness.

Pericytes in Glioblastoma: Hidden Regulators of Tumor Vasculature and Therapy Resistance

Glioblastoma IDH wild type (GB), the most common malignant primary brain tumor, is characterized by rapid proliferation, extensive infiltration into surrounding brain tissue, and significant resistance to current therapies. Median survival is only 15 months despite extensive clinical efforts. The tumor microenvironment (TME) in GB is highly specialized, supporting the tumor's aggressive behavior and its ability to evade conventional treatments. One critical component is the aberrant vascular network that complicates the delivery of chemotherapy across the blood-brain barrier. Antiangiogenic therapies emerged as a promising option but have shown limited efficacy in extending the survival of these patients. Comprehension of the complex vascular network of GB may be a key to overcoming the limitations of current therapies. Pericytes are gaining recognition within the context of the TME. These mural cells are essential for vascular integrity and may contribute to tumor progression and therapeutic resistance. Although their role has been evidenced in other tumors, they remain underexplored in GB. Pericytes are known to respond to tumor hypoxia and interact with vascular endothelia, influencing responses to DNA damage and antiangiogenic treatments. They actively regulate not only angiogenesis but also the different vasculogenic strategies for tumor neovascularization. Additionally, they affect leukocyte trafficking and tumor-associated macrophages. This review aims to integrate the various functions controlled by pericytes to favor deeper investigation into their actionable potential. Pericytes may represent a promising target for novel therapeutic strategies in order to improve patient outcomes.

Vascular Normalization: A New Window Opened for Cancer Therapies

Preclinical and clinical antiangiogenic approaches, with multiple side effects such as resistance, have not been proved to be very successful in treating tumor blood vessels which are important targets for tumor therapy. Meanwhile, restoring aberrant tumor blood vessels, known as tumor vascular normalization, has been shown not only capable of reducing tumor invasion and metastasis but also of enhancing the effectiveness of chemotherapy, radiation therapy, and immunotherapy. In addition to the introduction of such methods of promoting tumor vascular normalization such as maintaining the balance between proangiogenic and antiangiogenic factors and targeting endothelial cell metabolism, microRNAs, and the extracellular matrix, the latest molecular mechanisms and the potential connections between them were primarily explored. In particular, the immunotherapy-induced normalization of blood vessels further promotes infiltration of immune effector cells, which in turn improves immunotherapy, thus forming an enhanced loop. Thus, immunotherapy in combination with antiangiogenic agents is recommended. Finally, we introduce the imaging technologies and serum markers, which can be used to determine the window for tumor vascular normalization.