Amino acid sensors are central regulators that link nutrient availability to tumor adaptation. They coordinate metabolic homeostasis, modulate epigenetic landscapes via metabolite-driven chromatin remodeling, shape the immune microenvironment by controlling nutrient competition and stress signaling, and maintain redox balance under oxidative stress. This review examines how amino acid sensing circuits sustain tumor growth, plasticity, and immune evasion, highlighting their potential as therapeutic targets to exploit metabolic vulnerabilities and enhance anti-cancer efficacy.