Diffuse Intrinsic Pontine Glioma (DIPG): Breakthrough and Clinical Perspective

Bibliometric analysis of emerging trends and research foci in brainstem tumor field over 30 years (1992-2023)

PURPOSE

Over the past several decades, numerous articles have been published on brainstem tumors. However, there has been limited bibliometric analysis in this field. Therefore, we conducted a bibliometric analysis to elucidate the evolution and current status of brainstem tumor research.

METHODS

We retrieved 5525 studies published in English between 1992 and 2023 from the Web of Science Core Collection database. We employed bibliometric tools and VOSviewer to conduct the analysis.

RESULTS

We included a total of 5525 publications for further analysis. The annual publications have exhibited steady growth over time. The United States accounted for the highest number of publications and total citations. Among individual researchers, Liwei Zhang had the highest number of publications, while Cynthia Hawkins and Chris Jones shared the most citations, closely followed by Eric Bouffet in this field. The study titled "Diffuse brainstem glioma in children: critical review of clinical trials" stood out as the most cited work in this field. Keyword analysis revealed that immune therapy and epigenetic research are the focal points of this field.

CONCLUSIONS

Our bibliometric analysis underscores the enduring significance of brainstem tumors in the realm of neuro-oncology research. The field's hotspots have transitioned from surgery and radiochemotherapy to investigating epigenetic mechanisms and immune therapy.

Pediatric Diffuse Midline Glioma H3K27-Altered: From Developmental Origins to Therapeutic Challenges

Diffuse intrinsic pontine glioma (DIPG), now referred to as diffuse midline glioma (DMG), is a highly aggressive pediatric cancer primarily affecting children aged 4 to 9 years old. Despite the research and clinical trials conducted to identify a possible treatment for DIPG, no effective drug is currently available. These tumors often affect deep midline brain structures in young children, suggesting a connection to early brain development's epigenetic regulation targets, possibly affecting neural progenitor functions and differentiation. The H3K27M mutation is a known DIPG trigger, but the exact mechanisms beyond epigenetic regulation remain unclear. After thoroughly examining the available literature, we found that over 85% of DIPG tumors contain a somatic missense mutation, K27M, in genes encoding histone H3.3 and H3.1, leading to abnormal gene expression that drives tumor growth and spread. This mutation impacts crucial brain development processes, including the epithelial-mesenchymal transition (EMT) pathway, and may explain differences between H3K27M and non-K27M pediatric gliomas. Effects on stem cells show increased proliferation and disrupted differentiation. The genomic organization of H3 gene family members in the developing brain has revealed variations in their expression patterns. All these observations suggest a need for global efforts to understand developmental origins and potential treatments.

Harmaline to Human Mitochondrial Caseinolytic Serine Protease Activation for Pediatric Diffuse Intrinsic Pontine Glioma Treatment

Diffuse intrinsic pontine glioma (DIPG), affecting children aged 4-7 years, is a rare, aggressive tumor that originates in the pons and then spreads to nearby tissue. DIPG is the leading cause of death for pediatric brain tumors due to its infiltrative nature and inoperability. Radiotherapy has only a palliative effect on stabilizing symptoms. In silico and preclinical studies identified ONC201 as a cytotoxic agent against some human cancer cell lines, including DIPG ones. A single-crystal X-ray analysis of the complex of the human mitochondrial caseinolytic serine protease type C (hClpP) and ONC201 (PDB ID: 6DL7) allowed hClpP to be identified as its main target. The hyperactivation of hClpP causes damage to mitochondrial oxidative phosphorylation and cell death. In some DIPG patients receiving ONC201, an acquired resistance was observed. In this context, a wide program was initiated to discover original scaffolds for new hClpP activators to treat ONC201-non-responding patients. Harmaline, a small molecule belonging to the chemical class of β-carboline, was identified through Fingerprints for Ligands and Proteins (FLAP), a structure-based virtual screening approach. Molecular dynamics simulations and a deep in vitro investigation showed interesting information on the interaction and activation of hClpP by harmaline.

