耐顺铂人肺腺癌细胞系A549DDP的建立及耐药机制

采用递增顺铂（ＤＤＰ）浓度的方法，体外连续培养建成一株耐ＤＤＰ的人肺腺癌细胞系Ａ（５４９）ＤＤＰ，耐ＤＤＰ为亲代Ａ（５４９）的２４．４倍。在无ＤＤＰ的培养基中培养５月余，其耐药性仍稳定。Ａ（５４９）ＤＤＰ细胞内谷胱甘肽（ＧＳＨ）水平显著高于亲代细胞（Ｐ＜０．０１）。ＢＳＯ耗竭细胞内ＧＳＨ后，Ａ（５４９）ＤＤＰ细胞对ＤＤＰ敏感性增加５倍，ＢＳＯ对亲代Ａ（５４９）细胞无增敏作用，Ａ（５４９）ＤＤＰ细胞ＧＳＴ酶同功酶ＧＳＴ—π含量较Ａ（５４９）高１．６倍，却无ＧＳＴ基因扩增，表明ＧＳＨ／ＧＳＴ解毒系统参与Ａ（５４９）ＤＤＰ耐药性的产生。实验结果亦示Ａ（５４９）ＤＤＰ与卡铂及氨甲喋呤间存在交叉耐药，而与易产生ＭＤＲ或ａｔＭＤＲ之ＡＤＭ、ＶＣＲ、ＶＰ－１６、ＶＭ－２６无交叉耐药，Ａ（５４９）细胞无Ｐ－糖蛋白（Ｐ－ｇｐ）表达，Ｓｏｕｔｈｅｒｎｂｌｏｔ研究Ａ（５４９）ＤＤＰ无ｍｄｒｌＴｏｐｏⅡ基因扩增，提示Ａ（４５９）ＤＤＰ细胞系与ＭＤＲ及ａｔ－ＭＤＲ无交叉耐药。     

肝癌耐药细胞的诱导及其生物学特性的研究

目的诱导肝癌耐药细胞。研究其生物学特性。方法用“剂量递增筛选法”诱导肝癌耐药细胞；斑点杂交法等研究ＭＤＲ１ｍＲＮＡ的表达及ＧＳＴ的活性。结果经过近９个月的连续培养和１３７次的传代，诱导出耐ＡＤＲ２８倍的ＢＥＬ┐７４０２／ＡＤＲ细胞，并对５┐ＦＵ及ＶＣＲ亦有不同的耐药性。生物学特性研究结果发现，ＢＥＬ┐７４０２／ＡＤＲ细胞ＧＳＴ含量，较另两种细胞的ＧＳＴ明显增高（Ｐ＜０．０１）。ＢＥＬ┐７４０２／ＡＤＲ细胞内的ＭＤＲ１ｍＲＮＡ表达，与ＢＥＬ┐７４０２相比具有统计学差异（Ｐ＜０．０５）。结论诱导的肝癌耐药细胞ＢＥＬ┐７４０２／ＡＤＲ具有明显的多药耐药性     

阿霉素耐药及维拉帕米逆转后的细胞形态学变化

我们对诱导培养的一株Ｐ３８８／ＡＤＲ抗药株进行了形态学的研究：通过ＴＥＭ（透射电镜）观察到：取自腹水的Ｐ３８８／ＡＤＲ抗药株细胞形态不规则膜表面微绒毛增多，并出现较长而粗的微绒毛和小突（ＦＯＬＤ），即“抗药形态”，而敏感的Ｐ３８８／０只有短的微绒毛，即“敏感形态”。阿霉素作用Ｐ３８８／０细胞４８小时，膜表面微绒毛增多，胞浆内紊乱，线粒体增多，形态不一，但无长而粗的脊突；而作用Ｐ３８８／ＡＤＲ细胞则仍然为“抗药形态”，异博定逆转Ｐ３８８／ＡＤＲ抗药后，仍然为“抗药形态”，提示：抗药形态的变化可能不是单独由ＧＰ－１７０产生导致的，而可能有另外的调节因素。     

