Altered Expression of Epidermal Growth Factor Receptor Gene in a Classical Multidrug-resistant Variant of a Human Cancer Cell Line, KB

A variant clone resistant to high doses of colchicine (KB-C1) derived from human cancer KB cell line is resistant to various anticancer agents. The KB-C1 cells were much more resistant to epidermal growth factor and a chimeric toxin, EGF-Pseudomottas exotoxin (PE), than the parental KB cells. KB-C1 cells have decreased numbers of EGF-receptors, though the affinity of the receptors is similar to that in the parental KB cells. A drug-sensitive revertant (C1-R2) partially recovered its EGF-receptor activity. Northern blot analysis showed a decreased level of EGF-receptor mRNA in KB-C1 cells, while the multidrug-resistance gene, mdr-1 , was expressed at very high levels in KB-C1 cells, but not in KB or C1-R2 cells. The drug-resistant cells were less tumorigenic than the parental cells when injected into nude mice. A decreased expression of EGF-receptor in these cells may be one of the pleiotropic properties of multidrug-resistant cells and may perhaps represent the basis for their reduced tumorigenicity.     

Photodynamic Inactivation with Acridine Orange on a Multidrug-resistant Mouse Osteosarcoma Cell Line

Overcoming multidrug resistance (MDR) is an urgent issue to improve the prognosis of osteosarcoma patients. In this study, we undertook to clarify the effect of photodynamic therapy (PDT) with acridine orange (AO) on the MDR mouse osteosarcoma (MOS/ADR1) cell line, by comparing the outcome with the effect on a chemosensitive osteosarcoma (MOS) cell line. Cultured cells of MOS and MOS/ADR1 cell lines were exposed to AO at various concentrations for various times, followed by long- or short-term (10 or 1 min) illumination with blue light (466.5 nm) for excitation. Living cells were counted by means of the trypan blue exclusion test. The results showed that AO rapidly bound to DNA, RNA and lysosomes of living MOS and MOS/ADR1 cells and also that most tumor cells in both cell lines died rapidly (viability ratio to untreated cells: 1/1000) within 48 h under conditions of continuous or 15-min flash exposure to AO at concentrations above 1.0 μg/ ml plus 10-min illumination with blue light. Even after flash exposure to AO at concentrations above 1.0 μg/ml plus 1-min illumination, the viability of MOS/ADR1 cells decreased to a viability ratio of less than 1/1000 within 72 h. Based on these results, we concluded that AO with photo excitation has a strong cytocidal effect, not only on chemosensitive mouse osteosarcoma cells, but also on MDR mouse osteosarcoma cells. These results suggested that photodynamic therapy with AO may be a new approach to treating MDR human osteosarcomas.     

Reversal of P-Glycoprotein-mediated Paclitaxel Resistance by New Synthetic Isoprenoids in Human Bladder Cancer Cell Line

We isolated a paclitaxel‐resistant cell line (KK47/TX30) from a human bladder cancer cell line (KK47/WT) in order to investigate the mechanism of and reversal agents for paclitaxel resistance. KK47/TX30 cells exhibited 700‐fold resistance to paclitaxel and cross‐resistance to vinca alkaloids and topoisomerase II inhibitors. Tubulin polymerization assay showed no significant difference in the ratio of polymerized α‐ and β‐tubulin between KK47/WT and KK47/TX30 cells. Western blot analysis demonstrated overexpression of P‐glycoprotein (P‐gp) and lung resistance‐related protein (LRP) in KK47/TX30 cells. Drug accumulation and efflux studies showed that the decreased paclitaxel accumulation in KK47/TX30 cells was due to enhanced paclitaxel efflux. Cell survival assay revealed that verapamil and cepharanthine, conventional P‐gp modulators, could completely overcome paclitaxel resistance. To investigate whether new synthetic isoprenoids could overcome paclitaxel resistance, we synthesized 31 isoprenoids based on the structure of N‐solanesyl‐N, N′‐bis(3,4‐dimethoxybenzyl)ethylenediamine (SDB), which could reverse multidrug resistance (MDR), as shown previously. Among those examined, trans‐N, N′‐bis(3,4‐dimethoxybenzyl)‐.N‐solanesyl‐l,2‐diaminocyclohexane (N‐5228) could completely reverse paclitaxel resistance in KK47/TX30 cells. N‐5228 inhibited photoaffinity labeling of P‐gp by [³H]azidopine, suggesting that N‐5228 could bind to P‐gp directly and could be a substrate of P‐gp. Next, we investigated structural features of these 31 isoprenoids in order to determine the structural requirements for the reversal of P‐gp‐mediated paclitaxel resistance, suggesting that the following structural features are important for overcoming paclitaxel resistance: (1) a basic structure of 8 to 10 isoprene units, (2) a cyclohexane ring or benzene ring within the framework, (3) two cationic sites in close proximity to each other, and (4) a benzyl group with 3, 4‐dimethoxy functionalities, which have moderate electron‐donating ability. These findings may provide valuable information for the development of P‐gp‐mediated MDR‐reversing agents.     

