A 15,000 molecular weight glycoprotein (GCDFP-15) has been extracted and purified from gross breast cysts. Conventional and monoclonal antibodies have been developed against GCDFP-15 and it has been shown to be a plasma tumor marker substance for monitoring growth of breast carcinoma. Patients with progressing disease have increasing plasma levels of GCDFP-15 and patients with regressing disease have decreasing levels. The direction of change in plasma levels of GCDFP-15 during the first six weeks of chemical or hormonal therapy is predictive of the success or failure of that therapy, and the magnitude of change in GCDFP-15 levels is correlated with the length of remission. The detection of disease recurrence following mastectomy during the clinically disease-free period has also been demonstrated with the GCDFP-15 assay. Recently, it was noted that androgens could stimulate the secretion of GCDFP-15, independently of tumor growth, in patients with stage IV breast carcinoma. In preliminary studies, the androgen-induced secretion of GCDFP-15 has also been demonstrated in vitro in the T-47D breast carcinoma cell line. This application proposes to study this in vitro hormonal control of GCDFP-15 synthesis and secretion by T-47D cells. The secretory response of T-47D cells to weak and strong androgens, to estrogens, to progestogen, to corticoids, and to growth hormone and prolactin will be investigated. A c-DNA clone homologous to 75% of the GCDFP-15 mRNA has been isolated, and this will be utilized to determine the early kinetics of androgen action. Androgen receptor abundance, nuclear translocation, and nuclear processing will be investigated as a function of GCDFP-15 synthesis. The relationship of GCDFP-15 synthesis to growth and to the cell cycle will also be investigated. Verification of key concepts generated in vitro will be made in athymic nude mice carrying the T-47D tumor. The information gained from this study will throw valuable light on the phenomenon of fluoxymesterone-induced secretion of GCDFP-15, already observed in patients with breast cancer. The results may also suggest ways to modulate the androgen stimulation phenomenon to provide more effective therapy and more sensitive diagnostic methods to patients with breast cancer. The study will also provide a model of androgen-induced specific protein synthesis in human breast carcinoma cells. (D)