Effects of Cranial Radiation on Structural and Functional Brain Development in Pediatric Brain Tumors

Assessing learning and memory among patients with pediatric brain tumor (PBT): a comparison of measures

Patients with pediatric brain tumor (PBT) can have memory deficits due to tumor location, medical complications, and treatment. The main objective of this study was to investigate whether the California Verbal Learning Test-Children's Version (CVLT-C; 1994) and briefer Child and Adolescent Memory Profile (ChAMP; 2015) similarly identify such deficits. Seventy-five patients with PBT ages 8-16 (x ‾  = 13.1 years, SD = 2.1) were administered the ChAMP or CVLT-C. Rote verbal learning, long-term retrieval, and recognition were analyzed using standardized z-scores. Analyses of differences between measures did not reach statistical significance. Both measures indicated significant downward shifts across free retrieval trials from normative means, with scores approximately 1/3 (ChAMP) to 1/2 (CVLT-C) SD below means across learning and long-term retrieval trials. Scores on recognition trials did not differ significantly from the normative mean. Post-hoc analyses using a subset of the sample who received cranial irradiation (n = 45) similarly found no significant differences between memory measures. Additional post-hoc examination of proportion of participants falling within or below the "below average" range (≤8th percentile) revealed comparable performance between the two measures, whereas the proportion of participants falling at or below 1.5 SDs below the mean on retrieval trials was lower using ChAMP Lists as compared to the CVLT-C. Given the ChAMP is less demanding in terms of time and effort and utilizes more updated and representative normative data, this study supports the ChAMP as a useful tool to evaluate learning and memory within this population.

Management of first recurrence or progression of craniopharyngioma after resection alone: A systematic review and individual-participant data meta-analysis

The initial management of craniopharyngioma is generally either gross total resection (GTR) or subtotal resection (STR) with adjuvant radiotherapy (RT). However, the optimal management strategy for recurrent/progressive craniopharyngioma remains unclear. In this systematic review and individual participant data meta-analysis, we aimed to compare the outcomes of surgery and/or RT for the first recurrence/progression of craniopharyngioma after resection alone. The exposure was the treatment that was administered for the first recurrence/progression, and the outcomes were tumor regrowth and overall survival (OS). Subgroup analyses were performed by age at the treatment for the first recurrence/progression (<18 or ≥ 18 years old), duration between the first treatment and the first recurrence/progression (<2 or ≥ 2 years), and the initial treatment that was administered (STR or GTR). Of the 2932 studies screened, 11 studies reporting a total of 80 patients were included. Across almost all subgroups, patients who received RT for the first recurrence/progression had a significantly lower risk of tumor regrowth than those who did not, regardless of whether surgery was performed and the extent of resection. There was no significant association between the treatment administered for the first recurrence/progression and OS, except for patients with a recurrence/progression < 2 years after the first treatment, where GTR was associated with a higher risk of mortality. For patients with the first recurrence/progression of craniopharyngioma after resection alone, RT should be considered for better local control. In cases where RT is not administered, GTR is preferred over STR provided it can be safely performed, for improved local control.

High replication stress and limited Rad51-mediated DNA repair capacity, but not oxidative stress, underlie oligodendrocyte precursor cell radiosensitivity

Cranial irradiation is part of the standard of care for treating pediatric brain tumors. However, ionizing radiation can trigger serious long-term neurologic sequelae, including oligodendrocyte and brain white matter loss enabling neurocognitive decline in children surviving brain cancer. Oxidative stress-mediated oligodendrocyte precursor cell (OPC) radiosensitivity has been proposed as a possible explanation for this. Here, however, we demonstrate that antioxidants fail to improve OPC viability after irradiation, despite suppressing oxidative stress, suggesting an alternative etiology for OPC radiosensitivity. Using systematic approaches, we find that OPCs have higher irradiation-induced and endogenous γH2AX foci compared to neural stem cells, neurons, astrocytes and mature oligodendrocytes, and these correlate with replication-associated DNA double strand breakage. Furthermore, OPCs are reliant upon ATR kinase and Mre11 nuclease-dependent processes for viability, are more sensitive to drugs increasing replication fork collapse, and display synthetic lethality with PARP inhibitors after irradiation. This suggests an insufficiency for homology-mediated DNA repair in OPCs—a model that is supported by evidence of normal RPA but reduced RAD51 filament formation at resected lesions in irradiated OPCs. We therefore propose a DNA repair-centric mechanism of OPC radiosensitivity, involving chronically-elevated replication stress combined with ‘bottlenecks’ in RAD51-dependent DNA repair that together reduce radiation resilience.

