Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea.
Carcinogenesis. 2011 Apr;32(4):589-96. doi: 10.1093/carcin/bgq276. Epub 2010 Dec 20.
Previously, we demonstrated that leptin, a pleiotropic hormone produced by adipocytes, stimulates the growth of BG-1 ovarian cancer cells via the extracellular signal-regulated kinase signaling pathway. In this study, we further investigated the involvement of estrogen receptor (ER) pathway in the mechanism of leptin-induced ovarian cancer cell growth. Treatment with leptin (100 ng/ml) resulted in a significant increase in the cell growth of ERα-transfected OVCAR-3 and A2780 cells, whereas no significant difference was observed in ERβ-transfected cells. Downregulation of ERα using small interfering RNA completely reversed leptin-induced growth of BG-1 cells. Treatment with leptin resulted in ER transcriptional activation, i.e. nuclear localization of ER and increased expression of pS2, an estrogen-dependent gene. Luciferase reporter assay revealed that treatment of BG-1 cells with leptin (100 ng/ml) stimulated the expression of the reporter gene in the absence of estradiol (E2). To examine an involvement of Janus kinase 2/signal transducers and activators of transcription 3 (STAT-3) and phosphatidyl-inositol 3-kinase (PI3K)/Akt in leptin-induced pathway, we demonstrated that leptin increased phosphorylation of STAT-3 and Akt in BG-1 cells in a time- and dose-dependent manner. On the other hand, leptin-induced cell growth and ER transactivation were effectively blocked by specific STAT-3 inhibitor AG490 and, to a lesser extent, by PI3K inhibition. Further study with coimmunoprecipitation assay revealed that stimulation with leptin induced STAT-3 binding to ERα. Taken together, these results indicate that the stimulation of ovarian cancer cell growth by leptin involves, at least in part, ER transcriptional activation via the STAT-3 signaling pathways.
先前，我们证明了由脂肪细胞产生的多效性激素瘦素通过细胞外信号调节激酶信号通路刺激 BG-1 卵巢癌细胞的生长。在这项研究中，我们进一步研究了雌激素受体（ER）途径在瘦素诱导卵巢癌细胞生长机制中的作用。用瘦素（100ng/ml）处理导致 ERα 转染的 OVCAR-3 和 A2780 细胞的细胞生长显著增加，而在 ERβ 转染的细胞中没有观察到显著差异。使用小干扰 RNA 下调 ERα 完全逆转了瘦素诱导的 BG-1 细胞生长。瘦素处理导致 ER 转录激活，即 ER 的核定位和雌激素依赖性基因 pS2 的表达增加。荧光素酶报告基因检测显示，用瘦素（100ng/ml）处理 BG-1 细胞刺激了无雌二醇（E2）存在的报告基因的表达。为了研究 Janus 激酶 2/信号转导和转录激活因子 3（STAT-3）和磷脂酰肌醇 3-激酶（PI3K）/Akt 在瘦素诱导的通路中的参与，我们证明了瘦素以时间和剂量依赖的方式增加了 BG-1 细胞中 STAT-3 和 Akt 的磷酸化。另一方面，瘦素诱导的细胞生长和 ER 反式激活被特异性 STAT-3 抑制剂 AG490 有效阻断，并且在较小程度上被 PI3K 抑制阻断。用共免疫沉淀测定进行的进一步研究表明，瘦素刺激诱导 STAT-3 与 ERα 结合。总之，这些结果表明，瘦素刺激卵巢癌细胞生长至少部分涉及通过 STAT-3 信号通路的 ER 转录激活。
