miR-139过表达降低急性髓系白血病TRAIL耐受性

目的:探讨miR-139过表达对急性髓系白血病肿瘤坏死因子相关凋亡诱导配体(TNF-related apoptosis inducing ligand,TRAIL)耐受性的影响。方法:采用浓度为100、200、300和400 ng/ml TRAIL处理人急性髓系白血病K562、HL-60细胞及相对应的多药耐药K562/A02和HL-60/ADM细胞,采用CCK8法计算IC50值,以IC50法评价急性髓系白血病细胞对TRAIL的敏感性。RT-PCR检测miR-139在 TRAIL敏感细胞和耐药细胞中的表达。采用脂质体2000将miR-139 mimics转染至TRAIL耐药细胞株,RT-PCR检测转染效果,CCK8法检测细胞活力及IC50值,流式细胞仪检测细胞凋亡率。结果:在K562、K562/A02、HL-60和HL-60/ADM细胞中,HL-60/ADM细胞对TRAIL最为敏感,而K562细胞对TRAIL的耐药性最强。与敏感细胞株HL-60/ADM相比,miR-139在耐药细胞株K562中表达显著下降。转染miR-139 mimics后,K562细胞中miR-139表达和细胞凋亡率明显升高,而细胞存活率及IC50值明显降低。结论:miR-139在TRAIL耐药细胞株K562中低表达,过表达miR-139可能通过促进TRAIL诱导的细胞凋亡降低K562细胞对TRAIL的耐受性。     

联合应用bcr-abl融合基因反义寡核苷酸与c-myb基因反义寡核苷酸对K562细胞作用的研究

目的：研究联合应用ｂｃｒ－ａｂｌ融合基因硫代磷酸反义寡核苷酸（Ａｓｐｏ）及ｃ－ｍｙｂ基因Ａｓｐｏ对Ｋ５２细胞作用效果。方法：Ａｓｐｏ与Ｋ５６２细胞共培养后,台盼蓝拒染法计死活细胞数;甲基纤维素半固体培养法培养ＣＦＵ－Ｋ５６２;流式细胞仪测定细胞Ｐ２１０蛋白表达及细胞凋亡率;ＲＴ－ＰＣＲ半定量检测细胞ｂｃｒ－ａｂｌｍＲＮＡ;电镜观察凋亡细胞形态学改变。结果：例置显微镜下观察到联合应用两种Ａｓｐｏ时,浓度各为５ｕｍｏｌ／Ｌ组Ｋ５６２细胞仍呈克隆状态生长,作用２４ｈ细胞Ｐ２１０蛋白表达明显受抑制,表达率〈２％;作用１２０ｈ细胞生长抑制率为６１．７％,Ｐ２１０恢复为２５．７％,凋亡率为２２．５％。两种浓度各为１０ｕｍｏｌ／Ｌ组Ｋ５６２细胞生长疏散,作用１２０ｈ细胞生长抑制率达９２．２％,Ｐ２１０仍未恢复,凋亡率为２２．     

