RNA干扰技术逆转神经胶质瘤细胞多药耐药性

目的 探讨利用RNA干扰（RNAi）技术逆转神经胶质瘤细胞多药耐药性。方法 根据多药耐药基因1（MDR1）的碱基序列设计并合成短发夹RNA（shRNA）,构建逆转录病毒质粒载体,用阳离子脂质体法体外转染BT325细胞株,以增强型绿色荧光蛋白（EGFP）表达作为对照。采用定量PCR、Northern blot检测转染前后MDR1 mRNA的表达,Western blot检测蛋白表达;使用CCK-8试剂盒对转染后的细胞进行化疗药物敏感性试验,评价RNAi对多药耐药性的逆转作用。结果 成功构建RNAi质粒载体。共转染实验组RT-PCR定量MDR1 mRNA相对表达水平均有所下降（P〈0．05）;Northern blot表明,转染48h细胞干扰最强;Western blot显示,siRNA各转染组P-糖蛋白（P-gp）的表达分别降低12．9％、30．3％和4．8％,在48h抑制最强;而药物敏感试验显示,转染siRNA后细胞对药物的敏感性明显增强。结论 RNAi能够明显抑制神经胶质瘤细胞系MDR1 mRNA和P-gp蛋白的表达,进而对多药耐药性发挥明显的逆转作用,为基因治疗提供了一种新的手段。     

Inhibition of P-glycoprotein transport function and reversion of MDR1 multidrug resistance by cnidiadin

Purpose Overexpression of P-glycoprotein (Pgp) encoded by the MDR1 gene is one of the major obstacles to successful cancer chemotherapy. The goal of this study was to evaluate if, among other natural coumarins, cnidiadin, a furanocoumarin present in traditional Chinese medications and in a spice commonly used in Greek food, inhibits Pgp transport activity and has the potential to reverse MDR1 multidrug resistance.Methods Using MDR1-transfected Madin-Darby canine kidney (MDCK-MDR1) cells as a model of cells expressing the human MDR1 phenotype, and verapamil or CsA or both as positive control, we tested the capacity of six natural coumarins (umbelliferone, esculin, esculetin, cnidiadin, angelicin and psoralen) to induce the accumulation of rhodamine-123 (R-123) and [³H]-vinblastine ([³H]-VBL) and to modulate the photolabeling of Pgp by SDZ 212-122, a diazirin cyclosporin A. The growth-inhibitory effect of cnidiadin and its capacity to enhance the cell toxicity of vinblastine (VBL) or vincristine (VCR) was then evaluated by the WST-1 assay in two cell lines overexpressing Pgp (MDCK-MDR1 and vincristine-resistant KB/VCR).Results Cnidiadin was the only tested coumarin capable of significantly accumulating R-123 and [³H]-VBL and inhibiting Pgp photolabeling in MDCK-MDR1 cells. The dose-dependent increase in [³H]-VBL uptake (IC₅₀ 26.5 M) induced by cnidiadin in the dose range 1–100 M correlated with inhibition of Pgp photolabeling. At 10 M cnidiadin inhibited photolabeling by 59% and sensitized both MDCK-MDR1 and KB/VCR cells to vinca alkaloids.Conclusion Cnidiadin is a cytotoxic agent capable in vitro of competitively inhibiting the binding and efflux of drug by Pgp and of enhancing the cell toxicity of vinca alkaloids in two cell lines (MDCK-MDR1 and mutant human carcinoma KB/VCR) overexpressing Pgp. This suggests that diet or traditional preparation containing cnidiadin may contribute to the reversal of MDR1 multidrug resistance and may affect the bioavailability of Pgp substrates orally administered. However, due to its cell toxicity, clinical interest in cnidiadin as a chemosensitizer appears to be limited.     

Knockdown of MDR1 Increases the Sensitivity to Adriamycin in Drug Resistant Gastric Cancer Cells

Gastric cancer is one of the most frequently occurring malignancies in the world. Development of multipledrug resistance (MDR) to chemotherapy is known as the major cause of treatment failure for gastric cancer.Multiple drug resistance 1/P-glycoprotein (MDR1/p-gp) contributes to drug resistance via ATP-dependent drugefflux pumps and is overexpressed in many solid tumors including gastric cancer. To investigate the role of MDR1knockdown on drug resistance reversal, we knocked down MDR1 expression using shRNA in drug resistantgastric cancer cells and examined the consequences with regard to adriamycin (ADR) accumulation and drugsensitivity.Two shRNAs efficiently inhibited mRNA and protein expression of MDR1 in SGC7901-MDR1 cells.MDR1 knockdown obviously decreased the ADR accumulation in cells and increased the sensitivity to ADRtreatment. Together, our results revealed a crucial role of MDR1 in drug resistance and confirmed that MDR1knockdown could reverse this phenotype in gastric cancer cells.     

