NOS3 and neoplasm: In preclinical studies, the effect of 5-HTR2B antagonists on angiogenesis was evaluated: phosphorylation of serotonin-induced endothelial nitric oxide synthase (eNOS) was blocked in human umbilical vein endothelial cells (HUVEC) and in a murine lung cancer model, and was associated with decreased tumour microvessel density [5].