人慢性粒细胞白血病bcr-abl基因反义寡核苷酸对K562细胞株的凋亡诱导作用研究

背景与目的：随着人类基因组计划的完成,人们的研究重点已转向基因功能的研究,反义核酸技术无疑为这项宏伟工程提供了一个新的发展方向。目前,国内关于反义寡核苷酸诱导K562细胞凋亡的实验研究很少。本实验在体外构建针对人慢性粒细胞白血病(chronic myelogenou leukemia,CML)bcr-abl融合基因mRNA的反义寡核苷酸,探讨bcr-abl反义寡核苷酸对K562细胞凋亡的诱导作用。方法：以bcr-abl融合基因mRNA翻译起始点融合前区19个寡核苷酸为作用靶点,设计反义寡核苷酸,以其反义寡核苷酸序列转染人慢性粒细胞K562细胞,采用Hoechst染色法观察不同浓度寡核苷酸对K562细胞株的凋亡情况,采用蛋白[质]印迹法(Western blot)检测自噬凋亡蛋白LC3-Ⅱ的表达情况,采用流式细胞术(flow cytometry,FCM)检测细胞周期变化,采用JEM-4000EX电镜术检测细胞凋亡形态变化,通过DNA琼脂糖凝胶电泳检测K562细胞凋亡情况。结果：Hoechst染色结果显示,bcr-abl反义寡核苷酸能显著促进K562细胞的凋亡,且呈现一定的浓度依赖性。Westernblot检测结果显示,bcr-abl反义寡核苷酸各浓度组凋亡自噬蛋白LC3-Ⅱ表达水平明显高于对照组,差异有统计学意义(P<0.05)。FCM检测结果显示,bcr-abl反义寡核苷酸作用于K562细胞后,细胞周期阻滞于G₀/G₁期。各组G₀/G₁期、S期细胞数量与对照组相比,差异有统计学意义(P<0.05)。在JEM-4000EX电镜下可见明显的新月型凋亡小体。DNA琼脂糖凝胶电泳显示,10、30 μmol/mL bcr-abl反义寡核苷酸组可以明显观察到以180~200 bp碱基对整倍数出现明暗间隔的DNA梯状条带。结论：Bcr-abl反义寡核苷酸可显著诱导K562细胞凋亡,为临床上基因治疗人CML提供一定的参考。     

大黄素诱导耐药白血病细胞株K562/Adr凋亡及下调P210表达

 目的 研究大黄素对多药耐药白血病细胞株K562／Adr（KAR）增生、凋亡的影响及探讨bcr-abl、mdr-1基因在其中的变化。方法 应用四甲基偶氮唑蓝（MTT）比色法、DNA片段化分析及TdT酶介导的末端缺失原位标记（TUNEL）法检测大黄素对KAR细胞增生及凋亡的影响；RT-PCR法检测大黄素对KAR细胞bcr-abl、mdr-1基因mRNA表达的影响；Western blotting法检测大黄素对KAR细胞bcr-abl融合蛋白P210表达的影响。结果 大黄素能有效抑制KAR细胞的增生，作用72 h的IC50约为20μmol／L，并能诱导其凋亡,随药物作用浓度的增加，凋亡率也逐渐上升；大黄素下调KAR细胞bcr-abl、mdr-1基因mRNA的表达；也下调了KAR细胞P210蛋白的表达。结论 大黄素能有效抑制KAR细胞增生，诱导其凋亡；并可能通过下调bcr-abl和mdr-1 的表达起作用。     

The Inhibition Effect of Triptolide on Human Endometrial Carcinoma Cell Line HEC-1B: a in vitro and in vivo Studies

Background: To investigate the inhibitory effect and the underlying mechanism of triptolide on culturedhuman endometrial carcinoma HEC-1B cells and corresponding xenograft. Materials and Methods: For in vitrostudies, the inhibition effect of proliferation on HEC-1B cell by triptolide was determined by MTT assay; cellcycle and apoptosis of the triptolide-treated and untreated cells were detected by flow cytometry. For in vivostudies, a xenograft tumor model of human endometrial carcinoma was established using HEC-1B cells, thenthe tumor-bearing mice were treated with high, medium, and low-dose (8 μg, 4 μg and 2 μg/day) triptolide orcisplatin at 40 μg/day or normal saline as control. The mice were treated for 10-15 days, during which body weightof the mice and volume of the xenograft were weighted. Then expression of Bcl-2 and vascular endothelial growthfactor (VEGF) was analyzed by SABC immunohistochemistry. Results: Cell growth was significantly inhibitedby triptolide as observed by an inverted phase contrast microscope; the results of MTT assay indicated thattriptolide inhibits HEC-1B cell proliferation in a dose and time-dependent manner; flow cytometry showed thatlow concentration (5 ng/ml) of triptolide induces cell cycle arrest of HEC-1B cells mainly at S phase, while higherconcentration (40 or 80 ng/ml) induced cell cycle arrest of HEC-1B cells mainly at G2/M phase, and apoptosisof the cells was also induced. High-dose triptolide showed a similar tumor-inhibitory effect as cisplatin (-50%);high-dose triptolide significantly inhibited Bcl-2 and VEGF expression in the xenograft model compared tonormal saline control (P<0.05). Conclusions: triptolide inhibits HEC-1B cell growth both in vitro and in mousexenograft model. Cell cycle of the tumor cells was arrested at S and G2/M phase, and the mechanism may involveinduction of tumor cell apoptosis and inhibition of tumor angiogenesis.     

