Metabolic Profiling of Circulating and Tumour‐Infiltrating T Cells Uncovers Bioenergetic Checkpoints Linked With Immune and Clinical Skewing in Melanoma Patients

Metabolism is critical for immune cell functions. Tumours shape their microenvironment to render it metabolically hostile for infiltrating immune cells. While targeting immunometabolism emerges as a promising way to reinvigorate anticancer immunity, a deeper understanding of the metabolic disturbances of immune cells is needed. Here, we explored how the metabolic status of T cells governs immune skewing from circulating and tumour‐infiltrating CD4 + and CD8 + T cells of melanoma patients at a single‐cell level using the SCENITH method and targeted metabolomics. Circulating and tumour‐infiltrating T cells from patients displayed a decreased mitochondrial dependency associated with an enhanced glycolytic capacity and a skewed metabolic reprogramming upon stimulation. Such metabolic disturbances were linked to the activation status, immune checkpoint profile and functional orientation of T cells, underlining critical connections between T‐cell features and metabolic patterns. Targeted metabolomics within sorted CD4 + /CD8 + T cells identified a decrease in citrulline, cysteine and threonine within all subsets in patients, together with a sharp rise in sterol cholesterol CE(20:2) and ceramide dhCer(d18:0/22:0) within tumour‐infiltrating CD4 + T cells, and in glycerolipid DG(16:0/16:0) within CD8 + T cells in blood and tumour. We further outlined a metabolic‐checkpoint‐based signature composed of six genes coding enzymes/transporters connected to the imbalanced metabolites found within tumour‐infiltrating T cells ( LIPA , DGKA , GLUL , SLC38A1 , SLC7A7 , GCH1 ) that shape patients' clinical outcome. These findings outline the skewed bioenergetic profiles of T cells and depict metabolic checkpoints associated with immune subversion. Harnessing metabolic pathways is promising for developing innovative therapies to restore optimal anti‐tumour responses and improve clinical success.