Colon Cancer Growth and Dissemination Relies upon Thrombin, Stromal PAR-1, and Fibrinogen.

Thrombin-mediated proteolysis is a major determinant of metastasis, but is not universally important for primary tumor growth. Here, we report that colorectal adenocarcinoma represents one important exception whereby thrombin-mediated functions support both primary tumor growth and metastasis. In contrast with studies of multiple nongastrointestinal cancers, we found that the growth of primary tumors formed by murine and human colon cancer cells was reduced in mice by genetic or pharmacologic reduction of circulating prothrombin. Reduced prothrombin expression was associated with lower mitotic indices and invasion of surrounding tissue. Mechanistic investigations revealed that thrombin-driven colonic adenocarcinoma growth relied upon at least two targets of thrombin-mediated proteolysis, protease-activated receptor-1 (PAR-1) expressed by stromal cells and the extracellular matrix protein, fibrinogen. Colonic adenocarcinoma growth was reduced in PAR-1-deficient mice, implicating stromal cell-associated PAR-1 as one thrombin target important for tumor outgrowth. Furthermore, tumor growth was dramatically impeded in fibrinogen-deficient mice, offering the first direct evidence of a critical functional role for fibrinogen in malignant tumor growth. Tumors harvested from fibrinogen-deficient mice displayed a relative reduction in cell proliferative indices, as well as increased tumor necrosis and decreased tumor vascular density. Collectively, our findings established a functional role for thrombin and its targets PAR-1 and fibrinogen in the pathogenesis of colonic adenocarcinoma, supporting tumor growth as well as local invasion and metastasis.

Effects of recombinant factor VIIa on platelet function and clot structure in blood with deficient prothrombin conversion.

While recombinant factor VIIa (rFVIIa) shows promise as a broad-spectrum hemostatic agent, questions remain regarding the most appropriate dose and the best way to monitor its effects. In this study we tested the sensitivity of a thrombin dependent platelet assay, platelet contractile force, to the effects of rFVIIa in normal, factor-deficient, and inhibitor-containing blood samples. Dose dependent effects of rFVIIa on platelet contractile force (PCF) and clot elastic modulus (CEM) were measured in all blood samples. rFVIIa minimally affected PCF and CEM in normal blood clotted with thrombin or batroxobin. While rFVIIa minimally altered PCF and CEM in factor VIII (FVIII) deficient blood clotted with thrombin, rFVIIa increased PCF and CEM and shortened the lag phase in a dose dependent manner in batroxobin-induced clots. The effects of rFVIIa in factor IX (FIX) deficient blood mirrored the effects seen in FVIII deficient samples. Whether clotted with thrombin or batroxobin, baseline PCF and CEM were abnormally low in FVIII deficient samples containing FVIII inhibitors. In such samples, rFVIIa caused dose dependent improvement of PCF, CEM, and lag phases. In one patient with a spontaneous inhibitor, rFVIIa caused dose dependent increases in PCF and CEM in blood clotted with either enzyme. rFVIIa corrects the deficient thrombin generation seen in FVIII and FIX deficiency, and in blood containing FVIII inhibitors. As a consequence, platelet function is improved and clot structure is enhanced. Platelet contractile force and clot elastic modulus measurements are sensitive to the dose dependent effects of rFVIIa.

Prothrombin Himi; an abnormal prothrombin characterized by a defective thrombin activity.

An abnormal prothrombin has been detected in a 26-year-old female, who had no history of excessive bleeding. Prothrombin activity was approximately 10% when measured using either the classical one-stage assay or the assay with Echis carinatus venom, whereas prothrombin antigen level was normal. In keeping with current nomenclature practices, the abnormal prothrombin was designated "Prothrombin Himi". The electrophoretic behavior and calcium binding properties of Prothrombin Himi did not differ significantly from normal. Prothrombin Himi was isolated by chromatography on Q-Sepharose. Electrophoretic migration of the purified abnormal prothrombin on SDS-PAGE was normal. Upon prothrombin activation by Echis carinatus venom, the clotting activity produced from Prothrombin Himi was only 37% of the normal level after 90 minutes of the activation time, where as the amidolytic activity was almost the same as normal. The cleavage patterns of Prothrombin Himi by factor Xa or Echis carinatus venom investigated by SDS-PAGE, were found to be normal. These results indicate that Prothrombin Himi was characterized by a defective thrombin enzymatic activity.