RNA干扰和伊马替尼杀伤K562细胞效果的比较

目的比较RNA干扰（RNAi）和伊马替尼（imatinib）杀伤K562细胞的效果。方法设计有效的bcr—abl干扰shRNA序列，利用基因工程技术插入到干扰载体构建RNAi质粒。测序鉴定正确的RNAi质粒转染K562细胞，48h后荧光显微镜观察转染效率。RT—PCR技术检测K562细胞中bcr—abl表达水平。同时，伊马替尼作用K562细胞。利用凋亡分析、MTT增生实验和磷酸化的酪氨酸蛋白含量检测来评估RNAi和伊马替尼作用效果。结果与伊马替尼一样，RNAi使K562细胞凋亡增强，增生减少，磷酸化的酪氨酸蛋白含量减少。结论RNAi达到伊马替尼杀伤K562细胞的效果，有望在临床用于治疗慢性髓细胞白血病（CML）患者，尤其是那些对伊马替尼等化疗药物不敏感的CML患者。     

The Proteasomal Inhibitor MG132 Potentiates Apoptosis of Triptolide-Treated K562 Cells by Regulating the NF-KB Signal Pathway

OBJECTIVE To explore the anticancer mechanism of triptolide in human leukemia K562 cells,and to further determine whether the proteasomal inhibitor,MG132,can potentiate apoptosis in triptolide-treated K562 cells.METHODS Apoptosis was assessed via annexin V/PI doublelabeled cytometry.The expressions of the IκBα and NF-κB/p65 proteins in K562 cells was investigated using Western blotting.RESULTS The inhibitory rates of K562 cells treated by triptolide gradually increased in a dose-and time-dependent manner,and treatment with triptolide plus MG132 potentiated the apoptotic rate.Triptolide inhibited the degradation of the IκBα protein and the nuclear localization of NF-κB/p65 proteins induced by TNF-α,and MG132 potentiated the effect of triptolide.Triptolide plus MG132 almost completely blocked the NF-κB activation induced by TNF-α.CONCLUSION The anti-proliferative activities of triptolide and MG132 were related to the NF-κB signal pathway.     

Pycnogenol induces differentiation and apoptosis in human promyeloid leukemia HL-60 cells

Pycnogenol, rich of many phytochemicals of medical value, is a commercialized nutrient supplement extracted from the bark of European coastal pine. In this study, we investigated the anti-tumor effects of Pycnogenol on HL-60, U937 and K562 human leukemia cell lines. We found that Pycnogenol inhibited cell proliferation dose- and time-dependently, and the IC(50)s of Pycnogenol on HL-60, U937 and K562 cells were 150, 40 and 100 microg/ml, respectively. When HL-60 cells were incubated with low concentrations of Pycnogenol (50, 100 and 125 microg/ml) for 24 h, a prominent G0/G1 arrest was observed, followed by gradual accumulation of sub-G0/G1 nuclei. At 48 h of treatment, 50-70% of HL-60 cells differentiated, as evidenced by morphological changes, NBT reduction, induction of NSE activity, and increases of cell surface expression of CD11b. However, results from Annexin V/PI staining, DAPI staining and DNA fragmentation assay indicated that Pycnogenol induced HL-60, U937 and K562 cell apoptosis at their respective IC(50)s after 24 h of treatments. Pretreatment of z-DEVD-fmk, a caspase-3 specific inhibitor, not only decreased caspase-3 activity but also reduced the percentage of apoptotic cells induced by Pycnogenol. This indicated that caspase-3 activation was involved in Pycnogenol induced-apoptosis. In conclusion, Pycnogenol induced differentiation and apoptosis in leukemia cells. Our data suggest that Pycnogenol could serve as a potent cancer chemopreventive or chemotherapeutic agent for human leukemia.     

