Chang Yoon Soo, Cho Jae Yong, Cho Hyun A, Kim Hyung Jung, Chang Joon, Ahn Chul Min, Kim Sung Kyu, Kim Se Kyu
Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.
Cancer Biol Ther. 2006 Jun;5(6):586-92. doi: 10.4161/cbt.5.6.2658. Epub 2006 Jun 5.
Retinoic acids, which have shown potential chemopreventive and therapeutic activities for several neoplastic diseases in vitro, modulate the growth-promoting and anti-apoptotic activities of insulin-like growth factors (IGFs), in part by influencing the expression of insulin-like growth factor binding protein-3 (IGFBP-3). This study sought to investigate the effect of 9-cis retinoic acid (9cRA) on the expression of IGFBP-3 and the underlying mechanisms involving retinoic acid receptor-beta (RAR-beta). The pharmacologic activity of 9cRA was characterized by monitoring target modulation as well as by evaluating the underlying mechanisms in NSCLC cells. Treatment of 9cRA inhibited proliferation of a part of NSCLC cell lines including H460 cells in clinically-achievable concentrations and induced IGFBP-3 expression in dose- and time-dependent manners. Transient transfection with a reporter constructs driven by the human IGFBP-3 gene promoter indicated that 9cRA induces gene expression via the -534 to -445 region (relative to translation start site) of the IGFBP-3 promoter. Unilateral deletion and site-directed mutagenesis identified a retinoic acid responsive element (RARE), a direct repeat of two GGGTCA-related hexanucleotides separated by just 8 bp (DR-8-type response element). A cotransfection assay with a RAR-beta expression vector potentiated (and with siRNA for RAR-beta, diminished) the effect of 9cRA on IGFBP-3 expression. IGFBP-3 gene expression by 9cRA is mediated by a distinct DR-8 RARE located in the proximal region of the IGFBP promoter and involves the RAR-beta, a putative tumor suppressor in NSCLC.
维甲酸在体外已显示出对多种肿瘤疾病具有潜在的化学预防和治疗活性，它可调节胰岛素样生长因子（IGFs）的促生长和抗凋亡活性，部分是通过影响胰岛素样生长因子结合蛋白-3（IGFBP-3）的表达来实现的。本研究旨在探讨9-顺式维甲酸（9cRA）对IGFBP-3表达的影响以及涉及维甲酸受体-β（RAR-β）的潜在机制。通过监测靶点调节以及评估NSCLC细胞中的潜在机制来表征9cRA的药理活性。9cRA处理在临床可达到的浓度下抑制了包括H460细胞在内的部分NSCLC细胞系的增殖，并以剂量和时间依赖性方式诱导IGFBP-3表达。用由人IGFBP-3基因启动子驱动的报告基因构建体进行瞬时转染表明，9cRA通过IGFBP-3启动子的-534至-445区域（相对于翻译起始位点）诱导基因表达。单侧缺失和定点诱变鉴定出一个维甲酸反应元件（RARE），它是两个GGGTCA相关六核苷酸的直接重复，仅相隔8个碱基对（DR-8型反应元件）。用RAR-β表达载体进行共转染试验增强了（而用RAR-β的siRNA则减弱了）9cRA对IGFBP-3表达的影响。9cRA对IGFBP-3基因的表达是由位于IGFBP启动子近端区域的一个独特的DR-8 RARE介导，并涉及RAR-β，RAR-β是NSCLC中一种假定的肿瘤抑制因子。