MDR1短发夹RNA表达质粒的构建及其功能的初步研究

目的构建在哺乳动物细胞中表达MDR1短发夹RNA(short hairpin RNA,shRNA)的表达质粒,并初步探讨其对耐药肝癌细胞MDR1 mRNA的抑制作用及抗肿瘤药物耐药性的影响.方法根据Genbank中MDR1 mRNA设计的两条多聚核苷酸序列,退火形成双链DNA,再与经双酶切后的载体PGE-1连接,构建pshRNA-MDR1重组质粒,在脂质体的介导下转染肝癌细胞株BEL-7402/ADM,RT-PCR分析MDR1 mRNA的表达,MTT法检测阿霉素对细胞的半数抑制浓度(IC50).结果PCR和DNA测序证实了表达质粒构建成功,并能明显地抑制BEL-7402/ADM MDR1 mRNA的表达,对阿霉素的耐药指数降低了17.5倍(299.2/17.1).结论构建的pshRNA-MDR1表达质粒能有效地抑制转染细胞MDR1 mRNA,从而提高肿瘤细胞的药物敏感性.     

Survivin反义寡核苷酸对卵巢癌耐药细胞COC1/DDP抑制的实验研究

背景与目的: Survivin是近年发现的一种细胞凋亡抑制基因, 它与卵巢癌细胞的生长及耐药性密切相关,本研究探讨经脂质体介导的 survivin反义寡核苷酸 (Lip-ASODN)对人卵巢癌耐药细胞 COC1/DDP生长、凋亡及细胞周期的影响.方法:将脂质体介导的 survivin-ASODN转染 COC1/DDP细胞;细胞动力学检测、 MTT法观察细胞生长情况; RT-PCR检测 survivin mRNA的表达;通过 Western杂交检测 caspase-3蛋白及活性;流式细胞仪分析细胞凋亡率及细胞周期变化.结果:与空脂质体及 SODN组相比,经 survivin-ASODN作用后的 COC1/DDP细胞的生长受到明显抑制, 72 h的细胞生长抑制率可达( 68.3± 6.2)%( P< 0.05). Survivin mRNA的表达明显下降,而 caspase-3的活性增加,并呈时间依赖性. ASODN组细胞周期发生了明显变化,细胞被阻滞于 G0/G1期,占 79.21%, G2/M及 S期分别为 4.92%、 15.87%,均明显下降;细胞凋亡率为 33.18%,明显高于 SODN组及空脂质体组( P< 0.05).结论: Survivin ASODN能抑制人卵巢癌耐药细胞 COC1/DDP生长,降低 survivin mRNA的表达并诱导 COC1/DDP细胞凋亡.     

CPP32在耐药细胞中的活性及其意义

目的　探讨耐药细胞和药敏细胞中caspase - 3mRNA、蛋白的表达及相互关系 ,试图阐明caspase - 3在诱导耐药细胞凋亡中的作用。方法　利用胃癌耐药细胞系SGC790 1/ 0 8,通过RT -PCR研究caspase - 3的mRNA在细胞毒药物处理耐药细胞0h ,2 4h及药敏细胞 0h ,6h时的表达 ,用Western -blot检测其蛋白在耐药细胞中 0h ,6h ,2 4h ,30h的表达和药敏细胞中 0h ,6h ,2 4h的表达 ,DNAladder检测其特征性凋亡 ,MTT法检测细胞的存活率。结果　耐药细胞和药敏细胞在 0h ,2 4h表达的caspase- 3mRNA无显著性差异 ,蛋白表达在耐药细胞中 6h有微量表达 ,30h出现更小片断 ;药敏细胞在 6h时出现小片断 ,2 4h完全裂解。细胞DNA分析表明耐药细胞 30h出现典型的凋亡谱带 ;应用了caspase - 3抑制剂后细胞凋亡延迟。药敏细胞 6h出现典型的凋亡谱带 ,应用抑制剂后凋亡延迟。结论　提高耐药细胞用药量仍可以使耐药细胞凋亡 ,其凋亡的过程与耐药细胞相同 ,均有caspase - 3的激活 ,而抑制了caspase - 3的活性 ,凋亡可被抑制或是延迟 ,其差别在于耐药细胞需要较高的药物诱导浓度。耐药细胞与药敏细胞的凋亡机制的差别可能在于凋亡发生前的诸多因素产生的差异。     

