Takahashi Tetsuyuki, Uehara Hisanori, Bando Yoshimi, Izumi Keisuke
Department of Molecular and Environmental Pathology, Institute of Health Biosciences, The University of Tokushima Graduate School, 3-18-15, Tokushima-shi, Tokushima, Japan.
Mol Cancer Ther. 2008 Sep;7(9):2807-16. doi: 10.1158/1535-7163.MCT-08-0153.
Prostaglandin E2 (PGE2) plays a key role in osteolytic bone metastasis as well as roles in inflammation, cell growth, and tumor development. PGE2 exerts its effects by binding and activating E-prostanoid receptor (EP). In this study, we propose a new approach for blocking EP-mediated cell signaling using a soluble chimeric EP2 fragment. Mammalian expression vectors encoding several human EP2 cDNAs were introduced into 293 cells and the culture medium was tested for their function as a decoy receptor for PGE2. PGE2 binding assays revealed that culture medium containing the second extracellular region of EP2 (FuEP2/Ex2) had binding activity. FuEP2/Ex2 neutralized PGE2-induced cyclic AMP production, cyclic AMP-responsive element binding protein phosphorylation, and subsequent induction of cyclooxygenase-2, interleukin (IL)-1beta, and IL-6 mRNAs. In human osteoblasts, this culture medium neutralized the induction of receptor activator of nuclear factor-kappaB ligand mRNA. A stable transfectant expressing FuEP2/Ex2 was established from human prostate cancer PC-3 cells (PC3-FuEP2/Ex2). PC3-FuEP2/Ex2 cells grew at similar rates to vector control cells under normal culture conditions, although PGE2-induced growth stimulation was suppressed. Intraosseous injection of PC3-FuEP2/Ex2 cells into the tibia of athymic nude mice revealed that the degrees of tumor growth and osteolysis were decreased compared with control cell-injected mice, with decreased osteoclasts and increased apoptotic cells. Furthermore, the cyclooxygenase-2, IL-1beta, and IL-6 mRNA levels were reduced in the tumor lesions. These data suggest that FuEP2/Ex2 is useful for treating osteolytic bone metastasis and cancers that depend on EP signaling for their growth and development.
前列腺素E2（PGE2）在溶骨性骨转移中起关键作用，同时也参与炎症、细胞生长和肿瘤发展过程。PGE2通过结合并激活E-前列腺素受体（EP）发挥其作用。在本研究中，我们提出了一种使用可溶性嵌合EP2片段阻断EP介导的细胞信号传导的新方法。将编码几种人EP2 cDNA的哺乳动物表达载体导入293细胞，并检测其培养基作为PGE2诱饵受体的功能。PGE2结合试验表明，含有EP2第二个细胞外区域（FuEP2/Ex2）的培养基具有结合活性。FuEP2/Ex2中和了PGE2诱导的环磷酸腺苷（cAMP）产生、cAMP反应元件结合蛋白磷酸化以及随后环氧合酶-2、白细胞介素（IL）-1β和IL-6 mRNA的诱导。在人成骨细胞中，这种培养基中和了核因子-κB配体受体激活剂mRNA的诱导。从人前列腺癌PC-3细胞（PC3-FuEP2/Ex2）建立了表达FuEP2/Ex2的稳定转染细胞系。在正常培养条件下，PC3-FuEP2/Ex2细胞的生长速率与载体对照细胞相似，尽管PGE2诱导的生长刺激受到抑制。将PC3-FuEP2/Ex2细胞经骨内注射到无胸腺裸鼠的胫骨中，结果显示与注射对照细胞的小鼠相比，肿瘤生长和骨溶解程度降低，破骨细胞减少，凋亡细胞增加。此外，肿瘤病变中环氧化酶-2、IL-1β和IL-6 mRNA水平降低。这些数据表明，FuEP2/Ex2可用于治疗溶骨性骨转移以及依赖EP信号进行生长和发展的癌症。
