米哚妥林对P糖蛋白介导的多药耐药的逆转作用

目的评价新型激酶抑制剂类抗癌药米哚妥林逆转P糖蛋白(P-gp)介导肿瘤细胞多药耐药的作用,并探讨其可能机制。方法米哚妥林0.5,1和5μmol·L-1分别加入P-gp高表达的K562/A02和K562细胞中培养72 h,MTS法测定细胞存活率以检测细胞毒性。米哚妥林0.125,0.25和0.5μmol·L-1在K562/A02和K562细胞中与无毒剂量的P-gp底物多柔比星、紫杉醇或长春新碱共培养72 h,MTS法测定细胞存活率以检测逆转耐药作用。米哚妥林0.5和10μmol·L-1与P-gp荧光底物罗丹明123在耐药和敏感细胞中共同孵育30 min后用流式细胞术分析底物积累的变化。米哚妥林0.5μmol·L-1与耐药和敏感细胞共同孵育72 h,Western印迹法检测耐药蛋白和信号分子的表达,定量PCR检测MDR1基因表达的变化。将米哚妥林与P-gp膜蛋白共孵育,化学发光法测定剩余ATP的量,检测米哚妥林对P-gp ATP酶活性的影响。结果米哚妥林对P-gp高表达的K562/A02和亲本敏感细胞K562的细胞毒性无明显的差异,其中米哚妥林0.5μmol·L-1时2种细胞的存活率均达80%以上。米哚妥林0.5μmol·L-1在细胞水平即可有效逆转K562/A02对多种底物的耐药,而对敏感细胞无显著作用;米哚妥林能显著抑制P-gp的外排作用,增加底物Rh-123在K562/A02细胞中的积累,且效果好于阴性对照维拉帕米0.5和10μmol·L-1;米哚妥林对P-gp基因和蛋白表达以及AKT和ERK的表达与磷酸化水平均无影响;米哚妥林对P-gp的ATP酶活性具有明显的抑制作用。结论米哚妥林可抑制P-gp介导的药物外排并逆转P-gp介导的肿瘤多药耐药。     

桑皮苷A逆转K562/阿霉素耐药细胞化疗多药耐药的研究

目的 研究桑皮苷A对人白血病耐药细胞K562/阿霉素耐药细胞（K562/ADM）化疗耐药的影响。方法 实验分为溶媒（DMSO）对照组、阳性对照组(10μmol·L^-1维拉帕米处理48 h,再用5μg·mL^-1阿霉素孵育1 h或2μg·mL^-1罗丹明123孵育1.5 h)、阿霉素单用组(5μg·mL^-1阿霉素孵育1 h)、阿霉素合用桑皮苷A组(用5,10,20μmol·L^-1桑皮苷A处理48 h,再用5μg·mL^-1阿霉素孵育1 h)、罗丹明123合用桑皮苷A组(用5,10,20μmol·L^-1桑皮苷A处理48 h,再用2μg·mL^-1罗丹明123孵育1.5 h)。用噻唑蓝（MTT）实验初步确定桑皮苷A的逆转耐药作用;再以细胞内阿霉素蓄积实验,罗丹明123（Rho123）蓄积及外排实验进一步研究桑皮苷A的逆转耐药作用;分别用聚合酶链反应（PCR）和蛋白质印迹（Western blot）法检测桑皮苷A对K562/AD...     

洛美利嗪衍生物CJZ3对K562/DOX细胞阿霉素耐药的逆转作用

目的研究洛美利嗪衍生物CJZ3对K562/DOX细胞阿霉素耐药的逆转作用。方法应用流式细胞仪和MTT法观察了CJZ3对K562/DOX细胞P-糖蛋白(P-glycoprotein,P-gp)的抑制作用及对K562/DOX细胞阿霉素耐药的逆转作用。结果CJZ3能剂量相关性地增加K562/DOX细胞对罗丹明123(rhodamine123,Rh123)的摄取以及细胞内罗丹明Rh123的累计,明显抑制P-gp介导的Rh123外排,增强阿霉素对K562/DOX细胞的细胞毒作用,提高阿霉素诱导的K562/DOX细胞凋亡率,提高细胞Caspase-3活性,增加K562/DOX细胞内阿霉素水平。结论洛美利嗪衍生物CJZ3体外能明显抑制P-gp的外排功能,逆转P-gp介导的K562/DOX细胞的多药耐药性。     