By inhibiting Src,verapamil and dasatinib overcome multidrug resistance via increased expression of Bim and decreased expressions of MDR1 and survivin in human multidrug-resistant myeloma cells

The calcium channel blocker verapamil inhibits the transport function of multidrug resistance protein 1 (MDR1). Although verapamil acts to reverse MDR in cancer cells, the underlying mechanism remains unclear. In the present study, we investigated the mechanism of reversing MDR by verapamil in anti-cancer drug-resistant multiple myeloma (MM) cell lines. We found that verapamil suppresses MDR1 and survivin expressions and increases Bim expression via suppression of Src activation. Furthermore, dasatinib reversed the drug-resistance of the drug-resistant cell lines. These findings suggest that Src inhibitors are potentially useful as an anti-MDR agent for the treatment of malignant tumor cells.     

MDR1及MDR3短发夹RNA逆转乳腺癌细胞阿霉素耐药的实验研究

目的 研究靶向多药耐药(MDR)1及MDR3基因的短发夹RNA(shRNA)在逆转人乳腺癌阿霉素耐药细胞株MCF-7/Adr耐药中的作用.方法 真核质粒介导的针对MDR1及MDR3基因的shRNA转染细胞,空载体转染作为对照.Annexin-Ⅴ和PI双标法、流式细胞术、四甲基偶氮唑蓝(MTT)、逆转录聚合酶链反应(RT-PCR)、免疫组化分别检测细胞凋亡、细胞内阿霉素蓄积、细胞增殖活性及对阿霉素的IC50、MDR1及MDR3 mRNA及P-糖蛋白(P-gp)表达.结果 转染后,MDR1组及MDR3组MCF-7/Adr细胞凋亡率分别为30.21%±1.65%和22.07%±2.17%,与未转染组和空载体转染组比较差异有统计学意义(P＜0.01);MCF-7/Adr细胞内的阿霉素积聚浓度显著增加;MCF-7/Adr细胞存活率显著下降,MCF-7/Adr细胞对阿霉素IC50显著降低;相对于空载体转染组,MCF-7/Adr细胞中MDR1和MDR3 mRNA最高分别下降89.5%±0.8%和85.1%±1.2%,mRNA下降水平与孵育时间有关;P-gp表达明显降低,与未转染组和空载体转染组比较差异有统计学意义(P＜0.05).结论 shRNA可特异性地沉默MDR1及MDR3基因的表达,逆转P-gp介导的乳腺癌细胞阿霉素耐药,而MDR1的这种作用更为显著.     

XIAP和XAF1在急性白血病中的表达及其意义

目的:研究急性白血病(AL)患者中凋亡抑制蛋白XIAP和XIAP相关因子1(XAF1)的表达及其临床意义.方法: 以86例AL患者为研究对象,其中初诊未治患者56例,治疗后完全缓解期(CR)患者22例,缓解后复发患者8例,应用RT-PCR方法检测骨髓细胞中XIAP mRNA和XAF1mRNA表达.对照组为20名门诊非恶性血液病患者.结果: 对照组、初治组、缓解组和复发组的XIAP mRNA平均表达水平之间比较,差异具有显著性(F=58.77,P<0.01);对照组的XIAP mRNA平均表达水平为0.29±0.13,明显低于AL初治患者(0.98±0.30)(P<0.01)和缓解组(0.45±0.17)(P<0.05);缓解组的平均表达水平明显低于初治组(P<0.01);复发组的XIAP mRNA平均表达水平最高(1.23±0.30),不仅明显高于对照组和缓解组(P<0.01),也高于初治组(P<0.05). 对照组的XAF1 mRNA的阳性表达率为100%,明显高于初治组(51.79%)(P<0.01)和缓解组(77.27%)(P<0.05);初治组和复发组的阳性表达率(25%)明显低于缓解组(P<0.05),但初治组与复发组无显著性差异(P>0.05).XIAP mRNA和XAF1 mRNA表达在初治AML和ALL组比较均无显著性差异(P>0.05).结论: XIAP异常高表达和XAF1异常低表达可能在急性白血病发病和病情进展中起重要作用,为AL 的治疗提供了新思路.     

