急性白血病患者白血病细胞DNA拓扑异构酶Ⅱ活性与多药耐药的研究

目的：探讨急性白血病患者白血病细胞ＤＮＡ拓扑异构酶Ⅱ（ＤＮＡＴｏｐｏⅡ）活性与多药耐药的关系。方法：采用溴乙锭荧光法对１７例初治化疗前及２０例化疗后的急性白血病患者外周血或骨髓白血病细胞ＤＮＡＴｏｐｏⅡ活性进行测定，采用抗多药耐药单抗ＪＳＢⅠ检测１８例化疗后患者ｐ糖蛋白表达，采用ＲＴＰＣＲ法检测ｍｄｒ１基因表达。结果：白血病患者化疗前组ＴｏｐｏⅡ活性（０．６４１５±０．０５６１）较健康对照组（０．２３０４±０．０５９１）显著增高（Ｐ＜０．００５）。化疗后患者白血病细胞ＴｏｐｏⅡ活性（０．３５６３±０．１０１１）较化疗前组显著降低（Ｐ＜０．０５）。１５例临床疗效差，其中１２例ｐ１７０及ｍｄｒ１基因表达阳性、３例表达阴性，而ＴｏｐｏⅡ活性均降低。结论：ＴｏｐｏⅡ活性下降可能是患者对抗肿瘤药表现耐药的另一重要原因。     

拓扑异构酶Ⅱ与白血病多药耐药

白血病是化疗有效的恶性肿瘤之一,而多药耐药（ＭＤＲ）的产生是造成化疗失败的最大障碍。拓扑异构酶Ⅱ（ＴｏｐｏⅡ）介导的ＭＤＲ直接影响患对化疗的反应和预后。本就ＴｏｐｏⅡ的分子生物学特性、与白血病ＭＤＲ的关系、检测和意义以及克服ＭＤＲ的对策等方面进行综述。     

DNA拓扑异构酶Ⅱ与白血病细胞的不典型耐药

白血病细胞耐药是引起化疗失败的主要原因,机制复杂。DNA拓扑异构酶Ⅱ（TopoⅡ）表达异常是引起多药耐药（MDR）的主要机制之一,不同于P－170介导的经典耐药,被冠以下典型耐药（at-MDR)。本文就TOPOⅡ的生物学特性、介导at-MDR的机制、临床意义和逆转at-MDR的策略等方面进行综述。     

拓扑异构酶Ⅱ与白血病多药耐药

白血病是化疗有效的恶性肿瘤之一,而多药耐药(MDR)的产生是造成化疗失败的最大障碍。拓扑异构酶Ⅱ(TopoⅡ)介导的MDR直接影响患者对化疗的反应和预后。本文就TopoⅡ的分子生物学特性、与白血病MDR的关系、检测和意义以及克服MDR的对策等方面进行综述。     

DNA拓扑异构酶Ⅱ与白血病细胞的不典型耐药

白血病细胞耐药是引起化疗失败的主要原因,机制复杂。DNA拓扑异构酶Ⅱ(TopoⅡ)表达异常是引起多药耐药(MDR)的主要机制之一,不同于P-170介导的经典耐药,被冠以不典型耐药(at-MDR)。本文就TOPOⅡ的生物学特性、介导at-MDR的机制、临床意义和逆转at-MDR的策略等方面进行综述。     

DNA拓扑异构酶和端粒酶与白血病多药耐药关系

肿瘤细胞产生耐药性成为许多肿瘤治疗成败的关键，也是血液肿瘤化疗失败的重要原因，目前人们从不同的角度和水平对耐药的发生机制、逆转耐药的药物研究及相应的体内外实验等进行研究，指出多药耐药是多种因素共同作用的结果。近年来白血病的不典型耐药机制日益受到人们的重视，因此本文从DNA拓扑异构酶和端粒酶与白血病耐药的关系出发，阐述了白血病细胞多药耐药的抗凋亡机制，旨在为逆转白血病耐药及开发有效的逆转剂奠定理论基础。     

白血病多药耐药基因表达与细胞表面分化抗原表达的关系

作者对３７例未治白血病同时检测多药耐药基因ｍＲＮＡ水平及细胞表面分化抗原，探讨两种标志表达的关系及意义。发现在急性非淋巴细胞白血病（ＡＮＬＬ）中多药耐药基因表达增加与ＣＤ３４抗原表达相关，两种标志皆为阳性表达组（ＭＤＲ１＾＋／ＣＤ３４＾＋），化疗敏感性明显降低。结合文献报告所见，认为ＭＤＲ１＾＋／ＣＤ３４＾＋可做为ＡＮＬＬ化疗不敏感的预后指标。在急性淋巴细胞白血病中，多药耐药基因表达增加与ＣＤ３、     