Toremifene concentration and multidrug resistance in lung tumors

 In this pharmacokinetics study, concentrations of toremifene (TOR), a new antiestrogen, were measured after a 7-day oral treatment in serum, lung, and tumor tissue to determine the optimal dose of TOR for the modulation of clinical multidrug resistance in patients with lung cancer. Target levels of the antiestrogen were based on previous in vitro studies. Altogether, 18 patients with operable lung tumors were studied. TOR was given in an open, nonrandomized, phase I study at three different dose levels. The medication consisted of oral TOR given for 7 days at either 240, 480, or 600 mg/day before surgical removal of the tumor. At least five patients were scheduled to be included at each dose level, with all five receiving the full course of therapy before escalation of the dose. Blood samples for serum TOR concentration measurements were taken on days 0 and 7. Specimens of tumor and normal lung tissue of approximately 0.5 g were taken on day 7. The concentrations of TOR and its metabolites were determined in serum, lung, and tumor tissue at different dose levels. Altogether, 12 evaluable patients completed the scheduled treatment. The concentrations measured in serum, lung, and tumor tissue increased along with the dose used, such that the highest TOR values were achieved at 600 mg/day, with mean values being 4.9 μmol/l, 175.0 μmol/g, and 122.7 μmol/g, respectively. The concentrations of TOR and its metabolite N-demethyltoremifene were highest in lung tissue, but the values measured in tumor specimens were also well above the respective concentrations detected in serum samples. The TOR doses of 240 and 480 mg/day were well tolerated. One patient in the group treated at 600 mg/day had to discontinue the treatment because of headache and nausea. TOR given at doses ranging from 480 to 600 mg/day for 7 days will produce serum, lung, and tumor concentrations of the parent drug and its metabolites that have been shown to reverse multidrug resistance of cancer cells in vitro. As the 480-mg/day dose of TOR produced tumor concentrations high enough to reverse multidrug resistance without producing adverse drug reactions, the dose recommended for the foreseen clinical trials in the reversal of multidrug resistance would be 480 mg/day for 7 days. Received: 26 July 1995/Accepted: 15 May 1996     

Non-P-glycoprotein-mediated Atypical Multidrug Resistance in a Human Bladder Cancer Cell Line

A human bladder cancer cell line resistant to adriamycin (ADM), T24/ADM9 has been established in vitro by exposing T24 parent cells to progressively higher concentrations of the drug over a period of 12 months. The T24/ADM9 cells were found to be 9 times more resistant to ADM than the T24 parent, and showed various degrees of cross-resistance to an ADM derivative, vinca alkaloids and a DNA topoisomerase II (Topo ID-targeting agent, etoposide. No significant difference was observed in the cellular accumulation of ADM between the T24/ADM9 and T24 parent cells. A Northern blot analysis showed an overexpression of multidrug resistance-associated protein (MRP) mRNA, but no overexpression of multidrug resistance-1 (MDR1) mRNA was observed in the T24/ADM9 cells. A flow cytometric analysis showed that the MDR1 gene product, P-glycoprotein (Pgp), is not expressed on the T24/ADM9 cells. T24/ADM9 showed approximately the parental level of DNA Topo II catalytic activity. In Western blot and Northern blot analyses, however, the cellular level of DNA topo II was apparently much lower in T24/ADM9 than in the T24 parent. Thus, these results suggest that a decreased cellular level of DNA Topo II and an overexpression of MRP gene may be responsible for the expression of an MDR phenotype in the T24/ADM9 cells and that such non-Pgp-mediated, atypical MDR may develop in bladder cancer treated with chemotherapy including ADM.     

