Modified Hypoxia Inducible Factor 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.Graphical abstract

Characterization and functional analysis of novel circulating NK cell sub-populations

Natural killer (NK) cells are innate lymphoid cells having potent cytolytic function that provide host defense against microbial infections and tumors. Using our generated monoclonal antibody (mAb), named FE-1H10, new NK cell sub-populations in peripheral blood were identified. The molecules recognized by mAb FE-1H10 were expressed on a sub-population of CD3−CD56dim NK cells. The epitope recognized by mAb FE-1H10 was demonstrated to be N-glycan and proven to be different from CD57. Upon K562 stimulation, the CD56dimFE-1H10+ NK cell sub-population exhibited significantly lower cytolytic function with low ability to degranulate and release cytolytic granules compared to the CD56dimFE-1H10− NK cell sub-population. Moreover, the CD56dimFE-1H10+ NK cells produced less IFN-γ and TNF-α than the CD56dimFE-1H10− NK cells. We demonstrated here that mAb FE-1H10 could identify two sub-populations of circulating CD56dim NK cells with different functions. Our discovery of new sub-populations of NK cells improves our understanding of NK cell biology and may lead to the development of new approaches for NK cell therapy.

Less cholesterol means better tumor killing for cytotoxic T9 cells

In this issue, Ma et al. (https://doi.org/10.1084/jem.20171576) show that removal of cholesterol from CD8 T cells during type 9 differentiation increases their IL-9 production, persistence in vivo, and cytolytic function against tumors by preventing SUMOylation of liver X receptors.