Adarsha P. Malla

Glioblastoma (GBM) is a lethal, treatment-resistant brain cancer characterized by diffuse brain invasion, complex neuron–glioma signaling, and cellular, molecular, and spatial heterogeneity. Surgery is the current mainstay of treatment, aimed at maximizing tumor cytoreduction, decompressing the brain to improve neurologic function and providing material for analyses to inform prognostication and adjuvant treatment selection. To accurately model GBM surgical resection and tissue sampling in preclinical animal models, we developed the Maximal Safe Intracranial Surgery (MSIS) platform. MSIS integrated a miniaturized neurosurgical resection device and enabled a safe, tunable, and reproducible approach for intracranial tumor resection, multiregional biopsy, and longitudinal tissue sampling in murine models, with stereotactic, sterile, and high-viability tissue collection. MSIS was applied across five distinct orthotopic brain tumor models to reproducibly generate histologically and radiologically representative models of postsurgical GBM. Similar to humans, increasing the extent of resection correlated with improved animal survival, and recurrent growth patterns varied significantly by model type. Transcriptional profiles of matched primary versus postsurgical recurrent tumors revealed enrichment of margin-associated transcriptional states consistent with neuron–glioma signaling. Overall, the MSIS approach offers opportunities to model the standard of care, dissect the spatial and temporal dynamics of GBM, and pair therapeutic discovery with contextual tumor pathobiology. Significance: A clinically derived stereotactic resection platform models surgical resection in glioblastoma, enabling longitudinal tissue sampling and revealing conserved early-recurrence neuron-glioma programs in patient-derived models.

Brain tumors exhibit extensive metabolic reprogramming that supports proliferation, invasion, therapeutic resistance, and adaptation to dynamic microenvironmental conditions. These alterations provide opportunities for metabolic imaging approaches that extend beyond conventional anatomical neuroimaging. Hyperpolarized magnetic resonance imaging (hpMRI) has emerged as a novel metabolic imaging platform capable of non-invasively visualizing real-time cellular metabolism through dynamic nuclear polarization of carbon-13-labeled substrates. By dramatically enhancing magnetic resonance signal intensity, hpMRI enables interrogation of enzyme-specific metabolic pathways and provides unique insight into tumor energetics, metabolic heterogeneity, and treatment response. The distinct contribution of this review is an updated, brain tumor-specific, clinically oriented framework that integrates recent human evidence with longitudinal metabolic phenotyping, emerging pathway-specific probes, acquisition standardization, multimodal validation, and the remaining barriers to clinical implementation. Particular emphasis is placed on hyperpolarized [1-¹³C]pyruvate, which has demonstrated feasibility and safety in patients with gliomas and has enabled assessment of glycolytic metabolism, oxidative phosphorylation, tumor recurrence, and longitudinal treatment response. Serial changes in lactate and bicarbonate flux may also reflect evolution toward more glycolytic, heterogeneous, and treatment-resistant tumor phenotypes, supporting the potential prognostic value of hpMRI before conventional radiographic progression becomes evident. We also review emerging applications involving α-ketoglutarate metabolism, redox biology, glutathione cycling, perfusion imaging, and molecular characterization of clinically relevant alterations including IDH1, TERT, and c-MYC-associated metabolic programs. In addition, we discuss recent advances in acquisition methods, image standardization, and multimodal integration with conventional MRI and positron emission tomography. Although several technical and logistical challenges remain, hpMRI is an investigational, radiation-free metabolic imaging modality with potential applications in diagnosis, molecular stratification, and treatment monitoring; however, substantial technical, regulatory, logistical, and economic barriers currently limit routine clinical use, molecular stratification, therapeutic monitoring, and precision medicine approaches in neuro-oncology. Continued clinical translation and development of novel metabolic probes may further expand its role in brain tumors and other neurological diseases.

Infiltrating gliomas are challenging to treat, as the blood-brain barrier significantly impedes the success of therapeutic interventions. While some clinical trials for high-grade gliomas have shown promise, patient outcomes remain poor. Microbubble-enhanced focused ultrasound (MB-FUS) is a rapidly evolving technology with demonstrated safety and efficacy in opening the blood-brain barrier across various disease models, including infiltrating gliomas. Initially recognized for its role in augmenting drug delivery, the potential of MB-FUS to augment liquid biopsy and immunotherapy is gaining research momentum. In this review, we will highlight recent advancements in preclinical and clinical studies that utilize focused ultrasound to treat gliomas and discuss the potential future uses of image-guided precision therapy using focused ultrasound.

D-amino acids are increasingly recognized as important signaling molecules in the mammalian central nervous system. However, the D-stereoisomer of the amino acid with the fastest in vitro spontaneous racemization rate, cysteine, has not been examined in mammals. Using chiral high-performance liquid chromatography and an stereospecific luciferase assay, we identify endogenous D-cysteine in the mammalian brain. We identify serine racemase (SR), which generates the NMDA glutamate receptor co-agonist D-serine, as a candidate biosynthetic enzyme for D-cysteine. Levels of D-cysteine are enriched over twentyfold in the embryonic mouse brain compared to the adult. D-cysteine reduces the proliferation of cultured mouse embryonic neural progenitor cells (NPCs) by approximately 50%, effects not shared with D-serine or L-cysteine. The antiproliferative effect of D-cysteine is mediated by the transcription factors FoxO1 and FoxO3a. The selective influence of D-cysteine on NPC proliferation is reflected in overgrowth and aberrant lamination of the cerebral cortex in neonatal SR knockout mice. Finally, we perform an unbiased screen for D-cysteine-binding proteins in NPCs by immunoprecipitation with a D-cysteine-specific antibody followed by mass spectrometry. This approach identifies myristoylated alanine-rich C-kinase substrate (MARCKS) as a putative D-cysteine-binding protein. Together, these results establish endogenous mammalian D-cysteine and implicate it as a physiologic regulator of NPC homeostasis in the developing brain.