Absorption and antithrombotic activity of unfractioned heparin after intraduodenal administration in rats.

In the search for a more acceptable route of heparin administration that can also be used for long-term treatment, we evaluated the bioavailability and antithrombotic activity of intraduodenal administration of unfractioned heparin (UFH) in rats. A radioiodinate derivative of UFH was administered intraduodenally in rats in conjunction with unlabeled UFH. We found that radioactivity increases very rapidly in plasma, as well as on the surface of aortic and caval segments, so that peak radioactivity was already achieved within 5 min of drug administration. Subsequently, plasma radioactivity declined rapidly, although 1.5-2.5% of the total radioactivity administered was still circulating 3 h after drug administration. The plasma anti-Xa activity was much lower and longer lasting than expected from the radioactivity counts in both peripheral and portal blood, and its level was very similar in the two circulatory districts, never exceeding 023 U/ml. This suggests that extensive degradation of the drug already occurs during its gastrointestinal absorption. Nevertheless, in a stasis-induced venous thrombosis model, intraduodenal UFH prevented thrombus formation in a dose-dependent way (ED50, 2000 IU/kg). The maximum antithrombotic effect was observed when the drug was administered 30-60 min before ligature of the vena cava, and a 40% reduction of thrombus weight was still present at 180 min. Since antithrombotic kinetics does not match the kinetics of either the plasma or vessel-bound radioactivity but approaches what is found in anti-Xa activity, the antithrombotic activity of oral heparin may be dependent on the release of unlabeled endogenous glycosaminoglycans deposited in the vessels.

Systemic thrombin generation in cancer patients is correlated with extrinsic pathway activation.

Since the first report by Trousseau in 1865, several experimental and clinical studies have established that activation of coagulation is common in cancer. However, the biochemical basis of the activation of coagulation in cancer patients is still not completely understood. The current most accepted opinion is that initiation of coagulation in malignancy is driven primarily by activation of the extrinsic (tissue factor-dependent) pathway. In order to further prove that such a pathogenetic mechanism is actually involved in cancer patients, we correlated the plasma levels of activated factor VIIa (FVIIa), which represent a very small fraction of plasma FVII, with some well-established markers of systemic thrombin generation. Circulating FVIIa was measured using a prothrombin time-based assay that employs a truncated form of human recombinant tissue factor, while plasma levels of the thrombin-antithrombin complex, the prothrombin fragments 1 + 2 and D-dimer were determined by commercially available ELISA kits. The study was carried out in 37 patients with different types of cancer and 20 healthy controls. Plasma levels of FVIIa were significantly increased while those of FVII antigen (FVIIag) were decreased in cancer patients compared with controls. Furthermore, the FVIIa/ VIIag ratio was more than two-fold higher in cancer patients than in controls. In addition, an excess of thrombin generation was observed in cancer patients. Interestingly, a positive correlation between the FVIIa/VIIag ratio and the plasma levels of either D-dimer (Spearman's r = 0.325; P = 0.027) or prothrombin fragments 1 + 2 (r = 0.309; P = 0.034) was observed in cancer patients. In conclusion, our study further supports the hypothesis that the tissue factor/VIIa complex is the main determinant of coagulation activation in cancer patients. Large clinical studies will be necessary to determine whether FVIIa and the FVIIa/VIIag ratio are useful prognostic factors of thromboembolic events in cancer patients.

Combined overexpression of urokinase, urokinase receptor, and plasminogen activator inhibitor-1 is associated with breast cancer progression: an immunohistochemical comparison of normal, benign, and malignant breast tissues.

BACKGROUND: A strong positive correlation exists between the breast cancer tissue content of either urokinase-plasminogen activator (uPA) or plasminogen activator, inhibitor type I (PAI-1), quantified in the tissue extracts by immunoassays, and the survival of patients with breast cancer. Furthermore, several studies assign to the urokinase-type plasminogen activator receptor (uPAR) a pivotal role in triggering the proteolytic activity of the urokinase pathway involved in tumor stroma degradation, tumor spread and metastasis. However, the pattern of distribution of uPAR in normal and cancerous human tissue and the pattern of coexpression of activators and inhibitors that occurs in breast cancer tissues is not completely known. METHODS: The immunohistochemical localization of uPAR, uPA, tPA) and PAI-1 was evaluated by using the avidin-biotin immunoperoxidase technique and affinity-purified monoclonal antibodies from American Diagnostica Inc. Studies were performed in formalin fixed, paraffin-embedded tissue prepared from 23 surgically excised non-neoplastic breast tissues and 18 ductal breast carcinomas. RESULTS: While the expression of uPAR protein represents a constant feature of invasive ductal breast cancer, it was also observed in most of the breast tissue samples, including the normal breast tissues. The staining for uPAR was mainly localized on normal or tumoral epithelial cells, even if the co-expression of uPAR in stromal cells was frequently observed in adjacent slides. A semiquantitative analysis of immunohistochemical results showed that uPAR and PAI-1 were overexpressed in invasive breast cancer in comparison with normal and benign breast tissues. In addition, uPA was higher in both invasive breast carcinomas and benign breast lesions with respect to normal breast tissues. CONCLUSIONS: We showed that overexpression of uPAR, uPA, and its main inhibitor, PAI-1, is a constant feature of invasive ductal breast carcinomas. However, the expression of the above fibrinolytic reactants is not specific for breast cancer since positive staining for these molecules was frequently observed in benign breast lesions as well as in normal breast tissues. The combined increased expression of uPA and its cellular receptor, uPAR on the surface of tumor epithelial cells may account for the activation of the proteolytic system which occurs in breast cancer.