多药耐药基因与子宫颈癌化疗

肿瘤细胞对化疗药物产生多药耐药性是化疗失败的主要原因之一,肿瘤多药耐药的机制十分广泛,其中P-gp/mdrl介导的多药耐药是最经典的耐药机制.故本文就MDR1与宫颈癌化疗的关系进行回顾和总结.     

逆转录病毒载体介导MGMT和MDR1基因增强人脐血CD34+细胞对联合化疗抗性的研究

为探讨转染六氧甲基鸟嘌呤DNA甲基转移酶基因(MGMT)和多药耐药基因(MDR1)的人脐血CD34+细胞能否同时增强对卡氮芥(BCNU)和MDR1基因靶药的抗性,应用逆转录一聚合酶链反应(RT-PCR)从人肝组织中获得编码六氧甲基鸟嘌呤-DNA-甲基转移酶(MGMT)cDNA,构建双顺反子逆转录病毒载体G1Na-MGMT-IRES-MDR1,以电穿孔介导的基因转移法导入GP+E86和PA317病毒包装细胞,采用含BCNU和长春新碱(VCR)的培养基克隆选择后收集重组病毒上清于单向型GP+E86与双嗜型PA317包装细胞行乒乓交互感染,将含MGMT和MDR1双耐药基因重组病毒的上清在细胞生长因子刺激下重复感染经免疫磁珠分离系统(MACS)分离纯化后的人脐血CD34+细胞,用PCR,RT-PCR,Southern blot,Northern blot,FACS和MTT等方法检测外源MGMT与MDR1基因在CD34+细胞中的转移和表达.结果显示,DNA测序及酶切鉴定证实MGMTcDNA克隆和双顺反子逆转录病毒载体构建的正确性,MACS分离纯化后的人脐血CD34+细胞纯度平均达92%,回收率为75%,含双耐药基因重组病毒的上清最高滴度为5.8×105 cfu/ml,逆转录病毒载体介导的双耐药基因已整合入转染靶细胞中基因组并获得有效表达,同时传递不同的耐药表型,应用集落计数、PCR方法测定基因转导效率分别为18%和20%,巢式PCR及补救分析均未检测到辅助病毒存在,经双耐药基因修饰的脐血CD34+细胞对BCNU的IC50较对照组提高4.5倍,对VCR,柔红霉素(DNR)和秋水仙碱(COL)的IC50较未转染细胞分别高7.8,6.6和5.5倍.本研究对降低联合化疗骨髓毒性作用的肿瘤临床研究奠定了实验基础.     

表观遗传修饰与肿瘤

肿瘤的形成受遗传学修饰和表观遗传修饰的影响。长期以来人们一直认为基因突变参与肿瘤的形成,近年来越来越多的证据表明,表观遗传修饰在肿瘤进展中同样具有非常重要的作用。表观遗传调控可以影响基因转录活性而不涉及DNA序列的改变。本文介绍了肿瘤发生发展过程中出现的表观遗传修饰异常,以及通过干预表观遗传修饰治疗肿瘤的应用前景。     

表观遗传修饰在调控寿命中的作用

表观遗传修饰是生命现象中普遍存在的一类基因调控方式,主要包括DNA甲基化、组蛋白乙酰化和组蛋白甲基化等,通常协同调控基因表达。端粒是位于真核生物染色体末端的保护性结构,在端粒以及亚端粒区域中也存在丰富的表观遗传修饰。随着研究深入,发现表观遗传修饰在调控寿命过程中扮演着重要角色,而揭示衰老的有关机制有助于我们找到延长寿命的方法,具有重大的生物学意义和临床应用前景。     

表观遗传修饰与干细胞分化调控

干细胞具有自我更新和多种分化潜能的特性。干细胞向分化细胞的转变涉及到基因表达模式的改变,与自我更新有关的基因关闭．与细胞特化有关的基因激活。表观遗传调控机制,包括DNA甲基化、组蛋白修饰和微RNA（microRNA）介导的基因调控,在多个层面上控制发育过程中基因表达。近年研究表明,动态的表观遗传调控机制在干细胞自我更新和分化中起关键作用。     

癌表观遗传调控与癌症治疗

基因功能与表达模式异常是癌症的主要特征.日益增多的研究表明,DNA甲基化(DNAmethylation)、组蛋白修饰(histone modification)、染色质重塑(chromatin remodeling)以及microRNAs 介导的基因沉默等表观遗传调控方式的异常与癌症的发生发展密切相关.阐明癌症发生发展...     

