Glioma is the most malignant primary tumor of the central nervous system and is characterized by an extremely low overall survival. Recent breakthroughs in cancer therapy using immune checkpoint blockade have attracted significant attention. However, despite representing the most promising (immunotherapy) treatment for cancer, the clinical application of immune checkpoint blockade in glioma patients remains challenging due to the “cold phenotype” of glioma and multiple factors inducing resistance, both intrinsic and acquired. Therefore, comprehensive understanding of the tumor microenvironment and the unique immunological status of the brain will be critical for the application of glioma immunotherapy. More sensitive biomarkers to monitor the immune response, as well as combining multiple immunotherapy strategies, may accelerate clinical progress and enable development of effective and safe treatments for glioma patients.

Background: Inhibition of p38 MAPK signalling leads to glioblastoma multiform (GBM) tumourigenesis. Nevertheless, the molecular mechanism that induces p38 MAPK signalling pathway silencing during GBM genesis has yet to be determined. Identifying new factors that can regulate p38 MAPK signalling is important for tumour treatment. Methods: Flow cytometry, TUNEL assays, immunofluorescence, JC-1 assays, and western blot analyses were used to detect the apoptosis of GBM cells. The specific methods used to detect autophagy levels in GBM cells were western blot analysis, LC3B protein immunofluorescence, LC3B puncta assays and transmission electron microscopy. The functions of these critical molecules were further confirmed in vivo by intracranial xenografts in nude mice. Tumour tissue samples and clinical information were used to identify the correlation between RND2 and p62 and LC3B expression, survival time of patients, and tumour volumes in clinical patients. Results: By summarizing data from the TCGA database, we found that expression of the small GTPase RND2 was significantly increased in human glioblastomas. Our study demonstrated that RND2 functions as an endogenous repressor of the p38 MAPK phosphorylation complex. RND2 physically interacted with p38 and decreased p38 phosphorylation, thereby inhibiting p38 MAPK signalling activities. The forced expression of RND2 repressed p38 MAPK signalling, which inhibited glioblastoma cell autophagy and apoptosis in vitro and induced tumour growth in the xenografted mice in vivo. By contrast, the downregulation of RND2 enhanced p38 MAPK signalling activities and promoted glioma cell autophagy and apoptosis. The inhibition of p38 phosphorylation abolished RND2 deficiency-mediated GBM cell autophagy and apoptosis. Most importantly, our study found that RND2 expression was inversely correlated with patient survival time and was positively correlated with tumour size. Conclusions: Our findings revealed a new function for RND2 in GBM cell death and offered mechanistic insights into the inhibitory effects of RND2 with regard to the regulation of p38 MAPK activation.

Glioma is the most common and aggressive tumor type of the central nervous system and is associated with poor prognosis. To date, novel emerging immunotherapies have significantly improved outcomes for patients with various cancer types. Human endogenous retrovirus-H long terminal repeat-associating protein 2 (HHLA2), a newly discovered immune checkpoint molecule, has demonstrated its potential as a novel therapeutic target. Therefore, the present study aimed to investigate the clinical prognostic value of HHLA2 in gliomas and its mechanistic role. A systematic review of datasets from The Cancer Genome Atlas was performed. The RNA-seq data of a total of 669 cases were analyzed and the biological function of HHLA2 was predicted by Gene Ontology (GO) and pathway enrichment analysis. Immunohistochemistry labelling images for HHLA2 was obtained from the Human Protein Atlas. xCell was used to comprehensively analyze the model of tumor-infiltrating immune cell in glioma. The Cox proportional hazards regression model was used to predict outcomes for glioma patients. The results revealed that the expression levels of HHLA2 were significantly lower in high-grade glioma, as well as glioma with wild-type isocitrate dehydrogenase, no deletion of 1p/19q and telomerase reverse transcriptase promoter mutation. Receiver operating characteristic analysis revealed that HHLA2 was a predictor of the neural subtype. The tumor-infiltrating immune cell model indicated that HHLA2 was negatively associated with tumor-associated macrophages. GO analysis and pathway enrichment analysis revealed that HHLA2-associated genes were functionally involved in inhibition of neoplasia-associated processes. HHLA2 was significantly negatively correlated with certain genes, including interleukin-10, transforming growth factor-β, vascular endothelial growth factor and δ-like canonical Notch ligand 4, and other immune checkpoint molecules, including programmed cell death 1, lymphocyte activating 3 and CD276. Survival analysis indicated that high expression of HHLA2 predicted a favorable prognosis. In conclusion, the present study revealed that upregulation of HHLA2 is significantly associated with a favorable outcome for patients with glioma. Targeting HHLA2 as an immune stimulator may become a valuable approach for the treatment of glioma in clinical practice.

Identifying circulating glioma cells and their clusters as diagnostic markers by a novel detection platformDear editor:Diffused glioma is the leading cause of central nervous system tumor-related deaths worldwide. 1 As a non-invasive and convenient bio-marker, despite that circulating tumor cells (CTC) and their clusters show great feasibility in tumor diagnosis and management, 2 their isolation and identification remain challenging, limiting further clinical application. [3][4][5][6][7] Therefore, more efficient detection platforms are urgently required in this field. This inspired us to fabricate a novel platform to detect circulating glioma cells and their clusters for further evaluated their value in tumor diagnosis and management, and highlight the wider potential of CTC for clinical application.In this study, we performed a novel isolation method by size of epithelial tumor cells device. The isolation is carried out using a biocompatible parylene polymer membrane with a pore diameter of 8 μm under a high flow rate, enriching for CTCs without requiring tumor cell-specific capture antibodies.To test the capture efficiency of this device, two common malignant glioma cell lines, U87 and U251, were selected and spiked into healthy donors' blood samples. In detecting spiked U87 cells from blood samples at concentrations of 5, 10, 20, 50, 100, and 150 cells per 5 ml, the capture efficiency were 86.0%, 87.0%, 86.5%, 86.0%, 91.3%, and 92.9%, respectively. The capture efficiency were 80.0%, 77.0%, 81.5%, 78.6%, 84.3%, and 86.2% when detecting U251 cells from blood samples at above concentrations (Figure 1A-C). Besides, CTC cluster was not observed in any test, confirming that it was not artifact.We then investigate feasible identification methods for glioma CTC. Our data showed that Wright's staining, one convincing and feasible identification method, 8 could not distinguish glioma CTC from other brain tumors', indicating that identification methods based on tumor features cannot define CTC origin, which limit its diagnostic value (Figure 4A-C; Tables S1 and S2). However, highly specific identification methods targeted GBM-derived CTC, represented by STEAM staining, an antibody cocktail basedThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Liquid biopsy has entered clinical applications for several cancers, including metastatic breast, prostate, and colorectal cancer for CTC enumeration and NSCLC for EGFR mutations in ctDNA, and has improved the individualized treatment of many cancers, but relatively little progress has been made in validating circulating biomarkers for brain malignancies. So far, data on circulating tumor cells about glioma are limited, the application of circulating tumor cells as biomarker for glioma patients has only just begun. This article reviews the research status and application prospects of circulating tumor cells in gliomas. Several detection methods and research results of circulating tumor cells about clinical research in gliomas are briefly discussed. The wide application prospect of circulating tumor cells in glioma deserves further exploration, and the research on more sensitive and convenient detection methods is necessary.