转录因子E2F-1的研究进展

目的:总结国内外关于E2F-1在细胞增殖、凋亡及其在肿瘤中的作用的研究进展。方法:应用Medline及CNKI期刊全文数据库系统,以"E2F-1、细胞增殖、凋亡及肿瘤为关键词,检索1999-01-2009-12的相关文献,共检索英文文献1 453篇、中文文献29篇。纳入标准:1)E2F-1的来源和分子结构特征;2)E2F-1与细胞周期的关系;3)E2F-1和细胞增殖的关系;4)E2F-1和凋亡的关系;5)E2F-1和肿瘤的关系。根据纳入标准,附合分析条件的文献有52篇,最后纳入分析33篇。结果:E2F-1是细胞周期调节的关键因子,具有调节细胞增殖和凋亡的双重作用,在肿瘤中表现出抑癌基因和癌基因的功能。结论:E2F-1可能是抗肿瘤研究的靶点。     

Additive effect of adenovirus-mediated E2F-1 gene transfer and topoisomerase II inhibitors on apoptosis in human osteosarcoma cells

Recently, it has been demonstrated that Etoposide, a topoisomerase II inhibitor, can induce apoptosis in MDM2-overexpressing tumor cells by inhibition of MDM2 synthesis. We have previously shown that E2F-1 overexpression induces apoptosis of MDM2-overexpressing sarcoma cells, which is related to the inhibition of MDM2 expression. Therefore, the present study was designed to investigate the in vitro and in vivo effect of combined treatment of adenovirus-mediated E2F-1 and topoisomerase II inhibitors on the growth inhibition and apoptosis in human sarcoma cells. Two human sarcoma cell lines, OsACL and U2OS, were treated with topoisomerase II inhibitors (Etoposide and Adriamycin), alone or in combination with adenoviral vectors expressing beta-galactosidase (Ad-LacZ) or E2F-1 (Ad-E2F-1). E2F-1 expression was confirmed by Western blot analysis. Ad-E2F-1 gene transfer at a low dose (multiplicity of infection, 2) markedly increased the sensitivity of human sarcoma cells to topoisomerase II inhibitor treatment. This cooperative effect of E2F-1 and topoisomerase II inhibitors was less marked in SAOS-2 cells (p53 and pRb null). Topoisomerase II inhibitors also cooperated with E2F-1 overexpression to enhance tumor cell killing in an in vivo model using xenografts in nude mice. When combined with Adriamycin or Etoposide, E2F-1 adenovirus therapy resulted in approximately 95% and 85% decrease in tumor size, respectively, compared to controls (P<.05). These results suggest a new chemosensitization strategy that is effective in MDM2-overexpressing tumors and may have clinical utility.     

E1A sensitizes HER2/neu-overexpressing Ewing's sarcoma cells to topoisomerase II-targeting anticancer drugs

Overexpression of the HER2/neu oncogene is associated with tumorigenicity and drug resistance in many types of cancer. Three different human Ewing's sarcoma cell lines (TC71, RD, and A4573) were found to express high levels of the HER2/neu protein. Transduction of TC71 cells with the E1A gene using an adenoviral vector (Ad-E1A) down-regulated HER2/neu overexpression in those cells and increased cytostasis. E1A-induced apoptosis was demonstrated by both flow cytometric analysis and Western blot analysis using a poly(ADP-ribose) polymerase antibody. After transduction of the E1A gene into these cells, the sensitivity of these cells to VP-16 (etoposide) was enhanced 18-fold and to Adriamycin 5-fold. However, no change was seen in cisplatin sensitivity. E1A also significantly increased topoisomerase IIalpha protein expression, indicating that the up-regulation of topoisomerase IIalpha may be one of the mechanisms by which E1A enhanced the sensitivity to topoisomerase II-targeting anticancer drugs, such as VP-16 and Adriamycin, but not cisplatin. In summary, these studies demonstrated that Ad-E1A can down-regulate HER2/neu overexpression and up-regulate topoisomerase IIalpha expression in human Ewing's sarcoma cells, increasing their apoptosis rate and enhancing their sensitivity to VP-16 and ADRIAMYCIN:     

Activity of novel cytotoxic agents in lung cancer: epothilones and topoisomerase I inhibitors

The treatment of lung cancer--small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC)--is a significant challenge in oncology. The best reported median survival remains near 1 year in advanced NSCLC despite several decades of steady improvement and extensive research with traditional chemotherapy drugs and novel compounds targeted to different aspects of tumor cell growth and function (such as the epidermal growth factor receptor). Extensive-stage SCLC survival is only slightly better. Novel "targeted" therapeutic agents hold promise, but cytotoxic therapy remains the backbone of treatment. Many new cytotoxic agents are currently in development. In this review, we will focus on 2 classes of cytotoxins: epothilones and topoisomerase I inhibitors. Epothilones are microtubule stabilizers with a mechanism of action similar to that of the taxanes, with preclinical activity superior to that of the taxanes. Phase I trials have been completed for patupilone and ixabepilone, and there are encouraging phase II data with ixabepilone in NSCLC. A phase II trial of patupilone is ongoing. The camptothecins, which are topoisomerase I inhibitors, have a long history in the treatment of lung cancer, but the currently available drugs, topotecan and irinotecan, have limitations. Gimatecan and other novel camptothecins have superior preclinical activity and promising phase I/II data in NSCLC and SCLC.     

转录因子E2F-1 siRNA对胃癌MGC803细胞体外侵袭及增殖能力的影响

背景与目的:转录因子E2F-1作为细胞周期进程中重要的调控因子,与肿瘤的发生有着密切的关系.本研究通过转染人E2F-1基因的小干扰RNA (small interfering RNA,siRNA)表达质粒,探讨其对胃癌MGC803细胞中E2F-1表达及侵袭和增殖能力的影响.方法:用脂质体LipofectamineTM 2000将具有短发夹结构的人E2F-1 siRNA表达质粒转染至MGC803细胞,以逆转录-聚合酶链反应(RT-PCR)及蛋白印迹(Western blot)技术分别检测E2F-1 mRNA及蛋白的表达;应用体外侵袭实验及克隆实验分别检测E2F-1 siRNA表达质粒对MGC803细胞侵袭力和增殖能力的影响.结果:成功转染E2F-1 siRNA表达质粒48 h后.MGC803细胞中E2F-1基凶mRNA表达的抑制率超过90%;与未转染组及阴性对照组细胞比较,E2F-1蛋白的表达分别降低81.5%和79.6%.转染pSilencer4.1-E2F-1质粒组的穿膜细胞数(18.0±2.6)与阴性对照组(48.0±4.6)和空白对照组(54.0±5.6)比较差异有统计学意义(P<0.05),其细胞集落形成数(46.0±2.0)与阴性对照组(122.3±1.5)和空白对照组(128.7±2.1)比较差异也有统计学意义(P<0.05).结论:E2F-1 siRNA表达质粒可显著下调E2F-1基因在胃癌MGC803细胞中的表达,在一定程度上抑制胃癌细胞的侵袭和增殖.     

DNA topoisomerase I and II as targets for rational design of new anticancer drugs

BACKGROUND:: Topoisomerase I and II (topo I and II) are enzymes which alterthe topological state of DNA through DNA strand cleavage, strandpassage and religation. They participate in most aspects ofDNA metabolism and are therefore vital to the cell undergoingdivision. Only one form of topo I has been identified whereastwo isoenzymes of topo II have been described: the