Abstract 4064: hetIL-15 and Fenofibrate combination alters the metabolic fitness of tumor-infiltrating CD8+T cells leading to TNBC tumor eradication in mice

Abstract Introduction: Tumor-infiltrating cytotoxic CD8+T cells frequently undergo an altered state of differentiation referred to as "exhaustion" and, as a result, they fail to control tumor growth. IL-15 is a cytokine which stimulates the generation, proliferation and cytotoxic function of tumor CD8+T and NK cells. We have produced the native heterodimeric form of IL-15 (hetIL-15) which has advanced in clinical trials. The aim of this study was to overcome the exhaustion of the tumor-infiltrating CD8+T cells and to increase their cytotoxicity, using Fenofibrate (FF), a PPAR-α agonist, in combination with hetIL-15. Experimental Procedures: We have evaluated the therapeutic efficacy of hetIL-15 immunotherapy as a monotherapy and in combination with FF in the murine EO771 orthotopic breast cancer model. The effects of hetIL-15 and/or FF on immune cells and on tumor microenvironment were analyzed by flow cytometry, transcriptomics, metabolomics and proteomics. The metabolic profile of tumor-infiltrating T cells was performed with Seahorse analysis. Results and Conclusions: hetIL-15 monotherapy resulted in tumor eradication in 40% of treated mice and increased survival. Seahorse analysis of tumor-infiltrating CD8+T cells confirmed a rise in oxygen consumption rate (OCR) with substantial increase of spare respiratory capacity. Upon hetIL-15 treatment, tumor-infiltrating CD8+T cells showed elevated extracellular acidification rate (ECAR), resulting in a pronounced shift in the OCR/ECAR ratio in comparison to control, confirming their increased proliferating status. These tumor-infiltrating CD8+T cells also showed increased mitochondrial potential and/or mass and fatty acid (FA) uptake, as evidenced by increased MitoTracker and Bodipy staining, respectively. Transcriptomic analysis revealed increased expression of genes involved in several metabolic pathways such as oxidative phosphorylation, FA oxidation and glycolysis. Monotherapy with FF had no effect on tumor growth delay, whereas the FF- hetIL-15 combination resulted in complete eradication of the tumors in 85%. Combination therapy reshaped the tumor microenvironment, resulting in higher IFN-γ and in differentially expressed metabolites as shown by tumor proteomics and metabolomics, respectively. The combination treatment increased the mitochondrial function, FA uptake and OCR, revealing a more metabolically active phenotype. We conclude that hetIL-15 supports a favorable metabolic profile of intratumoral effector lymphocytes, important for their function. Our data suggest that metabolic reprogramming of tumor specific CD8+T cells using FF is a promising strategy to overcome T cell exhaustion and to promote survival in a metabolically hostile tumor microenvironment. Citation Format: Dimitris Stellas, Sevasti Karaliota, Vasiliki Stravokefalou, Katherine C. Goldfarbmuren, Breana Myers, George N. Pavlakis, Barbara K. Felber. hetIL-15 and Fenofibrate combination alters the metabolic fitness of tumor-infiltrating CD8+T cells leading to TNBC tumor eradication in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4064.