Rapid Peroxide Removal Limits the Radiosensitization of Diffuse Intrinsic Pontine Glioma (DIPG) Cells by Pharmacologic Ascorbate

Diffuse intrinsic pontine gliomas (DIPG) are an aggressive type of pediatric brain tumor with a very high mortality rate. Surgery has a limited role given the tumor's location. Palliative radiation therapy alleviates symptoms and prolongs survival, but median survival remains less than 1 year. There is no clear role for chemotherapy in DIPGs as trials adding chemotherapy to palliative radiation therapy have failed to improve survival compared to radiation alone. Thus, there is a critical need to identify tissue-specific radiosensitizers to improve clinical outcomes for patients with DIPGs. Pharmacologic (high dose) ascorbate (P-AscH-) is a promising anticancer therapy that sensitizes human tumors, including adult high-grade gliomas, to radiation by acting selectively as a generator of hydrogen peroxide (H2O2) in cancer cells. In this study we demonstrate that in contrast to adult glioma models, P-AscH- does not radiosensitize DIPG. DIPG cells were sensitive to bolus of H2O2 but have faster H2O2 removal rates than GBM models which are radiosensitized by P-AscH-. These data support the hypothesis that P-AscH- does not enhance DIPG radiosensitivity, likely due to a robust capacity to detoxify and remove hydroperoxides.

Classification of Brainstem Gliomas Based on Tumor Microenvironment Status

The inter-tumor heterogeneity of the tumor microenvironment (TME) and how it correlates with clinical profiles and biological characteristics in brainstem gliomas (BSGs) remain unknown, dampening the development of novel therapeutics against BSGs. The TME status was determined with a list of pan-cancer conserved gene expression signatures using a single-sample gene set enrichment analysis (ssGSEA) and was subsequently clustered via consensus clustering. BSGs exhibited a high inter-tumor TME heterogeneity and were classified into four clusters: "immune-enriched, fibrotic", "immune-enriched, non-fibrotic", "fibrotic", and "depleted". The "fibrotic" cluster had a higher proportion of diffuse intrinsic pontine gliomas (p = 0.041), and "PA-like" tumors were more likely to be "immune-enriched, fibrotic" (p = 0.044). The four TME clusters exhibited distinct overall survival (p < 0.001) and independently impacted BSG outcomes. A four-gene panel as well as a radiomics approach were constructed to identify the TME clusters and achieved high accuracy for determining the classification. Together, BSGs exhibited high inter-tumor heterogeneity in the TME and were classified into four clusters with distinct clinical outcomes and tumor biological properties. The TME classification was accurately identified using a four-gene panel that can potentially be examined with the immunohistochemical method and a non-invasive radiomics method, facilitating its clinical application.

Second course of re-irradiation in pediatric diffuse intrinsic pontine glioma : A case study

PURPOSE

Concomitant chemoradiation followed by repeat (dose-deescalated) irradiation has become standard of care in treating childhood diffuse intrinsic pontine glioma (DIPG) during first line treatment and at first progression. Progression after re-irradiation (re-RT) is in most cases symptomatic and either treated systemically with chemotherapy or new innovative approaches including targeted therapy. Alternatively, the patient receives best supportive care. Data on second re-irradiation in DIPG patients with second progression and good performance status are sparse. This is a case report of second short-term re-irradiation to shed further light on this option.

METHODS

Retrospective case report of a 6-year-old boy with DIPG receiving a second course of re-irradiation (with 21.6 Gy) as part of an individual multimodal approach in a patient with very low symptom burden.

RESULTS

The second course of re-irradiation was feasible and well tolerated. No acute neurological symptoms or radiation-induced toxicity occurred. Overall survival was 24 months after initial diagnosis.

CONCLUSION

A second course of re-irradiation can be an additional tool in patients with progressive disease after first- and second-line irradiation. It is unclear whether and to what extent it contributes to progression-free survival prolongation and if-since our patient was asymptomatic-progression-associated neurological deficits can be alleviated.

