TNFα诱导KS62／VCR和K562细胞凋亡及逆转其耐药作用的实验研究

目的　探讨肿瘤坏死因子 α(TNFα)体外诱导 K5 6 2 / VCR及 K5 6 2细胞凋亡 ,及其逆转 K5 6 2 / VCR细胞多药耐药 (MDR)的作用机制。方法　以光镜、电镜、流式细胞仪观察细胞凋亡 ;流式细胞仪检测 P- gp和 bcl- 2表达。MTT检测药物敏感性。结果　 (1) TNFα浓度 >10 0 U/ m l,作用时间 >4 8小时 ,2株细胞均可见典型凋亡现象 ,以 K5 6 2 / VCR细胞明显。 (2 )以 TNFα10 0 0 U/ ml处理后 ,K5 6 2 / VCR和 K5 6 2细胞凋亡率分别为 2 9.4 %和10 .7%。 (3) K5 6 2 / VCR经 TNFα10 0 0 U/ ml处理 72小时 P- gp表达率从 93.6 %降至 82 .4 % ,bcl- 2表达率从32 .9%降至 7.0 %。 (4 ) K5 6 2 / VCR和 K5 6 2细胞分别经 TNFα10 0 U/ ml和 10 0 0 U/ ml处理后 ,VCR、Ara- C和VP- 16的药物敏感性增加 (P<0 .0 5 )。结论　 (1) TNFα可诱导 K5 6 2 / VCR和 K5 6 2细胞凋亡 ,以前者更加敏感 ,且存在时间和剂量依赖性。 (2 )高浓度 TNFα可下调 bcl- 2表达 ,但不显著改变 P- gp表达。 (3) TNFα能增加 K5 6 2 /VCR和 K5 6 2细胞对 VCR、Ara- C和 VP- 16的药物敏感性 ,以 K5 6 2 / VCR细胞更明显。 (4 ) TNFα逆转 K5 6 2 / VCR多药耐药是通过诱导细胞凋亡 ,降低 bcl- 2表达 ,而非下调 P- gp表达途径实现     

TNFα诱导K562/VCR和K562细胞凋亡及逆转其耐药作用的实验研究

目的探讨肿瘤坏死因子α(TNFα)体外诱导K562/VCR及K562细胞凋亡,及其逆转K562/VCR细胞多药耐药(MDR)的作用机制.方法以光镜、电镜、流式细胞仪观察细胞凋亡;流式细胞仪检测P-gp和bcl-2表达.MTT检测药物敏感性.结果 (1)TNFα浓度>100 U/ml,作用时间>48小时,2株细胞均可见典型凋亡现象,以K562/VCR细胞明显.(2)以TNFα 1 000 U/ml处理后,K562/VCR和K562细胞凋亡率分别为29.4%和10.7%.(3)K562/VCR经TNFα 1 000 U/ml处理72小时P-gp表达率从93.6%降至82.4%,bcl-2表达率从32.9%降至7.0%.(4)K562/VCR和K562细胞分别经TNFα 100 U/ml和1 000 U/ml处理后,VCR、Ara-C和VP-16的药物敏感性增加(P<0.05).结论 (1)TNFα可诱导K562/VCR和K562细胞凋亡,以前者更加敏感,且存在时间和剂量依赖性.(2)高浓度TNFα可下调bcl-2表达,但不显著改变P-gp表达.(3)TNFα能增加K562/VCR和K562细胞对VCR、Ara-C和VP-16的药物敏感性,以K562/VCR细胞更明显.(4)TNFα逆转K562/VCR多药耐药是通过诱导细胞凋亡,降低bcl-2表达,而非下调P-gp表达途径实现.     

