Molecular Pathogenesis of Neoplasia

National Institute Of Neurological Disorders And Stroke

Investigators

Linked publications, trials & patents

Abstract

Protein Phosphatase 2A Inhibition and its Interaction with Chemotherapy and Radiotherapy: We previously studied the inhibitory activity of LB100, a first-in-class small molecular inhibitor of Protein Phosphatase 2A (PP2A), in a mouse xenograft human GBM animal model. This compound had potent effects against GBM when combined with radiation or chemotherapy. The Neurooncology Branch, NCI, tested LB100 as a chemosensitizer or radiosensitizer in GBM therapeutics. Protein Arginine Methyltransferase 5 Inhibition in Models of Glioblastoma Dr. Banasavadi, Head of the Molecular and Therapeutics Unit of the SNB, studies the role of Protein Arginine Methyltransferase 5 (PRMT5) in brain tumors. PRMT5 catalyzes the symmetric di-methylation of arginine residues and is overexpressed in GBM. His earlier research showed that inhibition of PRMT5 caused stem-like GBM tumor cells to become senescent. He also found that inhibition of PRMT5 and PP2A simultaneously produced a more significant anti-GBM effect than either agent alone (published in 2021). He published a manuscript on this research and another reviewing the medical and scientific literature on the potential use of PP2A inhibitors in brain tumor therapeutics (2021). In the subsequent study, he found that PRMT5 depletion enhanced trametinib-induced cytotoxicity in GBM by blocking the trametinib-induced AKT escape pathway. In orthotopic murine xenograft models, PRMT5 depletion extended the survival of tumor-bearing mice and adding trametinib to PRMT5 depletion further increased survival. This study was published in Neuro-Oncology Advances in 2022. His lab recently published a comprehensive review article regarding current perspectives and future directions of MEK inhibition in GBM [1]. Dr. Banasavadi's lab continued working on PRMT5-related projects to understand the role of PRMT5 in GBM therapy resistance. Tumor cells invariably develop resistance to Temozolomide (TMZ), the standard chemotherapeutic agent for glioblastoma. The mechanistic role of PRMT5 in treatment-resistant glioblastoma is unknown. To study this mechanism, patient-derived glioma stem-like cells (GSCs) that were treated with a PRMT5 inhibitor (LLY-283) or transfected with PRMT5 target-specific siRNA were subsequently treated with TMZ and subjected to in vitro functional and mechanistic studies. Dr. Banasavadi's group found that PRMT5 inhibition increased the cytotoxic effect of TMZ in GSCs [2]. Unbiased transcriptomic studies indicated that PRMT5 inhibition negatively enriched DNA damage repair genes. PRMT5 inhibition abrogated TMZ-induced G2/M cell cycle arrest. Importantly, combination treatment increased DNA double-strand breaks (ɣH2AX foci) and enhanced DNA damage (comet assay). Specifically, the LLY-283 treatment blocked homologous recombination repair in GSCs. In vivo, LLY-283 combined with TMZ significantly curbed tumor growth and prolonged the survival of tumor-bearing mice. Further, compared to monotherapy, there was a significant reduction in the proliferation marker Ki-67, and upregulated expression of the apoptosis marker cleaved caspase 3 and DNA damage response maker ɣH2AX. These results showed that concomitant treatment with LLY-283 and TMZ had significantly greater antitumor efficacy than either agent alone, suggesting that combination of PRMT5 inhibition and TMZ could be a novel therapeutic strategy for glioblastoma. The manuscript on this project is under review for the publication. A study preprint is available online (PMID: 39989968). Dr. Banasavadi collaborated on a project studying the “Simultaneous Targeting of Tumor Cells and Tumor-Associated Macrophages to Reprogram Glioblastoma Using Trypsinized Extracellular Vesicles Carrying Tumor Suppressive MicroRNA" [3]. One of the caveats of GBM therapy is poor drug delivery across the blood–brain barrier and an immunosuppressive tumor microenvironment (TME). Use of tumor-suppressive microRNAs (miRNAs) is a promising therapeutic strategy that can reprogram both tumor cells and the TME. Presently, inefficient delivery systems limit their clinical application. In this project, the collaborative group demonstrated that trypsin digestion of extracellular vesicles (EVs) enhanced the EV's' labeling efficiency with folate (FA), enabling the selective targeting of folate receptor (FR)-positive GBM cells and simultaneous targeting of tumor-associated macrophages (TAMs) [3]. FA-labeled trypsinized EVs (tEVs) loaded with miR-138 inhibited tumor growth, depolarized TAMs, and enhanced antitumor immunity. This study represents the first preclinical attempt to modulate tumor cells and innate immunity via miRNA-loaded tEVs, offering a novel and potentially effective therapeutic approach to GBM treatment. This project was published in the Journal “Nano Letters” in 2025 (DOI: 10.1021/acs.nanolett.5c01897). Study of an Etiologic Role of Human Endogenous Retroviruses in Glioma Pathogenesis We continued our research to evaluate the role of endogenous retroviruses in glioma pathogenesis. This research depended heavily on collaborations with the laboratories of Dr. Ashish Shah, Assistant Professor of Neurosurgery at the University of Miami School of Medicine, Dr. Avindra Nath in the Section of Infections of the Nervous System (SINS) in NINDS, and Dr. Zhengping Zhuang in NOB/NCI [4]. With the University of Miami and NINDS investigators recently, Dr. Shah was the first author of an article about human endogenous retrovirus K contributing to a stem cell niche in GBM (2). Dr. Ramsoomair at the University of Miami published an article with NIH and University of Miami investigators about the epitranscriptome of high-grade gliomas and its relevance as a therapeutic target (3). Sarah Rivas, a former trainee in the Surgical Neurology Branch and a summer student in Dr. Shah's lab, reviewed the scientific literature on the role of antiretroviral drug repositioning for GBM [5]. Immunotherapy of Glioblastoma The Protein Phosphatase 2A (PP2A) inhibitor described above, LB100, enhanced the antitumor effects of an immune checkpoint inhibitor in an animal model of glioblastoma. SNB investigators published a report with Dr. Zhuang and his NOB/NCI colleagues showing that pharmacologic inhibition of protein phosphatase-2A achieved durable immune-mediated antitumor activity when combined with PD-1 blockade. The NOB/NCI initiated a clinical trial combining a PP2A inhibitor with a PD-1 blocker. The SNB laboratory has also collaborated with NOB NCI to study vaccines in animal models of glioblastoma. Collaborative Efforts to Improve the Treatment of Brain and Spinal Neoplasms The Surgical Neurology Branch works with investigators in other NINDS branches, the Neuro-Oncology Branch, Laboratory of Pathology, and Clinical Genetics Branch of NCI, and other sites outside the NIH to find better ways to evaluate and treat brain and spinal malignancies. This year, several basic, translational, and clinical research publications and review articles about topics in neuro-oncology, vasculogenesis, and immunology resulted from these collaborative efforts [6-12].