Bench-to-bedside investigations of H3 K27-altered diffuse midline glioma: drug targets and potential pharmacotherapies

INTRODUCTION

H3 K27-altered diffuse midline glioma (DMG) is the most common malignant brainstem tumor in the pediatric population. Despite enormous preclinical and clinical efforts, the prognosis remains dismal, with fewer than 10% of patients surviving for two years after diagnosis. Fractionated radiation remains the only standard treatment options for DMG. Developing novel treatments and therapeutic delivery methods is critical to improving outcomes in this devastating disease.

AREAS COVERED

This review addresses recent advances in molecularly targeted pharmacotherapy and immunotherapy in DMG. The clinical presentation, diagnostic workup, unique pathological challenges, and current clinical trials are highlighted throughout.

EXPERT OPINION

Promising pharmacotherapies targeting various components of DMG pathology and the application of immunotherapies have the potential to improve patient outcomes. However, novel approaches are needed to truly revolutionize treatment for this tumor. First, combinational therapy should be employed, as DMG can develop resistance to single-agent approaches and many therapies are susceptible to rapid clearance from the brain. Second, drug-tumor residence time, i.e. the time for which a therapeutic is present at efficacious concentrations within the tumor, must be maximized to facilitate a durable treatment response. Engineering extended drug delivery methods with minimal off-tumor toxicity should be a focus of future studies.

Preliminary findings of German-sourced ONC201 treatment in H3K27 altered pediatric pontine diffuse midline gliomas

PURPOSE

H3K27 altered pediatric pontine diffuse midline gliomas (pDMG) have a poor prognosis, and conventional treatments offer limited benefits. However, recent advancements in molecular evaluations and targeted therapies have shown promise. The aim of this retrospective analysis was to evaluate the effectiveness of German-sourced ONC201, a selective antagonist of dopamine receptor DRD2, for the treatment of pediatric H3K27 altered pDMGs.

METHODS

Pediatric patients with H3K27 altered pDMG treated between January 2016 and July 2022 were included in this retrospective analysis. Tissue samples were acquired from all patients via stereotactic biopsy for immunohistochemistry and molecular profiling. All patients received radiation treatment with concurrent temozolomide, and those who could acquire GsONC201 received it as a single agent until progression. Patients who could not obtain GsONC201 received other chemotherapy protocols.

RESULTS

Among 27 patients with a median age of 5.6 years old (range 3.4-17.9), 18 received GsONC201. During the follow-up period, 16 patients (59.3%) had progression, although not statistically significant, the incidence of progression tended to be lower in the GsONC201 group. The median overall survival (OS) of the GsONC201 group was considerably longer than of the non-GsONC201 group (19.9 vs. 10.9 months). Only two patients receiving GsONC201 experienced fatigue as a side effect. 4 out of 18 patients in the GsONC201 group underwent reirradiation after progression.

CONCLUSION

In conclusion, this study suggests that GsONC201 may improve OS in pediatric H3K27-altered pDMG patients without significant side effects. However, caution is warranted due to retrospective design and biases, highlighting the need for further randomized clinical studies to validate these findings.

Therapeutic avenues for targeting treatment challenges of diffuse midline gliomas

Diffuse midline glioma (DMG) is the leading cause of brain tumor-related deaths in children. DMG typically presents with variable neurologic symptoms between ages 3 and 10. Currently, radiation remains the standard therapy for DMG to halt progression and reduce tumor bulk to minimize symptoms. However, tumors recur in almost 100% of patients and thus, DMG is still considered an incurable cancer with a median survival of 9-12 months. Surgery is generally contraindicated due to the delicate organization of the brainstem, where DMG is located. Despite extensive research efforts, no chemotherapeutic agents, immune therapies, or molecularly targeted therapies have been approved to provide survival benefit. Furthermore, the efficacy of therapies is limited by poor blood-brain barrier penetration and inherent resistance mechanisms of the tumor. However, novel drug delivery approaches, along with recent advances in molecularly targeted therapies and immunotherapies, have advanced to clinical trials and may provide viable future treatment options for DMG patients. This review seeks to evaluate current therapeutics at the preclinical stage and those that have advanced to clinical trials and to discuss the challenges of drug delivery and inherent resistance to these therapies.

