This proposal utilizes expertise in various biological disciplines in pursuit of our continuing goals. These consist of the analysis of the process of carcinogenesis in the mammary tissues of rats and mice and will, we hope, ultimately be applicable to the prevention, diagnosis and treatment of the corresponding human disease. The current proposal involves the study of the host and tissue factors which regulate transformability of mammary cells, as well as the growth and differentiation of normal, preneoplastic and neoplastic mammary cells. Nandi will use the in vitro transformation system developed in his laboratory, combined with in vivo and polymerase chain reaction analyses. His goal is to study the relationship of mitogenic stimuli and of the state of differentiation of the mammary gland to transformability of mouse mammary epithelial cells (MEC) by the chemical carcinogen N-methyl-N- nitrosourea (MNU). Additionally, a similar approach will be employed to determine the conditions necessary for the in vitro development of a variety of mammary lesions, including hormone-responsive and -unresponsive tumors, from rat MEC. Firestone's goal is to understand the molecular basis by which the opposing actions of glucocorticoid and of EGF-like growth factor may be involved in the regulation of growth of a rat mammary tumor cell line. These studies require the use of cell biological and recombinant DNA technology. Attempts will be made to isolate and characterize growth suppression- associated genes under glucocorticoid control, as well as the glucocorticoid-suppressible EGF-like growth factors by these rat tumor cells. Talamantes' objective is the analysis of longterm changes in the mammary gland and in the systemic hormonal environment of rats and mice. The identified changes are those associated with parity, pituitary grafts, and age, which profoundly influence susceptibility to chemical carcinogens in the development of mammary cancer. Talamantes' studies will utilize a variety of endocrine and molecular technics to measure circulating levels of mammogenic hormones and growth factors, as well as their receptors in MEC during physiological and experimental changes. Cunha's goal is to assess the role of connective tissue (embryonic and adult) in the regulation of growth and differentiation of normal, preneoplastic, and neoplastic mammary epithelia from mice and rats. His studies will use various approaches, including developmental biological, biochemical, and molecular technics.