Epigenetic mechanisms in paediatric brain tumours: regulators lose control

The Role of Chronic Inflammation in Pediatric Cancer

Inflammation plays a crucial role in wound healing and the host immune response following pathogenic invasion. However, unresolved chronic inflammation can result in tissue fibrosis and genetic alterations that contribute to the pathogenesis of human diseases such as cancer. Recent scientific advancements exploring the underlying mechanisms of malignant cellular transformations and cancer progression have exposed significant disparities between pediatric and adult-onset cancers. For instance, pediatric cancers tend to have lower mutational burdens and arise in actively developing tissues, where cell-cycle dysregulation leads to gene, chromosomal, and fusion gene development not seen in adult-onset counterparts. As such, scientific findings in adult cancers cannot be directly applied to pediatric cancers, where unique mutations and inherent etiologies remain poorly understood. Here, we review the role of chronic inflammation in processes of genetic and chromosomal instability, the tumor microenvironment, and immune response that result in pediatric tumorigenesis transformation and explore current and developing therapeutic interventions to maintain and/or restore inflammatory homeostasis.

Unravelling the mosaic: Epigenetic diversity in glioblastoma

Glioblastoma is the most common primary malignant brain tumour. Despite decades of intensive research in the disease, its prognosis remains poor, with an average survival of only 14 months after diagnosis. The remarkable level of intra- and interpatient heterogeneity is certainly contributing to the lack of progress in tackling this tumour. Epigenetic dysregulation plays an important role in glioblastoma biology and significantly contributes to intratumour heterogeneity. However, it is becoming increasingly clear that it also contributes to intertumour heterogeneity, which historically had mainly been linked to diverse genetic events occurring in different patients. In this review, we explore how DNA methylation, chromatin remodelling, microRNA (miRNA) dysregulation, and long noncoding RNA (lncRNA) alterations contribute to intertumour heterogeneity in glioblastoma, including its implications for advanced tumour stratification, which is the essential first step for developing more effective patient-specific therapeutic approaches.

Epigenetic reprogramming enables NF1A/B oncogenic role in SHH medulloblastoma

In this issue of Developmental Cell, Shiraishi et al. investigate the epigenetic changes occurring during the formation of SHH medulloblastoma and show that an epigenomic shift renders Nuclear Factor I family of transcription factors oncogenic.

A scoping review of diffuse hemispheric glioma, H3 G34-mutant: Epigenetic and molecular profiles, clinicopathology, and treatment avenues

Background

Survival of pediatric and young adults with malignant glioma remains poor despite progress in treatment. This is especially true for diffuse hemispheric glioma (DHG), H3 G34-mutant, which is often present in adolescent and young adult patients. This scoping review consolidates existing knowledge of DHG H3 G34-mutant and identifies future targets and therapeutic options. By streamlining this information, we aim to elucidate knowledge gaps in the field to better inform the community and motivate future research efforts.

Methods

In October 2024, MEDLINE, Embase, Cochrane Library, and Web of Science Core Collection were searched. Two reviewers screened all articles by title and abstract review and 3 independent reviewers extracted all studies meeting inclusion criteria relevant to H3G34R/V tumors (preclinical and clinical studies).

Results

Of the 2203 articles screened, 220 were deemed eligible (79 literature reviews, 7 systematic reviews, 63 preclinical studies, and 71 clinically oriented studies). We found that the United States and Acta Neuropathologica were the top country and journal contributors, respectively.

Conclusion

For this disease, it is critical to the field to conduct further research related to complexities of the tumor microenvironment, translation of preclinical studies to therapeutic early phase trials, and determining the role of targeted central nervous system drug delivery, so as to improve disease prognosis and survival.

