NOS2 and melanoma: In addition to the immediate burst of endothelial eNOS-dependent NO production upon melanoma cell arrest in the liver, a delayed iNOS (inducible NO synthase)-dependent cytotoxic NO induction after 4 h of cell injection into the mesenteric vein has also been demonstrated, which was partially due to the shear forces generated by melanoma cell arrest in the sinusoids, and produced from both sinusoidal lining cells and hepatocytes detected by double-labeling immunohistochemistry [15] (Figure 1: A – C).