CIAPIN1基因的生物学功能及其与肿瘤的相关性

CIAPIN1是近年通过克隆表达方法鉴定的新基因,已证实其主要受细胞因子的调控,是Ras信号通路的重要介导者。CIAPIN1基因存在显著的细胞凋亡抑制效应,在肿瘤细胞中高表达,能抑制肿瘤细胞的凋亡和促进其细胞周期进程。进一步的研究还发现,CIAPIN1可促进肿瘤新生血管的形成和肿瘤多药抵抗的产生等。     

MDR1反义RNA降低细胞KB_(v200)的耐药性

由ＭＤＲ１基因过度表达所引起的肿瘤细胞对化疗药物的耐药性,是导致化疗失败的主要原因之一．针对ＭＤＲ１中一段包含转录启始位点、翻译启始位点和转录正调控区的序列,设计了反义ＲＮＡ并将其克隆到逆转录病毒载体ｐＬＸＳＮ上．用脂质体包裹载体导入ＭＤＲ１高表达的耐药细胞ＫＢｖ２００中,在反义ＲＮＡ转染的细胞中,ＭＤＲ１在ｍＲＮＡ和蛋白水平的表达都有下降,细胞内药物的浓度有所提高,对长春新碱、阿霉素的耐药性分别下降了６５％和４７％．实验结果表明,反义ＲＮＡ对ＭＤＲ１的表达有抑制作用,从而使肿瘤细胞内的药物浓度升高,其耐药程度下降．     

中国仓鼠卵巢细胞表观遗传调控研究进展

中国仓鼠卵巢(Chinese hamster ovary, CHO)细胞因其具有可悬浮培养及进行蛋白质糖基化等翻译后修饰等优势,在生物制药重组蛋白生产方面具有不可替代的重要作用。但转基因沉默、表观遗传修饰等影响基因表达调控,造成CHO细胞表达稳定性降低而导致重组蛋白产量下降。本文对CHO细胞中表观遗传修饰包括DNA甲基化、组蛋白修饰和miRNA的作用研究,以及对基因表达调控的影响进行了综述。     

MRP基因与肿瘤的多药耐药性

在人肿瘤非典型性多药耐药机制的研究中发现了一个新的基因——多药耐药相关蛋白基因（MRP）.该基因位于人16号染色体P13∶3,编码1 531个氨基酸.其产物为多药耐药相关蛋白（MRP）,分子质量190 ku,故又名p190. MRP属ABC超家族成员,主要分布在细胞的质膜上.MRP的功能可能是在能量依赖的外排系统中发挥作用.除了一些肿瘤细胞系外,MRP基因的高表达还见于一些血液系肿瘤及乳腺癌等.MRP基因的高表达还可能与某些肿瘤的复发和预后有关.     

乳腺癌耐药蛋白介导多重耐药机制及其逆转

近年发现的乳腺癌耐药蛋白属于ATP结合框转运体家族中的G亚家族,是主要的介导肿瘤细胞多药耐药机制的跨膜转运蛋白之一,在临床抗肿瘤治疗中具有重要的意义。本文综述了乳腺癌耐药蛋白的结构特点、表达特征,及其介导的肿瘤细胞多重耐药机制与逆转等方面的研究进展,并展望了今后的研究方向。     

