Early microglial activation in the TME enables FLASH-RT to eradicate medulloblastoma while promoting neuron-astrocyte crosstalk to minimize toxicity in the hippocampus

bioRxiv (Cold Spring Harbor Laboratory) · 2026-03-18

Abstract Background FLASH-RT defines a promising treatment modality against medulloblastoma, as it minimizes treatment-related complications. To support its clinical translation, we dissected the cellular and molecular determinants of the FLASH response in the tumor-microenvironment (TME) and healthy hippocampus using an orthotopic human medulloblastoma mouse model treated with a hypo-fractionated FLASH regimen. Methods Five cohorts of 4 weeks-old UW228-MB-bearing female nude mice (n=57) were irradiated, or sham-irradiated using 3×10 Gy (BED=60), delivered 48h apart at 0.1 Gy/s (CONV) or 5.5×10 6 Gy/s (FLASH) using an electron beam (eRT6). Digital spatial profiling (DSP) was performed 24h after radiotherapy in one cohort, while the four other cohorts were followed for long-term tumor response, cognition, and neuroinflammation. Results Both CONV and FLASH-RT induced a complete and long-lasting anti-tumor response in 100% of animals associated with cognitive decline. However, more mice maintained a very good discrimination score after FLASH exposure (38%) than CONV (7%). DSP revealed a sustained microglial activation in the cerebellar tumor micro-environment, where FLASH enhanced expression of genes with phagocytic and proteolytic activity. In the tumor free hippocampus, FLASH exposure induced a preferential neuron/astrocyte transcriptional crosstalk, which manifested over protracted times to minimize neuroinflammation and cognitive complications. Conclusion The study shows the tumor-ablative efficacy of hypo-fractionated FLASH-RT in a human medulloblastoma mouse model. It is associated with qualitatively distinct transcriptional signatures prone to tumor and debris clearance mediated by microglial cells of the TME. Moreover, in the hippocampus, FLASH mitigates radiation-induced neurotoxicity by enhancing genes involved in synaptic plasticity, attenuating neuroinflammation, and preserving metabolic function. Key Points Complete response of medulloblastoma and reduction of neurotoxicity with hypo-fractionated FLASH regimen. Clearance-prone phagocytic and proteolytic activity in the microglia of the TME. Neuron/astrocyte transcriptional crosstalk in the hippocampus. Importance of the study This study constitutes a milestone for the future implementation of FLASH-RT in the treatment of children with brain cancer. It shows that FLASH does not protect medulloblastoma and on the contrary can be ablative when delivered in 3 fractions of 10 Gy. FLASH promotes a metabolically active, phagocytosis-prone phenotype in microglial cells consistent with immune activation and tumor surveillance, in contrast to the proliferative and immunosuppressive signaling programs induced by CONV. It also shows how FLASH may differentially shape long-term brain function in patients with brain tumors by modifying the transcriptional program of hippocampal subregions known to be critical for memory encoding, pattern separation, and consolidation. In summary, this study supports the idea that FLASH has the potential to shift treatment paradigms and change the dismal therapeutic outcome in patients with brain cancer.

Mechanisms, challenges and opportunities for FLASH radiotherapy in cancer

Nature reviews. Cancer · 2025-10-24 · 3 citations

Comparison of two electroacupuncture regimens on symptoms and brain structures in breast cancer survivors: A randomized, controlled trial.