Design considerations of an IL13Rα2 antibody-drug conjugate for diffuse intrinsic pontine glioma

Diffuse intrinsic pontine glioma (DIPG), a rare pediatric brain tumor, afflicts approximately 350 new patients each year in the United States. DIPG is noted for its lethality, as fewer than 1% of patients survive to five years. Multiple clinical trials involving chemotherapy, radiotherapy, and/or targeted therapy have all failed to improve clinical outcomes. Recently, high-throughput sequencing of a cohort of DIPG samples identified potential therapeutic targets, including interleukin 13 receptor subunit alpha 2 (IL13Rα2) which was expressed in multiple tumor samples and comparably absent in normal brain tissue, identifying IL13Rα2 as a potential therapeutic target in DIPG. In this work, we investigated the role of IL13Rα2 signaling in progression and invasion of DIPG and viability of IL13Rα2 as a therapeutic target through the use of immunoconjugate agents. We discovered that IL13Rα2 stimulation via canonical ligands demonstrates minimal impact on both the cellular proliferation and cellular invasion of DIPG cells, suggesting IL13Rα2 signaling is non-essential for DIPG progression in vitro. However, exposure to an anti-IL13Rα2 antibody-drug conjugate demonstrated potent pharmacological response in DIPG cell models both in vitro and ex ovo in a manner strongly associated with IL13Rα2 expression, supporting the potential use of targeting IL13Rα2 as a DIPG therapy. However, the tested ADC was effective in most but not all cell models, thus selection of the optimal payload will be essential for clinical translation of an anti-IL13Rα2 ADC for DIPG.

Ionizing Radiation Protein Biomarkers in Normal Tissue and Their Correlation to Radiosensitivity: Protocol for a Systematic Review

Background: Radiosensitivity is a significantly enhanced reaction of cells, tissues, organs or organisms to ionizing radiation (IR). During radiotherapy, surrounding normal tissue radiosensitivity often limits the radiation dose that can be applied to the tumour, resulting in suboptimal tumour control or adverse effects on the life quality of survivors. Predicting radiosensitivity is a component of personalized medicine, which will help medical professionals allocate radiation therapy decisions for effective tumour treatment. So far, there are no reviews of the current literature that explore the relationship between proteomic changes after IR exposure and normal tissue radiosensitivity systematically. Objectives: The main objective of this protocol is to specify the search and evaluation strategy for a forthcoming systematic review (SR) dealing with the effects of in vivo and in vitro IR exposure on the proteome of human normal tissue with focus on radiosensitivity. Methods: The SR framework has been developed following the guidelines established in the National Toxicology Program/Office of Health Assessment and Translation (NTP/OHAT) Handbook for Conducting a Literature-Based Health Assessment, which provides a standardised methodology to implement the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to environmental health assessments. The protocol will be registered in PROSPERO, an open source protocol registration system, to guarantee transparency. Eligibility criteria: Only experimental studies, in vivo and in vitro, investigating effects of ionizing radiation on the proteome of human normal tissue correlated with radio sensitivity will be included. Eligible studies will include English peer reviewed articles with publication dates from 2011–2020 which are sources of primary data. Information sources: The search strings will be applied to the scientific literature databases PubMed and Web of Science. The reference lists of included studies will also be manually searched. Data extraction and results: Data will be extracted according to a pre-defined modality and compiled in a narrative report following guidelines presented as a “Synthesis without Meta-analyses” method. Risk of bias: The risk of bias will be assessed based on the NTP/OHAT risk of bias rating tool for human and animal studies (OHAT 2019). Level of evidence rating: A comprehensive assessment of the quality of evidence for both in vivo and in vitro studies will be followed, by assigning a confidence rating to the literature. This is followed by translation into a rating on the level of evidence (high, moderate, low, or inadequate) regarding the research question. Registration: PROSPERO Submission ID 220064.

Epigenetic Regulation of the Hippocampus, with Special Reference to Radiation Exposure

The hippocampus is crucial in learning, memory and emotion processing, and is involved in the development of different neurological and neuropsychological disorders. Several epigenetic factors, including DNA methylation, histone modifications and non-coding RNAs, have been shown to regulate the development and function of the hippocampus, and the alteration of epigenetic regulation may play important roles in the development of neurocognitive and neurodegenerative diseases. This review summarizes the epigenetic modifications of various cell types and processes within the hippocampus and their resulting effects on cognition, memory and overall hippocampal function. In addition, the effects of exposure to radiation that may induce a myriad of epigenetic changes in the hippocampus are reviewed. By assessing and evaluating the current literature, we hope to prompt a more thorough understanding of the molecular mechanisms that underlie radiation-induced epigenetic changes, an area which can be further explored.

