In this renewal application we propose to continue our studies on the structure, enzyme activity, and biological role of both avian and human matrix metalloproteases (MMPs). A number of new approaches and model systems that were developed during the present period of support, along with the discovery of a new MMP, will be followed up and utilized to gain insight into specific aspects of normal and malignant cell behavior that are influenced directly by the MMPs. The study will be comprehensive in that an avian MMP will be cloned and identified, a human MMP will be characterized in vitro and in vivo, and a model system for angiogenesis will be examined in terms of the involvement of both avian and human MMPs. A new avian MMP, a 75-80 kDa gelatinase, has been detected, isolated, and partially characterized. We propose to clone and identify this enzyme which may be a new member of the MMP family. Its natural activator, inhibitor, and substrates will be sought, along with its embryonic tissue source and developmental pattern of expression. We will examine the activation of human proMMP-9 by a converging protease cascade involving serine proteases (uPA and plasmin) and a metalloprotease (MMP-3). The activation of proMMP-9 will be studied in a number of complex cell co-culture systems and an in vivo tumor invasion system. Advantage will be taken of a newly- discovered blocking function of some of our anti-MMP-9 monoclonal antibodies to delineate the contribution of MMP-9 activation. An in vivo angiogenesis model system has been established that can be directly observed, quantitated, and subjected to molecular intervention. The host of the model system is a chick embryo and thus our unique species-specific MMP reagents will be utilized to examine the catalytic role of chicken and human MMPs in the vascular remodeling that occurs during in vivo angiogenesis.