Ulloa-Navas, María José

Abstract Glioblastoma (GBM) remains the most lethal primary brain cancer due to its remarkable metabolic plasticity and therapeutic resistance. Here, we identify cholesterol dependency as a therapeutically exploitable vulnerability in GBM using two FDA-approved drugs: the H1 histamine antagonist clemastine and the retinoid X receptor agonist bexarotene. Combined treatment induces potent synergistic anti-tumor activity across patient-derived glioma models, suppressing proliferation, stemness, and survival at sub-IC50 concentrations. Mechanistically, this therapy disrupts cholesterol biosynthesis, transport, and homeostasis, triggering endoplasmic reticulum stress and activation of the unfolded protein response, ultimately leading to autophagy and apoptotic cell death. Orthotopic patient-derived glioma models recapitulate these mechanisms in vivo, where local intracranial administration significantly reduces tumor progression and prolongs survival using fourfold lower doses than systemic intraperitoneal delivery. Single-cell RNA sequencing revealed activation of regeneration and plasticity programs, accompanied by immune microenvironment remodeling and enhanced inflammatory signaling. Importantly, syngeneic models preserved immune cell composition, supporting future integration with immunotherapeutic strategies. Together, these findings establish cholesterol dysregulation–induced metabolic collapse as a promising therapeutic approach for GBM.

Abstract Glioblastoma is an aggressive brain cancer with poor prognosis. Recent evidence implicates metabolic reprogramming, including the hexosamine biosynthetic pathway (HBP) and pentose phosphate pathway (PPP), as critical for tumor survival, therapy resistance, and progression. HBP inhibition with a proprietary small molecule (G2Bz) reduced stemness and migration and increased apoptosis of GBM in vitro. HBP inhibition was concomitant with an accumulation of metabolites in the Pentose Phosphate Pathway (PPP). Therefore, we further inhibited HBP with G2Bz and/or PPP with 6-aminonicotinamide (6-AN) in primary patient-derived GBM lines and evaluated additive or synergistic effects. Ultrastructural and functional changes were examined by electron microscopy (EM), high content imaging of endoplasmic reticulum (ER) and lipid droplets (LD), extracellular-flux analysis, and lipid profiling. Synergism was validated in an orthotopic model receiving lipoparticle-encapsulated G2Bz via intranasal delivery and/or intraperitoneal 6-AN; tumor burden was monitored via bioluminescence. Dual inhibition of HBP/PPP revealed additive or synergistic anti-proliferative effect. EM displayed severe ultrastructural cell damage with mitochondrial disorganization, ER dilation, and cytoskeletal remodeling. These changes coincided with increased ROS generation and reduced spare respiratory capacity suggesting higher sensitivity and lower ability to fight stress. Reduced ER–mitochondria contacts accompanied by increased expression of BiP and ER expansion suggest an unfolded protein response. Loss of LDs were associated with downregulation of lipid biosynthesis regulator SREBF1 and an increase in free fatty acids with a rise in lipid peroxidation. Reduced mitochondria–LD contacts correlate with lower endogenous fatty acid oxidation and a shift to exogenous fatty acid utilization. Dual inhibition in-vivo, suppressed tumor growth compared to control. These findings support that dual inhibition of HBP/PPP synergistically disrupts tumor metabolism, promoting organelle disorganization and lipid remodeling and highlight metabolic co-targeting as a strategy to impair GBM metabolism.

ABSTRACT Glioblastoma (GBM), the most aggressive primary brain tumour in adults, presents significant challenges due to its universal recurrence and limited survival rates. A key driver of GBM progression is the subpopulation of brain tumour‐initiating cells (BTICs), which contribute to therapy resistance and interact with the tumour microenvironment, particularly the cellular components in the subventricular zone (SVZ). Extracellular vesicles (EVs) are critical mediators of intercellular communication, carrying bioactive molecules, such as proteins and RNAs, that can modulate the behaviour of recipient cells. This study investigates the role of EVs in GBM's communication with non‐cancer cells. We utilised the proximity‐labelling system TurboID to achieve global and unbiased labelling of proteins within GBM‐derived EVs. By inducing TurboID expression in primary‐cultured human BTICs from GBM patients, we achieved efficient biotinylation of EV proteins without compromising vesicle integrity, and performed proteomic analysis of biotinylated proteins, which revealed a diverse cargo within BTIC‐EVs. Our method marks the first implementation of TurboID for unbiased global labelling of EV protein cargo in primary cells. This approach facilitates the investigation of EV‐mediated communication and potential therapeutic targets, contributing to the understanding of GBM's complex interactions with the brain's microenvironment and identification of biomarkers for improved diagnosis and treatment response.

