Nitric oxide (NO), produced from L-arginine by NO synthases (NOS), is a short-lived molecule required for many physiological functions and contributing to different pathological conditions. In the last decade we have contributed to demonstrate that NO stimulates angiogenesis and mediates the effect of different angiogenic molecules. In human tumors NOS expression and activity correlate with tumor growth and aggressiveness, through angiogenesis stimulation and regulation of angiogenic factor expression. Recently, interrelations among the NOS pathway, prostanoids and tyrosin kinase receptors have been reported in regulating tumor progression and malignancy. In this complex scenario we hypothesize that the NOS/cGMP pathway is central for tumor...