Glioblastoma-initiating cell heterogeneity generated by the cell-of-origin, genetic/epigenetic mutation and microenvironment

HAS2 facilitates glioma cell malignancy and suppresses ferroptosis in an FZD7-dependent manner

Glioma is the most common malignant tumor in the central nervous system, and it is crucial to uncover the factors that influence prognosis. In this study, we utilized Mfuzz to identify a gene set that showed a negative correlation with overall survival in patients with glioma. Gene Ontology (GO) enrichment analyses were then undertaken to gain insights into the functional characteristics and pathways associated with these genes. The expression distribution of Hyaluronan Synthase 2 (HAS2) was explored across multiple datasets, revealing its expression patterns. In vitro and in vivo experiments were carried out through gene knockdown and overexpression to validate the functionality of HAS2. Potential upstream transcription factors of HAS2 were predicted using transcriptional regulatory databases, and these predictions were experimentally validated using ChIP-PCR and dual-luciferase reporter gene assays. The results showed that elevated expression of HAS2 in glioma indicates poor prognosis. HAS2 was found to play a role in activating an antiferroptosis pathway in glioma cells. Inhibiting HAS2 significantly increased cellular sensitivity to ferroptosis-inducing agents. Finally, we determined that the oncogenic effect of HAS2 is mediated by the key receptor of the WNT pathway, FZD7.

Enhancing Temozolomide (TMZ) chemosensitivity using CRISPR-dCas9-mediated downregulation of O6-methylguanine DNA methyltransferase (MGMT)

PURPOSE

Glioblastoma (GBM) stands out as the most prevalent and aggressive intracranial tumor, notorious for its poor prognosis. The current standard-of-care for GBM patients involves surgical resection followed by radiotherapy, combined with concurrent and adjuvant chemotherapy using Temozolomide (TMZ). The effectiveness of TMZ primarily relies on the activity of O6-methylguanine DNA methyltransferase (MGMT), which removes alkyl adducts from the O6 position of guanine at the DNA level, thereby counteracting the toxic effects of TMZ.

METHOD

In this study, we employed fusions of catalytically-inactive Cas9 (dCas9) to DNA methyltransferases (dCas9-DNMT3A) to selectively downregulation MGMT transcription by inducing methylation at MGMT promoter and K-M enhancer.

RESULT

Our findings demonstrate a significant reduction in MGMT expression, leading to intensified TMZ sensitivity in the HEK293T cell line.

CONCLUSION

This study serves as a proof of concept for the utilization of CRISPR-based gene suppression to overcome TMZ resistance and enhance the lethal effect of TMZ in glioblastoma tumor cells.

AMPK-mediated CD47 H3K4 methylation promotes phagocytosis evasion of glioma stem cells post-radiotherapy

Radiotherapy alters the tumor microenvironment and reprograms cellular metabolism. Transition of tumor cell phenotypes contributes to post-radiotherapy tumor recurrence. Low radiosensitivity of glioma stem cells is one of the reasons for radiotherapy failure. Here, we found that radiotherapy resulted in a higher proportion of infiltration of inflammatory macrophages in glioma non-stem cell grafts compared with that in glioma stem cell-transplanted tumors in a mouse model, where immunosuppressive macrophages dominated in the tumor microenvironment. In radioresistant glioma stem cells, ionizing radiation upregulated CD47 expression by AMP-activated protein kinase (AMPK), resulting in the inhibition of phagocytosis and the promotion of M2-like polarization in macrophages. Ionizing radiation promoted H3K4 methylation on CD47 promotor by downregulating KDM5A. Hyper-phosphorylated retinoblastoma protein RB maintained its dissociation status with KDM5A following AMPK activation, which inhibited the demethylated function of KDM5A. In contrast, in radiosensitive glioma non-stem cells, RB S807/S811 hypo-phosphorylation contributed to the binding of RB with KDM5A, which suppressed H3K4 methylation on CD47 promotor. In addition, ionizing radiation promoted H3K27 acetylation on CD47 promotor by HDAC7 in glioma stem cells. These data suggested that glioma stem cells reprogrammed the tumor immune microenvironment by epigenetic editing to escape macrophage phagocytosis after ionizing radiation. Targeting CD47 might be a potential strategy to sensitize glioblastoma to radiotherapy.