Epigenetic Regulation of a Powdery Mildew Resistance Gene in Medicago truncatula

Dear Editor, Medicago truncatula is a model legume that is conge- neric with alfalfa （Medicago sativa）, a forage crop of global importance. Over the last decade, tremendous genetic and genomic tools have been developed for this model system, which has greatly facilitated the study of various aspects of legume genomics and biology. From an applied perspective, genomic information gained from M. truncatula is particu- larly useful for genetic improvement of cultivated alfalfa, a crop that is not amenable to genetic analysis because of its allogamous and autotetraploid nature （Yang et al., 2008）. For instance, M. truncatula can be used to clone the orthologs of many economically important genes in alfalfa,     

DC-CIK对K562/A多药耐药基因mdr1表达的影响

目的：体外观察树突状细胞（dendritic cell,DC）联合细胞因子诱导的杀伤细胞（cytokine inducedkiller,CIK）对K562/A细胞株多药耐药基因mdr1表达的影响。方法：采集健康人的外周血,分离出单个核细胞（peripheral blood mononuclear cell,PBMC）,在体外加入多种细胞因子经诱导生成DC及CIK细胞,以流式细胞仪检测其表面标志,将DC细胞内加入K562/A细胞裂解物致敏后,再与CIK细胞混合培养48小时。将致敏后的DC-CIK细胞与K562/A及K562分组培养后以荧光定量PCR检测其mdr1基因表达的情况,PBMC作为对照组。结果：RT-PCR中可见K562/A＋DC-CIK组中mdr1 mRNA表达较K562/A明显降低,经荧光定量PCR观察到K562/A内mdr1 mRNA表达为K562的10.27倍、K562/A/PBMC略低于未处理的K562/A（P〉0.05）,K562/A/DC-CIK细胞中mdr1 mRNA含量较K562/A、K562/A/PBMC少（P〈0.05）。DC-CIK细胞与细胞株混合培养后,mdr1基因表达较混合培养前明显降低。结论：实验数据显示DC-CIK可使耐药细胞株内mdr1基因表达下调。但K562与DC-CIK混合培养后该基因降低不明显,提示该基因在细胞中存在着基础表达,意义在于维持细胞内稳态。目前针对逆转白血病耐药的研究较少,需要多进行相关研究以拓宽细胞免疫治疗在逆转耐药领域的应用。DC-CIK是具有发展潜力的抗肿瘤方法。本实验将为下一阶段研究逆转耐药的机制提供依据,DC-CIK细胞免疫疗法有望成为逆转肿瘤耐药的新方法。     

GALNT14 Involves the Regulation of Multidrug Resistance in Breast Cancer Cells

GALNT14 is a member of N-acetylgalactosaminyltransferase enzyme family and mediates breast cancer cell development. Here, we find that GALNT14 regulates multidrug resistance (MDR) in breast cancer. The expression of GALNT14 is associated with MDR in breast cancer. Higher level of GALNT14 facilitates MCF-7 cells to resist Adriamycin, whereas knockdown of GALNT14 sensitizes cells to Adriamycin. Moreover, the expression of GALNT14 associates with the expression of P-gp, the efflux pump localized on the cell membrane, which could be the underlying mechanism of how GALNT14 induces MDR. In-depth analysis shows that GALNT14 regulates the stability of P-gp. Finally, GALNT14 associates with higher level of P-gp in chemotherapy-resistant human breast cancer tissues. Taken together, our studies reveal a molecular mechanism in breast cancer MDR.     