细胞凋亡与白血病耐药

本文概述了凋亡相关的基因、酶及其他蛋白因子、激素受体、离子、细胞内微管结构改变等诸多因素在白血病耐药中发挥的作用，分析了凋亡和白血病耐药间的密切联系，从凋亡角度揭示了白血病耐药机制的复杂性。由于白血病耐药的机制常因不同的白血病类型、不同的药物而不同，因此，上述各凋亡相关因素与耐药的关系也不能适用于所有各类白血病对各种抗肿瘤药物的耐药。     

白血病细胞多药耐药现象研究进展

白血病细胞对化疗药物产生耐药性是化疗失败的主要原因之一。多药耐药现象(MDR)是近年来人们关注的热点。多药耐药性是指肿瘤细胞除对一种药物耐药外,也对其它结构和不同作用机制的药物产生交叉耐药性。主要包括多药耐药基因介导的多药耐药现象、谷胱甘肽转移酶和拓扑异构酶活性改变引起的多药耐药现象。MDR基因表达引起的多药耐药现象和白血病的关系最为密切,研究得最为深入。本文就这方面的进展做一综述。     

鲍曼不动杆菌整合子流行现状与多重耐药相关性研究

[目的]了解我院鲍曼不动杆菌整合子流行情况,并探讨整合子与鲍曼不动杆菌多重耐药的关系。[方法]收集我院2009年9月至2010年1月临床分离的鲍曼不动杆菌共56株,用纸片扩散法检测鲍曼不动杆菌对19种抗生素的敏感性,用整合酶PCR方法检测I类、Ⅱ类和Ⅲ类整合子基因。[结果]鲍曼不动杆菌耐药现象十分严重。56株菌株中有41株检出I类整合子,阳性率73．2％,其中8株为I类和Ⅱ类杂交整合子,2株为I类和Ⅲ类杂交整合子。I类整合子阳性株对多种药物的耐药率均高于阴性株,且I类整合子阳性株多重耐药率（90．2％）明显高于阴性株（30％）（P〈0．0L）。[结论]I类整合子在我院鲍曼不动杆菌中检出率很高并与其多重耐药性关系密切。     

DNA topoisomerase II: a primer on the enzyme and its unique role as a multidrug target in cancer chemotherapy

Based on the weight of evidence accrued in the past eight years, there is little question that the nuclear enzyme, topoisomerase II, serves as a common intracellular target for the cytotoxic effect of drugs of widely varying structure. The enzyme appears to be unique as a chemotherapy target in that it is recruited into a lethal process under the influence of drug. Its role contrasts sharply with other more classical chemotherapy targets, such as dihydrofolate reductase, whose activity must be successfully inhibited for the expression of cytotoxicity. Resistance to inhibitors of this enzyme frequently results from marked elevations in intracellular enzyme content. In contrast, the presence of topoisomerase is required for drug effect, and, in general, the greater the cellular content of the enzyme, the more sensitive the cell will be to these agents. However, important issues remain unresolved. The biochemical events that are initiated by cleavable complex formation and result in cell death must be more fully defined. It is likely a better understanding of the drug-enzyme interaction will be required for rational drug development. Finally, those aspects of the drug-topoisomerase interaction that confer therapeutic selectivity and/or clinical resistance are of paramount importance if the phenomenon is ever to be fully exploited.     

