Gut microbiota alterations affect glioma growth and innate immune cells involved in tumor immunosurveillance in mice.

Glioma is a CNS tumor with few therapeutic options. Recently, host microbiota has been involved in the immune modulation of different tumors, but no data are available on the possible effects of the gut-immune axis on brain tumors. Here, we investigated the effect of gut microbiota alteration in a syngeneic (GL261) mouse model of glioma, treating mice with two antibiotics (ABX) and evaluating the effects on tumor growth, microbe composition, natural killer (NK) cells and microglia phenotype. We report that ABX treatment (i) altered the intestinal microbiota at family level, (ii) reduced cytotoxic NK cell subsets, and (iii) altered the expression of inflammatory and homeostatic proteins in microglia. All these findings could contribute to the increased growth of intracranial glioma that was observed after ABX treatment. These results demonstrate that chronic ABX administration alters microbiota composition and contributes to modulate brain immune state paving the way to glioma growth.

Microbiota and glioma: a new perspective from association to clinical translation.

Gliomas pose a significant challenge in oncology due to their malignant nature, aggressive growth, frequent recurrence, and complications posed by the blood-brain barrier. Emerging research has revealed the critical role of gut microbiota in influencing health and disease, indicating its possible impact on glioma pathogenesis and treatment responsiveness. This review focused on existing evidence and hypotheses on the relationship between microbiota and glioma from progression to invasion. By discussing possible mechanisms through which microbiota may affect glioma biology, this paper offers new avenues for targeted therapies and precision medicine in oncology.

Discussion on the relationship between gut microbiota and glioma through Mendelian randomization test based on the brain gut axis.

BACKGROUND: In the realm of Gut-Brain axis research, existing evidence points to a complex bidirectional regulatory mechanism between gut microbiota and the brain. However, the question of whether a causal relationship exists between gut microbiota and specific types of brain tumors, such as gliomas, remains unresolved. To address this gap, we employed publicly available Genome-Wide Association Study (GWAS) and MIOBEN databases, conducting an in-depth analysis using Two-Sample Mendelian Randomization (MR). METHOD: We carried out two sets of MR analyses. The preliminary analysis included fewer instrumental variables due to a high genome-wide statistical significance threshold (5×10-8). To enable a more comprehensive and detailed analysis, we adjusted the significance threshold to 1×10-5. We performed linkage disequilibrium analysis (R2 <0.001, clumping distance = 10,000kb) and detailed screening of palindromic SNPs, followed by MR analysis and validation through sensitivity analysis. RESULTS: Our findings reveal a causal relationship between gut microbiota and gliomas. Further confirmation via Inverse Variance Weighting (IVW) identified eight specific microbial communities related to gliomas. Notably, the Peptostreptococcaceae and Olsenella communities appear to have a protective effect, reducing glioma risk. CONCLUSION: This study not only confirms the causal link between gut microbiota and gliomas but also suggests a new avenue for future glioma treatment.

Modification of redox processes in astroglial cells induced by microbial and viral infections.

BACKGROUND: The authors hypothesized that the cell redox state might be modified during microbial and viral infections. To detect and evaluate changes in astroglial cell redox state, rat C6 glioma cells after exposure to lipopolysaccharide (LPS) or after herpes simplex virus type 1 (HSV-1) inoculation were used. Redox state modification of glioma cells was determined by the change in menadione-induced superoxide yield. MATERIAL/METHODS: Menadione-induced superoxide formation was registered by the lucigenin-enhanced chemiluminescence (CL) method. RESULTS: The results demonstrate that exposure of C6 glioma cells to LPS for 24 hours resulted in a dose-dependent increase in the mitotic index and integral intensity of menadione-induced lucigenin-enhanced CL. Menadione-induced ROS generation in C6 cells during HSV-1 infection changed depending on the time after HSV-1 inoculation. CONCLUSIONS: The redox state of astroglial cells is modified during microbial and viral infections. The use of redox-active quinones is an informative model for determining cell redox state change and analyzing cells' functional state.

Glioma and temozolomide induced alterations in gut microbiome.