Lipid-based nanoparticles to address the limitations of GBM therapy by overcoming the blood-brain barrier, targeting glioblastoma stem cells, and counteracting the immunosuppressive tumor microenvironment

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor, characterized by high heterogeneity, strong invasiveness, poor prognosis, and a low survival rate. A broad range of nanoparticles have been recently developed as drug delivery systems for GBM therapy owing to their inherent size effect and ability to cross the blood-brain barrier (BBB). Lipid-based nanoparticles (LBNPs), such as liposomes, solid lipid NPs (SLNs), and nano-structured lipid carriers (NLCs), have emerged as the most promising drug delivery system for the treatment of GBM because of their unique size, surface modification possibilities, and proven bio-safety. In this review, the main challenges of the current clinical treatment of GBM and the strategies on how novel LBNPs overcome them were explored. The application and progress of LBNP-based drug delivery systems in GBM chemotherapy, immunotherapy, and gene therapy in recent years were systematically reviewed, and the prospect of LBNPs for GBM treatment was discussed.

Fluoxetine enhances the antitumor effect of olfactory ensheathing cell-thymidine kinase/ganciclovir gene therapy in human glioblastoma multiforme cells through upregulation of Connexin43 levels

Glioblastoma multiforme (GBM) is the most invasive form of primary brain astrocytoma, resulting in poor clinical outcomes. Herpes simplex virus thymidine kinase/ganciclovir (HSV-TK/GCV) gene therapy is considered a promising strategy for GBM treatment. Since Connexin43 (Cx43) expression is reduced in GBM cells, increasing Cx43 levels could enhance the effectiveness of gene therapy. The present study aims to examine the impact of fluoxetine on HSV-TK/GCV gene therapy in human GBM cells using human olfactory ensheathing cells (OECs) as vectors. The effect of fluoxetine on Cx43 levels was assessed using the western blot technique. GBM-derived astrocytes and OECs-TK were Cocultured, and the effect of fluoxetine on the Antitumor effect of OEC-TK/GCV gene therapy was evaluated using MTT assay and flow cytometry. Our results showed that fluoxetine increased Cx43 levels in OECs and GBM cells and augmented the killing effect of OECs-TK on GBM cells. Western blot data revealed that fluoxetine enhanced the Bax/Bcl2 ratio and the levels of cleaved caspase-3 in the coculture of OECs-TK and GBM cells. Moreover, flow cytometry data indicated that fluoxetine increased the percentage of apoptotic cells in the coculture system. This study suggests that fluoxetine, by upregulating Cx43 levels, could strengthen the Antitumor effect of OEC-TK/GCV gene therapy on GBM cells.

Non-animal glioblastoma models for personalized treatment

Glioblastoma is an extremely lethal cancer characterized by great heterogeneity at different molecular and cellular levels. As a result, treatment options have moved far from systemic and universal therapies toward targeted treatments and personalized medicine. However, for successful translation from preclinical studies to clinical trials, experiments must be performed on reliable disease models. Numerous experimental models have been developed for glioblastoma, ranging from simple 2D cell cultures to study the nature of the disease to complex 3D models such as neurospheres, organoids, tissue-slice cultures, bioprinted models, and tumor on chip, as perfect prototypes to evaluate the therapeutic potential of different drugs. The presence of multiple research models is consistent with the complexity and molecular diversity of glioblastoma. The advantage of such models is the recapitulation of the tumor environment, and in some cases the preservation of immune system components as well as the creation of simple vessels. There are also two case studies translating in vitro studies on glioblastoma organoids to patients as well as four ongoing clinical trials using glioblastoma models, indicating high clinical potential of glioblastoma models.

Oxamate enhances the efficacy of CAR-T therapy against glioblastoma via suppressing ectonucleotidases and CCR8 lactylation

BACKGROUND

Chimeric antigen receptor (CAR)-T immunotherapy fails to treat solid tumors due in part to immunosuppressive microenvironment. Excess lactate produced by tumor glycolysis increases CAR-T immunosuppression. The mechanism of lactate inducing the formation of immunosuppressive microenvironment remains to be further explored.

