Metabolic constraints in the tumor microenvironment constitute a barrier to effective antitumor immunity and similarities in the metabolic properties of T cells and cancer cells impede the specific therapeutic targeting of metabolism in either population. To identify distinct metabolic vulnerabilities of CD8+ T cells and cancer cells, we developed a high-throughput in vitro pharmacologic screening platform and used it to measure the cell type–specific sensitivities of activated CD8+ T cells and B16 melanoma cells to a wide array of metabolic perturbations during antigen-specific killing of cancer cells by CD8+ T cells. We illustrated the applicability of this screening platform by showing that CD8+ T cells were more sensitive to ferroptosis induction by inhibitors of glutathione peroxidase 4 (GPX4) than B16 and MC38 cancer cells. Overexpression of ferroptosis suppressor protein 1 (FSP1) or cytosolic GPX4 yielded ferroptosis-resistant CD8+ T cells without compromising their function, while genetic deletion of the ferroptosis sensitivity–promoting enzyme acyl-CoA synthetase long-chain family member 4 (ACSL4) protected CD8+ T cells from ferroptosis but impaired antitumor CD8+ T-cell responses. Our screen also revealed high T cell–specific vulnerabilities for compounds targeting NAD+ metabolism or autophagy and endoplasmic reticulum (ER) stress pathways. We focused the current screening effort on metabolic agents. However, this in vitro screening platform may also be valuable for rapid testing of other types of compounds to identify regulators of antitumor CD8+ T-cell function and potential therapeutic targets.

Purpose To understand why some patients respond to immunotherapy but many do not, a clear picture of the tumor microenvironment (TME) of head and neck squamous cell carcinoma (HNSCC) is key. Here we review the current understanding on the immune composition per HNSCC subsite, the importance of the tumor's etiology and the prognostic power of specific immune cells. Recent Findings Large cohort data are mostly based on deconvolution of transcriptional databases. Studies focusing on infiltrate localization often entail small cohorts, a mixture of HNSCC subsites, or focus on a single immune marker rather than the interaction between cells within the TME. Summary Conclusions on the prognostic impact of specific immune cells in HNSCC are hampered by the use of heterogeneous or small cohorts. To move forward, the field should focus on deciphering the immune composition per HNSCC subsite, in powered cohorts and considering the molecular diversity in this disease. Keywords Head and neck squamous cell carcinoma . Tumor microenvironment . Innate and adaptive immune system . Tumor infiltrating lymphocytes . Prognosis . HNSCC subsites Irene H. Nauta and Tara Muijlwijk contributed equally to this work. This article is part of the Topical Collection on Head and Neck Cancers

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