The gut microbiome is fundamental in neurogenesis processes. Alterations in microbial constituents promote inflammation and immunosuppression. Recently, in immune-oncology, specific microbial taxa have been described to enhance the effects of therapeutic modalities. However, the effects of microbial dysbiosis on glioma are still unknown. The aim of this study was to explore the effects of glioma development and Temozolomide (TMZ) on fecal microbiome in mice and humans. C57BL/6 mice were implanted with GL261/Sham and given TMZ/Saline. Fecal samples were collected longitudinally and analyzed by 16S rRNA sequencing. Fecal samples were collected from healthy controls as well as glioma patients at diagnosis, before and after chemoradiation. Compared to healthy controls, mice and glioma patients demonstrated significant differences in beta diversity, Firmicutes/Bacteroides (F/B) ratio, and increase of Verrucomicrobia phylum and Akkermansia genus. These changes were not observed following TMZ in mice. TMZ treatment in the non-tumor bearing mouse-model diminished the F/B ratio, increase Muribaculaceae family and decrease Ruminococcaceae family. Nevertheless, there were no changes in Verrucomicrobia/Akkermansia. Glioma development leads to gut dysbiosis in a mouse-model, which was not observed in the setting of TMZ. These findings seem translational to humans and warrant further study.

MicroRNA-133b expression associates with clinicopathological features and prognosis in glioma.

BACKGROUND: Recently, microRNA-133b (miR-133b) dysregulation has been shown to play a key role in several human cancers, as well as glioma. In this study, we aimed to investigate the clinical significance and prognostic value of miR-133b in glioma. METHODS: Real-time quantitative PCR was employed to measure the expression level of miR-133b in tissues. Survival analysis was carried out by using the log-rank test and Kaplan-Meier method. Prognostic factors for overall survival were identified by univariate and multivariate analyses using the Cox proportional hazards regression model. RESULTS: The expression level of miR-133b was significantly lower in glioma tissues compared with matched non-cancerous brain tissues (p < .05). Its level was strongly correlated with Karnofsky Performance Scale score (p < .001) and WHO grade (p < .001). Kaplan-Meier survival and log-rank analysis indicated that the decreased expression of miR-133b was strongly correlated with shorter overall survival of patients with glioma (log-rank test, p = .03). CONCLUSIONS: The current investigation demonstrated that miR-133b level is useful for predicting the prognosis of patients with glioma.

Amount of satellite DNA in four experimentally induced tumors of the central nervous system. Quantitative changes in a glioblastoma producing C-type particles.

The quantitative preservation of satellite NA was studied in several central nervous system (CNS) neoplasms; four tumor lines deriveo from 3-methylcholanthrene implantation into the CNS of mice were compared with brain and tissue cultures of normal mouse cells by analytical centrifugation in cesium chlorie. Three tumors showed no detectable difference from normal cells; nuclear and whole cell preparations were comparable. Only a glioblastoma line proucing C-type particles (TC509) revealed a significant difference from normal cells and exhibited a decrease of approximately 20% in satellite DNA or 2% of the total DNA on repeated examination for 1 year. C-type RNA virus may be related to relative decreases in satellite DNA observed in TC509.

Spatial distribution of proliferating cells in avian sarcoma virus-induced gliomas.

We studied the regional distribution of proliferating tumor cells in five avian sarcoma virus-induced gliomas. The labeling index and spatial distribution of [3H]thymidine (dThd)-labeled tumor cells were determined in serial sections of each tumor with a computer-assisted digitizing system. The density of [3H]dThd-labeled cells showed marked regional variation in each tumor, and the ratio of the density of [3H]dThd-labeled cells in tumor periphery to tumor center varied from 0.86 to 1.38. The labeling index generally, but not always, reflected [3H]dThd-labeled cell density. This study indicates that proliferating pools of glioma tumor cells exhibit regional variability in concentration and that the highest numbers of proliferating cells may be predominantly located in central regions of tumor and not in tumor periphery as assumed previously. In all tumors, large numbers of proliferating cells were present in all parts of the tumor.

Space-time clustering patterns of gliomas in The Netherlands suggest an infectious aetiology.

