NOS2 and digestive system neoplasm: Notably, macrophages upregulated the inducible nitric oxide synthase (iNOS) transcription to generate NO from L-arginine during the pathogenesis of Helicobacter pylori [45], as the intracellular presence of excessive NO production led to constant gastric mucosal disturbance, chronic gastritis, and a multi-step complex pathway and process that initiates gastrointestinal tumor formation.