METHODS

Immunocyte subpopulations and molecular characteristics were analyzed in the orthotopic xenografts of nude mice using flow cytometry assay and immunohistochemical staining after oxamate, a lactate dehydrogenase A (LDHA) inhibitor, and control T or CAR-T cells injection alone or in combination. RT-qPCR, western blot, flow cytometry, immunofluorescence, luciferase reporter assay, chromatin immunoprecipitation and ELISA were performed to measure the effect of lactate on the regulation of CD39, CD73 and CCR8 in cultured glioma stem cells, CD4 + T cells or macrophages.

RESULTS

Oxamate promoted immune activation of tumor-infiltrating CAR-T cells through altering the phenotypes of immune molecules and increasing regulatory T (Treg) cells infiltration in a glioblastoma mouse model. Lactate accumulation within cells upregulated CD39, CD73 and CCR8 expressions in both lactate-treated cells and glioma stem cells-co-cultured CD4 + T cells and macrophages, and intracellular lactate directly elevated the activities of these gene promotors through histone H3K18 lactylation.

CONCLUSIONS

Utilizing lactate generation inhibitor not only reprogramed glucose metabolism of cancer stem cells, but also alleviated immunosuppression of tumor microenvironment and reduced tumor-infiltrating CAR-Treg cells, which may be a potential strategy to enhance CAR-T function in glioblastoma therapy.

Clinical Significance of Early Venous Filling Detected via Preoperative Angiography in Glioblastoma

Preoperative angiography in glioblastoma (GBM) often shows arteriovenous shunts and early venous filling (EVF). Here, we investigated the clinical implications of EVF in GBM as a prognostic and vascular mimicry biomarker. In this retrospective multicenter study, we consecutively enrolled patients who underwent angiography with a GBM diagnosis between 1 April 2013 and 31 March 2021. The primary and secondary endpoints were the differences in overall survival (OS) and progression-free survival (PFS), respectively, between cases with and without EVF. Of the 133 initially enrolled patients, 91 newly diagnosed with GBM underwent preoperative angiography and became the study population. The 6-year OS and PFS were significantly worse in the EVF than in the non-EVF group. Moreover, 20 GBM cases (10 with EVF and 10 without EVF) were randomly selected and evaluated for histological vascular mimicry. Except for two cases that were difficult to evaluate, the EVF group had a significantly higher frequency of vascular mimicry than the non-EVF group (0/8 vs. 5/10, p = 0.04). EVF on preoperative angiography is a robust prognostic biomarker for GBM and may help detect cases with a high frequency of histological vascular mimicry.

EGFRvIII Promotes the Proneural–Mesenchymal Transition of Glioblastoma Multiforme and Reduces Its Sensitivity to Temozolomide by Regulating the NF-κB/ALDH1A3 Axis

(1) Background: Glioblastoma multiforme (GBM) is the most common and malignant intracranial tumor in adults. At present, temozolomide (TMZ) is recognized as the preferred chemotherapeutic drug for GBM, but some patients have low sensitivity to TMZ or chemotherapy resistance to TMZ. Our previous study found that GBM patients with EGFRvIII (+) have low sensitivity to TMZ. However, the reasons and possible mechanisms of the chemoradiotherapy resistance in GBM patients with EGFRvIII (+) are not clear. (2) Methods: In this study, tissue samples of patients with GBM, GBM cell lines, glioma stem cell lines, and NSG mice were used to explore the causes and possible mechanisms of low sensitivity to TMZ in patients with EGFRvIII (+)-GBM. (3) Results: The study found that EGFRvIII promoted the proneural–mesenchymal transition of GBM and reduced its sensitivity to TMZ, and EGFRvIII regulated of the expression of ALDH1A3. (4) Conclusions: EGFRvIII activated the NF-κB pathway and further regulated the expression of ALDH1A3 to promote the proneural–mesenchymal transition of GBM and reduce its sensitivity to TMZ, which will provide an experimental basis for the selection of clinical drugs for GBM patients with EGFRvIII (+).

