Increased Blood Concentration of IgG Degradation Products in Prostate Cancer.

For elucidation of the mechanisms of IgG binding with human plasminogen in prostate cancer patients, we propose an original ELISA on polystyrene plates with immobilized heavy and light plasminogen chains. The level of IgG bound to plasminogen heavy chain in the serum of prostate cancer patients significantly exceeded that in healthy volunteers. IgG treated with plasmin more actively (by more than 2 times) bound plasminogen heavy chain than intact IgG. These findings indicate the involvement of lysine-binding sites of plasminogen heavy chain in the interaction with the C-terminal lysine of IgG and their fragments. ROC analysis of ELISA data showed significant differences between serum samples from patients with prostate cancer and benign prostatic hyperplasia. It is hypothesized that IgG in the tumor region undergo proteolysis and their products appear in the circulation.

PO-17 - Identification of IgG bound to plasminogen in oncologic diseases.

INTRODUCTION: The binding of plasminogen (Pg) to cell receptors and extracellular ligands facilitates its activation to plasmin, which stimulates the extracellular matrix degradation, neoangiogenesis and tumor invasion. Plasmin can also degrade IgG thereby exposing C-terminal lysine residues. Previously, we have found IgG specifically bounded to Pg in the plasma of patients with malignant tumors. AIM: To identify IgG degraded by plasmin in the plasma of cancer patients. MATERIALS AND METHODS: Methods of ELISA were used for comparative research of levels of IgG bound to Pg in plasma of patients with the prostate cancer (PC, n=25) and lung cancer (LC, n=17). Plasma of healthy donors (n=29) was used as control. All patients signed informed consent for participation in this study. Affinity chromatography on Pg-sepharose was used for the quantification of IgG. Carboxypeptidase was used for remove of C-terminal lysine residues of the IgG. The program ATTESTAT was used for nonparametric analysis. RESULTS: The frequency of occurence of elevated levels of IgG to Pg in plasma was detected in 68% of patients with PC, 59% of patients with LC and only 12% of healthy women and 10% of healthy men. The quantification of antibodies in plasma samples showed that the quantity of IgG to Pg in patients with PC was 27% from the total amount of IgG and in healthy men - 9%. Treatment of diluted plasma samples with carboxypeptidase B abolished the elevated levels of IgG to Pg, as well as the specific activity of the purified IgG to Pg-sepharose. CONCLUSIONS: C-terminal lysine residues which are formed as a result of degradation of native IgG with plasmin can bind to lysine binding sites on the kringle domains of Pg. Increased levels of these degraded IgG can be marker at cancer.

Autoantibodies to plasminogen and their role in tumor diseases.

Plasma level of IgG autoantibodies to plasminogen was measured by ELISA in patients with benign prostatic hyperplasia (n=25), prostatic cancer (n=17), lung cancer (n=15), and healthy volunteers (n=44). High levels of IgG to plasminogen were found in 2 (12%) of 17 healthy women, in 1 (3.6%) of 27 specimens in a healthy man, in 17 (68%) of 25 specimens in prostatic cancer, in 10 (59%) of 17 specimens in lung cancer, and in 5 (30%) of 15 specimens in benign prostatic hyperplasia. Comparison of plasma levels of anti-plasminogen IgG by affinity chromatography showed 3-fold higher levels in patients with prostatic cancer vs. healthy men.

[Structure and functions of plasminogen/plasmin system].

The main physiological function of plasmin is a blood clot fibrinolysis and restore normal blood flow. To date, however, it became apparent that in addition to thrombolysis plasminogen/plasmin system plays an important physiological and pathological role in the degradation of extracellular matrix, embryogenesis, cell migration, tissue remodeling, wound healing, angiogenesis, inflammation and tumor cells migration. This review focuses on the structural features of plasminogen, the regulation of its activation by physiological plasminogen activators, inhibitors of plasmin and plasminogen activators, the role of the plasminogen binding to fibrin, cellular receptors and extracellular ligands in performing various functions by formed plasmin.

[Fibrinolysis components and angiogenesis regulation by example of burn-induced corneal neovascularization in rabbits].

Increased plasminogen level in tear fluid was found within 28 days and increased plasmin activity in 1-3 and 21 days after alkali burn of cornea, this is the time of cornel ulcers development. Increased plasminogen level and plasmin activity in cornea, conjunctiva and intraocular fluid was found in three days after trauma. Subconjunctival injections of angiostatin K1-4,5 (a product of plasminogen metabolism) during 3 weeks resulted in significant suppression of corneal neovascularization within 14 days and of active branching of the vessels in the following. The use of angiostatin reduced depth and area of corneal ulcers. Obtained data shows the promising potential of development of medications based on angiostatin K1-4,5 for suppression of corneal neovascularization and for treatment of diseases associated with corneal ulceration.

Inhibitory effect of angiostatins on activity of the plasminogen/plasminogen activator system.

Angiostatins, kringle-containing fragments of plasminogen, are potent inhibitors of angiogenesis. Effects of three angiostatin forms, K1-3, K1-4, and K1-4.5 (0-2 microM), on the rate of native Glu-plasminogen activation by its physiological activators in the absence or presence of soluble fibrin were investigated in vitro. Angiostatins did not affect the intrinsic amidolytic activities of plasmin and plasminogen activators of tissue type (tPA) and urokinase type (single-chain scuPA and two-chain tcuPA), but inhibited conversion of plasminogen to plasmin in a dose-dependent manner. All three angiostatins suppressed Glu-plasminogen activation by tcuPA independently of the presence of fibrin, and the inhibitory effect increased in the order: K1-3 < K1-4 < K1-4.5. The inhibitory effects of angiostatins on the scuPA activator activity were lower and further decreased in the presence of fibrin. Angiostatin K1-3 (up to 2 microM) had no effect, while 2 microM angiostatins K1-4 and K1-4.5 inhibited the fibrin-stimulated Glu-plasminogen activation by tPA by 50 and 100%, respectively. The difference in effects of the three angiostatins on the Glu-plasminogen activation by scuPA, tcuPA, and tPA in the absence or presence of fibrin is due to the differences in angiostatin structures, mechanisms of action, and fibrin-specificity of plasminogen activators, as well as due to the influence of fibrin on the Glu-plasminogen conformation. Angiostatins in vivo, which mimic plasminogen-binding activity, can inhibit plasminogen activation stimulated by various proteins (including fibrin) of extracellular matrix, thereby blocking cell migration and angiogenesis. The data of this work indicate that the inhibition of Glu-plasminogen activation under the action of physiological plasminogen activators by angiostatins can be implicated in the complex mechanism of their antiangiogenic and antitumor action.