A New Quinoline Derivative MS-209 Reverses Multidrug Resistance and Inhibits Multiorgan Metastases by P-glycoprotein-expressing Human Small Cell Lung Cancer Cells

Development of distant metastases and acquired multidrug resistance (MDR) are major problems in therapy for human small cell lung cancer (SCLC). MS-209 is a novel quinoline compound, which reverses P-glycoprotein (P-gp)-mediated MDR. We previously reported that MS-209 reversed in vitro MDR of human SCLC (SBC-3/ADM and H69/VP) cells expressing P-gp. In the present study, we determined the therapeutic effect of MS-209 in combination with chemotherapy against multiorgan metastases of MDR SCLC cells. SBC-3/ADM cells expressing P-gp were highly resistant to etoposide (VP-16), adriamycin (ADM), and vincristine (VCR) in vitro , compared with parental SBC-3 cells lacking P-gp expression. MS-209 restored chemosensitivity of SBC-3/ADM cells to VP-16, ADM, and VCR in a dose-dependent manner in vitro. Intravenous injection with SBC-3 or SBC-3/ADM cells produced metastatic colonies in the liver, kidneys and lymph nodes in natural killer (NK) cell-depleted severe combined immunodeficiency (SCID) mice, though SBC-3/ ADM cells more rapidly produced metastases than did SBC-3 cells. Treatment with VP-16 and ADM reduced metastasis formation by SBC-3 cells, whereas the same treatment did not affect metastasis by SBC-3/ADM cells. Although MS-209 alone had no effect on metastasis by SBC-3 or SBC-3/ADM cells, combined use of MS-209 with VP-16 or ADM resulted in marked inhibition of metastasis formation by SBC-3/ADM cells to multiple organs. These findings suggest that MS-209 reversed the MDR of SBC-3/ADM cells, but not SBC-3 cells, growing in the various organs, and inhibited metastasis formation in vivo. Therefore, this chemosensitizing agent, MS-209, may be useful for treatment of refractory SCLC patients with multiorgan metastases.     

TAM对非小细胞肺癌经NVB-DDP方案诱导耐药性逆转的临床观察

目的:以大剂量三苯氧胺(Tamoxifen,TAM)逆转非小细胞肺癌经多次长春瑞滨-顺铂方案治疗后所产生的多药耐药性,提高疗效。方法:研究前均以流式细胞技术检测患者外周血淋巴细胞(PBL)中P-gp的表达。将72例对长春瑞滨-顺铂方案治疗产生耐药性的非小细胞肺癌患者随机分成两组,每组36例。A组为三苯氧胺治疗组,B组为对照组。A组患者在本次研究中每次化疗前3天及化疗第1、2天口服TAM100mg,每日2次,化疗方案为长春瑞滨25mg/m2,iv,d1,8;顺铂40mg/m2ivd1～3,每28天重复,不少于2周期。B组不服用TAM,仅进行化疗,方案同A组。每周期结束后均检测P-gp的表达并评价临床疗效。结果:两组患者在本研究前PBL中P-gp均呈阳性,A组的总有效率为33.3%(12/36),并有47.2%(17/36)P-gp转阴或显著降低;B组总有效率为13.9%(5/36),P-gp无转阴或显著下降者。经统计学处理,两组临床有效率P<0.01,P-gp转阴率P<0.01,其差异均具有显著性。结论:大剂量TAM对经多次长春瑞滨-顺铂方案治疗后产生了耐药性的患者有较好的逆转作用,可使疗效再次提高。     

