NOS2 and neoplasm: Reactive nitrogen species (RNS) form a multidimensional regulatory network in the tumor microenvironment (TME) through three core mechanisms: autonomous generation by tumor cells (via hypoxia/HIF-1α and inflammation/NF-κB-driven iNOS upregulation) and immune cells (e.g., TAMs and TANs via TLR-mediated iNOS activation), intracellular modulation of key tumor cell functions (proliferation, apoptosis, invasion, and metabolic reprogramming), and intercellular signaling interactions with immune, stromal, and vascular components.