Yin Ping, Lin Zhihong, Cheng You-Hong, Marsh Erica E, Utsunomiya Hiroki, Ishikawa Hiroshi, Xue Qing, Reierstad Scott, Innes Joy, Thung Stephen, Kim J Julie, Xu Eugene, Bulun Serdar E
Division of Reproductive Biology Research, Department of Obstetrics and Gynecology, Feinberg School of Medicine at Northwestern University, Chicago, Illinois 60611, USA.
J Clin Endocrinol Metab. 2007 Nov;92(11):4459-66. doi: 10.1210/jc.2007-0725. Epub 2007 Sep 4.
Uterine leiomyomas are smooth muscle cell tumors that cause irregular uterine bleeding and pregnancy loss in many reproductive-age women. Progesterone stimulates their growth, whereas treatment with progesterone receptor (PR) antagonists or selective progesterone receptor modulators shrinks these tumors. Molecular mechanisms underlying these observations are unknown.
Bcl-2 is a key protein that inhibits apoptosis. It was proposed that growth enhancement of leiomyoma cells by progesterone was mediated via bcl-2 induction. Here we test the hypothesis that PR regulates the bcl-2 gene by directly binding to its promoter.
The pure progesterone agonist R5020 increased the total number of viable primary human leiomyoma smooth muscle (LSM) cells in culture. Progesterone or R5020 (10(-6) m) significantly increased bcl-2 mRNA levels after 2 and 4 h by 9.2- and 3.4-fold, respectively, in LSM cells. Transient transfection with deletion mutants of bcl-2 promoter showed that the -1281/-258-bp region conferred responsiveness to progesterone induction in the presence of PR-A. We identified a palindromic progesterone response element (PRE) at -553/-539 bp. EMSA showed that PR in nuclear extracts from LSM cells bound specifically to this PRE. Chromatin immunoprecipitation-PCR confirmed in situ recruitment of PR to the -629/-388-bp region bearing the PRE. In vivo, bcl-2 mRNA levels correlated significantly with total PR mRNA levels in leiomyoma tissues.
Taken together, progesterone via PR interacts with the bcl-2 promoter to induce its expression in leiomyoma tissue. This may explain, in part, the progesterone-dependent enhancement of growth in uterine leiomyoma.
子宫平滑肌瘤是平滑肌细胞肿瘤，在许多育龄妇女中会导致子宫不规则出血和流产。孕酮会刺激其生长，而用孕酮受体（PR）拮抗剂或选择性孕酮受体调节剂进行治疗可使这些肿瘤缩小。这些观察结果背后的分子机制尚不清楚。
Bcl-2是一种抑制细胞凋亡的关键蛋白。有人提出，孕酮对平滑肌瘤细胞生长的促进作用是通过诱导Bcl-2介导的。在此，我们检验PR通过直接结合其启动子来调节bcl-2基因的假说。
纯孕酮激动剂R5020增加了培养的原代人平滑肌瘤平滑肌（LSM）细胞的存活总数。在LSM细胞中，孕酮或R5020（10⁻⁶ m）在2小时和4小时后分别使bcl-2 mRNA水平显著增加9.2倍和3.4倍。用bcl-2启动子缺失突变体进行瞬时转染表明，在存在PR-A的情况下，-1281/-258-bp区域赋予了对孕酮诱导的反应性。我们在-553/-539 bp处鉴定出一个回文孕酮反应元件（PRE）。电泳迁移率变动分析（EMSA）表明，LSM细胞核提取物中的PR特异性结合到这个PRE上。染色质免疫沉淀-PCR证实PR在体内原位募集到带有PRE的-629/-388-bp区域。在体内，平滑肌瘤组织中bcl-2 mRNA水平与总PR mRNA水平显著相关。
综上所述，孕酮通过PR与bcl-2启动子相互作用，诱导其在平滑肌瘤组织中的表达。这可能部分解释了子宫平滑肌瘤中依赖孕酮的生长增强现象。
