Vivacqua Adele, Bonofiglio Daniela, Recchia Anna Grazia, Musti Anna Maria, Picard Didier, Andò Sebastiano, Maggiolini Marcello
Department of Pharmaco-Biology, University of Calabria, 87030 Rende (CS), Italy.
Mol Endocrinol. 2006 Mar;20(3):631-46. doi: 10.1210/me.2005-0280. Epub 2005 Oct 20.
The growth of both normal and transformed epithelial cells of the female reproductive system is stimulated by estrogens, mainly through the activation of estrogen receptor alpha (ERalpha), which is a ligand-regulated transcription factor. The selective ER modulator tamoxifen (TAM) has been widely used as an ER antagonist in breast tumor; however, long-term treatment is associated with an increased risk of endometrial cancer. To provide new insights into the potential mechanisms involved in the agonistic activity exerted by TAM in the uterus, we evaluated the potential of 4-hydroxytamoxifen (OHT), the active metabolite of TAM, to transactivate wild-type ERalpha and its splice variant expressed in Ishikawa and HEC1A endometrial tumor cells, respectively. OHT was able to antagonize only the activation of ERalpha by 17beta-estradiol (E2) in Ishikawa cells, whereas it up-regulated c-fos expression in a rapid manner similar to E2 and independently of ERalpha in both cell lines. This stimulation occurred through the G protein-coupled receptor named GPR30 and required Src-related and epidermal growth factor receptor tyrosine kinase activities, along with the activation of both ERK1/2 and phosphatidylinositol 3-kinase/AKT pathways. Most importantly, OHT, like E2, stimulated the proliferation of Ishikawa as well as HEC1A cells. Transfecting a GPR30 antisense expression vector in both endometrial cancer cell lines, OHT was no longer able to induce growth effects, whereas the proliferative response to E2 was completely abrogated only in HEC1A cells. Furthermore, in the presence of the inhibitors of MAPK and phosphatidylinositol 3-kinase pathways, PD 98059 and wortmannin, respectively, E2 and OHT did not elicit growth stimulation. Our data demonstrate a new mode of action of E2 and OHT in endometrial cancer cells, contributing to a better understanding of the molecular mechanisms involved in their uterine agonistic activity.
雌激素主要通过激活雌激素受体α（ERα）刺激女性生殖系统正常和转化上皮细胞的生长，ERα是一种配体调节的转录因子。选择性雌激素受体调节剂他莫昔芬（TAM）已被广泛用作乳腺癌的雌激素受体拮抗剂；然而，长期治疗会增加子宫内膜癌的风险。为了深入了解TAM在子宫中发挥激动活性的潜在机制，我们评估了TAM的活性代谢物4-羟基他莫昔芬（OHT）分别在Ishikawa和HEC1A子宫内膜肿瘤细胞中反式激活野生型ERα及其剪接变体的潜力。OHT仅能拮抗Ishikawa细胞中17β-雌二醇（E2）对ERα的激活，而在两种细胞系中，它都能以类似于E2的快速方式上调c-fos表达，且不依赖于ERα。这种刺激是通过名为GPR30的G蛋白偶联受体发生的，需要Src相关和表皮生长因子受体酪氨酸激酶活性，以及ERK1/2和磷脂酰肌醇3-激酶/AKT途径的激活。最重要的是，OHT与E2一样，刺激了Ishikawa和HEC1A细胞的增殖。在两种子宫内膜癌细胞系中转染GPR30反义表达载体后，OHT不再能够诱导生长效应，而对E2的增殖反应仅在HEC1A细胞中被完全消除。此外，分别在存在丝裂原活化蛋白激酶（MAPK）和磷脂酰肌醇3-激酶途径抑制剂PD 98059和渥曼青霉素的情况下，E2和OHT均未引发生长刺激。我们的数据证明了E2和OHT在子宫内膜癌细胞中的一种新作用模式，有助于更好地理解其子宫激动活性所涉及的分子机制。