氟哌啶醇在K562/Dox细胞中对P-糖蛋白及氯离子通道的影响

目的　探讨氟哌啶醇 (Hal)对人红白血病耐药细胞K5 6 2 /Dox的逆转耐药作用 ,以及对P 糖蛋白 (P gp)和肿胀激活的氯离子通道的影响。方法　应用乳酸脱氢酶法 (LDH) ,测定Hal对瘤细胞增殖的抑制作用。以半定量逆转录聚合酶链反应 (RT PCR) ,分析经Hal处理后 3种耐药基因mRNA表达的变化。将瘤细胞荷载氯离子敏感染料MQAE后 ,以荧光分光光度计测定低渗环境中Hal对K5 6 2 /Dox细胞肿胀激活的氯离子通道的影响 ;应用ZM库尔特血球计数仪及 2 5 6频道测定仪 ,测定低渗环境中瘤细胞的体积变化 ,以判断Hal对细胞调节性体积减小 (RVD)的影响。结果　Hal对K5 6 2 /Dox细胞的耐药性具有明显的逆转作用 ,在 12 .5 0 ,6 .2 5和 3.12 μmol/L浓度时 ,其对K5 6 2 /Dox细胞耐药性的逆转倍数分别为 8.6 1,4 .35和 2 .2 5。RT PCR结果显示 ,用 12 .5 0 μmol/LHal处理K5 6 2 /Dox细胞后 ,P gp和多药耐药相关蛋白 (MRP)mRNA表达水平均降低 ,并呈现时间依赖性 ,分别较原水平下降 76 .3%和 6 4 .6 % (P <0 .0 5 ) ;谷胱甘肽硫转移酶π(GSTπ)mRNA的表达水平于用药后第 2天下降6 6 .1% ,第 3天回升 (P <0 .0 5 )。K5 6 2 /Dox细胞的氯离子浓度检测结果显示 ,单纯低渗刺激可使K5 6 2 /Dox细胞中MQAE荧光强度下降 (34.4 6± 5 .91     

Tetramethylpyrazine reverses multidrug resistance in breast cancer cells through regulating the expression and function of P-glycoprotein

Tumor multidrug resistance (MDR) has become the major obstacle to cancer chemotherapy. Recent studies suggest that tetramethylpyrazine (TMP) could reverse tumor MDR although the mechanism by which TMP overcomes tumor MDR remains elusive. Therefore, in this study, we examined the effects of TMP on MDR in drug-resistant breast cancer cells and investigated the underlying mechanisms. MCF-7 cells and the derived P-glycoprotein (Pgp) overexpressing MCF-7/dox cells were treated with TMP, and their growth was examined by MTT assay. Doxorubicin accumulation in the cells was evaluated by flow cytometry, and the expression of Pgp was detected by Western blot and RT–PCR analysis. The results showed that TMP increased the intracellular concentration of doxorubicin and inhibited Pgp-mediated efflux of doxorubicin in a dose-dependent manner. Moreover, TMP inhibited the ATPase activity of P-gp and suppressed the expression of Pgp in MCF-7/dox cells. Taken together, these data suggest that TMP has potential application in the treatment of chemotherapy-resistant breast cancer.     

HSP27高表达与人白血病多药耐药细胞K562/VCR的关系

背景与目的:白血病细胞多药耐药(multidrug resistance,MDR)是白血病化疗失败的常见原因,虽然已有研究揭示了一些肿瘤MDR机制,但目前仍然不能完全解释MDR现象。本文旨在应用蛋白质组学方法筛选白血病耐药相关蛋白,并研究其与白血病MDR的关系,为进一步阐明白血病MDR发生的分子机制提供理论依据。方法:二维聚丙烯酰胺凝胶电泳(two-dimensional electrophoresis,2-DE)技术分离白血病细胞K562和人白血病耐药细胞K562/VCR的总蛋白,用基质辅助激光解吸电离飞行时间质谱(matrix assisted laser desorption/ionization-time offlight-mass spectrometry,MALDI-TOF-MS)对差异表达的蛋白质点进行鉴定。应用反义核酸技术将分离鉴定差异表达蛋白的反义核酸转染至耐药细胞,Western blot检测转染后差异蛋白的表达情况,MTT法检测转染后细胞存活率,流式细胞仪检测转染后细胞凋亡率。结果:在K562/VCR细胞与K562细胞中鉴定出一差异表达蛋白点,并用质谱分析证实其为热休克蛋白27(heat shock protein27,HSP27)。用HSP27反义核酸转染K562/VCR细胞,在不同浓度长春新碱作用下,HSP27反义核酸转染的K562/VCR细胞的存活率较对照错义核酸转染组明显降低(P<0.05),流式细胞仪显示细胞凋亡率为16.37%,明显高于对照组(P<0.05)。结论:HSP27在K562/VCR细胞中高表达,其表达抑制后,K562/VCR细胞对长春新碱的敏感性增强。     