Leptomeningeal dissemination in pediatric brain tumors

Leptomeningeal disease (LMD) in pediatric brain tumors (PBTs) is a poorly understood and categorized phenomenon. LMD incidence rates, as well as diagnosis, treatment, and screening practices, vary greatly depending on the primary tumor pathology. While LMD is encountered most frequently in medulloblastoma, reports of LMD have been described across a wide variety of PBT pathologies. LMD may be diagnosed simultaneously with the primary tumor, at time of recurrence, or as primary LMD without a primary intraparenchymal lesion. Dissemination and seeding of the cerebrospinal fluid (CSF) involves a modified invasion-metastasis cascade and is often the result of direct deposition of tumor cells into the CSF. Cells develop select environmental advantages to survive the harsh, nutrient poor and turbulent environment of the CSF and leptomeninges. Improved understanding of the molecular mechanisms that underlie LMD, along with improved diagnostic and treatment approaches, will help the prognosis of children affected by primary brain tumors.

Engineered extracellular vesicles (EVs): Promising diagnostic/therapeutic tools for pediatric high-grade glioma

Diffuse intrinsic pontine glioma (DIPG) is a highly malignant brain tumor that mainly occurs in children with extremely low overall survival. Traditional therapeutic strategies, such as surgical resection and chemotherapy, are not feasible mostly due to the special location and highly diffused features. Radiotherapy turns out to be the standard treatment method but with limited benefits of overall survival. A broad search for novel and targeted therapies is in the progress of both preclinical investigations and clinical trials. Extracellular vesicles (EVs) emerged as a promising diagnostic and therapeutic candidate due to their distinct biocompatibility, excellent cargo-loading-delivery capacity, high biological barrier penetration efficiency, and ease of modification. The utilization of EVs in various diseases as biomarker diagnoses or therapeutic agents is revolutionizing modern medical research and practice. In this review, we will briefly talk about the research development of DIPG, and present a detailed description of EVs in medical applications, with a discussion on the application of engineered peptides on EVs. The possibility of applying EVs as a diagnostic tool and drug delivery system in DIPG is also discussed.

Applications and current challenges of chimeric antigen receptor T cells in treating high-grade gliomas in adult and pediatric populations

High-grade gliomas (HGGs) continue to be some of the most devastating diseases in the USA. Despite extensive efforts, the survival of HGG patients has remained relatively stagnant. Chimeric antigen receptor (CAR) T-cell immunotherapy has recently been studied in the context of improving these tumors' clinical outcomes. HGG murine models treated with CAR T cells targeting tumor antigens have shown reduced tumor burden and longer overall survival than models without treatment. Subsequent clinical trials investigating the efficacy of CAR T cells have further shown that this therapy could be safe and might reduce tumor burden. However, there are still many challenges that need to be addressed to optimize the safety and efficacy of CAR T-cell therapy in treating HGG patients.

High Intra-Tumor Transforming Growth Factor Beta 2 Level as a Predictor of Poor Treatment Outcomes in Pediatric Diffuse Intrinsic Pontine Glioma

Here, we report that tumor samples from newly diagnosed pediatric diffuse intrinsic pontine glioma (DIPG) patients express significantly higher levels of transforming growth factor beta 2 (TGFB2) messenger ribonucleic acid (mRNA) than control pons samples, which correlated with augmented expression of transcription factors that upregulate TGFB2 gene expression. Our study also demonstrated that RNA sequencing (RNAseq)-based high TGFB2 mRNA level is an indicator of poor prognosis for DIPG patients, but not for pediatric glioblastoma (GBM) patients or pediatric diffuse midline glioma (DMG) patients with tumor locations outside of the pons/brainstem. Notably, DIPG patients with high levels of TGFB2 mRNA expression in their tumor samples had significantly worse overall survival (OS) and progression-free survival (PFS). By comparison, high levels of transforming growth factor beta 3 (TGFB3) mRNA expression in tumor samples was associated with significantly better survival outcomes of DIPG patients, whereas high levels of transforming growth factor beta 1 (TGFB1) expression was not prognostic. Our study fills a significant gap in our understanding of the clinical significance of high TGFB2 expression in pediatric high-grade gliomas.

