Abstract 2882: Characteristic immunomodulatory role of myeloid galectin-9 in the brain tumor microenvironment

Abstract

Abstract Galectin-9 is a member of galectin family with carbohydrate-recognition domains that specifically bind to β-galactoside. Increasing reports have suggested that galectin-9 can bind and interact with immune-modulatory molecules including TIM-3 in several pathophysiological conditions, especially in T cells. However, to date, little is known about the galectin-9 in myeloid cells under tumor microenvironment. In this study, we explored the expressional characteristics and roles of galectin-9 in the brain tumor microenvironment using an intracranial mouse brain tumor model and in vitro system. We found that expression level of galectin-9 was markedly elevated in ipsilateral hemisphere compared to contralateral hemisphere of intracranial brain tumor model. FACS analyses showed that galectin-9 expression was higher in CD45highCD11bhigh macrophages and CD45midCD11bhigh microglia as well as lymphocytes from ipsilateral region than those from contralateral region. In addition, galectin-9 levels were increased after exposure to GL26 brain tumor cells in in vitro co-culture system using primary microglia. Interestingly, phagocytic activity, a key function of myeloid cells, was significantly reduced in galecin-9+ microglia compared to galecin-9- microglia when co-cultured with GL26-GFP cells. Furthermore, SIRPα levels were higher in galectin-9+ microglia than galecin-9- microglia. Similar results were observed in macrophages. Collectively, these findings suggest that galectin-9 may be an important modulatory molecule in myeloid cells under brain tumor microenvironment. Citation Format: Chanju Lee, Dahee Yu, Eun Jung Park. Characteristic immunomodulatory role of myeloid galectin-9 in the brain tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2882.