Targeting UDP-α-D-glucose 6-dehydrogenase alters the CNS tumor immune microenvironment and inhibits glioblastoma growth

Glioblastoma(GBM,WHO grade IV glioma)is the most common and lethal malignant brain tumor in aduts with a dismal prognosis.The extracellular matrix(ECM)supports GBM progression by promoting tumor cell proliferation,migration,and immune escape.Uridine diphosphate(UDP)-glucose 6-dehydrogenase(UGDH)is the rate-limiting enzyme that catalyzes the biosynthesis of glycosaminoglycans that are the principal component of the CNS ECM.We investigated how targeting UGDH in GBM infuence$the GBM immune microenvironment,including tumor-associated microglia/macrophages(TAMs)and T cells.TAMs are the main im-mune effector cells in GBM and can directly target tumor cells if properly activated.In co-cultures of GBM cells and human primary macrophages,UGDH knockdown in GBM cells pro-moted macrophage phagocytosis and M-like polarization.In orthotropic human GBM xeno-grafts and syngeneic mouse glioma models,targeting UGDH decreased ECM deposition,increased TAM phagocytosis marker expression,reduced M2-like TAMS and inhibited tumor growth.UGDH knockdown in GBM cells also promoted cytotoxic T cell ifltration and activa-tion in orthotopic syngeneic mouse glioma models.The potent and in-human-use small mole-cule GAG synthesis inhibitor 4-methylumbelliferone(4-MU)was found to inhibit GBM cell proliferation and migration in vitro,mimic the macrophage and T-cell responses to UGDH knockdown in vitro and in vivo and inhibit growth of orthotopic murine GBM.Our study shows that UGDH supports GBM growth through multiple mechanisms and supports the development of ECM-based therapeutic strategies to simultaneously target tumor cells and their microenvi-ronment.