EFFECT OF BUNGARUS MULTICINCTUS CRUDE VENOM AND ITS COMPONENTS ON TUMOR CELLS

Bungarus multicinctus crude venom is a mixture of many kinds of enzyme proteins, non-enzyme proteins and toxic multipeptids, including a-BTX), b-bungarotoxin (b-BTX), k-bungarotoxin (k-BTX), and so on. Many of these components have the apoptosis-inducing effect. All kinds of apoptosis-inducing factors from snake venom have been found, such as a-BTX[1], b-BTX[2], a-BTX-ACHRs[3], L-amino acid oxidase (LAO)[4], Apoxin I[5], vascular apoptosis-inducing protein (VAP)[6], VAP2[7], glycy…     

Inhibition of apoptosis by bcr-abl fusion gene in K562 cells

Chronicmyel0idleukemia(CML)isahematologicalmalignancycharacterizedbyaninitialchronicphaseofexpandedclonalhematop0iesiswithcontinueddifferentiationintomaturemyeloidcells.Itscyt0genetichallmarkisthephiladelphiachromosome(Ph),ort(9;22)(q34.l;qll.2);thisbalancedtranslocati0nresultedinthecreationofachimericbcr-ablgene,whichisthemolecularbiologyfeatureofCML.Thebcr-ablhasbeenprovedtocausehumanCML-likesyndromeinmice.Toelucidatetheeffectofachimericbcr-ablgeneinCML,weobservedtheapopt0sisofK562cell…     

靶向激活蛋白激酶PKR对白血病K562细胞增殖的影响及机制

背景与目的:由t(9;22)(q34;q11)导致的bcr-abl融合基因在慢性粒细胞白血病(chronic myeloid leukemia,CML)发病中起着重要的作用.本研究运用CML特异的bcr/abl融合基因的mRNA与外源重组反义RNA形成双链RNA (double strand RNA,dsRNA)能激活双链RNA依赖性蛋白激酶(double-stranded RNA-dependent protein kinase,PKR)的策略,研究其对白血病K562细胞增殖的影响及可能的机制.方法:将dsRNA类似物聚肌苷酸-聚胞啶酸(Polyriboinosinic Polyribocytidylic Acid,polyIC)、含ber/abl融合基因序列40bp的逆转录病毒载体RV-40AS、RV-40AS 2-氨基嘌呤(2-aminopurine,2AP)和含绿色荧光蛋白(green fluorescent protein,GFP)的逆转录病毒载体RV-GFP作用于K562细胞,并以ECV304细胞作对照细胞株.通过细胞计数、MTT法和半固体集落形成实验检测其对细胞生长增殖的影响,用流式细胞仪检测处理前后细胞周期的变化,用Western blot法检测细胞内PKR、磷酸化PKR(phosphated PKR,p-PKR)、真核翻译启始因子2α(eukaryotic initiation factor-2α,eIF2α)、磷酸化eIF2α(phosphated eIF2α,p-eIF2α)蛋白表达的变化,用3H-亮氨酸掺入实验检测细胞总蛋白合成水平的变化.结果:polyIC对K562细胞和ECV304细胞生长和增殖均具有非特异性抑制作用.而RV-40AS仅对K562细胞具有特异性的抑制效应.PKR抑制剂能阻断RV-40AS对K562 细胞的抑制效应.polyIC和RV-40AS作用K562细胞24 h 后,S期细胞减少[polyIC组(37.26±2.35)%,未处理组(58.53±5.42)%,P＜0.05;RV-40AS组(31.48±3.65)%,未处理组(58.53±5.42)%,P＜0.05],G0/G1期细胞增多[pdylC组(50.97±2.18)%,未处理组(36.44±4.20)%,P＜0.05;RV-40AS组(57.47±3.61)%, 未处理组(36.44±4.20)%,P＜0.05].polyIC处理K562细胞组、ECV304细胞组以及RV-40AS处理K562细胞组的p-PKR和p-eIF2α蛋白表达显著上调,且总蛋白合成水平下降[RV-40AS处理的K562细胞组(3.5±1.9)cpm/ng,未处理组(26.8±2.6)cpm/ng,P＜0.05].结论:外源重组反义RNA与bcr/abl融合基因的mRNA形成的dsRNA可通过激活PKR而抑制K562细胞的生长增殖,其机制是通过活化的PKR使蛋白合成启始因子eIF2a磷酸化,从而阻断细胞内蛋白合成的启动,及阻止细胞周期进程来实现.     

