The proposed research is organized around an investigation of the nutrient requirements of normal mammalian cells and an analysis of the changes in growth factor requirements that are associated with malignancy. Growth promoting substances will be isolated from serum or other undefined supplements that are currently needed for growth of unaltered primary cultures. Fractions of increasing biological activity will be prepared until a degree of purity is achieved that will permit chemical characterization of the active substance(s). Defined media containing only those nutrients needed by each cell type will then be prepared and used to evaluate differences between normal and malignant cells in their requirements for growth factors and in their responses to growth-regulating substances. The goals of the proposed research are to provide improved and highly defined media for investigations that utilize normal mammalian cells and to provide new insight into differences between normal and malignant cells.