四氢异喹啉类化合物HZ08逆转白血病K562/DOX细胞多药耐药性的试验研究

目的:探讨四氢异喹啉类化合物HZ08对人白血病多药耐药K562/DOX细胞的逆转作用及其可能的机制。方法:采用MTT法检测HZ08的体外细胞毒性及其对阿霉素(DOX)的增敏作用,采用逆转倍数(RF)值评价其逆转效果;应用流式细胞仪分析细胞内罗丹明123(Rh123)潴留量的变化和DOX浓度,评价P糖蛋白(P-gp)的功能;采用Western blot法及免疫细胞化学法测定mdr1基因产物P-gp的表达;同时以人白血病敏感细胞株K562/S细胞为对照进行比较试验。结果:与K562/S细胞比较,HZ08可明显增强DOX对K562/DOX的细胞毒性,RF值增加;HZ08能浓度相关性地增加K562/DOX细胞对Rh123的摄取以及细胞内Rh123的潴留,明显抑制P-gp介导的Rh123外排;K562/DOX细胞膜上P-gp呈强阳性表达,但HZ08对K562/DOX细胞P-gp表达水平无明显影响;HZ08可显著增加K562/DOX细胞内DOX浓度。结论:HZ08可通过抑制K562/DOX细胞P-gp的功能、增加耐药细胞内DOX的浓度而增强K562/DOX细胞对DOX的敏感性,其可能成为有效的多药耐药逆转剂的候选药物。     

五味子甲素对K562/ADR、HL60/ADR、MCF-7/ADR多药耐药逆转机制的研究

目的探讨五味子甲素(schizandrin A or deoxyschizan-drin,schA)对白血病细胞K562/ADR、HL60/ADR、乳腺癌细胞MCF-7/ADR多药耐药的逆转作用,并初步探讨其逆转机制。方法 MTT法检测schA对耐药细胞的逆转作用;流式细胞仪检测schA对细胞内柔红霉素、罗丹明-123含量和细胞表面P-gp表达水平的变化;用Real-time PCR方法检测schA对细胞内mdr1 mRNA和mrp1 mRNA表达;生化检测法检测schA对细胞内GSH含量的变化。结果耐药逆转实验显示:不同浓度的schA对作用机制不同的化疗药物耐药产生不同的逆转效果;蓄积实验表明schA可增加柔红霉素、罗丹明123在耐药细胞内的蓄积,并且有良好的剂量依赖关系;schA处理K562/ADR、HL60/ADR细胞24 h后,能降低P-gp蛋白和mdr1、mrp1基因的表达;schA处理K562/ADR、HL60/ADR细胞4 h后,可降低细胞内谷胱甘肽含量。结论 schA对耐药机制不同的细胞株K562/ADR、HL60/ADR均有耐药逆转作用,推测可能是与抑制细胞表面的P-gp蛋白功能和表达,降低mdr1、mrp1耐药基因的表达和降低细胞内谷胱甘肽含量有关,schA通过影响上述机制,进而增加细胞内的药物浓度,达到有效杀灭肿瘤细胞的作用。     

透明质酸寡糖逆转白血病细胞系K562/ADR多药耐药的研究

目的研究透明质酸寡糖(o-HAs)的体外逆转白血病多药耐药细胞(K562/A02)的耐药性,并对其逆转机制进行探讨。方法以四甲基偶氮唑盐微量酶反应比色法(MTT法)检测o-HAs对K562/A02细胞的多药耐药逆转活性;以流式细胞术检测o-HAs对K562/A02细胞内抗癌药物盐酸多柔比星(ADR)累积的影响。结果在100μg.mL-1浓度时o-HA4、o-HA6、o-HA8、o-HA10使ADR对K562/A02的半数抑制浓度(IC50)由61.6μg.mL-1分别降低至30.17、30.04、32.29、33.33μg.mL-1。细胞中ADR的累积量增加至原来的3.90、3.92、3.76、3.39倍。结论 o-HAs在体外具有较强的逆转K562/A02细胞多药耐药的活性。     