To test the hypothesis that infectious exposures may be involved in glioma aetiology, we have analysed space-time clustering and seasonal variation using population-based data from the South of The Netherlands between 1983 and 2001. Knox tests for space-time interactions between cases were applied, with spatial coordinates of the addresses at time of diagnosis, and with distance to the Nth nearest neighbour. Data were also analysed by a second order procedure based on K-functions. Tests for heterogeneity and Edwards' test for sinusoidal variation were applied to examine seasonal variation of incidence. There was statistically significant space-time clustering in the Eastern, but not in the Western part of the region. Clustering was only present in adults, particularly in less densely populated areas. There was no evidence for seasonal variation. The results support a role for infectious exposures in glioma aetiology that may act preferentially in certain geographical areas.

Infection of human brain cells by HIV-1: restricted virus production in chronically infected human glial cell lines.

OBJECTIVE: To study expression of HIV-1 in human glial cell lines. DESIGN: Chronically HIV-1-infected glial cell lines were established to evade potential artefacts resulting from unphysiological viral entry (i.e., transfection). These cell lines were used to study viral expression and regulation. METHODS: Chronically infected glial cell lines were established by terminal dilution cloning of human glioma cells exposed to HIV-1. Virus production and expression were assayed by measuring reverse transcriptase activity, p24-antigen levels and syncytia-inducing capacity in C8166 target cells (extracellular), or by indirect immunoperoxidase staining, immunoblot analysis, and p24- and Nef-antigen-capture enzyme-linked immunosorbent assays (intracellular). HIV-long terminal repeat (LTR)-dependent expression of the chloramphenicol acetyltransferase reporter gene was determined in transient transfection assays. RESULTS: Culture supernatant from chronically HIV-1-infected glial cells contained only low levels of virus compared with chronically HIV-infected fibroblasts and T-lymphoma cells. Detailed study of HIV-antigen expression in representative glial cell line TH4-7-5 indicated the presence of all major structural proteins, albeit at low levels, and of Vif, Tat, Rev and Nef. Intracellular levels of Nef exceeded p24-antigen levels by approximately 10-fold. Virus was recovered from TH4-7-5 cells by cocultivation with blood-derived target cells, indicating that low-level virus production is not due to defective provirus. Prominent negative regulatory element (NRE)-mediated suppression of exogenous HIV-LTR activity was observed in TH4-7-5 cells and was unequalled by chronically HIV-producing fibroblast cells or by uninfected fibroblast and glial cells. CONCLUSIONS: Our results suggest that restricted virus production by chronically infected glial cells involves LTR-mediated regulation of virus expression.

Replication of measles virus in a cell culture from a glioblastoma of human origin.

A cell culture from a glioblastoma of human origin infected with the Edmonston strain of measles virus produced and released infectious measles virus. All cellular types seemed to be involved in the process of virus replication. Staining with hematin-eosin revealed the presence of eosinophilic intracytoplasmic and intranuclear inclusions. Examination with the electron microscope revealed viral nucleocapsids in the cytoplasm and, rarely, in the nuclei of infected cells.

Morphogenesis of measles virus on C6 rat glioma cells.

Rat glioma cells (C6) persistently infected with measles virus show a locally dissociated distribution of budding processes at the cell surface.

Presence and absence of virus particles in hybridomas secreting monoclonal antibodies against gliomas.

Hybridoma clones were produced by fusion of splenocytes from glioma-immunized hosts and the X63-Ag8.653 mouse myeloma line and Y3-Ag.1.2.3. rat myeloma line. Oncornavirus particles were found in all clones descending from the mouse myeloma line. No virus particles could be found in either the spleens of immunized Balb/c mice and Fischer rats or in the rat myeloma line and the hybridomas derived from it.

Falsification of tetrazolium dye (MTT) based cytotoxicity assay results due to mycoplasma contamination of cell cultures.

