Modified HIF expression in CD8+ T cells increases anti-tumor efficacy

Adoptive transfer of anti-tumor cytotoxic T cells is a novel form of cancer immunotherapy, and a key challenge is to ensure the survival and function of the transferred T cells. Immune cell survival requires adaptation to different micro-environments, and particularly to the hypoxic milieu of solid tumors. The HIF transcription factors are an essential aspect of this adaptation, and we undertook experiments to define structural determinants of HIF that would potentiate anti-tumor efficacy in cytotoxic T cells. We created retroviral vectors to deliver ectopic expression of HIF-1ɑ and HIF-2ɑ in mouse CD8+ T cells, together or individually, and with or without sensitivity to their oxygen-dependent inhibitors Von Hippel-Lindau (VHL) and Factor Inhibiting HIF (FIH). We found that HIF-2ɑ, but not HIF-1ɑ, drives broad transcriptional changes in CD8+ T cells, resulting in increased cytotoxic differentiation and cytolytic function against tumor targets. We further found that a specific mutation replacing the hydroxyl group acceptor site for FIH in the HIF-2ɑ isoform gives rise to the most effective anti-tumor T cells after adoptive transfer in vivo. Lastly, we show that co-delivering an FIH-insensitive form of HIF-2ɑ with an anti-CD19 chimeric antigen receptor greatly enhances cytolytic function of human CD8+ T cells against lymphoma cells. These experiments provide a means to increase the anti-tumor efficacy of therapeutic CD8+ T cells via ectopic expression of the HIF transcription factor.Competing Interest StatementThe authors have declared no competing interest.View Full Text