2-甲氧基雌二醇对白血病细胞K562增生、凋亡及细胞周期的影响

 目的 探讨2-甲氧基雌二醇（2-ME）对体外培养的慢性粒细胞白血病（CML）急变期细胞系bcr-abl（+）K562细胞增生、凋亡及细胞周期的影响。方法 将不同浓度和作用时间的2-ME与K562细胞共同培养，采用相差显微镜观察细胞的形态学变化；四甲基偶氮唑蓝（MTT）法检测2-ME对K562细胞增生的抑制作用；流式细胞术分析2-ME对K562细胞凋亡及细胞周期的影响。结果 1~ 16μmol／L浓度的2-ME在24、36、48及60 h均可明显抑制K562细胞增生，并在一定范围内呈时间和剂量依赖性；2-ME作用后G0／G1期细胞增加，并伴随细胞凋亡峰和凋亡率的升高。结论 2-ME可抑制K562细胞增生，诱导其凋亡，为2-ME的临床应用提供实验依据。     

Synergistic growth inhibitory effects of interferon-alpha and lovastatin on bcr-abl positive leukemic cells

The chimeric bcr-abl tyrosine kinase is of crucial pathogenic importance in chronic myeloid leukemia (CML). As shown, bcr-abl activates the ras pathway by phosphorylation of adapter proteins such as Grb-2 and Crkl. Functional inhibition of p21ras might partially inhibit the mitogenic signaling by bcr-abl. By depletion of cellular mevalonate pools, p21ras proteins can be rendered non-functional as a result of deficient post-translational protein farnesylation. We investigated the pharmacologic effect of mevalonate depletion by lovastatin in conjunction with interferon-alpha 2b (INF-alpha 2b) in bcr-abl positive K562 cells. At various concentrations, both drugs synergistically reduced cell proliferation of CML line K562 in a liquid culture system as well as clonal growth of colony forming units in a patient with newly diagnosed CML. Lovastatin and IFN-alpha 2b in combination led to cell cycle arrest and resulted in significant reduction of phosphorylation on tyrosine, serine, and threonine protein residues. IFN-alpha 2b alone showed little effect on protein phosphorylation but strongly enhanced lovastatin driven loss of phosphorylation. Subsequently, DNA fragmentation occurred in 50% of cells. In conclusion, exposure to IFN-alpha 2b and lovastatin synergistically inhibited proliferation of bcr-abl positive cells and resulted in loss of protein phosphorylation and subsequent apoptosis in K562 cells. Our in vitro model suggests further investigations are required of the potential value of HMG-CoA reductase inhibitors as adjunct to therapy of CML with interferon.     

双向凝胶电泳分析三尖杉酯碱诱导K562细胞凋亡

背景与目的:三尖杉酯碱(harringtonine,HT)作为一种抗肿瘤药,已广泛用于治疗急、慢性髓系白血病,并已获得了良好的疗效。目前的研究表明其抗肿瘤作用与诱导肿瘤细胞凋亡有关,但具体分子机制不详。本研究主要是分析HT诱导K562细胞凋亡的蛋白谱,寻找凋亡相关蛋白。方法:应用AnnexinⅤ和PI双染法,通过流式细胞术区分HT诱导K562细胞凋亡早期和凋亡晚期阶段;进一步采用双向凝胶电泳技术和计算机辅助图像分析方法,对HT诱导凋亡的K562细胞与对照K562细胞进行分离和比较。结果:10μg/mlHT作用于K562细胞5h和24h,凋亡早期细胞(AnnexinⅤ+/PI-)分别为28.3%和18.1%(P<0.01),凋亡晚期细胞(AnnexinⅤ+/PI+)分别为9.1%和20.2%(P<0.01)。配比分析对照组细胞和凋亡早期组、晚期组细胞的蛋白图谱,统计分析表明:对照组K562细胞可分离出1300±50个蛋白点,组内蛋白点匹配率为(88.3±2.0)%。凋亡晚期组细胞中有10个蛋白点发生了明显和稳定的质和量的改变(P<0.01),其中8个蛋白点在凋亡后表达量上调,1个蛋白点表达下调,1个蛋白点只在对照细胞内表达。结论:差异表达的蛋白可能是三尖杉酯碱诱导K562细胞凋亡的相关蛋白。     