Convection-enhanced delivery of nanoencapsulated gene locoregionally yielding ErbB2/Her2-specific CAR-macrophages for brainstem glioma immunotherapy

Locoregional delivery of chimeric antigen receptor (CAR)-modified T (CAR-T) cells has emerged as a promising strategy for brain tumors. However, the complicated ex vivo cell manufacturing procedures and the rapid progression of the disease have limited its broader applications. Macrophages (MΦs) exhibit unique effector functions and a high degree of infiltration within the solid tumor microenvironment (TME), especially in the brain, where MΦs function as structural support, and the main immune effector cells of the CNS represent 5-12% of brain cells. Here, we report a synthetic universal DNA nanocarrier for in situ genetic editing of intratumoral MΦs with an ErbB2-specific CAR to direct their phagocytic activity towards tumors and subsequently initiate a locoregional antitumor immune response. Specifically, we demonstrated that when delivered locoregionally, the RP-182 peptide, located in the shell of a nanoparticle, targeted MΦs and reprogrammed M2-like tumor-associated macrophages (TAMs) to an antitumor M1-like phenotype. Subsequently, the CAR gene-laden DNA nanocomplex can be used to introduce ErbB2-targeted CAR, and the generated CAR-MΦs then act as "living" cures, thereby serially clearing the invasive tumor cells. Our work demonstrates a practical antitumor immunotherapy for brainstem gliomas (BSGs) that may be broadly applicable for patients suffering from other ErbB2-positive solid malignancies.

Immune Microenvironment and Immunotherapies for Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine glioma (DIPG) is a primary glial glioma that occurs in all age groups but predominates in children and is the main cause of solid tumor-related childhood mortality. Due to its rapid progression, the inability to operate and insensitivity to most chemotherapies, there is a lack of effective treatment methods in clinical practice for DIPG patients. The prognosis of DIPG patients is extremely poor, with a median survival time of no more than 12 months. In recent years, there have been continuous breakthroughs for immunotherapies in various hematological tumors and malignant solid tumors with extremely poor prognoses, which provides new insights into tumors without effective treatment strategies. Meanwhile, with the gradual development of stereotactic biopsy techniques, it is gradually becoming easier and safer to obtain live DIPG tissue, and the understanding of the immune properties of DIPG has also increased. On this basis, a series of immunotherapy studies of DIPG are under way, some of which have shown encouraging results. Herein, we review the current understanding of the immune characteristics of DIPG and critically reveal the limitations of current immune research, as well as the opportunities and challenges for immunological therapies in DIPG, hoping to clarify the development of novel immunotherapies for DIPG treatment.

IMP075 targeting ClpP for colon cancer therapy in vivo and in vitro

ONC201 is a well-known caseinolytic protease (ClpP)activator with established benefits against multiple tumors, including colorectal cancer (CRC). In this study, we investigated the anticancer effects and associated mechanisms of the ClpP agonist IMP075, derived from ONC201. Acute toxicity and CCK-8 assayswere employed to determine the safety of IMP075. The effectiveness of IMP075 was investigated in HCT116 cells and a mouse xenograft tumor model. Additionally, the properties of IMP075 were evaluated by pharmacokinetic,CYP inhibition, and hERG inhibition assays. Finally, isothermal titration calorimetry (ITC), differential scanning fluorimetry (DSF), cellular thermal shift assay (CETSA), molecular dynamics simulations, point mutations, and shRNA experiments were employed to elucidate the potential mechanism of IMP075. Compared with ONC201, IMP075 exhibited similar toxicity and improved antitumor effects in vitro and in vivo. Interestingly, the affinity and agonistic effects of IMP075 on ClpP were superior to ONC201, which allowed IMP075 to disrupt respiratory chain integrity at lower doses in HCT116 cells, leading to mitochondrial dysfunction. Furthermore, molecular dynamics simulations demonstrate that IMP075 forms two pairs of hydrogen bonds with ClpP, maintaining ClpP in an agonistic state. Importantly, the antiproliferative activity of IMP075 significantly decreased following ClpP knockdown. Our findings substantiate that IMP075 exerts excellent antitumor effects against CRC by activating ClpP-mediated impairment of mitochondrial function. Due to its superior properties, IMP075 appears to be have huge prospects for application.