Evaluation of toremifene for reversal of multidrug resistance in renal cell cancer patients treated with vinblastine

Purpose: Expression of P-glycoprotein (Pgp), which confers the multidrug resistance (MDR) phenotype, is thought to contribute to the insensitivity of renal cell cancer (RCC) to chemotherapy. The development of Pgp inhibitors for clinical application has been hampered by unacceptable toxicity at doses required to achieve adequate cellular concentration. Toremifene is able to reverse MDR and sensitise RCC to vinblastine in vitro. However, in vivo toremifene is tightly bound to serum proteins, in particular the acute phase protein α₁-acid glycoprotein (AAG), which may limit tissue availability. In this phase I–II study we assessed the tolerability of short courses of high dose toremifene in combination with vinblastine and evaluated the key determinants of MDR reversal in vivo. Methods: Twenty-seven patients with metastatic RCC received escalating doses of oral toremifene for 3 days every 2 weeks in combination with vinblastine 6 mg/m² i.v. on day 3 of each cycle. The serum concentration of toremifene, its metabolites and AAG were measured and the effect of patients' serum on inhibition of Pgp in vitro was determined. Results: Twenty-six patients were evaluable for response. Eight patients (31%) had stable disease and 18 patients (69%) progressive disease. The mean serum concentration of toremifene at 780 mg daily for 3 days was 7.82 μM [standard deviation (SD) 2.48, range 2.50 to 14.70], which exceeds that known to reverse MDR in vitro. The serum concentration of the major metabolite of toremifene, N-demethyltoremifene, which also reverses MDR, was 5.13 μM (SD 1.78, range 1.80 to 9.00). In 60% of patients the pre-treatment AAG concentration was above that known to block the effects of toremifene in vitro. However, addition of serum from patients on toremifene to MCF-7 adr cells in vitro inhibited Pgp-mediated efflux of rhodamine 123. Conclusions: We have shown that short course, high-dose toremifene in combination with vinblastine is generally well tolerated and that the concentration of toremifene required to reverse MDR in vitro is achievable in vivo. Received: 7 July 1999 / Accepted: 15 November 1999     

Circumvention of Atypical Multidrug Resistance with Tumor Necrosis Factor

Some "multidrug-resistant" (MDR) cell lines are not associated with a defect in drug accumulation or with the overexpression of P-glycoprotein. These cell lines are defined as "atypical MDR" (at-MDR) and they often express altered or mutated topoisomerase II. We investigated the ability of tumor necrosis factor to reverse at-MDR (in the human ovarian cancer cell line A2780 DX3) on the basis of its efficacy in potentiating in vitro topoisomerase II-targeted drugs, and because there is convincing evidence that the synergy is due to an increased number of topoisomerase-associated strand-breaks as well as to an increased level of extractable topoisomerase     

非霍奇金淋巴瘤多药耐药逆转的临床研究

目的 :探讨环胞霉素 A(Cs A)联合他莫昔芬 (TAM)逆转非霍奇金淋巴瘤 (NHL )多药耐药的临床疗效。方法 :采用免疫组织化学标记链亲和素生物素法检测 NHL的 P-糖蛋白表达。将 P-糖蛋白表达阳性者分层随机分为两组 ,比较 Cs A联合 TAM加化疗组与单用化疗组的疗效。结果 :P-糖蛋白的阳性表达率在初治 NHL 为 9.6 % ,在复发难治 NHL 为 79.2 % (P<0 .0 0 1)。Cs A联合 TAM对逆转 NHL 的多药耐药有一定作用 ,加逆转剂组的化疗疗效高于不加逆转剂组 (P<0 .0 5 )。结论 :Cs A联合 TAM逆转 NHL 的多药耐药是安全和具有一定疗效的。     

Multidrug Resistance Phenotype in the RMS-GR Human Rhabdomyosarcoma Cell Line Obtained after Polychemotherapy