K562及其耐药细胞系多药耐药机制的蛋白质组学研究

 目的 探讨K562及其耐药细胞系蛋白差异表达情况。方法 应用二维荧光差异电泳结合质谱技术,经过相应软件处理找出K562和K562耐药细胞之间蛋白质表达质和量的变化。结果 二维电泳发现11个差异蛋白点,质谱鉴定出9个表达差异的蛋白质,其中4种蛋白质能量代谢有关;3种蛋白质与细胞信号转导有关;2种蛋白与细胞增殖相关。9种差异表达蛋白质中,6种在K562/ADM中表达增加,3种表达降低。结论 研究表明应用2D-DIGE结合质谱技术为白血病多药耐药机制研究是一种新的可靠手段,对于揭示耐药细胞与敏感细胞蛋白组学变化和蛋白质之间的相互作用提供新的思路。     

氯丙嗪对耐药细胞系K562/AO2多药耐药逆转作用的研究

目的研究氯丙嗪对耐药细胞系K562/AO2多药耐药逆转作用.方法应用免疫组化观察K562/AO2细胞系的耐药蛋白表达情况,用MTT法测定不同浓度的氯丙嗪对K562/AO2细胞系耐药逆转作用,用流式细胞术测定不同浓度的氯丙嗪与K562/AO2细胞作用后细胞内罗丹明的蓄积情况,用半定量RT-PCR法测定氯丙嗪对K562/AO2细胞多药耐药基因(mdr-1)mRNA表达的影响.结果K562/AO2细胞不但P-gp表达阳性,而且肺耐药相关蛋白(lung resistanceelatedprotein,LRP)表达也阳性;氯丙嗪能增强多柔比星对K562/AO2细胞的杀伤作用(单用ADM组、氯丙嗪0.75 μg/mL+ADM组、氯丙嗪1.5μg/m L+ADM组和氯丙嗪3μg/mL+ADM组对K562/AO2的抑制率分别为5.2%、25.9%、39.1%和74.8%)增加K562/AO2细胞内罗丹明的蓄积(对照组、氯丙嗪0.75 μg/mL组、氯丙嗪1.5 μg/mL组和氯丙嗪3μg/mL组细胞内的荧光强度的均值分别为1.87、10.28、48.75和65.63)对K562/AO2细胞mdr-1 mRNA表达无明显影响(对照组mdr-1和β-actin的面积比为0.41,氯丙嗪组为0.42).结论氯丙嗪对K562/AO2细胞的耐药有较强的逆转作用,并呈剂量依赖关系.     

Inhibition of sorcin reverses multidrug resistance of K562/A02 cells and MCF-7/A02 cells via regulating apoptosis-related proteins

Purpose

Sorcin, a 22-kDa calcium-binding protein, renders cancer cells resistant to chemotherapeutic agents, thus playing an important role in multidrug resistance (MDR). But the mechanisms mediated by sorcin still remain quite elusive. This study aim to explore whether sorcin silencing could restore chemosensitivity in MDR cancer cells and seek to identify the functional mechanisms mediated by sorcin.

Methods

To investigate the mechanisms of sorcin-silencing-induced chemosensitivity, transient expression of sorcin-siRNAs was performed in doxorubicin-induced MDR cell lines, K562/A02 and MCF-7/A02. Sensitivity to five chemotherapeutic agents was evaluated by analysis of cell survival and cell apoptosis.

Results

In this report, we show that down-regulation of sorcin did not alter expression or function of P-gp, but actually induced cell apoptosis and chemosensitivity in K562/A02 and MCF-7/A02. We also observe that silencing of sorcin-enhanced chemotherapeutic agent effects partly through regulating apoptosis-related protein, including Bcl-2, Bax, c-jun and c-fos.

