Glioblastoma (GBM) tumors are enriched in immune-suppressive myeloid cells and are refractory to immune checkpoint therapy (ICT). Targeting epigenetic pathways to reprogram the functional phenotype of immune-suppressive myeloid cells to overcome resistance to ICT remains unexplored. Single-cell and spatial transcriptomic analyses of human GBM tumors demonstrated high expression of an epigenetic enzyme - histone 3 lysine 27 demethylase (KDM6B) in intra- tumoral immune-suppressive myeloid cell subsets. Importantly, myeloid-cell specificKdm6bdeletion enhanced pro-inflammatory pathways and improved survival in GBM tumor-bearing mice. Mechanistic studies elucidated that the absence ofKdm6benhances antigen-presentation, interferon response and phagocytosis in myeloid cells by inhibiting mediators of immune suppression includingMafb, Socs3andSirpa. Further, pharmacological inhibition of KDM6B mirrored the functional phenotype ofKdm6bdeleted myeloid cells and enhanced anti-PD1 efficacy. Thus, this study identified KDM6B as an epigenetic regulator of the functional phenotype of myeloid cell subsets and a potential therapeutic target to improve response to ICT.
INTRODUCTION
Current treatments for glioblastoma (GBM) are minimally effective and the prognosis for patients is uniformly poor despite multimodal therapy. While prior studies have examined intratumoral injection of oncolytic virus DNX-2401 into recurrent tumor, the potential of DNX-2401 delivered into the surgical resection cavity using tumor-tropic human mesenchymal stem cells (MSCs) has not been evaluated. We hypothesize that using a fibrin scaffold for transplanting MSCs loaded with DNX-2401 (MSCs-DNX-2401) into the resection cavity will improve MSC and viral delivery, kill residual tumor cells, decrease GBM recurrence, and improve overall survival.
METHODS
MSCs-DNX-2401 were either seeded in fibrin or suspended in PBS and placed in the upper wells of a transwell with U87 tumor cells plated below. After 1 wk, U87 cells were counted to compare rates of cellular killing to evaluate release of DNX-2401 from fibrin-seeded MSCs. U87 tumor cells were then transduced with mCherry-Luciferase and implanted in 20 mice. Fluorescence-guided surgical resection of glioma xenografts was performed on day 10. Either MSCs (control) or MSCs-DNX-2401 (treatment) were seeded in fibrin and implanted in the resection cavity. Postoperative bioluminescence imaging was used to evaluate extent of residual disease and weekly serial imaging was used to monitor tumor recurrence in each group.
RESULTS
Transwell experiments demonstrate significant cytotoxic killing of U87 tumor cells with MSCs-DNX-2401 seeded in fibrin having comparable oncolytic activity to MSC-DNX-2401 without fibrin. In vivo studies show four mice in the treatment group (40%) demonstrating complete responses to delivery of MSCs-DNX-2401 using fibrin. Kaplan-Meier survival analysis demonstrates survival benefit with prolonged median and overall survival in the treatment group (P < .05).
CONCLUSION
This translational study validates the overall treatment paradigm for delivering oncolytic virotherapy into the tumor resection cavity using MSCs seeded in fibrin to decrease tumor recurrence and prolong overall survival. This project represents an important preliminary step for eventual application of this technology in human patients.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.