Mycoplasma contamination of cell cultures is a frequently observed problem. Due to the inconspicuous growth in cell cultures, periodical screening procedures represent the only protection. Many influences of mycoplasma on cell culture parameters have been described. We addressed the question of whether mycoplasma contamination affects the most frequently used cytotoxicity assay, the tetrazolium based MTT assay. We contaminated C6 glioma cells with mycoplasma and performed MTT assays with doxorubicin, vincristine, etoposide and cisplatinum under various conditions. Contaminated cells demonstrated significant different results when tested with the MTT assay than mycoplasma free controls. Differences were not detectable when cells were counted as toxicity assay. Due to an additional reduction of tetrazolium by mycoplasmas, contaminated cells appeared up to 15 fold resistant to doxorubicin, vincristine and etoposide, but not to cisplatinum. Differences decreased with decreasing drug doses and decreasing plated cell count. Our findings confirm the compelling need for periodical mycoplasma screening, especially when tetrazolium based cytotoxicity assay (MTT) are used.

Studies on interactions of dTK-HSV mutants with neurons in vitro.

Thymidine kinase negative (dTK-) mutants of herpes simplex virus type 1 (HSV-1) multiplied well in rat brain glioma cells. A proportion (less than 1%) of glioma cells survived the infection with HSV and were designated "survivor" glioma cells. Survivor cells of dTK- mutant virus infection ceased to produce infectious virus after two passages and were highly resistant to both HSV-1 and HSV-2 but not to vesicular stomatitis virus (VSV). Flow cytometric studies indicated morphological differences between parental and survivor glioma cells, and HSV-1 specific antigens as well as DNA were detected in the survivor glioma cells, but only in early passages. Sensitivity to superinfection with HSV appears to correlate to loss of HSV-specific viral DNA in the survivor glioma cells. Survivor glioma cells after several subcultures lost their ability to resist superinfecting HSV, reverted morphologically to the appearance of parental glioma cells and also lost significant amount of HSV-1 specific DNA. These transient survivor glioma cells became persistently infected-virus producer cells upon HSV infection.

Differential susceptibility of a rat glioma cell line and its clones to herpes simplex virus types 1 and 2.

A rat glioma cell line, C6-BU-1, showed differential susceptibility to herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2), namely, all the HSV-1 strains tested so far persisted in this cell line but the HSV-2 strains did not. Two clones were derived from C6-BU-1 cells and designated C-17 and C-72. The C-72 as well as the parental C6-BU-1 cells supported the replication of HSV-1, but not that of HSV-2. In contrast, C-17 was highly resistant to both HSV-1 and HSV-2. Hydrocortisone treatment converted C-17 to being susceptible to HSV-1, but not to HSV-2. Therefore, C6-BU-1 cells consist of subpopulations heterogeneous in susceptibility to HSV-1 which may be possibly interchangeable.

[Reproduction of Japanese encephalitis virus in human glioma cells, 118MGC: inhibitory effect of host factor(s)].

Japanese encephalitis viruses (JEV) were well propagated in human glioma cells, 118MGC until the first 24 hrs after virus infection. However, after 24 hrs, virus growth rate was quickly reduced. This unusual pattern of virus growth was different from the cases in others cells, e.g. IMR-32, Vero and C6/36 cells. The fact that actinomycin-D retained the high yields of JEV in 118MGC cells suggests that some suppressing factors against JEV replication are produced in MGC cells. Interestingly, culture fluids of 118MGC cells indicated inhibitory effect to JEV reproduction, but other culture fluids from several cell lines had no effect. This inhibitory effect of the MGC-culture fluids was lost by heat-treatment at 60 C. In addition, the infectivity of JEV was rapidly decreased by the incubation with MGC-culture fluids. These findings suggest that 118MGC cells produce and secret some inhibitory factors against JEV replication.

[Type-C viral particles in cell cultures of chemically induced glioma in Sprague-Dawley rats]. / Virusnye chastitsy tipa C v kul'turakh kletok khimicheski vyzvannoi gliomy u krysy linii Sprague-Dawley.

Long-term cultures of a glioma induced in a Sprague-Dawley rat exposed to methylnitrosourea were examined by thin-section electron microscopy. Budding and extracellular lying C-type virus particles were numerous in several samples of the highpassage cultures. This is the first report of a chemically induced rat glioma associated with C-type virus particles. Studies with an aim to characterize this rat glioma associated virus are in progress.