PROS1 and Arterial thrombosis: It could be speculated that the higher risk for arterial thrombosis in subjects with protein C deficiency could be ascribed to the potent cytoprotective effects of the protein C pathway [30].Protein S deficiency, rather than antithrombin deficiency, is associated with artherial thrombosis because of the synthesis of protein S by endothelial cells, whereas antithrombin is synthesized by hepatocytes.