Conclusion

This offers the rationale for the development of therapeutic strategies down-regulating sorcin expression for the treatment of cancer, especially for the reversal of MDR.     

Dasatinib reverses the multidrug resistance of breast cancer MCF-7 cells to doxorubicin by downregulating P-gp expression via inhibiting the activation of ERK signaling pathway

Multidrug resistance (MDR) is one of the major obstacles to the efficiency of cancer chemotherapy, which often results from the overexpression of drug efflux transporters such as P-glycoprotein (P-gp). In the present study, we determined the effect of dasatinib which was approved for imatinib resistant chronic myelogenous leukemia (CML) and (Ph⁺) acute lymphoblastic leukemia (ALL) treatment on P-gp-mediated MDR. Our results showed that dasatinib significantly increased the sensitivity of P-gp-overexpressing MCF-7/Adr cells to doxorubicin in MTT assays; thus lead to an enhanced cytotoxicity of doxorubicin in MCF-7/Adr cells. Additionally, dasatinib increased the intracellular accumulation, inhibited the efflux of doxorubicin in MCF-7/Adr cells, and significantly enhanced doxorubicin-induced apoptosis in MCF-7/Adr cells. Further studies showed that dasatinib altered the expression levels of mRNA, protein levels of P-gp, and the phosphorylation of signal–regulated kinase (ERK) both in time-dependent (before 24 h) and dose-dependent manners at concentrations that produced MDR reversals. In conclusion, dasatinib reverses P-gp-mediated MDR by downregulating P-gp expression, which may be partly attributed to the inhibition of ERK pathway. Dasatinib may play an important role in circumventing MDR when combined with other conventional antineoplastic drugs.     

GCS induces multidrug resistance by regulating apoptosis-related genes in K562/AO2 cell line

We have previously shown that the expression of glucosylceramide synthase (GCS) gene in drug-resistant K562/AO2 human leukemia cell was higher than that in drug-sensitive K562 cell, and the sensitivity to adriamycin of K562/AO2 cell was enhanced by inhibiting GCS. It is concluded that the overexpression of GCS gene is one of the reasons which lead to multidrug resistance (MDR) of leukemia cell. Meanwhile, we also found that higher expression of Bcl-2 gene and protein were exhibited in K562/AO2 cell compared with K562 cell. Basing on this, we hypothesized that the high expression of GCS gene which results in MDR of leukemia cell is correlated with Bcl-2 signal transduction. In order to validate the hypothesis, the inhibition of GCS gene in K562/AO2 cell was observed by using chemical suppressor PPMP and siRNA targeted at GCS, and applying RT-PCR and flow cytometry, the expression levels of apoptosis-related gene Bcl-2 and Bax were analyzed before and after inhibiting GCS gene in K562/AO2 cell. The results demonstrated that the gene and protein of Bcl-2 in K562/AO2 cell were both down-regulated significantly after GCS gene being inhibited; however, the Bax mRNA expression had no apparent change in different groups. This suggested that GCS gene may contributed to MDR of human leukemia cell K562/AO2 by Bcl-2 signal transduction.     

Characterization of the ATPase activity of the Mr 170,000 to 180,000 membrane glycoprotein (P-glycoprotein) associated with multidrug resistance in K562/ADM cells