多药耐药基因1多态性研究进展

多药耐药基因1(MDR1)产物P糖蛋白在药物的吸收、分布、代谢和分泌以及药物间的相互作用方面起了很大作用.耐药的程度取决于化疗所致MDR1表达的上调情况.DNA序列差异通过多种机制引起表型的改变,单核苷酸多态性是序列差异的最多见的类型.不同民族和群体中MDR1的基因多态性和P-gp表达和功能有关.     

MDR1基因下调逆转人白血病阿霉素耐药细胞株K562/ADM的耐药性

目的：探讨RNA干扰（RNAi）人MDR1基因对人白血病阿霉素耐药细胞株K562/ADM耐药性的影响。方法：应用针对人MDR1基因的RNAi质粒pENTRTM/U6-MDR1转染人白血病阿霉素耐药细胞株K562/ADM和亲本细胞株K562,48 h后实时荧光定量PCR检测MDR1 mRNA表达,流式细胞术检测P-gp蛋白表达和P-gp功能,MTT法检测细胞对ADM的耐药性。结果：与未转染细胞相比,K562/ADM耐药细胞pENTRTM/U6-MDR1组的MDR1 mRNA和P-gp蛋白表达和功能均显著下降（ P <0.05）,对阿霉素的耐药性显著降低（ P <0.05）。结论：MDR1基因下调可逆转人白血病阿霉素耐药细胞株对阿霉素的耐药性。     

Construction of double suicide genes system controlled by MDR1 promoter with targeted expression in drug-resistant glioma cells

The multiple drug resistance protein (MDR1) is frequently overexpressed in human glioma. The aim of this study is to clone the MDR1 promoter from C6/ADR, construct the double suicide genes expressive vector controlled by MDR1 promoter, and explore its targeted expression in C6/ADR cells. MDR1 promoter from C6/ADR genomic DNA, which was linked with T vector, was amplified by using Polymerase chain reaction (PCR). After cut by NdeI and HindIII, MDR1 promoter was cloned into pcDNA3-TK (thymidine kinase) plasmid. The cytosine deaminase (CD) gene from pcDNA3-CD-TK plasmid was directly cloned into the above vector to construct pcDNA3-MDR1-promoter-CD-TK vector. Then this vector was transfected into C6 and C6/ADR cells respectively by liposome. After selection by G418, the tumor cell lines were stably established. Then these cell lines were examined through PCR and RT-PCR to respectively detect the integration and expression of TK and CD genes. The results showed the length and sequence of MDR1 promoter amplified by PCR were confirmed by DNA sequencing. The pcDNA3-MDR1-promoter-CD-TK expression vectors were constructed successfully. PCR indicated the double suicide genes were integrated into C6 and C6/ADR cells. RT-PCR reveled that CD and TK genes expressed in C6/ADR/CD-TK cells, whereas not in C6/CD-TK cells. In conclusions, construction of expressive vector containing double suicide genes controlled by MDR1 promoter with targeted expression in C6/ADR will provide a sound basis for targeted gene therapy for multidrug resistance (MDR) glioma.     

电穿孔法介导醛脱氢酶基因与多药耐药基因的转移和表达

背景与目的：将不同类型的耐药基因同时导入造血细胞,以扩大耐药范围和进行体内选择是基因治疗的重要策略,这类载体基因片段较长,进行基因转移有一定的难度。本研究旨在寻找安全有效的长片段基因转移G1Na-AIM以NdeⅠ酶切线性化,电穿孔法转导PA317细胞,经长春新碱（VCR）和4－氢过氧化环磷酰胺（4－HC）选择后,应用Southern blot法确定原病毒的整合,逆转录聚合酶链反应（RT－PCR）和流式细胞术（FCM）分析转移基因的表达,筑巢式聚合酶链反应（nested PCR)检验转移系统的安全性。结果：电穿孔法有效介导了ALDH1与MDR1基因的同时转移,Southern blot法证实ALDH1与MDR1基因稳定整合至宿主细胞基因组,RT－PCR检测到转移基因的转录,FCM测定下游基因MDR1蛋白表达增高4倍,转导率达98％。nested PCR未检测到辅助病毒（env)。结论：电穿孔法安全有效地介导了ALDH1与MDR1基因的共移和高表达。     

VEGFR1和MDR1在胃癌中的表达及意义

目的:探讨VEGFR1和MDR1在胃癌中的表达及意义.方法:采用免疫组化SP法检测VEGFR1和MDR1在胃癌中的表达及与分化程度的关系;比较VEGFR1和MDR1在胃癌中的表达相关性.结果:VEGFR1在高、中、低度分化胃癌的表达率依次为15/53(28%)、19/43(44%)、37/54(68%); 在低分化胃癌组织中的表达明显高于高分化和中分化胃癌组织(P＜0.05).MDR1在高、中、低度分化胃癌的表达率依次为18/53(34%)、21/43(48%)、41/54(76%); 在低分化胃癌组织中的表达明显高于高分化和中分化胃癌组织 (P＜0.05).结论:VEGFR1和MDR1在胃癌中的表达具有一致性,可能在胃癌的多药耐药中扮演重要角色.     