Nimotuzumab as Additional Therapy for GLIOMA in Pediatric and Adolescent: A Systematic Review

INTRODUCTION

Pediatric gliomas represent the most common brain tumor in children and its higher grades are associated with higher recurrence and low survival rate. All therapeutic modalities are reported to be insufficient to achieve satisfactory result, with follow-up treatment such as adjuvant radiotherapy and chemotherapy recommended to increase survival and hinder tumor progression. Nimotuzumab is a monoclonal antibody that acts as an inhibitor of epidermal growth factor receptor found on the surface of glioma cells and had been studied for its usage in pediatric gliomas in recent years.

METHODS

A systematic review is performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. A through literature search was conducted on PubMed, Scopus, Cochrane, and clinicaltrials.gov database. Articles were selected systematically based on the PRISMA protocol and reviewed completely. The relevant data were summarized and discussed. We measured overall survival, progression-free survival, and adverse Events (AE) for nimotuzumab usage as an adjunct therapy in pediatric glioma population.

RESULT

From 5 studies included for qualitative analysis, 151 patients are included with overall survival (OS) that vary from 3.2-22.8 mo, progression-free survival (PFS) from 1.7-21.6 mo, and relatively low serious adverse events (0-21) are recorded. Follow-up ranged from 2.4-66 mo with four studies reporting diffuse intrinsic pontine glioma (DIPG) patients and only one study reporting nimotuzumab usage in pediatric high-grade glioma (HGG) patients with better outcome in HGG patients than DIPG.

CONCLUSION

There are no significant differences in the PFS and OS of nimotuzumab as adjunct therapy for pediatric compared to result of standard therapy in majority of previous studies. There were also no differences in the AE of nimotuzumab for pediatric glioma between studies, and low event of serious adverse events indicating its safety. But still there is an evidence of possible benefit of nimotuzumab as adjuvant therapy in pediatric glioma. We recommend further studies with larger number of patients that may lead to possibly different results. There should also be more studies with better level of evidence to further validate the effect of nimozutumab on pediatric glioma.

A Prognostic Model for Brain Glioma Patients Based on 9 Signature Glycolytic Genes

Objective

To screen glycolytic genes linked to the glioma prognosis and construct the prognostic model.

Methods

The relevant data of glioma were downloaded from TCGA and GTEx databases. GSEA of glycolysis-related pathways was carried out, and enriched differential genes were extracted. Screening out prognostic-related genes with conspicuous significance and construction of the prognostic model were conducted by multivariate Cox regression analysis and Lasso regression analysis. The model was evaluated, and cBioPortal was used to analyze the mutation of the model gene. The expression of the model gene in tumor and normal colon tissue was analyzed. The model was used to evaluate the prognosis of patients in different groups to verify the applicability of the model.

Results

339 differentially glycolytic-related genes were enriched in REACTOME_GLYCOLYSIS, GLYCOLYTIC_PROCESS, HALLMARK_GLYCOLYSIS, and other pathways. We obtained 9 key prognostic genes and constructed the prognostic evaluation model. The 3-year AUC values of the ROC curve display model are greater than 0.75, which indicates that the accuracy of the model is good. The relation of age and risk score to prognosis is shown by univariate and multivariate Cox analysis. The expression of SRD5A3, MDH2, and B3GAT3 genes was significantly upregulated in the tumor tissues, while the HDAC4 and G6PC2 genes were downregulated. The mutation rate of MDH2 and HDAC4 genes was the highest. This model could effectively distinguish the risk of poor prognosis of patients in any age stage.

Conclusion

The prognostic assessment models based on glycolysis-related nine-gene signature could accurately predict the prognosis of patients with GBM.