干扰α烯醇化酶对耐药细胞株K562/A02耐药性的影响

目的肿瘤耐药的产生是肿瘤治疗失败的主要原因之一,α烯醇化酶(eno1)与肿瘤细胞耐药产生和发展密切相关。探究eno1对人慢性粒细胞白血病耐药细胞株K562/A02生长及耐药的影响。方法筛选3株稳定干扰eno1的细胞系K562/A02-sheno1和对照细胞系K562/A02-shcon;采用细胞计数法测定细胞生长速率,MTT法测定细胞增殖能力,细胞内罗丹明123含量测定细胞外排药物能力,real-time PCR反应测定基因mRNA表达水平,Western blot实验测定基因蛋白表达水平。结果与敏感性细胞株K562相比,eno1在耐药细胞株K562/A02中为高表达状态,其在mRNA水平和蛋白水平表达分别增高(2.85±0.56)倍和(1.43±0.05)倍;而K562/A02细胞生长速率与K562细胞相比差异无显著性。K562/A02-sheno1细胞系与对照组K562/A02-shcon相比生长速率降低,对抗肿瘤药物紫杉醇和阿霉素的敏感性均增强,且K562/A02-sheno1细胞系中罗丹明123含量也明显增高。K562/A02-sheno1细胞系中耐药相关基因MDR1表达水平降低。结论稳定干扰eno1表达能抑制K562/A02细胞生长,有效逆转K562/A02细胞耐药性,提高其对药物的敏感性,其机制与MDR1基因表达相关。     

PHI逆转K562/A02细胞阿霉素耐药的机制

目的 探讨异硫氰酸苯乙酯(PHI)逆转K562/A102细胞株阿霉素(ADM)耐药的可能机制.方法 将耐ADM的人慢性粒细胞白血病K562/A02细胞株分别与不同浓度(0,5,10,20,30,40和50μM)的PHI共同孵育后,流式细胞术检测细胞周期、细胞内ADM浓度以及P-糖蛋白1(P-gp1)表达水平;逆转录聚合酶链反应(RT-PCR)检测PHI作用前后细胞内mdr1 mRNA的转录水平.结果 与对照组相比,联合作用48 h后,随着PHI浓度的增加G2期细胞逐渐减少,G1期细胞明显增多,而S期细胞无明显变化;K562/A02细胞内ADM平均荧光强度均高于对照组,K562/A02细胞mdrl mRNA表达下降和P-gp1表达下调(P＜0.05).结论 PHI逆转K562/A02细胞耐药机制可能与细胞G1期阻滞和P-gp1表达下调有关.     

洛美利嗪逆转K562/ADM细胞多药耐药性

目的研究洛美利嗪(lomerizine,Lom)逆转K562/ADM细胞多药耐药性的作用及机制。方法MTT法检测细胞毒作用,流式细胞仪研究Lom对ADM和长春新碱(vincristine,VCR)的K562/ADM细胞凋亡诱导作用的影响及对罗丹明123(rhodamine 123,Rh123)外排和P-糖蛋白(P-glycoprotein,P-gp)表达的作用。结果Lom明显提高ADM对K562/ADM多药耐药细胞的细胞毒作用及ADM和VCR的凋亡诱导作用,3,10和30 μmol·L^-1 Lom使K562/ADM对ADM的IC₅₀值由79.03 μmol·L^-1分别降至28.14,8.16和3.16 μmol·L^-1。Lom增加胞内ADM的蓄积浓度并抑制Rh123外排;但作用72 h后对K562/ADM细胞P-gp表达无影响。结论Lom通过抑制P-gp的活性逆转K562/ADM细胞的多药耐药性。     