The effect of antisense epidermal growth factor receptor (EGFR) RNA on the proliferation of human glioma cells and induction of cell apoptosis

Malignantgliomaisoneofthemostdevastatingdiseases.Theprognosisofpatientshasnotbeenimprovedevenwhenthecurrentlyavailablec0mbinedtherapiesareused.Astheknowledge0ftumorbi0l0gyandmoleculargeneticshasgreatlyincreasedoverthepastdecades,ithasbeenshownthattumorigenesisbasicallyresultsfromtheactivation0fprotooncogenesandinactivati0n0ftumorsuppressorgenes.Sincegenesencodinggrowthfactorsandtheirreceptorsarecloselyrelatedtooncogenes,muchattentionhasbeenfocusedontheroleofgrowthfactorsandtheirreceptorsinthep…     

VEGF反义寡核苷酸抑制大鼠胶质瘤生长的时间与剂量的效应关系

目的在大鼠脑内原位注射反义寡核苷酸观察胶质瘤的生长抑制情况的时间与剂量的效应关系。方法所有大鼠均在立体定向导引下右尾状核区接种1×106C6胶质瘤细胞。不同时间和剂量VEGF反义寡核苷酸均在立体定向导引下原穿刺靶点注射。其中实验Ⅰ组在接种细胞的同时原位注射1000μmol/L的VEGF反义寡核苷酸,而实验Ⅱ组则同时注射2000μmol/L的VEGF反义寡核苷酸。对照Ⅰ组为对照。实验Ⅲ和Ⅳ组在细胞接种后的1和2周各原位注射1次,共2次,每次实验Ⅲ组为1000μmol/L、实验Ⅳ组为2000μmol/L的VEGF反义寡苷核酸。对照Ⅱ组为对照。实验V组仅在接种后2周注射1次2000μmol/L的VEGF反义寡核苷酸,并设对照Ⅲ组为对照。实验3周时处死所有的大鼠,解剖出全脑标本,观察肿瘤的生长情况,测量肿瘤大小。结果实验Ⅰ组的抑瘤率为94.5％,实验Ⅱ组的抑瘤率为100％。实验Ⅲ组的抑瘤率为91.5％,实验Ⅳ组为100％,实验Ⅴ组抑瘤率为87.8％。实验组和对照组的肿瘤体积比较有非常显著的差异。结论 原位应用VEGF反义寡核苷酸能取得很好的抗血管生成的治疗效果,抑瘤效果有明显的浓度依赖性。原位早期使用足量反义核酸能取得更好的效果。     

多药耐药基因MDR1及P-gp蛋白在乳腺癌组织中的表达及临床意义

目的：检测乳腺癌组织中多药耐药基因MDR1及P-gp蛋白的表达,并探讨其表达与临床病理因素的关系及MDR1与P-gp的相关性.方法：采用荧光定量RT-PCR （FQ-RT-PCR）法检测61例乳腺癌、22例对照组（包括11例乳腺良性疾病、11例癌旁正常组织）中MDR1基因的表达,同时采用免疫组化法检测上述标本中P-gp蛋白的表达.结果：乳腺癌组织中MDR1基因扩增率为50.82%（31/61）,与正常对照组相比差异有统计学意义,P=0.000 6.乳腺癌中P-gp蛋白阳性率为42.62%（26/61）,其表达与年龄、肿瘤大小、淋巴结转移、ER、PR、月经状况无关;MDR1基因扩增率高于P-gp蛋白表达,二者呈高度相关,但并不完全相符.结论：乳腺癌中存在多药耐药基因MDR1及P-gp蛋白的表达,且其表达呈正相关.检测上述基因及其蛋白的表达,可预测乳腺癌的多药耐药.     