Journal of Clinical Oncology · 2025-05-28

12119 Background: Although electroacupuncture (EA) has shown usefulness in managing neuropsychiatric symptoms in cancer survivors, a specific acupoint regimen has not been established. We conducted a randomized, controlled, patient- and assessor-blinded pilot trial to compare two EA regimens on neuropsychiatric symptoms and associated brain structural changes in breast cancer survivors. (Clinicaltrials.gov: NCT05283577). Methods: Breast cancer survivors who self-reported cognitive impairment, fatigue, insomnia, or psychological distress were randomized (1:1) to receive ten weekly therapeutic EA to target either neuropsychiatric-specific (nEA) or non-neuropsychiatric-specific (sham EA, sEA) acupoints. Outcomes were assessed using patient-reported outcomes (EORTC QLQ-C30, FACT-Cog, MFSI-SF), neurocognitive tests (CANTAB), and neuroimaging (measuring gray matter, white matter, cerebrospinal fluid, diffusion tensor metrics, and volume and mean intensity of the hippocampus) before and after treatment. We computed group-specific treatment effect sizes (Glass's Δ) adjusted for baseline variability using linear mixed models. A Pearson’s correlation analysis was performed between the neurocognitive scores and the imaging metrics. Multiple testing was controlled via the Benjamini-Hochberg method, with statistical significance set at P-adjusted < 0.05. Adverse events (AEs) were graded with CTCAE v5. Results: Thirty-five participants were recruited, of which five dropped out, leaving 30 (86%) completing all treatment sessions. The average (±SD) age was 58.2 ±12.2 years, with 66% non-Hispanic White, 77% holding a Bachelor’s degree or higher, 94% received systemic treatment and/or radiotherapy for cancer, 86% reporting ≥2 neuropsychiatric symptoms. Both groups showed statistically significant pre-post medium-to-large effect sizes in perceived cognitive function, fatigue, and quality of life. nEA group observed significant improvement in cognitive domains of attention (ES=0.708, P-adjusted=0.004), memory (ES=0.488, P-adjusted=0.026), and emotional functioning (ES=0.664, P-adjusted=0.004). Neuroimages showed greater gray matter volume change (P=0.0327) and post-treatment hippocampus mean intensity (P=0.0468) in nEA versus sEA. In the nEA group, correlations were observed between attention and gray matter volume (P=0.0198) and between executive function and hippocampus volume (P=0.0204). All AEs were grade 2 or lower: nEA participants reported pain (n=1) and bleeding (n=1), while sEA participants reported numbness (n=2), bruising (n=1), nausea (n=1), and redness (n=1). Conclusions: Ten weeks of electroacupuncture targeting neuropsychiatric-related acupoints, compared to sham acupoints, improves neuropsychiatric symptoms in breast cancer survivors, supported by clinically relevant structural brain changes. Clinical trial information: NCT05283577 .

Modification of the microstructure of the CERN- CLEAR-VHEE beam at the picosecond scale modifies ZFE morphogenesis but has no impact on hydrogen peroxide production

Radiotherapy and Oncology · 2025-05-20 · 11 citations

<h2>Abstract</h2><h3>Background</h3> FLASH radiotherapy has emerged as a promising advancement in radiation oncology, demonstrating the potential to minimize normal tissue toxicity while preserving tumoricidal efficacy. However, the precise beam parameters required for clinical translation remain to be fully defined. <h3>Methods</h3> To optimize beam parameters for clinical application, we employed Very High Energy Electrons (VHEE) at the CLEAR facility, capable of targeting deep-seated tumors. These were used alongside a FLASH-validated Intermediate Energy Electron (IIE) beam and a 160–225 keV X-ray beam, collectively delivering dose rates from 1 Gy/min to 10¹¹ Gy/s. High-throughput chemical assays investigated the radiochemical effects across this dose range, while zebrafish embryos provided an <i>in vivo</i> model to evaluate biological responses and developmental outcomes. This study offers the first comprehensive analysis of FLASH effects across a wide spectrum of dose rates and temporal parameters, from early physico-chemical interactions to complex biological systems. <h3>Results</h3> Data from CLEAR demonstrated that beam intensity, particularly bunch charge, is a critical determinant of the FLASH effect, and uncovered an unforeseen biological response when electrons are delivered over the picosecond timescale. <h3>Conclusion</h3> Our findings suggest that scanning strategies employing high intensity beamlets may be optimal for the clinical implementation of FLASH radiotherapy. These insights are pivotal for guiding the development of future FLASH protocols in radiation oncology.

Plasmid DNA Strand Breaks Are Dose Rate Independent at Clinically Relevant Proton Doses and Under Biological Conditions

Radiation Research · 2025-02-27 · 5 citations

We investigated the effect of proton FLASH radiation on plasmid DNA. Purified supercoiled pBR322 plasmids were irradiated with clinical doses (≤10 Gy) of protons at ultra-high and conventional dose rates using the Paul Scherrer Institute (PSI) isochronous cyclotron. The proton beam in this clinical facility has been validated to produce the FLASH effect in preclinical models. Plasmid samples were irradiated under various oxygen tensions, scavenger levels, pH conditions and Fe (II) concentrations as these biochemical parameters vary across tissues and tumors. Over the range of doses used, plasmid DNA strand breaks were found to be dose rate independent at all conditions investigated. Irradiation within the Bragg peak and spread-out Bragg peak increased clustered strand breaks, except in the presence of scavengers. With this model system, we demonstrate conclusively that plasmid DNA strand breakage is dose rate independent at doses below 10 Gy and does not constitute a high throughput assay endpoint predictive of the biological effect of FLASH.