细胞色素P4501A1,2D6和谷胱甘肽硫转移酶基因多态性与肺癌易感性的研究

目的探讨细胞色素Ｐ４５０１Ａ１（ＣＹＰ１Ａ１），２Ｄ６（ＣＹＰ２Ｄ６）和谷胱甘肽硫转移酶（ＧＳＴＭ１）基因多态性与肺癌易感性的关系。方法用病例对照研究方法及ＰＣＲ┐ＲＦＬＰ等技术检测原发性肺癌和住院对照各５９例，分析ＣＹＰ１Ａ１基因ＭｓｐＩＣ型、ＣＹＰ２Ｄ６Ｃｈ型（Ｔ／Ｔ型）和ＧＳＴＭ１缺陷型〔ＧＳＴＭ１（－）〕三种纯合突变型频率分布及其交互作用。结果突变型在病例和对照组的频率分别为（ＣＹＰ１Ａ１ＭｓｐＩＣ型２５．４％、１５．３％（Ｐ＝０．１７），ＣＹＰ２Ｄ６ＣｈＴ／Ｔ型３５．６％，４７．５％（Ｐ＝０．２６），ＧＳＴＭ１（－）型５７．６％、４９．２％（Ｐ＝０．４６），无显著性差异。协同分析发现在男性中，１１．６％（５／４３）肺癌兼有ＭｓｐＩＣ型和ＧＳＴＭ１（－）型，对照组无１例（０／４３），Ｐ＝０．０３。结论结果提示在男性中ＣＹＰ１Ａ１ＭｓｐＩＣ型和ＧＳＴＭ１（－）型可能协同增加患肺癌的危险性。     

肝癌多药耐药细胞株P—gp,MRP,GST—π表达水平的观察

为研究人肝癌多药耐药细胞株的耐药机理，应用ＢＥＬ－７４０２细胞株，通过不断提高培养液中阿霉素（Ｄｏｘｏｒｕｂｉｃｉｎ）的浓度，长期筛选培养，得到肝癌多药耐药株ＢＥＬ－７４０２／Ｄｏｘ。经ＭＴＴ法检测ＢＥＬ－７４０２对长春新碱（ＶＣＲ）等８种抗癌药的抗性提高了２７倍～１１００倍。采用流式细胞技术检测了细胞株表面ＭＤＲ１蛋白Ｐ－ｇｐ、多药耐药相关蛋白ＭＲＰ及谷脱甘肽硫转移酶ＧＳＴ－π的表达；用ＲＴ－ＰＣＲ方法检测了ＭＤＲ及ＭＲＰ基因表达水平。流式细胞分析发现，９３．５％～９７．４％的ＢＥＬ－７４０２／Ｄｏｘ细胞表面Ｐ－ｇｐ表达阳性；８４．７％～９０．２％的ＢＥＬ－７４０２／Ｄｏｘ细胞表面ＭＲＰ表达阳性；ＢＥＬ－７４０２细胞与ＢＥＬ－７４０２／Ｄｏｘ细胞ＧＳＴ－π的表达无明显变化。ＲＴ－ＰＣＲ证实此细胞株中有ＭＤＲ及ＭＲＰｍＲＮＡ的较高表达。     

半乳糖基修饰的反义硫代寡核苷酸对肝癌多药耐药细胞株MDR_1基因过度表达的抑制作用

设计合成三种互补ＭＤＲ１ｍＲＮＡ的反义硫代寡核苷酸（ＡＳＯＤＮ），分别互补ＭＤＲ１ｍＲＮＡ序列起始区、含ＡＵＧ起始密码子区及针对Ｌｏｏｐ形成位点区的序列，作用于阿霉素（ＤＯＸ）诱导的肝癌多药耐药细胞株ＢＥＬ－７４０２／ＤＯＸ。经流式细胞分析及ＲＴ－ＰＣＲ的方法检测，发现三种ＡＳＯＤＮ均能不同程度地降低ＢＥＬ－７４０２／ＤＯＸ细胞膜表面Ｐ－ＧＰ含量；同时ＭＤＲ１ｍＲＮＡ的表达也有轻度降低，其中尤以互补ＭＤＲ１ｍＲ－ＮＡＬｏｏｐ形成位点的ＡＳＯＤＮ抑制作用最强。以导向配体Ｇａｌ１０－ＰＬＬ修饰此ＡＳＯＤＮ后，作用于ＢＥＬ－７４０２／ＤＯＸ细胞，发现与相同剂量未修饰ＡＳＯＤＮ比较，Ｐ－ＧＰ含量由７６．８％降至１９．８％；对ＡＤＭ的ＩＣ５０由１．２８μｇ／ｍｌ降至０．４２μｇ／ｍｌ。实验说明，半乳糖基修饰的互补ＭＤＲ１ｍＲＮＡＬｏｏｐ形成位点的ＡＳＯＤＮ能够明显降低肝癌多药耐药细胞膜表面Ｐ－ＧＰ的含量，并较大程度地逆转多药耐药细胞ＢＥＬ－７４０２／ＤＯＸ对化疗药物的耐受性。     