多药耐药基因MDR1及P-gp蛋白在乳腺癌组织中的表达及临床意义

目的检测乳腺癌组织中多药耐药基因MDR1及P-gp蛋白的表达,并探讨其表达与临床病理因素的关系及MDR1与P-gp的相关性。方法采用荧光定量RT-PCR(FQ-RT-PCR)法检测61例乳腺癌、22例对照组(包括11例乳腺良性疾病、11例癌旁正常组织)中MDR1基因的表达,同时采用免疫组化法检测上述标本中P-gp蛋白的表达。结果乳腺癌组织中MDR1基因扩增率为50.82%(31/61),与正常对照组相比差异有统计学意义,P=0.0006。乳腺癌中P-gp蛋白阳性率为42.62%(26/61),其表达与年龄、肿瘤大小、淋巴结转移、ER、PR、月经状况无关;MDR1基因扩增率高于P-gp蛋白表达,二者呈高度相关,但并不完全相符。结论乳腺癌中存在多药耐药基因MDR1及P-gp蛋白的表达,且其表达呈正相关。检测上述基因及其蛋白的表达,可预测乳腺癌的多药耐药。     

Increased AP-1 activity in drug resistant human breast cancer MCF-7 cells

The expression, DNA binding, and transactivating activity of activator protein 1 (AP-1) was examined in a series of multidrug resistant (MDR) MCF-7 human breast cancer cells that have increasing levels of MDR1 gene expression. We observed an increase in the amount of both c-jun and c-fos mRNA in cells with 12-, 65-, or 200-fold higher resistance to adriamycin when compared to drug-sensitive MCF-7 wild type (WT) cells. Electrophoretic mobility shift assays (EMSA) demonstrated an increase in the DNA binding activity of an AP-1 complex in nuclear extracts from MDR MCF-7 cells when compared to extracts from WT cells. We observed a proportional increase in luciferase expression from a reporter vector containing consensus AP-1 binding sites in transiently transfected MDR cells when compared to WT cells, indicating that AP-1 mediated gene expression is increased in drug-resistant MCF-7 cells. Since the MDR1 promoter contains a putative AP-1 binding site, we used EMSA to examine AP-1 binding activity to an oligonucleotide probe that contained the relevant MDR1 promoter sequences (–123 to –108). Nuclear extracts from resistant MCF-7 cells displayed an increased level of DNA binding of Jun/Jun dimers to the probe, indicating that AP-1 was capable of binding to this promoter site. A luciferase reporter construct containing triplicate copies of the MDR1 promoter sequence was expressed at higher levels in transiently transfected MDR cells when compared to expression in WT cells. Co-transfection of WT cells with a c-jun expression vector and either of the AP-1 luciferase constructs demonstrated that c-jun could activate gene expression from both the consensus and the MDR1 AP-1 sites in a dose dependent manner. In addition, RT-PCR and western blot analysis showed that levels of MDR1 mRNA and Pgp were increased in c-jun transfected WT cells. Taken together, these data indicate that increased AP-1 activity may be an important mediator of MDR by regulating the expression of MDR1.     

Impact of BCRP/MXR, MRP1 and MDR1/P-Glycoprotein on thermoresistant variants of atypical and classical multidrug resistant cancer cells

The impact of the ABC transporters breast cancer resistance protein/mitoxantrone resistance associated transporter (BCRP/MXR), multidrug resistance-associated protein 1 (MRP1) and multidrug resistance gene-1/P-glycoprotein (MDR1/PGP) on the multidrug resistance (MDR) phenotype in chemoresistance and thermoresistance was investigated in the parental human gastric carcinoma cell line EPG85-257P, the atypical MDR subline EPG85-257RNOV, the classical MDR subline EPG85-257RDB and their thermoresistant counterparts EPG85-257P-TR, EPG85-257RNOV-TR and EPG85-257RDB-TR. Within the atypical MDR subline EPG85-257RNOV expression of BCRP/MXR and of MRP1 were clearly enhanced (vs. parental and classical MDR lines). MDR1/PGP expression was distinctly elevated in the classical MDR subline EPG85-257RDB (vs. parental and atypical MDR sublines). In all thermoresistant counterparts basal expression of BCRP/MXR, MRP1 and MDR1/PGP was increased relative to thermosensitive sublines. Although it could be shown that the overexpressed ABC transporters were functionally active, however, no decreased drug accumulations of doxorubicin, mitoxantrone and rhodamine 123 were observed. Thus, expression of BCRP/MXR, MRP1 and MDR1/PGP was found to be dependent on the appropriate type of chemoresistance; correlating with a classical or atypical MDR phenotype. Within the thermoresistant variants, however, the increase in ABC transporter expression did obviously not influence the MDR phenotype.