瓦他拉尼对乳腺癌耐药蛋白介导的肿瘤多药耐药的逆转研究

目的观察新型激酶抑制剂类抗癌药瓦他拉尼(vatalanib)逆转肿瘤细胞多药耐药(MDR)的效果,研究其对乳腺癌耐药蛋白(BCRP)、P-糖蛋白(P-gp)、多药耐药相关蛋白1(MRP1)的作用,探讨其作用机制。方法应用MTS法或SRB法检测瓦他拉尼对耐药细胞与敏感细胞的细胞毒性和逆转MDR的效果;分别以罗丹明(Rh-123)、米托蒽醌(MX)、阿霉素(ADR)为P-gp、BCRP、MRP1的荧光底物,应用流式细胞术检测该药对P-gp、BCRP、MRP1外排功能的影响;应用Western blot检测该药对耐药细胞中BCRP蛋白表达水平的影响,并研究其对细胞增殖相关信号分子的影响;应用qRT-PCR检测其对耐药细胞中BCRP基因表达水平的影响;通过超速离心法制备BCRP转运蛋白的粗膜,检测瓦他拉尼对BCRP的ATPase活性的影响。结果无毒剂量的瓦他拉尼(5μmol·L-1)可有效逆转BCRP高表达的肿瘤细胞株HEK293/ABCG2对MX、ADR和托泊替康(TOPT)的耐药,而对P-gp高表达的肿瘤细胞株K562/A02和MRP1高表达的肿瘤细胞株HEK293/ABCC1的耐药无逆转作用。该药能够下调耐药肿瘤细胞的BCRP基因和蛋白的表达水平,并具有时间和剂量依赖效应,但对BCRP外排MX的功能无明显抑制作用。该药可以激活BCRP的ATPase活性,但并不改变BCRP的构象,对耐药和敏感细胞中AKT和ERK的表达及其磷酸化水平也均无明显影响。结论瓦他拉尼可有效、特异地逆转BCRP介导的肿瘤MDR,其机制可能是通过下调耐药肿瘤细胞中BCRP基因和蛋白的表达来达到逆转MDR的效果。     

屈洛苷芬对K562耐阿霉素细胞株耐药性的逆转作用

目的：研究屈洛昔芬（DRO）对耐阿霉素（ADR）K562细胞株（K562／A02)多药耐药性（MDR）的逆转作用及逆转机制。方法：用DRO分别处理K562／A02和K562敏感株。MTT法观察DRO影响K562／A02对ADR化学敏感性的变化。DRO 10μmol/L处理K562／A02前后,通过RT－PCR和免疫细胞化学染色,分析MDR1、GSTπ基因表达的变化,采用流式细胞技术测定细胞内ADR浓度的变化。结果：DRO显著逆转K562／A02的MDR,在20,10和5μmol/L浓度时,对ADR的化学敏感性分别增加到14、13和4倍,逆转活性与维拉帕米相当。MDR1和GSTπ的mRNA和蛋白表达在DRO 10μmol/L处理后第2天开始下降,第5天明显降低。用20、10和5μmol/L浓度的DRO处理两株细胞,K562／A02细胞内ADR积累分别增加到2．9、2．3和1．5倍。但DRO不能明显增加K562细胞内的ADR的浓度。结论：DRO对K562／A02的MDR有较强的逆转活性,逆转强度与维拉帕米相当,其逆转机制有多种不同的途径。     