Classical cytotoxic treatment of rhabdomyosarcoma (RMS), the most common soft tissue malignancy in children, is often accompanied by significant morbidity and poor response. Chemotherapy may induce multidrug resistance (MDR) associated with the expression of P-glycoprotein, a drug efflux pump which modifies the sensitivity of tumoral cells to drugs. To analyze MDR in RMS we used the RMS-GR cell line, obtained from an embryonal rhabdomyosarcoma treated in vivo with polychemotherapy. The RMS-GR cells showed cross-resistance to vincristine, doxorubicin and actinomycin D, the drugs of choice in the conventional treatment of RMS. Polymerase chain reaction (PCR) analysis showed that these RMS cells overexpressed mdr1 /P-glycoprotein. The pattern of resistance and the level of P-glycoprotein expression were similar to those found in the resistant RMS TE.32.7.DAC cell line obtained in vitro . Southern blot analysis showed that mdr1 overexpression was not due to amplification of the gene. Our results showed that the in vivo treatment of embryonal RMS may induce an MDR phenotype mediated by mdr1 /P-glycoprotein in RMS cells.     

阿霉素加热化疗对抗人肝癌耐药细胞多药耐药性的实验研究

 目的　观察比较阿霉素 ( ADM)化疗与 43℃加热化疗对耐药人肝癌细胞模型 - 772 1 /Adm(以下简称 772 1 /Adm细胞 )的敏感性及细胞内药物浓度的影响。方法　以人肝癌细胞模型 -772 1 /Adm为研究对象 ,采用水浴加温法、体外细胞毒试验 ( MTT法 )、流式细胞技术 ,观察阿霉素( ADM)化疗与加热化疗后细胞的存活率及细胞内阿霉素浓度的变化。结果　 ( 1 )阿霉素化疗、加热化疗 30、60 min后 772 1 /Adm细胞存活率分别为 70 .2 %、40 .8%和 60 .2 %、37.4% ;( 2 )流式细胞仪检测显示阿霉素化疗、加热化疗 30 min后细胞内阿霉素浓度分别为 41 .3%、92 .0 %。结论　加热可以显著对抗 772 1 /Adm的耐药性 ,提高其对阿霉素的敏感性 ,这与加热提高了细胞内药物浓度有关。     

甲基莲心碱对耐长春新碱人胃癌细胞多药耐药性逆转机制的初步研究

目的探讨新的钙阻断剂甲基莲心碱(Nef)对耐长春新碱人胃癌细胞多药耐药性(MDR)的逆转作用及其机制。方法采用MTT比色法,检测药物的细胞毒作用;应用免疫细胞化学SP法及流式细胞术,检测Nef对人胃癌细胞Bcl-2蛋白表达的影响。结果 10μmol/L Nef对SGC7901及SGC7901/VCR无显著细胞毒作用;2.5、5、10μmol/L Nef能使VCR对SGC7901/VCR细胞的IC50从2.32μg/ml依次下降至0.340、0.128、0.053μg/ml,逆转倍数分别为6.8、18.1、43.8。当Nef浓度为10μmol/L时,逆转SGC7901/VCR多药耐药活性较VRP高(P<0.01);SGC7901/VCR细胞中Bcl-2蛋白表达水平较SGC7901细胞高,经Nef处理后,SGC7901/VCR细胞中Bcl-2蛋白表达水平明显下降,表明Nef能下调SGC7901/VCR细胞中Bcl-2蛋白表达水平。结论甲基莲心碱在体外能逆转耐长春新碱人胃癌细胞(SGC7901/VCR)的多药耐药性,其机制可能与下调Bcl-2蛋白表达水平有关。     