SPC－A－1／DDP耐药细胞株的建立及其生物学特性的初步观察

目的建立耐药细胞株，观察其生物学特性。方法采用体外诱变和药压的方法，建立耐顺铂（ＤＤＰ）的人肺腺癌细胞株ＳＰＣ－Ａ－１的耐药株（ＳＰＣ－Ａ－１／ＤＤＰ）。结果ＳＰＣ－Ａ－１／ＤＤＦ耐药细胞株能耐受的ＤＤＰ浓度为耐ＤＤＰ细胞株的１．５～１５倍，且细胞增殖和传代及耐药性均甚稳定。其倍增时间为３４．３５±０．３５３６ｈ，细胞被抑制５０％时的药物浓度（ＩＣ５０）为４５μｇ／ｍｌ，耐药指数为５．６２５，集落形成率为５３．９７％±２．４９３２％。结论ＳＰＣ－Ａ－１／ＤＤＰ耐药株可以作为研究抗癌药物耐药性机制的实验模型。     

应用等位基因特异性PCR和多重差别PCR检测肺癌患者CYP1A1和GSTM1的遗传多态性

本文对等位基因特异性ＰＣＲ（Ａｌｅｌｅｓｐｅｃｉｆｉｃ,ＡＳ）和多重差别（Ｍｕｌｔｉｐｌｅｘｄｉｆｅｒｅｎｔｉａｌ,ＭＤ）ＰＣＲ技术进行了优化,并用此法联合检测了１０５例江苏地区健康人群及６８例肺癌患者ＣＹＰ１Ａ１、ＧＳＴＭ１的等位基因型。结果表明：ＡＳＰＣＲ及ＭＤＰＣＲ采用的设立双参照扩增体系,可一次同时检测ＣＹＰ１Ａ１和ＧＳＴＭ１的等位基因型。在肺癌患者组中,ＣＹＰ１Ａ１的突变型Ｖａｌ／Ｖａｌ的频率１２／６８（１７．６％）约为健康组９／１０５（８．５７％）的２０５倍,而ＧＳＴＭ１纯合缺失的频率,肺癌组为３９／６８（５７３％）,与健康对照组４２／１０５（４０％）相比,亦有显著增加（Ｐ＜０．０５）。     

晚期非小细胞肺癌ＧＳＴＰ１、ＸＲＣＣ１基因多态性与铂类药物疗效的关系

目的　探讨谷胱甘肽Ｓ转移酶Ｐ１（ＧＳＴＰ１）和Ｘ线修复交叉互补基因１（ＸＲＣＣ１）基因多态性与晚期非小细胞肺癌（ＮＳＣＬＣ）患者化疗疗效的关系。方法　经病理学确诊的晚期ＮＳＣＬＣ患者９４例,化疗前取静脉血采用ＤＮＡ测序法检测ＧＳＴＰ１和ＸＲＣＣ１基因多态性,给予铂类为主方案化疗（顺铂７５ｍｇ／ｍ２,ｄ１）,２～３周期后评价疗效,记录疾病进展时间（ＴＴＰ）,分析ＧＳＴＰ１和ＸＲＣＣ１基因多态性与化疗疗效的关系。结果　在９４例晚期ＮＳＣＬＣ患者中,携带ＧＳＴＰ１Ａ／Ａ基因４９例,Ｇ／Ａ基因３４例,Ｇ／Ｇ基因１１例;携带ＸＲＣＣ１Ｇ／Ｇ基因５２例,Ｇ／Ａ基因３５例,Ａ／Ａ基因７例,均符合Ｈａｒｄｙ Ｗｅｉｎｂｅｒｇ遗传平衡规律。携带ＧＳＴＰ１Ｇ／Ａ＋Ｇ／Ｇ基因型的有效率为４４.４４％,显著高于Ａ／Ａ基因型的２０.４１％（Ｐ＜０.０５）;携带ＸＲＣＣ１Ｇ／Ｇ基因型与Ｇ／Ａ＋Ａ／Ａ基因型的有效率差异无统计学意义（Ｐ＞０.０５）;两基因多态性的联合分析显示,同时携带ＧＳＴＰ１Ｇ／Ａ＋Ｇ／Ｇ和ＸＲＣＣ１Ｇ／Ａ＋Ａ／Ａ基因型的有效率最高,为６６.６７％,但未见统计学意义（Ｐ＞０.０５）。９４例患者中有５例失访,８９例患者的中位ＴＴＰ为６.５个月,携带ＧＳＴＰ１Ｇ／Ａ＋Ｇ／Ｇ基因型的中位ＴＴＰ为８.０个月,Ａ／Ａ基因型为６.０个月,两者差异有统计学意义（Ｐ＜０.０１）;携带ＸＲＣＣ１Ｇ／Ｇ基因型的中位ＴＴＰ为７.０个月,Ｇ／Ａ＋Ａ／Ａ基因型为６.５个月,两者差异无统计学意义（Ｐ＞０.０５）;联合分析显示同时携带ＧＳＴＰ１Ｇ／Ａ＋Ｇ／Ｇ和ＸＲＣＣ１Ｇ／Ａ＋Ａ／Ａ基因型的中位ＴＴＰ最长,为９.５个月,各组间差异有统计学意义（Ｐ＜０.０１）。结论　ＧＳＴＰ１基因多态性与晚期ＮＳＣＬＣ患者接受铂类为主化疗方案的疗效及预后有关,同时携带ＧＳＴＰ１Ｇ／Ａ＋Ｇ／Ｇ和ＸＲＣＣ１Ｇ／Ａ＋Ａ／Ａ基因型患者的化疗有效率高,预后好,但因样本量较小,需要扩大样本进一步验证。     

