Inhibition of metastasis of syngeneic murine melanoma in vivo and vasculogenesis in vitro by monoclonal antibody C11C1 targeted to domain 5 of high molecular weight kininogen.

Metastasis of malignant tumors is a major cause of morbidity and mortality. Inhibition of tumor growth in distant organs is of clinical importance. We have demonstrated that C11C1, a murine monoclonal antibody to the light chain region of high molecular weight kininogen (HK), reduces growth of murine multiple myeloma in normal mice and human colon cancer in nude mice. C11C1 inhibits angiogenesis by reducing tumor microvascular density by blocking binding of HK to endothelial cells. We now evaluate the anti-metastatic effect of C11C1 on C57BL/6 mouse lung metastatic model using B16F10 melanoma cells. The tail veins of mice were injected with 0.5 × 10(6) cells of melanoma B16F10. One group received C11C1 and the other received saline (control) intraperitoneally. When mice were killed at 28 days, 6 of 10 control mice had detectable metastatic pulmonary nodules which stained positive with an antibody against S-100 protein, a tumor antigen present in malignant melanoma cells. In the C11C1 groups, none of the mice showed metastatic foci in their lungs. We showed that C11C1 inhibits endothelial cell tube formation in a 3-D collagen fibrinogen gel model by inhibiting the rate of cleavage of HK by plasma kallikrein without changing the binding affinity for HK. These studies demonstrate that a monoclonal antibody to HK has the potential to prevent metastasis with minimal side effects.

Spatially distinct production of reactive oxygen species regulates platelet activation.

Platelets play a key role in hemostasis and changes in redox balance are known to alter platelet activation and aggregation. Interestingly, activation of platelets leads to production of reactive oxygen species (ROS), but the role(s) of these ROS remain unclear. Using flow cytometry and chemiluminescence, agonist-induced ROS generation was found to be spatially distinct with stimulation through the major collagen receptor GPVI inducing only intraplatelet ROS while thrombin induced production of extracellular ROS. Platelet activation by either the GPVI-selective agonist convulxin or thrombin was differentially regulated by ROS generation. Thus, surface expression of CD62P, CD40L, or activated integrin alphaIIbbeta3 was abrogated by pharmacologic antioxidants but externalization of phosphatidylserine was not inhibited. Furthermore, extracellular antioxidants SOD/catalase markedly inhibited thrombin-, but not convulxin-, induced CD62P expression and alphaIIbbeta3 activation. The data suggest that ROS selectively regulate biochemical steps in platelet activation and that distinct source(s) of ROS and discrete redox-sensitive pathway(s) may control platelet activation in response to GPVI or thrombin stimulation. Thus, targeting ROS with site-specific antioxidants may differentially regulate platelet activation via thrombin or collagen.