咯萘啶逆转肿瘤多药耐药及其作用机制

目的:利用mdr1~ 的人白血病和乳腺癌多药耐药(MDR)细胞系K562/A02和MCF-7/ADR研究咯萘啶(pyronaridine,PND)对MDR的逆转作用及其机制.方法:采用MTT法、荧光分光光度法、荧光显微镜法、流式细胞仪法和RT-PCR法分别测定PND单独或与阿霉素(DOX)合用,对肿瘤细胞的生长抑制、诱导凋亡、细胞内药物浓度、mdr1基因表达的影响.结果:PND对敏感及耐药细胞均具有生长抑制作用,半数抑制剂量(IC_(50))根据不同细胞在5.10-18.66μmol/L之间;低毒剂量PND显著增强DOX对耐药细胞的细胞毒和诱导凋亡作用,且增加DOX在耐药细胞内的蓄积及减少罗丹明(Rh123)的外排.RT-PCR结果显示,PND对mdr1基因无下调作用.结论:PND可作为第三代P-糖蛋白(P-gp)抑制剂,通过下调P-gp药物外排泵功能而产生强大的逆转MDR效应.     

复方藤梨根制剂体外对MDR细胞株K562/ADR和K562/VCR细胞积聚和外排阿霉素(ADR)的影响研究

目的 :探讨复方藤梨根制剂 (FFTLG)对肿瘤化疗增敏的作用机理。方法 :以MTT法观察FFTLG对MDR细胞的逆转作用 ,以FCM技术测定FFTLG作用MDR细胞后对阿霉素的积聚和外排影响。结果 :10mg/ml和 2 0mg/ml的FFTLG对K5 6 2 /ADR的逆转倍数是 7.5 3和 10 .31倍 (P <0 .0 5 ) ;2 0mg/ml的FFTLG对K5 6 2 /VCR的逆转倍数是 6 .18倍 ;10mg/ml和2 0mg/ml的FFTLG可增加K5 6 2 /ADR和K5 6 2 /VCR细胞内ADR的积聚分别是 77.6 % ,80 .1%和 5 0 .9% ,4 5 .2 % ,且可减少ADR的外排。结论 :FFTLG通过增加MDR细胞内的ADR积聚及减少外排机制而实现对化疗的增敏作用     

延长洛美利嗪作用时间可增加K562/A02细胞对阿霉素的敏感性

目的：研究洛美利嗪在高浓度、长时间作用于肿瘤细胞时，对多药耐药的逆转作用。探讨洛美利嗪逆转肿瘤细胞多药耐药的机制。方法：将不同浓度的洛美利嗪与人红白血病细胞系K562及其耐药细胞系K562／A02（耐阿霉素）共孵育24、48或72小时，然后分别向细胞中加入阿霉素，采用MTT法检测细胞毒作用；以流式细胞术测定两种细胞系内罗丹明123的潴留以反映P-糖蛋白的外排功能；利用Fluo-3／AM检测细胞内游离钙离子浓度。结果：细胞与洛美利嗪预温孵后，阿霉素对K562／A02细胞的IC50值减小，细胞内Rh123潴留增多，细胞内游离钙离子浓度明显升高。结论：洛美利嗪高浓度，长时间作用于K562／A02细胞，可以抑制细胞上P-糖蛋白的功能活性，使细胞对化疗药的敏感性增强，其机制可能与升高细胞内钙离子有关。     

Modulation of P-glycoprotein activity by the substituted quinoxalinone compound QA3 in adriamycin-resistant K562/A02 cells

QA3 is a derivative of the substituted 1,3-dimethyl-1H-quinoxalin-2-ones, which are compounds that may selectively antagonize P-glycoprotein (P-gp) in multidrug resistance (MDR) cancer cells. Our previous work identified QA3 as a candidate compound for reversing MDR in cancer cells. In the present study, we found that QA3 significantly decreases the intracellular level of ATP, stimulates ATPase activity in membrane microsomes and decreases protein kinase C (PKC) activity. These results indicated that QA3 inhibits P-gp activity by blocking ATP hydrolysis and ATP regeneration. Furthermore, QA3 triggered and increased adriamycin-induced K562/A02 cell apoptosis as evidenced by Annexin V-FITC plus PI staining. Western blot analysis showed that the levels of cleaved caspase-9 and cleaved caspase-3 proteins increased, and similarly, the levels of procaspase-9 and procaspase-3 decreased after QA3 treatment. Consequently, poly ADP-ribose polymerase (PARP) activity increased as evidenced by the presence of the PARP cleavage product in K562/A02 cells. QA3 also enhanced the potency of adriamycin against K562/A02 cells as demonstrated by increased apoptosis and activation of caspase-9,-3 and PARP. These data support the observation that P-gp activity is inhibited after QA3 treatment. Moreover, these results indicate that QA3 is a novel MDR reversal agent with potent inhibitory action against P-gp MDR cancer cells.     