卵巢癌细胞株 SKOV3/ADM的多药耐药性逆转研究

目的：研究糖脂合成酶抑制剂杠基棕榈酰胺吗啡丙醇（DL－threo-1-phenyl-2-palmitoylamino-3-morpholino-1-propanol,PPMP)对卵巢癌多药耐药细胞株SKOV3／ADM的中性鞘糖脂成分－单己糖神经酰胺（monohexosylceramide,CMH)含量的影响,探讨PPMP对SKOV3／ADM多药耐药性的逆转作用。方法：收集SKOV3细胞和PPMP处理前后的SKOV3／ADM细胞,采用改良的Hakamort's方法提取中性鞘糖脂,用高效薄层层析技术（HPTLC）分析CMH含量变化,用体外细胞毒实验技术（MTT）检测PPMP对SKOV3／ADM耐药性的逆转作用。结果：耐药株SKOV3／ADM与其敏感株SKOV3相比,CMH含量明显增高,25μmol/L PPMP作用SKOV3／ADM细胞48h可完全抑制其CMH的合成;PPMP可增加SKOV3／ADM细胞对阿霉素、长春新碱的敏感性,但PPMP浓度不同时这种作用没有显著性差异。结论：糖脂合成酶抑制剂PPMP可有效抑制多药耐药卵巢癌细胞的中性鞘糖脂成分CMH的合成,并对卵巢癌细胞多药耐药性有逆转作用。     

High Concentration of Daunorubicin and Daunorubicinol in Human Malignant Astrocytomas after Systemic Administration of Liposomal Daunorubicin

The value of chemotherapy in patients with malignant astrocytoma remains controversial. In our laboratories in vitro experiments with organotypic spheroid cultures showed superior effectiveness of anthracyclines. Systemic administration did not provide in therapeutic concentrations so far. Because recent studies on Daunorubicin in liposomes in the treatment of Kaposi sarcoma have shown effectiveness with diminished systemic toxicity, we administered intravenously a single dose of Daunorubicin in liposomes in eight patients at different intervals prior to surgery (12–50h). In samples taken from tumor, tumor-edge and where possible from adjacent brain, the levels of Daunorubicin and its active metabolite Daunorubicinol were assessed with high performance liquid chromatography. Here we report that high concentrations of Daunorubicin and Daunorubicinol were found in malignant gliomas after systemic administration of liposomal Daunorubicin.     

柔红霉素在耐药细胞株K562/ADR内的异常分布

目的 了解化疗药物在糖蛋白（Pgp)耐药细胞株K562/ADR亚细胞结构的异常分布及其与耐药的关系。方法 采用共聚焦激光扫描显微镜、荧光法和RT-PCR等方法,研究柔红霉素（DNR）在K562/ADR细胞亚细胞结构的分布及其与耐药的关系。以及维拉帕米尔（verapamil)、布雷菲尔得菌素（brefeldinA)、氯喹对细胞内DNR异常分布的影响,将3种特异染色线粒体、高尔基体、溶酶体的荧光物质Rh123、DBD-ceramide、中性红作为探针、鉴定分隔储留DNR的细胞器。结果 在K562ADR细胞中,DNR荧光主要集中在核周和周边胞浆,核内及胞浆其他部位荧光很少,这种分布方式与Rh123荧光在该细胞的分布极其相似,与DNR在敏感细胞K562/S细胞核、浆均匀分布不同,verapamil可逆转DNR在K562/ADR的异常分布,而氯喹、brefeldinA无此作用。结论 DNR在耐药细胞的异常分布参与了肿瘤细胞耐药的形成,Pgp在过程中发挥了重要作用。     

汉防己甲素逆转白血病细胞株K562/ADM多药耐药性机制研究

目的 研究汉防己甲素(TTD)对慢性粒细胞白血病急性变白血病细胞株K562／ADM多药耐药(MDR)逆转的机理。方法 采用流式细胞仪检测细胞内化疗药物的浓度及细胞表面P糖蛋白(P-gp)的表达；荧光定量PCR法检测MDR1 mRNA；通过流式细胞仪检测Anexin—V判断凋亡细胞的数量。结果 10μmol/L的TTD处理K562／ADM细胞后，细胞内阿霉素(ADM)的浓度明显提高；K562／ADM细胞MDR1 mRNA／P-gp的表达下降；TTD能增强ADM致细胞凋亡的作用。结论 汉防己甲素的耐药逆转机制除了下调MDR1 mRNA／P-gp的表达引起细胞内抗癌药物的积聚外，增加抗癌药物致细胞凋亡也是耐药逆转的重要原因。．     