低剂量地西他滨联合伊马替尼对K562细胞的增殖抑制作用

 目的　研究低剂量地西他滨（DAC）联合伊马替尼（IM）对K562细胞株的增殖抑制作用及对bcr-abl表达的影响。方法　单药及两药联合后,通过四甲基偶氮唑蓝（MTT）法观察药物对K562细胞株的增殖抑制作用,流式细胞术检测药物对K562细胞株早期凋亡率及细胞周期,巢式反转录-聚合酶链反应（RT-PCR）半定量检测药物对K562细胞株bcr-abl mRNA表达。结果　DAC与IM单药对K562细胞的抑制作用呈浓度时间依赖性。两药联合用药抑制作用较单药组明显（F＝43.947、165.580、321.193、296.101,均P＜0.05）,24、 48、72 h各浓度组与对照组比较差异均有统计学意义（F＝202.759、168.457、417.538,均P＜0.05）。DAC及IM单药作用药物对K562细胞株均使G1期细胞明显增多,IM 0.2 μmol／L作用于K562细胞株48 h可见6.7 %早期凋亡细胞,IM 0.2 μmol／L联合DAC 4 μmol／L早期凋亡细胞增加至8.4 %。bcr-abl mRNA表达水平降低,DAC 4 μmol／L作用48 h后可降低K562细胞中bcr-abl mRNA表达（约14 %）,IM 0.2 μmol／L降低约40 %,联合用药表达量明显降低（约60 %）。联合用药组与单药组比较差异有统计学意义（F＝71.981,P＜0.05）。结论　DAC 对K562细胞的增殖抑制作用与细胞周期阻滞、诱导凋亡及降低bcr-abl mRNA表达有关,两药联合可显著抑制K562细胞增殖。     

葛根总黄酮诱导白血病细胞株凋亡及其分子机制的研究

 目的　探讨葛根总黄酮（PR）对慢性粒细胞白血病（CML）细胞株K562和急性早幼粒细胞白血病（APL）细胞株NB4细胞增殖及凋亡的影响。方法　采用MTT法检测PR对K562细胞、NB4细胞的增殖抑制率;光学显微镜及荧光显微镜观察细胞形态改变;Hoechest33258荧光染色AnnexinV／PI双染法检测细胞凋亡率;DNA PI染色法分析细胞周期及亚二倍体峰。Western blot分别检测NB4细胞JNK、PARP、bcl-2、Caspase3,K562细胞bcr-abl、p53、bcl-2、Fas／FasL蛋白表达的变化。结果　12.5～200 μg／ml PR均能抑制K562、NB4细胞增殖。光学显微镜及荧光显微镜下观察到核固缩、凋亡小体等典型的细胞凋亡改变;Annexin V+／PI-细胞呈时间-剂量依赖性增加;DNA PI染色法发现细胞亚二倍体比例增加,G1期比例下降、S期比例增加。PR呈时间-剂量依赖性抑制K562细胞、NB4细胞增殖,诱导细胞凋亡。不同浓度PR干预后K562细胞bcr-abl蛋白水平呈浓度依赖性下调（F＝18.74,P＜0.05）,而bcl-2则无明显变化;p53 表达呈浓度依赖性上调;Fas／FasL 表达无明显变化。NB4细胞JNK、PARP及Caspase 3蛋白表达与PR浓度呈正相关,与凋亡抑制蛋白bcl-2则呈负相关（F＝42.32,P＜0.05）。结论　PR能有效抑制K562、NB4细胞增殖,阻滞细胞周期进程,诱导细胞凋亡,但分子机制不同。提示一定浓度PR具有较广谱的抗白血病效应。     

The Proteasomal Inhibitor MG132 Potentiates Apoptosis of Triptolide-Treated K562 Cells by Regulating the NF-κB Signal Pathway

