Amino acid metabolic regulatory network in tumor immune escape: mechanistic exploration and intervention directions.

Tumor immune escape is not determined solely by immune checkpoints, suppressive cytokines, or changes in immune-cell composition; it is also organized by the metabolic architecture of the tumor microenvironment. Reprogrammed amino acid metabolism contributes to this process by redistributing nutrients, generating immunoregulatory metabolites, and reshaping immune-cell states. Rather than viewing individual amino acid pathways as independent mechanisms, this review proposes a network framework in which nutrient competition, metabolite-mediated communication, and immune-state stabilization are mechanistically coupled across tumor, immune, stromal, vascular, and microbiota-associated compartments. We define four properties of this network: cross-pathway convergence on shared immune outcomes, division of metabolic labor among cell populations, spatial and temporal context dependence, and compensatory feedback that sustains immune suppression. Within this framework, we examine how tryptophan, glutamine, methionine, arginine, and emerging pathways such as asparagine regulate T-cell dysfunction, regulatory T-cell persistence, myeloid polarization, dendritic-cell impairment, and resistance to immune checkpoint blockade. We further discuss how network-level understanding may improve biomarker development and guide cell-selective, temporally optimized, and rational combination strategies. Conceptualizing amino acid metabolism as an interconnected regulatory system may better explain the context-dependent effects of metabolic interventions and support precision immunometabolic therapy.