Modified Hypoxia-Inducible Factor Expression in CD8+ T Cells Increases Antitumor Efficacy

Abstract

Adoptive transfer of antitumor cytotoxic T cells is an emerging form of cancer immunotherapy. A key challenge to expanding the utility of adoptive cell therapies is how to enhance the survival and function of the transferred T cells. Immune-cell survival requires adaptation to different microenvironments and particularly to the hypoxic milieu of solid tumors. The hypoxia-inducible factor (HIF) transcription factors are an essential aspect of this adaptation. In this study, we undertook experiments to define structural determinants of HIF that potentiate antitumor efficacy in cytotoxic T cells. We first created retroviral vectors to deliver ectopic expression of HIF1α and HIF2α in mouse CD8⁺ T cells, together or individually and with or without sensitivity to the oxygen-dependent HIFα inhibitors Von Hippel–Lindau and factor-inhibiting HIF (FIH). HIF2α, but not HIF1α, drove broad transcriptional changes in CD8⁺ T cells, resulting in increased cytotoxic differentiation and cytolytic function against tumor targets. A specific mutation replacing the hydroxyl group–acceptor site for FIH in HIF2α gave rise to the most effective antitumor T cells after adoptive transfer in vivo. In addition, codelivering an FIH-insensitive form of HIF2α with an anti-CD19 chimeric antigen receptor greatly enhanced cytolytic function of human CD8⁺ T cells against lymphoma cells both in vitro and in a xenograft adoptive transfer model. These experiments point to a means to increase the antitumor efficacy of therapeutic CD8⁺ T cells via ectopic expression of the HIF transcription factor. See related Spotlight on p. 364