Liver Carcinogenesis: A small electrophoretic class of soluble proteins of target organs contains the principal protein-carcinogen conjugates of three families of carcinogens. In pursuit of the possible role in carcinogenesis of one such conjugate, and of the interaction between carcinogen and target protein from which it arises, the following are broad aims of the proposed research: 1. Characterization of the principal soluble liver azoprotein of azo dye preneoplastic liver. 2. Identification of the principal protein target of azocarcinogens in liver. Cell Transformation to Malignancy: The goal is to investigate the extracellular fibrinolytic activities that may have specifically associated with cells transformed by viruses or chemicals. Extracellular activators and inhibitors of fibrinolysin will be isolated from cultured cells and characterized. Effects of the additions of the activators and inhibitors on normal and transformed cells will be studied, in order to learn whether the fibrinolysin activating activities of transformed cells are in part responsible for some of the characteristics associated with cell transformation to malignancy.