We are looking at a number of dynamic protein–protein interactions that regulate cell proliferation, migration, and invasion, with roles in cancer progression and metastasis. A current emphasis is on the interactions of Raf kinase inhibitor protein, which is involved in tumor growth and metastasis, with its cognate binding partners in the cell. We are interested in defining not only the sites of interaction and their biophysical parameters but also their roles in the regulation of cellular processes related to normal and pathological physiology.