Potential of DNMT and its Epigenetic Regulation for Lung Cancer Therapy

Lung cancer, the leading cause of mortality in both men and women in the United States, is largely diagnosed at its advanced stages that there are no effective therapeutic alternatives. Although tobacco smoking is the well established cause of lung cancer, the underlying mechanism for lung tumorigenesis remains poorly understood. An important event in tumor development appears to be the epigenetic alterations, especially the change of DNA methylation patterns, which induce the most tumor suppressor gene silence. In one scenario, DNA methyltransferase (DNMT) that is responsible for DNA methylation accounts for the major epigenetic maintenance and alternation. In another scenario, DNMT itself is regulated by the environment carcinogens (smoke), epigenetic and genetic information. DNMT not only plays a pivotal role in lung tumorigenesis, but also is a promising molecular bio-marker for early lung cancer diagnosis and therapy. Therefore the elucidation of the DNMT and its related epigenetic regulation in lung cancer is of great importance, which may expedite the overcome of lung cancer.Key Words: Lung cancer, epigenetic regulation, DNA methylation, DNMT, gene silence, epigenetic therapy.     

蛋白激酶C对多药耐药调控作用

化疗是目前治疗恶性肿瘤的主要手段之一 ,尽管新的抗癌药物及化疗方案不断推出 ,但治疗效果仍无显著提高 ,其主要原因之一是肿瘤细胞对化疗药物产生多药耐药 (ｍｕｌ ｔｉｄｒｕｇｒｅｓｉｓｔａｎｃｅ ,ＭＤＲ)。ＭＤＲ是指对一种药物耐药的肿瘤 ,同时对另一些与之化学结构、作用机制完全不同的药物产生交叉耐药。其发生机制复杂 ,其中ｍｄｒ1基因编码的Ｐ 糖蛋白 (Ｐ ＧＰ)表达是ＭＤＲ产生的主要机制之一。近年来的研究表明 ,蛋白激酶Ｃ(ｐｒｏｔｅｉｎｋｉｎａｓｅＣ ,ＰＫＣ)参与了调控ＭＤＲ形成过程。蛋白激酶Ｃ是一种钙离子、磷脂依…     

DNA Methylation-Dependent Epigenetic Regulation of Gene Expression in MCF-7 Breast Cancer Cells

To identify epigenetically-regulated genes in breast cancer, MCF-7 cells were exposed to 250nM 5-aza or 5-aza + 50nM TSA for 3 weeks followed by a 5 week recovery period after treatment withdrawal and gene expression patterns were examined by microarray analysis. We identified 20 genes that are associated with a >2-fold increase in expression in response to the demethylating treatment but returned to control levels after treatment withdrawal. RT-PCR verified that the genes identified were expressed at low or undetectable levels in control MCF-7 cells, but increased expression in treated cells. Most of these putative epigentically-regulated genes in MCF-7 cells do not contain CpG islands. In fact, these genes could be classified based upon their promoter CpG features, including genes with: (i) typical CpG features (CpG islands), (ii) intermediate CpG features (weak CpG islands), and (iii) atypical CpG features (no CpG islands). Prototype genes from each class (including CpG-deficient genes) were shown to be methylation-sensitive (subject to CpG methylation and responsive to demethylating agents), suggesting that not all gene targets of DNA methylation in breast cancer will contain a CpG island. Based upon the results of the current study and observations from the literature, we propose expansion of the current model for methylation-dependent regulation of gene expression to include genes lacking typical CpG islands. The expanded model we propose recognizes that all promoter CpG dinucleotides represent legitimate targets for DNA methylation and that the methylation of specific CpG dinucleotides in critical domains of regulatory regions can result in gene silencing.      

P-糖蛋白对结肠癌多药耐药的影响

结肠癌是常见的消化道恶性肿瘤。对术后患者以及无法采用手术治疗的患者,临床多采用化疗、放疗等综合性治疗方法。随着大量化疗药物在临床的广泛使用,结肠癌多药耐药性成为化疗失败的最主要原因。研究表明,P-糖蛋白(P-glycoprotein, P-gp)作为ATP结合盒(ABC)转运蛋白超家族成员之一,与多种肿瘤的多药耐药相关,其介导的多药耐药已经成为目前研究的热点。本文旨在通过对P-糖蛋白的结构、耐药机制以及逆转P-糖蛋白介导的结肠癌多药耐药新发现进行阐述,引导读者对P-糖蛋白在结肠癌多药耐药中的作用有更深入的了解。