On the other hand, when inappropriate and excessive NO production occurs, NO takes on a pathological role, being associated with the development of different diseases, such as neurological and inflammatory diseases, atherosclerosis, pain and cancer.[2, 3, 4] NO is generated as a product of the enzymatic oxidation of l‐Arg to l‐Cit, by the heme‐containing enzyme nitric oxide synthase (NOS).[5] There are three distinct isoforms of NOS: the endothelial NOS (eNOS) and neuronal NOS (nNOS) are constitutive and calcium dependent„ and catalyze the production of low and pulsating NO levels. The gene discussed is NOS3; the disease is cancer.