Immunosuppression within the tumor microenvironment (TME) poses a significant challenge to the efficacy of Chimeric Antigen Receptor (CAR) T-cell therapy in solid tumors, including glioblastoma (GBM), the most common and deadly primary brain tumor. Tumor and TME-residing immunosuppressive cells can hijack program death 1(PD1) pathway to evade antitumor T-cell immunity by upregulating its ligand, PD-L1. Thus, targeting PD-L1 emerges as a promising therapeutic strategy to simultaneously eliminate tumor cells and immunosuppressive components within the TME. We developed a novel PD-L1-targeting CAR T-cell therapy, MC9999, and investigated its therapeutic effects against GBM. The antigen-specific cytotoxicity of MC9999 CAR T-cells was firmly validated using a LN229 GBM cell line and its PD-L1-deficient variant, as well as patient-derived brain tumor-initiating cells (BTICs). Furthermore, in vivo therapeutic antitumor effects were confirmed in orthotopic GBM models through intracranial administration of MC9999 CAR T-cells. To pave the way to the translation of MC9999 CAR T-cell therapy to patient bedside, we established a unique experimental system using patient-specific CAR T-cells against their own tumor and immunosuppressive cells. High-quality, patient-specific MC9999 CAR T-cells were manufactured using T cells isolated from peripheral blood, while paired autologous BTICs were generated to serve as target cells. Autologous immunosuppressive cells include monocyte-derived M2 macrophages from patient’s peripheral blood and tumor-associated macrophages (TAMs) isolated from patient’s tumor. Data from multiple patients’ samples consistently demonstrated that these patient-specific MC9999 CAR T-cells elicited robust cytotoxicity against autologous GBM tumor and TME-residing immunosuppressive cells, supporting our hypothesis that targeting PD-L1 effectively address both tumor and its TME. Immunohistochemistry (IHC) staining of our GBM patients’ tissues showed that PD-L1 expression was restricted to tumor cells and macrophages /microglia within the tumor, with no expression detected in neurons, astrocytes, oligodendrocytes, or blood vessels. These findings suggest that MC9999 CAR T-cells can be safely delivered to the brain without compromising normal cell populations. Ongoing studies are underway to further validate the safety profile of MC9999 CAR T-cell therapy. Collectively, the data obtained from this preclinical study support the effectiveness, feasibility and safety of local administration of MC9999 CAR T-cells as a promising new approach for GBM treatment. These encouraging results have motivated us to prepare an Investigational New Drug application to initiate a phase I clinical trial. Citation Format: Yan Luo, Yaqing Qie, Maria J. Ulloa-Navas, Jesus E. Sanchez-Garavito, Vanessa K. Jones, Martha E. Gadd, Mieu M. Brooks, Tanya Hundal, Andrew D. Brim, Isas K. Vazquez-Rosario, Haidong Dong, Alfredo Quinones-Hinojosa, Hong Qin. Intracranial delivery of MC9999 CAR T-cell therapy: a novel strategy to simultaneously eliminate GBM tumors and immunosuppressive components in the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4812.

ABSTRACT Neurodegenerative pathologies including multiple sclerosis (MS) are consistently associated with energy deficit in the central nervous system (CNS). This might directly impact myelinating oligodendrocytes as these are particularly vulnerable to metabolic insults. Importantly, oligodendroglial dysfunction and myelin alterations occur in most, if not all neurodegenerative diseases, and are associated with axonal pathology/loss. Thus, elucidating metabolic mechanisms required for oligodendroglial myelin maintenance and axonal support might be crucial to identify therapeutic targets to achieve neuroprotection. While monocarboxylates are important energy fuels for the CNS, their role in myelinating oligodendrocyte function remains unclear. Here we show that, just like neurons, myelinating oligodendrocytes express high affinity monocarboxylate transporter 2 (MCT2) both in mice and humans, which is downregulated in progressive MS. While deletion of MCT2 in mouse oligodendrocytes did not affect the survival of these cells, it resulted in downregulation of lipid synthesis-associated enzymes and failure of myelin maintenance. Moreover, axonal upregulation of lactate dehydrogenase A concomitant with axonal damage was observed but could be alleviated by ketogenic diet. We conclude that oligodendroglial MCT2 is required for myelin maintenance and axonal support, which becomes altered in progressive MS, but may be compensated for by specific metabolic therapies. Graphical abstract

Abstract Extracellular vesicles (EVs) are emerging as powerful players in cell‐to‐cell communication both in healthy and diseased brain. In Parkinson's disease (PD)—characterized by selective dopaminergic neuron death in ventral midbrain (VMB) and degeneration of their terminals in striatum (STR)—astrocytes exert dual harmful/protective functions, with mechanisms not fully elucidated. Here, this study shows that astrocytes from the VMB‐, STR‐, and VMB/STR‐depleted brains release a population of small EVs in a region‐specific manner. Interestingly, VMB‐astrocytes secreted the highest rate of EVs, which is further exclusively increased in response to CCL3, a chemokine that promotes robust dopaminergic neuroprotection in different PD models. The neuroprotective potential of nigrostriatal astrocyte‐EVs is investigated in differentiated versus undifferentiated SH‐SY5Y cells exposed to oxidative stress and mitochondrial toxicity. EVs from both VMB‐ and STR‐astrocytes counteract H 2 O 2 ‐induced caspase‐3 activation specifically in differentiated cells, with EVs from CCL3‐treated astrocytes showing a higher protective effect. High resolution respirometry further reveals that nigrostriatal astrocyte‐EVs rescue neuronal mitochondrial complex I function impaired by the neurotoxin MPP + . Notably, only EVs from VMB‐astrocyte fully restore ATP production, again specifically in differentiated SH‐SY5Y. These results highlight a regional diversity in the nigrostriatal system for the secretion and activities of astrocyte‐EVs, with neuroprotective implications for PD.