Abstract The tumor microenvironment is frequently hypoxic and characterized by a scarcity of nutritional resources, including limited glucose availability. As effector T cells have high energy demands, tumor metabolism can contribute to T-cell dysfunction and exhaustion. In this study, we assessed hypoxia in spleen and tumor tissue from tumor-bearing C57BL/6J mice using RT-PCR, histology, and flow cytometry. Next, CD8+ T cells isolated from C57BL/6J or P14+ mice were transduced with a Thy1.1 (control) or Thy1.1-myoglobin (Mb) packaging retrovirus, and Mb expression was confirmed by RT-PCR and Western blot. The metabolism of these cells was analysed using flow cytometry, TEM, FIB-SEM, Seahorse assays, metabolomics, and luminescence-based approaches. Furthermore, effector function was measured in vitro by flow cytometry. P14+ CD45.1+ CD8+ Mb-transduced and control T cells were transferred into B16F10-gp33 or MC38-ova tumor-bearing mice and analysed by flow cytometry and histology. Finally, B16F10-gp33 tumor-bearing mice received additional treatment with an anti-PD-1 checkpoint inhibitor. Here, we demonstrate that expression of the oxygen-binding protein myoglobin in T cells can enhance their mitochondrial and glycolytic metabolic functions. Metabolites and TCA cycle intermediates were markedly increased in the presence of myoglobin and were associated with elevated ATP levels. Myoglobin-expressing T cells exhibited reduced HIF-1α expression after activation and during infiltration into the tumor microenvironment. Accordingly, myoglobin expression increased effector T-cell function against tumor cells in vitro, accompanied by reduced superoxide levels. Following adoptive transfer into tumor-bearing mice, myoglobin expression promoted greater infiltration into the tumor microenvironment. Although myoglobin-expressing T cells showed increased effector cytokine expression, PD-1 remained detectable and targetable by anti-PD-1 monoclonal antibodies, which—when combined with transfer of myoglobin-expressing T cells—achieved maximal efficacy in delaying tumor growth. Taken together, we show that expression of myoglobin in T cells enhances their metabolism, infiltration into tumor tissue, and effector function against cancer cells. Citation Format: Julia Werner, Haifeng Xu, Georgios Theodorakis, Ichiro Katahira, Mitrajit Ghosh, Michal Gorzkiewicz, Luisa de Sousa Santos, Ann Kathrin Bergmann, Max Anstötz, Anne Busch, Diran Herebian, Sascha Dietrich, Carsten Berndt, Ertan Mayatepek, Aleksandra Pandyra, Dirk Brenner, Philipp Lang. Myoglobin expression boosts T-cell metabolism and antitumor effector function abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2806.
Werner et al. (Fri,) studied this question.