Differentiating unirradiated mice from those exposed to conventional or FLASH radiotherapy using MRI

bioRxiv (Cold Spring Harbor Laboratory) · 2025-02-06

Background and purpose: The FLASH effect expands the therapeutic ratio of tumor control to normal tissue toxicity observed after delivery of ultra-high (>100 Gy/s FLASH-RT) vs. conventional dose rate radiation (CONV-RT). In this first exploratory study, we assessed whether ex-vivo Magnetic Resonance Imaging (MRI) could reveal long-term differences after FLASH-RT and CONV-RT whole-brain irradiation. Materials and methods: Female C57BL/6 mice were divided into three groups: control (non-irradiated), conventional (CONV-RT 0.1 Gy/s), and ultra-high dose rates (FLASH-RT 1 pulse, 5.5 × 10^6 Gy/s), and received 10 Gy of whole-brain irradiation in a single fraction at 10 weeks of age. Mice were evaluated by Novel Object Recognition cognitive testing at 10 months post-irradiation and were sampled at 13 months post-irradiation. Ex-vivo brains were imaged with a 14.1 Tesla/26 cm magnet with a multimodal MRI protocol, including T2-weighted TurboRare (T2W) and diffusion-weighted imaging (DWI) sequences. Results: In accordance with previous results, cognitive tests indicated that animals receiving CONV-RT exhibited a decline in cognitive function, while FLASH-RT performed similarly to the controls. MRI showed decreased hippocampal mean intensity in the CONV-RT mice compared to controls but not in the FLASH-RT group. Comparing CONV-RT to control, we found significant changes in multiple whole-brain diffusion metrics, including the mean Apparent Diffusion Coefficient (ADC) and Mean Apparent Propagator (MAP) metrics. By contrast, no significant diffusion changes were found between the FLASH-RT and control groups. In an exploratory analysis compared to controls, regional diffusion metrics were primarily altered in the basal forebrain and the insular cortex after CONV-RT, and after FLASH-RT, a trend reduction was also observed. Conclusion: This study presents initial evidence that MRI can uncover clear changes in the brain after CONV-RT but not after FLASH-RT. The MRI results aligned with the observed cognitive protection after FLASH-RT, indicating the potential use of MRI to analyze the FLASH response.

Temporal Effects of Dose and Fractionation of FLASH and Conventional Irradiation on Hippocampal Neurogenesis and Mechanisms of FLASH-Induced Neuroprotection

International Journal of Radiation Oncology*Biology*Physics · 2025-09-01

Preclinical Models for Assessing the Impact of Cranial Irradiation on Executive Function

Neuromethods · 2025-01-01

Dehydrozingerone Improves Mood and Memory in Diabetic Mice via Modulating Core Neuroimmune Genes and Their Associated Proteins

ACS Pharmacology & Translational Science · 2025-05-19 · 4 citations

Patients with poorly managed diabetes are at a greater risk of developing dementia and experiencing accelerated brain aging due to elevated blood glucose levels. Furthermore, patients with diabetes frequently encounter challenges with memory, recall, and concentration while carrying out their daily activities. The goal of this study was to investigate whether dehydrozingerone, a structural half-analog of curcumin, might improve mood and cognition in diabetics using a well-established mouse model of type 2 diabetes (T2DM) induced by a high-fat diet (HFD) and low streptozotocin (STZ) doses. Dehydrozingerone (DH) at 50 mg/kg orally for 2 weeks improved hippocampal and medial prefrontal cortex (mPFC)-dependent mood and memory in diabetic mice. An integrated transcriptome and proteome analysis revealed that 26 genes encoding mitochondrial energetics (Cox6), insulin resistance (Etnppl), lipid metabolism (Apod, Plin4), accelerated brain aging (Gm11639), and inflammation (Ighg2c) are differentially expressed in the diabetic mouse brain at both the mRNA and protein levels. Further, bioinformatic analysis revealed that these differentially expressed genes (DEGs) and proteins (DEPs) play a critical role in a variety of biological functions, including ion transport, calcium signaling, cellular senescence, mitochondrial energy, autophagy, neuronal plasticity, and cognition. Additionally, anomalies in the glutamine-glutamate/GABA cycle could exacerbate diabetes-related cognitive deficits. Treatment with DH had a variety of advantages, including decreased neuroinflammation and neuronal cell death as well as the promotion of critical genes and proteins necessary to promote cognitive performance. As a consequence, DH may be a potential treatment option for diabetics with persistent neuroinflammation and cognitive impairments.