载体表达小干扰RNA逆转卵巢癌的多药耐药

目的:探讨载体表达的小干扰RNA(smallinterferingRNA,siRNA)逆转卵巢癌细胞多药耐药的可行性。方法:浓度梯度诱导法建立人卵巢癌阿霉素耐药细胞株OVCAR/AR;脂质体介导将MDR1特异性siRNA的表达载体(pSN/mdr1a和pSN/mdr1b)转染OVCAR/AR细胞;实时定量RT-PCR检测MDRlmRNA的表达;流式细胞术检测P-gp的表达,罗丹明试验检测P-gp的药物转运功能;MTT法检测OVCAR/AR细胞对化疗药的抵抗性。结果:转染pSN/mdr1a和pSN/mdr1b后,OVCAR/AR细胞的MDR1mRNA和P-gp的表达均显著下降,P-gp的转运功能减少,OVCAR/AR细胞对阿霉素、泰素的耐药性逆转。结论:载体表达的siRNA可持久有效地抑制卵巢癌耐药细胞MDR1mRNA和P-gp的表达,并逆转其多药耐药。     

环胞菌素A 逆转数种人类胶质瘤细胞多药耐药性的体外实验研究

 目的　探讨环胞菌素A体外逆转人类胶质瘤细多药耐药性的作用及其机理。方法　采用有MDR1和MRP表达的人类胶质瘤细系 ,通过放射自显影观察应用环胞菌素A前后抗癌药物在细胞内的积累与外排量。结果　在有MDR1和MRP表达的人类胶质瘤细胞系中 ,加入环胞菌素A后细胞内抗癌药物积累量显著增加 (P <0 .0 5 )。结论　环胞菌素A可增加耐药细胞对抗癌药的敏感性 ,在体外能有效地逆转入类胶质瘤细胞的多药耐药性。其作用机制除了与细胞膜上的P -糖蛋白竞争性结合、抑制药物外排 ,对MRP过度表达的胶质瘤细胞系也有逆转作用 ,这可能与细胞类型有关。     

Multidrug Resistance in Cultured Human Leukemia and Lymphoma Cell Lines Detected by a Monoclonal Antibody, MRK16

Forty cultured human leukemia and lymphoma cell lines never exposed to anticancer agents in culture, apart from doxorubicin (ADM)-resistant K562/ADM, were examined for reactivity with a monoclonal antibody, MRK16 in F(ab')₂ form [MRK16-F(ab')₂], which recognizes P-glycoprotein (P-gp). The relative resistance index to various drugs was calculated by dividing the 50% growth inhibitory concentration (IC₅₀) of the test cell line by IC₅₀ of K562, which was the negative control in the antibody experiment. MRK16-F(ab')₂ reacted with four cell lines, K562/ADM, KYO-1, HEL and CMK, which had relative resistance index values of 2 or more to vincristine (VCR), vindesine, vinblastine, ADM, daunorubicin, mitoxantrone (MIT), etoposide (VP-16) and actinomycin-D (ACT-D). The level of resistance to VCR and ADM in these cell lines decreased significantly in the presence of 10 μ M verapamil in vitro . Significant expression of mRNA of P-gp gene was also detected in K562/ADM, KYO-1 and HEL. MRK16-F(ab')₂ did not react with 36 other cell lines. Among them, three cell lines, PL-21, P31/FUJ and KOPM-28, had relative resistance index values of 2 or more to anthracyclines, MIT and VP-16, but not to vinca alkaloids or ACT-D. The level of ADM-resistance in these cell lines did not decrease significantly in the presence of 10 μ M verapamil. Five cell lines, ATL-1K, HL-60, KMOE-2, ML-1 and U266, had relative resistance index values of 2 or more to some of the drugs, but not to the others, and 19 other cell lines did not. These results indicate that the reactivity of MRK16-F(ab')₂ correlates with a relative resistance index of 2 or more to all these drugs in cultured human leukemia and lymphoma cell lines.