OBJECTIVE To explore the anticancer mechanism of triptolide in human leukemia K562 cells,and to further determine whether the proteasomal inhibitor,MG132,can potentiate apoptosis in triptolide-treated K562 cells.METHODS Apoptosis was assessed via annexin V/PI double-labeled cytometry.The expressions of the IκBα and NF-κB/p65 proteins in K562 cells was investigated using Western blo ing.RESULTS The inhibitory rates of K562 cells treated by triptolide gradually increased in a dose-and time-dependent manner,and treatment with triptolide plus MG132 potentiated the apoptotic rate.Triptolide inhibited the degradation of the IκBα protein and the nuclear localization of NF-κB/p65 proteins induced by TNF-α,and MG132 potentiated the effect of triptolide.Triptolide plus MG132 almost completely blocked the NF-κB activation induced by TNF-α.CONCLUSION The anti-proliferative activities of triptolide and MG132 were related to the NF-κB signal pathway.     

Imatinib-resistant K562 cells are more sensitive to celecoxib, a selective COX-2 inhibitor: role of COX-2 and MDR-1

Selective inhibition of the BCR/ABL tyrosine kinase by imatinib (STI571, Glivec/Gleevec) is the therapeutic strategy in patients with chronic myelogenous leukemia (CML). Despite significant hematologic and cytogenetic responses with imatinib, mainly due to the mutations in the Abl kinase domain, resistance occurs in patients with advanced disease. In the present study on imatinib-resistant K562 cells (IR-K562), however, no such mutations in the Abl kinase domain were observed. Further studies revealed the over-expression of COX-2 and MDR-1 in IR-K562 cells suggesting the possible involvement of COX-2 in the development of resistance to imatinib. So, we sought to examine the effect of celecoxib, a selective COX-2 inhibitor, on IR-K562 cells. The results clearly indicate that celecoxib is more effective in IR-K562 cells with a lower IC50 value of 10 microM compared to an IC50 value of 40 microM in K562 cells. This increase in the sensitivity of IR-K562 cells towards celecoxib suggests that the development of resistance in IR-K562 cells is COX-2 dependent. Further studies revealed down-regulation of MDR-1 by celecoxib and a decline in p-Akt levels. Celecoxib-induced apoptosis of IR-K562 cells led to release of cytochrome c, PARP cleavage and decreased Bcl2/Bax ratio. Also, celecoxib at 1 microM concentration induced apoptosis in IR-K562 cells synergistically with imatinib by reducing the IC50 value of imatinib from 10 to 6 microM. In conclusion, the present study indicates over-expression of COX-2 and MDR-1 in IR-K562 cells and celecoxib, a COX-2 specific inhibitor, induces apoptosis by inhibiting COX-2 and down-regulating MDR-1 expression through Akt/p-Akt signaling pathway.     

肝素干预长春新碱诱导的K562细胞凋亡

目的探讨肝素对长春新碱诱导的K562细胞凋亡及增生的影响。方法肝素预处理K562细胞1h,再经长春新碱（0．05mg／L）处理24h,应用Hoechst33342染色、DNA电泳、FMC等方法检测细胞凋亡。Trypanblue染色及MTr法检测细胞毒性及增生反应。结果Hoechst33342荧光染色见长春新碱凋亡诱导组细胞凋亡率达40．10％,肝素25、50、100、200U／ml组凋亡率依次为32．47％、29．70％、25．50％、19．53％（均P〈0．05）。随肝素浓度增加DNA电泳凋亡梯带亮度逐渐减弱至消失。FACS检测凋亡诱导组凋亡率为21．61％,肝素25～200U／ml组凋亡率依次为13．64％、11．75％、8．59％、6．03％（均P〈0．05）。肝素各组处理K562细胞24h后细胞存活率、活细胞总数及细胞增生水平与正常对照组比较差异均有统计学意义（P〉0．05）。结论肝素浓度在200U／ml内对K562细胞无毒性作用及增生影响,在25～200U／ml以浓度依赖性方式抑制由长春新碱诱导的K562细胞凋亡。