补骨脂素逆转多药耐药细胞系K562/ADR耐药性研究

目的　研究补骨脂素对白血病细胞阿霉素耐药株(K5 6 2 /ADR)多药耐药 (multidrugresistance,MDR)性的逆转作用及其机制。方法　采用MTT法检测药物细胞毒性作用 ,高效液相色谱法检测细胞内阿霉素 (ADR)的浓度 ,流式细胞术测定细胞P 糖蛋白 (P gp)的表达。 结果　补骨脂素 (1～ 2 0 μmol·L-1)能不同程度地降低ADR对K5 6 2 /ADR细胞的IC50 。 2 0 μmol·L-1能显著提高ADR在K5 6 2 /ADR细胞内的浓度 ,降低K5 6 2 /ADR细胞P gp的表达。 结论　补骨脂素能逆转K5 6 2 /ADR细胞的MDR ,其机制与抑制P gp的功能及其表达 ,增加细胞内ADR的积累有关     

Substituted tetrahydroisoquinoline compound B3 inhibited P-glycoprotein-mediated multidrug resistance in-vitro and in-vivo

P-glycoprotein (P-gp) mediated multidrug resistance (MDR) is one of the main obstacles in tumour chemotherapy. A promising approach to reverse MDR is the combined use of nontoxic and potent P-gp inhibitor with conventional anticancer drugs. We have examined the potential of a newly synthesized tetrahydroisoquinoline derivative B3 as a MDR-reversing agent. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was used to examine the effect of B3 on the cytotoxicity in K562/A02 and MCF-7/ADM cells caused by doxorubicin (adriamycin). Accumulation and efflux of P-gp substrate rhodamine123 in K562/A02 and primary cultured rat brain microvessel endothelial cells (RBMECs) were measured to evaluate the inhibitory effect of B3 on P-gp. The K562/A02 xenograft model in nude mice was established to examine MDR-reversing efficacy of B3 in-vivo. The results indicated that co-administration of B3 resulted in an increase on chemosensitivity of K562/A02 and MCF-7/ADM cells to doxorubicin in a dose-dependent manner. Rhodamine123 accumulation in K562/A02 cells and RBMECs were significantly enhanced after the incubation with various concentrations of B3. Furthermore, B3 inhibited the efflux of rhodamine123 from RBMECs. Co-administration of B3 with doxorubicin significantly decreased weight and volume of tumour in nude mice. In conclusion, B3 is a novel and potent MDR reversal agent with the potential to be an adjunctive agent for tumour chemotherapy.     

