Cancer is a major health issue in the United States. It is characterized by uncontrolled cell replication, leading to the formation of a tumor. If detected early, such a primary tumor remains localized and is easily removed by surgery. However, if left untreated, cells detach from the primary tumor, migrate into a blood vessel at one point in the body, and out at another, forming secondary tumors. These metastatic tumors can be much harder to identify and remove, as they often form at great distances from the original tumor. Thus, understanding and controlling how cells remain attached to each other and how they migrate is integral to treating cancer. To these ends, we have been studying how secreted factors regulate cell adhesion and motility. Regulation of adhesion and motility involves integrating signaling molecules and actin binding proteins. Phospholipase D (PLD) and paxillin are two such molecules which link signaling to the cytoskeleton. We hypothesize that these proteins form a complex, and work together to regulate cytoskeletal function. Unfortunately, studying human cells is difficult due to their immense complexity. Therefore, we study adhesion and motility in Dictyostelium discoideum, a simpler organism that displays many of the characteristics of human cells. We then apply what we have learned to breast cancer cells to better understand why they detach and migrate away from a primary tumor. This work is expected to identify novel targets for the development of pharmacological strategies designed to prevent the motility and invasiveness associated with cancer during metastasis, leading to more effective treatments and better health outcomes.