Development and epigenetic regulation of Atypical teratoid/rhabdoid tumors in the context of cell-of-origin and halted cell differentiation

Atypical teratoid/rhabdoid tumors (AT/RTs) are aggressive brain tumors primarily observed in infants. The only characteristic, recurrent genetic aberration of AT/RTs is biallelic inactivation of SMARCB1 (or SMARCA4). These genes are members of the mSWI/SNF chromatin-remodeling complex, which regulates various developmental processes, including neural differentiation. This review explores AT/RT subgroups regarding their distinct SMARCB1 loss-of-function mechanisms, molecular features, and patient characteristics. Additionally, it addresses the ongoing debate about the oncogenic relevance of cell-of-origin, examining the influence of developmental stage and lineage commitment of the seeding cell on tumor malignancy and other characteristics. Epigenetic dysregulation, particularly through the regulation of histone modifications and DNA hypermethylation, has been shown to play an integral role in AT/RTs' malignancy and differentiation blockage, maintaining cells in a poorly differentiated state via the insufficient activation of differentiation-related genes. Here, the differentiation blockage and its contribution to malignancy are also explored in a cellular context. Understanding these mechanisms and AT/RT heterogeneity is crucial for therapeutic improvements against AT/RTs.

Antagonism Between DUX4 and DUX4c Highlights a Pathomechanism Operating Through β-Catenin in Facioscapulohumeral Muscular Dystrophy

Aberrant expression of the transcription factor DUX4 from D4Z4 macrosatellite repeats on chromosome 4q35, and its transcriptome, associate with pathogenesis in facioscapulohumeral muscular dystrophy (FSHD). Forced DUX4 expression halts skeletal muscle cell proliferation and induces cell death. DUX4 binds DNA via two homeodomains that are identical in sequence to those of DUX4c (DUX4L9): a closely related transcriptional regulator encoded by a single, inverted, mutated D4Z4 unit located centromeric to the D4Z4 macrosatellite array on chromosome 4. However, the function and contribution of DUX4c to FSHD pathogenesis are unclear. To explore interplay between DUX4, DUX4c, and the DUX4-induced phenotype, we investigated whether DUX4c interferes with DUX4 function in human myogenesis. Constitutive expression of DUX4c rescued the DUX4-induced inhibition of proliferation and reduced cell death in human myoblasts. Functionally, DUX4 promotes nuclear translocation of β-CATENIN and increases canonical WNT signalling. Concomitant constitutive expression of DUX4c prevents β-CATENIN nuclear accumulation and the downstream transcriptional program. DUX4 reduces endogenous DUX4c levels, whereas constitutive expression of DUX4c robustly suppresses expression of DUX4 target genes, suggesting molecular antagonism. In line, DUX4 expression in FSHD myoblasts correlates with reduced DUX4c levels. Addressing the mechanism, we identified a subset of genes involved in the WNT/β-CATENIN pathway that are differentially regulated between DUX4 and DUX4c, whose expression pattern can separate muscle biopsies from severely affected FSHD patients from healthy. Finally, blockade of WNT/β-CATENIN signalling rescues viability of FSHD myoblasts. Together, our study highlights an antagonistic interplay whereby DUX4 alters cell viability via β-CATENIN signalling and DUX4c counteracts aspects of DUX4-mediated toxicity in human muscle cells, potentially acting as a gene modifier for FSHD severity. Importantly, direct DUX4 regulation of the WNT/β-CATENIN pathway informs future therapeutic interventions to ameliorate FSHD pathology.

Combination of BMI1 and MAPK/ERK inhibitors is effective in medulloblastoma

BACKGROUND

Epigenetic changes play a key role in the pathogenesis of medulloblastoma (MB), the most common malignant pediatric brain tumor.

METHODS

We explore the therapeutic potential of BMI1 and MAPK/ERK inhibition in BMI1High;CHD7Low MB cells and in a preclinical xenograft model.

RESULTS

We identify a synergistic vulnerability of BMI1High;CHD7Low MB cells to a combination treatment with BMI1 and MAPK/ERK inhibitors. Mechanistically, CHD7-dependent binding of BMI1 to MAPK-regulated genes underpins the CHD7-BMI1-MAPK regulatory axis responsible of the antitumour effect of the inhibitors in vitro and in a preclinical mouse model. Increased ERK1 and ERK2 phosphorylation activity is found in BMI1High;CHD7Low G4 MB patients, raising the possibility that they could be amenable to a similar therapy.

CONCLUSIONS

The molecular dissection of the CHD7-BMI1-MAPK regulatory axis in BMI1High;CHD7Low MB identifies this signature as a proxy to predict MAPK functional activation, which can be effectively drugged in preclinical models, and paves the way for further exploration of combined BMI1 and MAPK targeting in G4 MB patients.