In fact, preceding reports have indicated that NO enhanced fibrosarcoma and squamous carcinoma cell adhesion to the endothelium [58, 81]; breast tumor cells adhered to sites of microcirculation that show an increase in NO production [83] and NOS inhibitors blocked the adhesion and transmigration of small cell lung carcinoma and breast tumor cell to the endothelium [19, 75] pointing out a predominant role of NO in cancer cell adhesion to the endothelium; however, the mechanism (sGC-PKG or S-nitrosylation) or the actors involved are unknown. This evidence concerns the gene PRKG1 and fibrosarcoma.