A quantitative comparison of dual control of a hormone response element of progestins and glucocorticoids in the same cell line

• Published in: Molecular endocrinology (Baltimore, Md.) Vol. 3; no. 8; pp. 1270 - 1278
• Main Authors: NORDEEN, S. K, KUÊHNEL, B, LAWLER-HEAVNER, J, BARBER, D. A, EDWARDS, D. P
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Endocrine Society 01.08.1989
• Subjects: Biological and medical sciences; Breast Neoplasms; Fundamental and applied biological sciences. Psychology; Gene expression; Glucocorticoids - physiology; Humans; Mammary Tumor Virus, Mouse - genetics; Molecular and cellular biology; Molecular genetics; Plasmids; Progesterone - physiology; Promoter Regions, Genetic; Receptors, Glucocorticoid - physiology; Receptors, Progesterone - physiology; Regulatory Sequences, Nucleic Acid; Transfection; Tumor Cells, Cultured; Human; Steroid hormone; Transcription promoter; Gene expression; Glucocorticoid; Progestagen; Cell line; Transfection; Hormonal regulation; Tumor; Mammary gland; Progesterone; Sex steroid hormone; Hormonal receptor
• ISSN: 0888-8809; 1944-9917
• DOI: 10.1210/mend-3-8-1270

Progesterone receptor-containing T47D human breast cancer cells are responsive to progestins but fail to respond to other steroid hormones, in particular dexamethasone, because they have no measurable levels of receptors for estrogens, androgens, or glucocorticoids. To quantitatively study dual responsiveness of the mouse mammary tumor virus (MMTV) promoter to progestins and glucocorticoids, we have stably transfected T47D cells with a glucocorticoid receptor (GR) expression vector. A cloned derivative (A1-2) was isolated that expresses a normal, full length GR, as assessed by steroid binding and Western immunoblot with a monoclonal anti-GR antibody. Moreover, GR is expressed at levels (80,000-100,000 molecules per cell) comparable to the high levels of endogenous progesterone receptor (200,000 molecules per cell). In A1-2 cells transiently transfected with an MMTV-chloramphenicol acetyl transferase reporter gene, induction by glucocorticoid was substantially greater (5-fold) than induction mediated by progestins. These results suggest that glucocorticoids may be the primary regulator of MMTV.