The Mr 170,000 to 180,000 membrane glycoprotein associated with multidrug resistance (P-glycoprotein) is involved in drug transport mechanisms across the plasma membrane of multidrug-resistant cells. We have recently reported the purification of P-glycoprotein. The purified P-glycoprotein was found to have an ATPase activity, which might be coupled with the active efflux of anticancer drugs. In the present study, we have further studied the properties of the P-glycoprotein ATPase activity by an immobilized enzyme assay procedure using a P-glycoprotein-antibody-Protein A-Sepharose complex. GTP was also hydrolyzed by the P-glycoprotein, although less efficiently than ATP. The ATPase activity of P-glycoprotein had an optimal pH range around neutrality (pH 6.5-7.4). The detergent concentration of 3-[(3-cholamidopropyl)dimethyl-ammonio]-1-propane sulfonate used for protein solubilization was essential for enzyme recovery. Maximum activity was obtained when 0.1-0.2% 3-[(3-cholamidopropyl)dimethyl-ammonio]-propane sulfonate was used, while higher concentrations markedly inhibited the ATPase activity. The ATPase activity was dependent on Mg2+; maximum activity was obtained at 2-10 mM. Manganese and cobalt could substitute for magnesium as ionic cofactors. Divalent cations such as Ca2+, Zn2+, Ni2+, Cd2+, and Cu2+ inhibited the Mg2+-catalyzed ATP hydrolysis. N-Ethylmaleimide and vanadate inhibited the ATPase activity, while sodium azide or ouabain had no effect. Anticancer agents such as vincristine and Adriamycin did not affect the enzyme activity. In contrast, verapamil and trifluoperazine, agents which inhibit active drug efflux and restore drug sensitivity in resistant cells, caused an increase in the P-glycoprotein ATPase activity suggesting that P-glycoprotein might be the target molecule of these agents.     

人参皂甙Rh2逆转P-gp介导的MCF-7/ADM多药耐药性的基础研究

目的：研究人参皂甙Rh：在逆转多药耐药（MDR）方面的作用及其机理。方法：Rh：和阿霉素单独或联合作用于MCF-7及MCF-7／ADM细胞，应用MTT法确定各组细胞的IC50。罗丹明123加入各组细胞，流式细胞仪分析Rh2和维拉帕米抑制罗丹明123外排的情况。RT—PCR检测各组mdrl mRNA表达量及流式细胞仪检测各组P—gP的表达情况。结果：Rh2可以显著降低MCF-7／ADM的ADM IC50（P〈0．05），对MCF-7细胞没有影响。Rh2和维拉帕米可以增加MCF-7／ADM细胞内罗丹明123荧光表达率（P〈0．05），Rh3比维拉帕米抑制罗丹明123外排作用更强。在MCF-7细胞内Rh2和维拉帕米无此作用。Rh2对MCF-7／ADM细胞mdrl mRNA表达及P—gP表达没有影响。结论：人参皂甙Rh2可以有效逆转P—gP介导的人乳腺癌细胞耐药细胞系MCF-7／ADM的耐药性。     

MDR1基因短发卡样RNA表达载体逆转K562/A02人白血病细胞多药耐药的研究

目的构建MDR1基因短发卡样RNA(shRNA)真核表达载体,观察对K562/A02人白血病细胞株MDR1基因的沉默作用以及对P-糖蛋白(P-gp)表达及功能的影响。方法以基因重组技术构建表达质粒,转染重组质粒pEGFP-C1/U6/MDR1-A和pEGFP-C1/U6/MDR1-B至K562/A02细胞株,通过半定量RT-PCR和蛋白质印迹法,检测MDR1基因表达及P-gp表达水平的变化;以MTT法检测阿霉素(ADM)对K562/A02细胞的半数抑制浓度(IC_(50));高效液相色谱(HPLC)法检测细胞内ADM含量。结果构建的2种重组质粒pEGFP-C1/U6/MDR1-A和pEGFP-C1/U6/MDR1-B均明显抑制K562/A02细胞株MDR1基因表达,抑制率最高为48．2%±2．5%;同时抑制P-gp蛋白的表达,抑制率最高为50．67%。对ADM药物敏感性的相对逆转效率分别为40．8%和62．4%;同时使K562/ A02细胞内ADM含量增加。结论shRNA表达载体可明显抑制K562/A02细胞MDR1 mRNA的转录和P-gp蛋白的表达,增加K562/A02细胞内ADM含量,恢复K562/A02细胞对化疗药物的敏感性,逆转MDR1基因编码蛋白P-gp介导的多药耐药。     

Presence of classical multidrug resistance and P-glycoprotein expression in human neuroblastoma cells

