A disintegrin isolated from the venom of the Middle American rattlesnake (Crotalus simus tzabcan) named tzabcanin [39], which has 71 amino acids and contains the canonical RGD-binding domain, exhibits a weak or null cytotoxic effect on cancer cell lines [39], but remarkable inhibitory effect of fibronectin- and vitronectin-dependent cell adhesion. Here, FN1 is linked to cancer.