Glioblastoma multiforme (GBM) is a highly malignant cancer with one of the highest mortality rates. The average survival is less than 2 years after diagnosis even with current therapies, which include chemotherapy and radiation. Furthermore, GBM has shown severe resistance to immunotherapies such as immune checkpoint blockade, which mainly target CD8 T cells. Recently, several studies showed that γδ T cells can be an alternative target of immunotherapy. Unlike conventional ab T cells, γδ T cells recognize stress-induced surface antigens such as NKG2D ligands and phosphoantigens. Because GBM cells highly express NKG2D ligands, γδ T cells could be good target for immunotherapy. However, a basic understanding of γδ T cell-mediated antitumor immunity is lacking. Using single-cell transcriptomic analysis, we analyzed the characteristics of GBM-infiltrating γδ T cells. Because γδ T cells were highly suppressed by the poorly oxygenated microenvironment of brain tumors, we inhibited tumor cell respiration using metformin, a drug used for type 2 diabetes, and found that this sufficiently reinvigorated γδ T cells. Reinvigorated γδ T cells had enhanced expression of NKG2D and multiple cytokines. In conclusion, this study highlights the importance of γδ T cells in GBM and the potential for new druggable pathways through reinvigoration of γδ T cells. Citation Format: Jang Hyun Park, Heung Kyu Lee. The mechanism of γδ T cell-mediated antitumor immunity in Glioblasotma multiforme [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO013.