Background: The role of P-glycoprotein (Pgp) associated multidrug resistance for neuroblastoma patients is controversial. Therefore we asked whether at all the typical functional features of the multidrug resistance phenotype could be found in neuroblastoma cells and studied the prognostic relevance of Pgp expression.Patients and methods: Tumor touch preparations and tumor cell infiltrated bone marrow smears of 62 neuroblastoma patients were investigated. The expression of Pgp was determined by a highly sensitive immunosandwich technique. Drug resistance studies were performed by exposing cells to Pgp-dependent cytostatic drugs in tissue cultures. Intracellular drug accumulation was examined by rhodamine-123 fluorescence microscopy.Results: Pgp expression was demonstrable for the SK-N-SH cell line, but not detectable in CHP-100 and ten other neuroblastoma cell lines by immunocytochemistry. In tissue cultures, SK-N-SH cells showed a relative resistance to vincristine and adriamycin (45.1 and 12.7-fold resp.) and reduced intracellular accumulation of rhodamine-123 which could be normalized by the Pgp blocker verapamil.Pgp expression was detected by immunocytochemistry in 14 out of 62 tumors (22.6%). No correlation was found to the stage of the disease (P = 0.33), histopathological grading (P = 0.82), N-myc oncoprotein expression (P = 0.76) or N-myc oncogene amplification (P = 0.20). Kaplan–Meier analysis of event free survival for stage 4 tumors revealed a weak trend of inferior survival for patients with Pgp positive tumors (log-rank analysis: P = 0.069).Conclusions: Though Pgp expression is detectable and functional in neuroblastoma cells, but its presence does not provide much information to the complex phenomenon of chemotherapy resistance in patients.     

Reversal mechanism of multidrug resistance by verapamil: direct binding of verapamil to P-glycoprotein on specific sites and transport of verapamil outward across the plasma membrane of K562/ADM cells

The calcium channel blocker verapamil has been shown to reverse multidrug resistance (T. Tsuruo et al., Cancer Res. 41: 1967-1972, 1981), but the mechanism of action of this agent has not been fully elucidated. A radioactive photoactive analogue of verapamil, N-[benzoyl-3,5-3H-(+/-)-5-[(3,4-dimethoxyphenetyl)methylamino]-2- (3,4-dimethoxyphenyl)-2-isopropyl-N-p-azidobenzoylpentylamine, was used to label the plasma membranes of a human myelogenous leukemia cell line (K562), a multidrug-resistant subline selected for resistance to Adriamycin (K562/ADM) and its revertant cell (R1-3). Sodium dodecyl sulfate-polyacrylamide gel electrophoretic fluorograms revealed the presence of an intensely radiolabeled Mr 170,000-180,000 protein in the membranes from K562/ADM but not from the drug-sensitive parental K562 and revertant R1-3 cells. The Mr 170,000-180,000 verapamil acceptor was immunoprecipitated by monoclonal antibody MRK16 specific for P-glycoprotein associated with multidrug resistance, indicating that P-glycoprotein in the plasma membrane is a major target of verapamil in K562/ADM cells. The photolabeling of P-glycoprotein with N-[benzoyl-3,5-3H]-(+/-)-5-[(3,4-dimethoxyphenetyl)methylamino]-2- (3,4-dimethoxyphenyl)-2-isopropyl-N-p-azidobenzoylphentylamine was significantly blocked by other calcium channel blockers, nicardipine and diltiazem, that have been shown to overcome multidrug resistance. In addition, the photolabeling was partially blocked by Adriamycin, vincristine, and colchicine, suggesting that the specific binding sites for verapamil on P-glycoprotein are closely related to the binding sites for these calcium channel blockers and antitumor agents. To determine whether verapamil could be a substrate for P-glycoprotein, the cellular accumulation of [3H]verapamil into K562 and K562/ADM was evaluated. The accumulation of [3H]verapamil in the multidrug-resistant cells was 30% of K562 cells and increased when K562/ADM cells were treated with vincristine and nicardipine at 5 microM, indicating that the P-glycoprotein transports verapamil as well as other antitumor agents in the multidrug-resistant cells. These results suggest that verapamil enhances antitumor agent retention through competition for closely related binding sites on P-glycoprotein.     

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。