白血病细胞与正常外周血淋巴细胞的PARP活性及本底DNA链断裂的比较研究

聚腺苷二磷酸核糖聚合酶[poly(ADP-ribose)polymerase,PARP]是广泛存在于有核细胞中的多功能酶。当细胞DNA发生损伤时,PARP可作为细胞内的分子感受器,识别、结合到DNA断裂处,并被激活。激活的PARP可催化组蛋白H1、拓扑异构酶Ⅰ及Ⅱ、DNA聚合酶、RNA聚合酶、DNA连接酶、Ca~(2 )/Mg~(2 )依赖的核酸内切酶及PARP自身等多种核内受体蛋白的聚ADP-核糖基化作用,传递损伤信息,引发损伤所致级联反应,最终决定细胞的命运:修复损伤或凋亡。因此,PARP对维持细胞的正常功能具有极为重要的作用,其异常可能是导致细胞死亡失控的因素之一,癌变正是这种失控的一种后果。为了探讨PARP与细胞恶性变之间的关系,采集了14例健康供血员血样和4例初诊白血病病人血样,比较研究了白血病细胞与正常人外周血淋巴细胞的PARP活性。同时,应用彗星法(comet assay)研究了细胞内本底DNA链断裂及染色质结构。研究发现,与正常人外周血淋巴细胞相比,外周血白血病细胞中含有异常高的PAPP活性,在急性淋巴细胞白血病、慢性淋巴细胞白血病、慢性粒细胞白血病细胞中检出大量的本底DNA链断裂。这一结果表明:①外周血白血病细胞中异常高的PARP活性和大量存在的本底DNA链断裂可能为其临床诊断提供有效的辅助指标。②外周血白血病细胞中异常高的PARP活     

米非司酮逆转K562/A02细胞多药耐药的研究

目的研究孕激素拮抗剂米非司酮对白血病多药耐药细胞K562／A02的逆转作用及其机制。方法MTT法检测米非司酮作用72h后K562／A02细胞增殖及其对阿霉素杀伤敏感性的变化；流式细胞术检测米非司酮作用前后K562／A02细胞表面P糖蛋白的表达和细胞内柔红霉素的浓度；免疫组化法观察米非司酮作用前后K562／A02细胞凋亡相关蛋白bcl-2、Bax、caspase-3的表达；RT—PCR检测米非司酮作用后对K562／A02细胞内葡萄糖神经酰胺合成酶（GcS）mRNA表达的影响。结果2．5、5．0和10．0μmol／L米非司酮不抑制K562／A02细胞的增殖，但上述浓度的米非司酮作用后K562／A02细胞对阿霉素的敏感性较前分别增强了1．68、4．17和10．71倍。K562／A02细胞表面P糖蛋白的表达为（49．03±5．32）％，10μmol／L米非司酮作用72h后降低到（28．60±2．13）％（P〈0．01）；K562／A02细胞内柔红霉素的浓度为（61．07±8．61）％，而10μmol／L米非司酮作用后升高到（92．72±3．48）％（P〈0．01）。经10μmol／L米非司酮作用后，bcl-2蛋白表达由（56±9）％降低到（37±6）％（P〈0．05）；Bax蛋白由（40±5）％升高到（87±10）％（P〈0．01）；caspase-3蛋白则由（36±7）％升高到（89±6）％（P〈0．01）。RT—PCR结果显示K562／A02细胞GcS mRNA的表达较K562细胞明显升高，10μmol／L米非司酮能明显降低K562／A02细胞内GcS mRNA的表达。结论米非司酮可逆转白血病K562／A02细胞的多药耐药，且具有剂量依赖性。10μmol／L米非司酮能明显逆转白血病K562／A02细胞的多药耐药，其机制与降低P糖蛋白的水平，调节凋亡相关蛋白bcl-2、Bax、caspase-3的表达，降低GcS mRNA有关。     

鲍曼不动杆菌整合子与耐药性的相关性研究

目的调查鲍曼不动杆菌中Ⅰ类、Ⅱ类和Ⅲ类整合子的存在情况,分析整合子与鲍曼不动杆菌耐药性的关系。方法测定93株鲍曼不动杆菌对抗菌药物的敏感性;应用简并引物PCR方法,同时扩增整合子5’保守区的I类、Ⅱ类和Ⅲ类整合酶基因,对阳性PCR产物用限制性内切酶Hinf I作限制片段长度多态性（RFLP）分析进行整合子分类。结果 22株鲍曼不动杆菌检测出Ⅰ类整合子,未检出Ⅱ类和Ⅲ类整合子。Ⅰ类整合子阳性的菌株对抗菌药物的耐药率普遍比整合子阴性的菌株高。结论鲍曼不动杆菌临床分离株的耐药性强,细菌的多重耐药性与Ⅰ类整合子的存在相关。     

鲍曼不动杆菌整合子与耐药性的相关性研究

目的 调查鲍曼不动杆菌中Ⅰ类、Ⅱ类和Ⅲ类整合子的存在情况,分析整合子与鲍曼不动杆菌耐药性的关系.方法 测定93株鲍曼不动杆菌对抗菌药物的敏感性;应用简并引物PCR方法,同时扩增整合子5’保守区的Ⅰ类、Ⅱ类和Ⅲ类整合酶基因,对阳性PCR产物用限制性内切酶HinfⅠ作限制片段长度多态性(RFLP)分析进行整合子分类.结果 ...     