Differential trajectories of neurocognitive functioning in females versus males following treatment for pediatric brain tumors

BACKGROUND

Female and male trajectories of cerebellar and lobar brain structures are sexually dimorphic, making sex a potential candidate moderator of neurocognitive late effects from radiation treatment. We sought to evaluate longitudinal neurocognitive functioning in male versus female children treated for posterior fossa brain tumors.

METHODS

Fifty-one female and 63 male survivors of posterior fossa tumors completed neuropsychological testing at 2 timepoints. We included patients treated with surgical resection, chemotherapy, and radiation therapy. Multilevel mixed modeling was used to predict IQ score as a function of patient sex following treatment (~2 or ~4 years post treatment). Effect sizes were used as a measure of clinical significance.

RESULTS

Multilevel models resulted in a significant sex by time interaction (F = 6.69, P = 0.011). Females' cognitive scores were considerably higher compared with males at 4 years posttreatment. Females demonstrated an average improvement of 7.61 standard score IQ points compared with a decline of 2.97 points for males at 4 years follow-up. Effect sizes for female IQ compared with male IQ at 4 years posttreatment were between 0.8 and 0.9.

CONCLUSION

Trajectories of neurocognitive functioning following posterior fossa tumor treatment differed between female and male children. Sexual dimorphism in radiation late effects may alter treatment decisions in children. Research into sex-specific neuroprotective mechanisms underlying neurocognitive development following pediatric brain tumor treatments is warranted.

Therapeutic Efficacy of Immune Stimulatory Thymidine Kinase and fms-like Tyrosine Kinase 3 Ligand (TK/Flt3L) Gene Therapy in a Mouse Model of High-Grade Brainstem Glioma

PURPOSE

Diffuse intrinsic pontine glioma (DIPG) bears a dismal prognosis. A genetically engineered brainstem glioma model harboring the recurrent DIPG mutation, Activin A receptor type I (ACVR1)-G328V (mACVR1), was developed for testing an immune-stimulatory gene therapy.

EXPERIMENTAL DESIGN

We utilized the Sleeping Beauty transposase system to generate an endogenous mouse model of mACVR1 brainstem glioma. Histology was used to characterize and validate the model. We performed RNA-sequencing analysis on neurospheres harboring mACVR1. mACVR1 neurospheres were implanted into the pons of immune-competent mice to test the therapeutic efficacy and toxicity of immune-stimulatory gene therapy using adenoviruses expressing thymidine kinase (TK) and fms-like tyrosine kinase 3 ligand (Flt3L). mACVR1 neurospheres expressing the surrogate tumor antigen ovalbumin were generated to investigate whether TK/Flt3L treatment induces the recruitment of tumor antigen-specific T cells.

RESULTS

Histologic analysis of mACVR1 tumors indicates that they are localized in the brainstem and have increased downstream signaling of bone morphogenetic pathway as demonstrated by increased phospho-smad1/5 and Id1 levels. Transcriptome analysis of mACVR1 neurosphere identified an increase in the TGFβ signaling pathway and the regulation of cell differentiation. Adenoviral delivery of TK/Flt3L in mice bearing brainstem gliomas resulted in antitumor immunity, recruitment of antitumor-specific T cells, and increased median survival (MS).

CONCLUSIONS

This study provides insights into the phenotype and function of the tumor immune microenvironment in a mouse model of brainstem glioma harboring mACVR1. Immune-stimulatory gene therapy targeting the hosts' antitumor immune response inhibits tumor progression and increases MS of mice bearing mACVR1 tumors.

Neurocognitive and Psychosocial Outcomes in Pediatric Brain Tumor Survivors

The late neurocognitive and psychosocial effects of treatment for pediatric brain tumor (PBT) represent important areas of clinical focus and ongoing research. Neurocognitive sequelae and associated problems with learning and socioemotional development negatively impact PBT survivors' overall health-related quality of life, educational attainment and employment rates. Multiple factors including tumor features and associated complications, treatment methods, individual protective and vulnerability factors and accessibility of environmental supports contribute to the neurocognitive and psychosocial outcomes in PBT survivors. Declines in overall measured intelligence are common and may persist years after treatment. Core deficits in attention, processing speed and working memory are postulated to underlie problems with overall intellectual development, academic achievement and career attainment. Additionally, psychological problems after PBT can include depression, anxiety and psychosocial adjustment issues. Several intervention paradigms are briefly described, though to date research on innovative, specific and effective interventions for neurocognitive late effects is still in its early stages. This article reviews the existing research for understanding PBT late effects and highlights the need for innovative research to enhance neurocognitive and psychosocial outcomes in PBT survivors.