Early researchers have discovered that the endothelium‐derived relaxation factor (EDRF) is NO gas.[20] Inhaled NO has been applied in various treatments of several diseases, such as cancers and cardiovascular diseases.[21] In fact, all the three forms of NOS, including neuronal NOS, endothelial NOS and inducible NOS have been detected in different kinds of tumours. Here, NOS2 is linked to neoplasm.