高血压伴胰岛素抵抗与动脉粥样硬化相关性研究

目的 探讨高血压伴胰岛素抵抗与颈动脉粥样硬化的相关性.方法 选择符合入选标准的高血压患者60例,根据胰岛素抵抗指数≥2.8为胰岛素抵抗诊断标准,将其分为高血压伴胰岛素抵抗组(EH伴IR)27例,高血压无胰岛素抵抗组(EH无IR)33例,另选20例体检健康者为正常对照组.对所有受试者进行一般检查及血糖、血脂等生化检查,运...     

The histone deacetylase inhibitor sodium butyrate induces DNA topoisomerase II alpha expression and confers hypersensitivity to etoposide in human leukemic cell lines

The differentiating agent and histone deacetylase inhibitor, sodium butyrate (NaB), was shown previously to cause a transient, 3-17-fold induction of human DNA topoisomerase II alpha (topo II alpha) gene promoter activity and a 2-fold increase in topo II alpha protein early in monocytic differentiation of HL-60 cells. This observation has now been extended to other short chain fatty acids and aromatic butyrate analogues, and evidence is presented that human topo II alpha promoter induction correlates closely with histone H4 acetylation status. Because increased topo II alpha expression is associated with enhanced efficacy of topo II-poisoning antitumor drugs such as etoposide, the hypothesis tested in this report was whether NaB pretreatment could sensitize HL-60 myeloid leukemia and K562 erythroleukemia cells to etoposide-triggered DNA damage and cell death. A 24-72 h NaB treatment (0.4-0.5 mM) induced topo II alpha 2-2.5-fold in both HL-60 and K562 cells and caused a dose-dependent enhancement of etoposidestimulated, protein-linked DNA complexes in both cell lines. At concentrations with minimal effects on cell cycle kinetics (0.4 mM in HL-60; 0.5 mM in K562), NaB pretreatment also modestly enhanced etoposidetriggered apoptosis in HL-60 cells, as determined morphologically after acridine orange/ethidium bromide staining, and substantially increased K562 growth inhibition and poly(ADP-ribose)polymerase cleavage after etoposide exposure. Therefore, a temporal window may exist whereby a differentiating agent may sensitize experimental leukemias to a cytotoxic antitumor agent. These results indicate that histone deacetylase inhibitors should be investigated for etoposide sensitization of other butyrate-responsive hematopoietic and nonhematopoietic tumor lines in vitro and in vivo.     

Drug features that contribute to the activity of quinolones against mammalian topoisomerase II and cultured cells: correlation between enhancement of enzyme-mediated DNA cleavage in vitro and cytotoxic potential.

CP-115,953 [6,8-difluoro-7-(4'-hydroxyphenyl)-1-cyclopropyl-4- quinolone-3-carboxylic acid] is a novel quinolone that is highly active against topoisomerase II in vitro and in mammalian cells in culture (M. J. Robinson, B. A. Martin, T. D. Gootz, P. R. McGuirk, M. Moynihan, J. A. Sutcliffe, and N. Osheroff, J. Biol. Chem. 266:14585-14592, 1991). However, the features of the drug that contribute to its activity towards mammalian systems have not been characterized. Therefore, CP-115,953 and a series of related quinolones were examined for their activity against calf thymus topoisomerase II and cultured mammalian cells. CP-115,953 stimulated DNA cleavage mediated by the type II enzyme with a potency that was approximately 600-fold greater than that of the antimicrobial quinolone ciprofloxacin and approximately 50-fold greater than that of the antineoplastic drug etoposide. As determined by the ability to enhance enzyme-mediated DNA cleavage, quinolone activity towards calf thymus topoisomerase II was enhanced by the presence of a cyclopropyl group at the N-1 ring position and by the presence of a fluorine at C-8. Furthermore, the 4'-hydroxyphenyl substituent at the C-7 position was critical for the potency of CP-115,953 towards the mammalian type II enzyme. In this regard, the aromatic nature of the C-7 ring as well as the presence and the position of the 4'-hydroxyl group contributed greatly to drug activity. Finally, the cytotoxicity of quinolones in the CP-115,953 series towards mammalian cells paralleled the in vitro stimulation of DNA cleavage by topoisomerase II rather than the inhibition of enzyme-catalyzed DNA relaxation. This correlation strongly suggests that these quinolones promote cell death by converting topoisomerase II to a cellular poison.