Fusion between Glioma Stem Cells and Mesenchymal Stem Cells Promotes Malignant Progression in 3D-Bioprinted Models

The interaction between glioma stem cells (GSCs) and mesenchymal stem cells (MSCs) in the glioma microenvironment is considered to be an important factor in promoting tumor progression, but the mechanism is still not fully elucidated. To further elucidate the interaction between GSCs and MSCs, two 3D-bioprinted tumor models (low-temperature molding and coaxial bioprinting) were used to simulate the tumor growth microenvironment. Cell fusion between GSCs and MSCs was found by the method of Cre-LoxP switch gene and RFP/GFP dual-color fluorescence tracing. The fused cells coexpressed biomarkers of GSCs and MSCs, showing stronger proliferation, cloning, and invasion abilities than GSCs and MSCs. In addition, the fused cells have stronger tumorigenic properties in nude mice, showing the pathological features of malignant tumors. In conclusion, GSCs and MSCs undergo cell fusion in 3D-bioprinted models, and the fused cells have a higher degree of malignancy than parental cells, which promotes the progression of glioma.

Cell-of-Origin and Genetic, Epigenetic, and Microenvironmental Factors Contribute to the Intra-Tumoral Heterogeneity of Pediatric Intracranial Ependymoma

Intra-tumoral heterogeneity (ITH) is a complex multifaceted phenomenon that posits major challenges for the clinical management of cancer patients. Genetic, epigenetic, and microenvironmental factors are concurrent drivers of diversity among the distinct populations of cancer cells. ITH may also be installed by cancer stem cells (CSCs), that foster unidirectional hierarchy of cellular phenotypes or, alternatively, shift dynamically between distinct cellular states. Ependymoma (EPN), a molecularly heterogeneous group of tumors, shows a specific spatiotemporal distribution that suggests a link between ependymomagenesis and alterations of the biological processes involved in embryonic brain development. In children, EPN most often arises intra-cranially and is associated with an adverse outcome. Emerging evidence shows that EPN displays large intra-patient heterogeneity. In this review, after touching on EPN inter-tumoral heterogeneity, we focus on the sources of ITH in pediatric intra-cranial EPN in the framework of the CSC paradigm. We also examine how single-cell technology has shed new light on the complexity and developmental origins of EPN and the potential impact that this understanding may have on the therapeutic strategies against this deadly pediatric malignancy.

In vitro biomimetic models for glioblastoma-a promising tool for drug response studies

The poor response of glioblastoma to current treatment protocols is a consequence of its intrinsic drug resistance. Resistance to chemotherapy is primarily associated with considerable cellular heterogeneity, and plasticity of glioblastoma cells, alterations in gene expression, presence of specific tumor microenvironment conditions and blood-brain barrier. In an attempt to successfully overcome chemoresistance and better understand the biological behavior of glioblastoma, numerous tri-dimensional (3D) biomimetic models were developed in the past decade. These novel advanced models are able to better recapitulate the spatial organization of glioblastoma in a real time, therefore providing more realistic and reliable evidence to the response of glioblastoma to therapy. Moreover, these models enable the fine-tuning of different tumor microenvironment conditions and facilitate studies on the effects of the tumor microenvironment on glioblastoma chemoresistance. This review outlines current knowledge on the essence of glioblastoma chemoresistance and describes the progress achieved by 3D biomimetic models. Moreover, comprehensive literature assessment regarding the influence of 3D culturing and microenvironment mimicking on glioblastoma gene expression and biological behavior is also provided. The contribution of the blood-brain barrier as well as the blood-tumor barrier to glioblastoma chemoresistance is also reviewed from the perspective of 3D biomimetic models. Finally, the role of mathematical models in predicting 3D glioblastoma behavior and drug response is elaborated. In the future, technological innovations along with mathematical simulations should create reliable 3D biomimetic systems for glioblastoma research that should facilitate the identification and possibly application in preclinical drug testing and precision medicine.