Tumor hypoxia represses γδ T cell-mediated antitumor immunity against brain tumors

Abstract

The anatomic location and immunologic characteristics of brain tumors result in strong lymphocyte suppression. Consequently, conventional immunotherapies targeting CD8 T cells are ineffective against brain tumors. Tumor cells escape immunosurveillance by various mechanisms, and tumor cell metabolism can affect the metabolic states and functions of tumor-infiltrating lymphocytes. Oxygen tension is one important factor influencing immune responses. Here, we discovered that brain tumor cells had a particularly high demand for oxygen, which affected γδ T cell-mediated antitumor immune responses but not those of conventional T cells. Specifically, tumor hypoxia activated the γδ T cell protein kinase A (PKA) pathway at a transcriptional level, resulting in repression of NKG2D expression. Alleviating tumor hypoxia reinvigorated NKG2D expression and the antitumor function of γδ T cells. These results reveal a hypoxia-mediated mechanism by which brain tumors and γδ T cells interact and emphasize the importance of γδ T cells for antitumor immunity against brain tumors.