1. Galectin-9 Mediates the Functions of Microglia in the Hypoxic Brain Tumor Microenvironment.
- Author
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Lee C, Yu D, Kim HS, Kim KS, Chang CY, Yoon HJ, Won SB, Kim DY, Goh EA, Lee YS, Park JB, Kim SS, and Park EJ
- Subjects
- Animals, Mice, Humans, Cell Line, Tumor, Glioblastoma pathology, Glioblastoma metabolism, Glioblastoma genetics, Glioma pathology, Glioma metabolism, Glioma genetics, Mice, Inbred C57BL, Macrophages metabolism, Macrophages pathology, Male, Tumor Microenvironment, Microglia metabolism, Microglia pathology, Brain Neoplasms pathology, Brain Neoplasms metabolism, Brain Neoplasms genetics, Galectins metabolism, Galectins genetics
- Abstract
Galectin-9 (Gal-9) is a multifaceted regulator of various pathophysiologic processes that exerts positive or negative effects in a context-dependent manner. In this study, we elucidated the distinctive functional properties of Gal-9 on myeloid cells within the brain tumor microenvironment (TME). Gal-9-expressing cells were abundant at the hypoxic tumor edge in the tumor-bearing ipsilateral hemisphere compared with the contralateral hemisphere in an intracranial mouse brain tumor model. Gal-9 was highly expressed in microglia and macrophages in tumor-infiltrating cells. In primary glia, both the expression and secretion of Gal-9 were influenced by tumors. Analysis of a human glioblastoma bulk RNA sequencing dataset and a single-cell RNA sequencing dataset from a murine glioma model revealed a correlation between Gal-9 expression and glial cell activation. Notably, the Gal-9high microglial subset was functionally distinct from the Gal-9neg/low subset in the brain TME. Gal-9high microglia exhibited properties of inflammatory activation and higher rates of cell death, whereas Gal-9neg/low microglia displayed a superior phagocytic ability against brain tumor cells. Blockade of Gal-9 suppressed tumor growth and altered the activity of glial and T cells in a mouse glioma model. Additionally, glial Gal-9 expression was regulated by hypoxia-inducible factor-2α in the hypoxic brain TME. Myeloid-specific hypoxia-inducible factor-2α deficiency led to attenuated tumor progression. Together, these findings reveal that Gal-9 on myeloid cells is an immunoregulator and putative therapeutic target in brain tumors. Significance: Galectin-9 serves as an immune checkpoint molecule that modulates the functional properties of microglia in the brain tumor microenvironment and could potentially be targeted to effectively treat brain tumors., (©2024 American Association for Cancer Research.)
- Published
- 2024
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