抗多药耐药基因肽核酸与反义寡脱氧核苷酸增强K562／ADM细胞的敏感性和促进凋亡

AIM: To investigate the reversal effect and apoptosis enhancement of peptide nucleic acid (PNA) and antisenseoligodeoxyribonucleotide (ASODN) targeted to multidrug resistance gene (mdrl) on human multidrug resistantleukemia K562/ADM cells. METHODS: A 15-mer PNA and the same sequence of ASODN, complementary to the5' end of the AUG initiator codon-containing region of mdrl messenger RNA (MDR1-PNA, MDR1-ASODN), weredesigned and synthesized. Proliferation and sensitivity to adriamycin of K562/ADM cells treated with MDRI-PNAand MDR1-ASODN were analyzed with a MTT colorimetric assay. Apoptotic morphologies, P-glycoprotein (P-gp)expression, intracellular adriamycin accumulation, and cell cycle were measured. RESULTS: MDRI-PNA 1 to 10μmol/L and MDR1-ASODN 2 to 20 μmol/L alone had no inhibitory effects on the proliferation of K562/ADM cells,but significantly inhibited the growth of K562/ADM cells cultured in adriamycin-containing medium. After treatment with MDRI-PNA and MDRI-ASODN, intracellular adriamycin accumulation in K562/ADM cells increasedgreatly and P-gp synthesis was strikingly reduced. The resistance to adriamycin of the drug-resistant cells waspartly reversed and the cells were induced to apoptosis by adriamycin. The reversal efficacy of MDR1-PNA was3.1-fold higher than that of the same sequence of MDR-ASODN, but neither MDRI-PNA nor MDRI-ASODNcould completely block the mdrllP-gp expression. CONCLUSION: Sequence-special PNA targeted to mdr1 genemore effectively than the same sequence of MDR1-ASODN inhibited the expression of P-glycoprotein to overcomethe drug-resistance.     

Sambutoxin sensitizes K562/ADR to adrimycin by inhibiting expression of P-glycoprotein

OBJECTIVE To investigate the reverse effects of sambutoxin, a representative derivative of 4-hydroxy-2-pyridone with antibacterial, antifungal and antitumor effects, on multidrug resistance(MDR) of K562/ADR cells to adriamycin(ADR) and to elucidate its potential molecular mechanism. METHODS We first investigated the dose-dependent cytotoxic effects of sambutoxin as single treatment on K562 and K562/ADR cells by MTT and CCK-8 assay in order to select the suitable dosage of sambutoxin in the combination treatment. The cytotoxicity of ADR combined with sambutoxin on K562 and K562/ADR cells were also determined by MTT and CCK-8 assays. Then, effects of sambutoxin on the intracellular accumulation of ADR in K562/ADR cells were determined using flow cytometry. The effect of sambutoxin on the efflux function and expression of P-gp in K562/ADR cells was evaluated by Rhodamine123(Rh123) accumulation assay and Western blotting assay respectively. 3 D interactions of human P-gp with sambutoxin, verapamil and adriamycin predicted by docking studies conducted using Sybyl2.1 sofware. Next, the effect of combination treatment of sambutoxin and ADR on the apoptosis of K562/ADR cells was determined by Hoechst 33342 nuclear staining. The expression of the apoptosis related proteins were detected by Western blotting assay. Effect of sambutoxin and ADR on reactive oxygen species(ROS) level in K562/ADR cells was evaluated detected by the DCFH-DA method using fluorescence microscopy and flow cytometry. Effect of sambutoxin and ADR on EGFR/MAPK and PI3 K/AKT/m TOR signaling pathways in K562/ADR cells was evaluated by Western blotting assay. RESULTS Sambutoxin treatment potently enhanced the susceptibility of K562/ADR cells to ADR in a dose manner and the reversal effect was much more prominent in K562/ADR cells. Sambutoxin increased the intracellular accumulation of ADR and Rh123 in K562/ADR cells. Sambutoxin inhibited protein expression of P-gp through Akt/NF-κB pathway in K562/ADR cells. Molecular docking display sambutoxin with P-gp(PDB code:6 QEX) formed two hydrogen bonds with GLN-725 and ASN-721, total Score was 8.29. Co-administration ADR with sambutoxin remarkably increased ADR-induced apoptosis through mitochondrial pathway, including down-regulation of anti-apoptotic protein Bcl-2, up-regulation of proapoptotic protein Bax, up-regulation of cleaved caspase3, and cleaved PARP, augmented ROS in K562/ADR cells. Moreover, ADR combined with sambutoxin could down-regulate the EGFR/MAPK and PI3 K/AKT/m TOR survival pathway in K562/ADR cells. CONCLUSION Sambutoxin reverses MDR of K562/ADR cells to ADR by downregulating P-gp expression and increasing ROS level, as well as, inducing apoptosis. These fundamental findings provide evidence for further clinical research in application of sambutoxin as an assistant agent for chemotherapy of cancer.