Nordeen S K, Kühnel B, Lawler-Heavner J, Barber D A, Edwards D P
Department of Pathology, University of Colorado Health Sciences Center, Denver 80262.
Mol Endocrinol. 1989 Aug;3(8):1270-8. 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.
含有孕酮受体的T47D人乳腺癌细胞对孕酮有反应，但对其他类固醇激素无反应，尤其是地塞米松，因为它们没有可检测到的雌激素、雄激素或糖皮质激素受体水平。为了定量研究小鼠乳腺肿瘤病毒（MMTV）启动子对孕酮和糖皮质激素的双重反应性，我们用糖皮质激素受体（GR）表达载体稳定转染了T47D细胞。分离出一个克隆衍生物（A1-2），通过类固醇结合和用单克隆抗GR抗体进行的Western免疫印迹评估，它表达正常的全长GR。此外，GR的表达水平（每细胞80000-100000个分子）与内源性孕酮受体的高水平（每细胞200000个分子）相当。在用MMTV-氯霉素乙酰转移酶报告基因瞬时转染的A1-2细胞中，糖皮质激素的诱导作用（5倍）比孕酮介导的诱导作用大得多。这些结果表明糖皮质激素可能是MMTV的主要调节因子。