On the mechanism of salicylate-induced hypothrombinaemia.

The mechanism of salicylate-induced hypothrombinaemia has been investigated in the rabbit. Administration of methyl salicylate produced a significant decrease in prothrombin complex activity, in the activity of clotting factors II, VII and X but no significant change in factor V activity. Metabolic studies with [3H]vitamin K1 showed that salicylate increased the plasma concentration ratio of [3H]vitamin K1-epoxide: [3H]vitamin K1. The results are consistent with the concept that salicylate produces its anticoagulant effect, like the coumarin anticoagulants, by interruption of the physiologically important vitamin K1-epoxide cycle at the epoxide reductase.

Liver failure with steatonecrosis after jejunoileal bypass: recovery with parenteral nutriton and reanastomosis.

Two women, aged 41 and 51 years, developed jaundice, encephalopathy, and hypoprothrombinemia during rapid weight loss four and 12 months after jejunoileal bypass for refractory obesity. Both were treated for liver failure and received a prolonged course of nutrition parenterally and orally. Serial liver biopsy specimens demonstrated extensive alcoholic-like hepatitis and cirrhosis that improved with nutritional repletion and reanastomosis. Postoperative biopsy specimens later demonstrated minimal portal fibrosis in one patient and inactive mild cirrhosis in the other. Although previous reports indicate that patients usually die when they develop liver failure of this severity after jejunoileal bypass, prolonged intensive nutritional repletion was associated with sufficient clinical and histologic improvement in these two patients so that intestinal reanastomosis could be performed safely.

[Missing thrombinemia in the so-called hypercoagulability following physical exertion (proceedings)]. / Fehlende Thrombinämie bei der sogenannten Hyperkoagulabilität nach körperlicher Anstrengung.

A common topic of discussion for many years has been whether stress induces hypercoagulability and/or hyperfibrinolysis. Ten healthy volunteers were subjected to strenuous physical effort on a bicycle ergometer. Blood samples were collected 10 min before and immediately after exercise. The well-known activation of blood coagulation was demonstrated by significant shortening of the activated partial thromboplastin time, thrombin and reptilase times. However, no fibrinopeptide A (FPA) was generated, nor did the ethanol gelatin test turn positive. A significant shortening of the euglobulin lysis time was indicative of fibrinolysis but no fibrin(ogen) degradation products (FDP) could be detected. These results show that the so-called hypercoagulability is not accompanied by thrombin-mediated release of fibrinopeptide A, and suggest that the activation of coagulation does not involve fibrinogen to fibrin conversion.

Hereditary thrombocytopathy: a familial bleeding disorder due to impaired platelet coagulant activity.

A family with a bleeding disorder due to congenital thrombocytopenic thrombocytopathy is described, with ten affected members in three generations. The disorder is inherited as an autosomal dominant trait and is characterized by thrombocytopenia, morphologically abnormal platelets, prolonged bleeding time, platelet coagulant activity deficiency and abnormal platelets, prolonged bleeding time, platelet coagulant activity deficiency and abnormal platelet aggregation. Patients' platelets adhered to collagen, but aggregation was reversible and the release of platelet constituents was minimal. Aggregation with ADP was similarly reversible, but the platelet response to thrombin was normal. These defects in platelet aggregation and release were not corrected by addition of normal plasma indicating an intrinsic abnormality of platelets. By definition thrombocytopathy consists of a deficiency in platelet coagulant activity. It was shown that the deficiency of platelet coagulant activity caused a delay and decrease in the conversion of prothrombin to thrombin, and it is proposed that the lack of thrombin accounts for the defective release reaction and the reversible aggregation. An adequate haemostatic plug due to decreased release of ADP, together with instability of the plug provide an explanation for the bleeding tendency in thrombocytopathy.