5—氟脲嘧啶对耐顺铂人肺腺癌细胞A549^DDP的程序依赖性逆转作用

用耐顺铂（ＣＤＤＰ）人肺腺癌细胞系Ａ５４９ＤＤＰ作模型，研究了５－ＦＵ对ＣＤＤＰ耐药的程序依赖性逆转作用。５－氟脲嘧啶（５－ＦＵ）预处理Ａ５４９ＤＤＰ２４ｈ后立即给予ＣＤＤＰ，ＣＤＤＰ细胞毒性增加３．９倍；５－ＦＵ预处理Ａ５４９ＤＤＰ后间隔２４或４８ｈ再给予ＣＤＤＰ，其细胞毒性分别增加２０倍和２５０倍，甚至较亲代细胞Ａ５４９更为敏感；如先给ＣＤＤＰ后给５－ＦＵ则细胞毒性仅增加１．８倍。５－ＦＵ对亲代细胞亦有类似效应但细胞毒性增加程度明显低于耐药细胞。５－ＦＵ预处理后间隔２４，４８ｈ，细胞内ＧＳＨ含量逐渐降低，与细胞毒性逐渐增加相一致。如用ＢＳＯ耗竭Ａ５４９ＤＤＰ细胞内ＧＳＨ，ＣＤＤＰ细胞毒性增加６．４倍，仅能部分逆转ＣＤＤＰ耐药。５－ＦＵ明显抑制ＭＲＰ的表达，但对ＧＳＴπ的表达无影响。在５－ＦＵ预处理后的无药间隔时间内，给予无毒浓度的三苯氧胺则有明显的协同效应。结论：程序性给予５－ＦＵ通过降低细胞内ＧＳＨ含量和抑制ＭＲＰ的表达能完全逆转ＣＤＤＰ耐药     

Sensitivity to anthracyclines in P388/dx leukaemia cells

It has been demonstrated previously that neoplastic cells with reduced oxygen consumption are more sensitive to doxorubicin8. We have examined the relationship between doxorubicin sensitivity and oxygen consumption of P388 murine leukaemia cell line (P388) and of a doxorubicin resistant subline (P388/dx). Oxygen utilization by P388/dx cells was higher than that found in the sensitive line. A variety of calcium antagonists, including channel blockers and intracellular antagonists (verapamil, trifluoperazine, dantrolene, TMB-8, nitrendipine) or membrane acting drugs (lucensomycin), enhanced the cytotoxic activity of doxorubicin in P388 and markedly in P388/dx subline. This action was accompanied by a reduction of oxygen consumption more pronounced in the resistant cells. These findings emphasizé the correlation between oxygen uptake, instead of calcium dependent processes, and doxorubicin responsiveness. The calcium ionophores A 23187 failed to alter doxorubicin activity in P388 and P388/dx leukaemia.     

Protein kinase C isoforms in multidrug resistant P388/ADR cells: a possible role in daunorubicin transport.

To identify the role of protein kinase C (PKC) isoforms in multidrug resistance in tumor cells, we examined the PKC isoform pattern in the multidrug resistant P388/ADR cell line and studied the effect of down regulation of PKC isoforms on intracellular daunorubicin accumulation and P-glycoprotein expression. Using monoclonal antibodies to PKC alpha, beta and gamma and flow cytometry technique we showed that P388/ADR cells overexpressed PKC alpha and beta as compared to drug sensitive P388 cells. Prolonged treatment of P388/ADR cells with phorbol myristate acetate (PMA), a procedure that is known to down regulate PKC, resulted in the down regulation of total PKC activity and the PKC beta isoform (at the protein level) that was accompanied by the correction of daunorubicin accumulation in P388/ADR cells. The level of expression of P-glycoprotein in PMA treated cells was similar to that of untreated cells. These results suggest that PKC beta regulates the drug efflux function of P-glycoprotein.     

Differential agglutination of P388 adriamycin-sensitive and P388 adriamycin-resistant leukemia cells

Cell surface modification was studied in a subline of murine leukemia resistant to adriamycin (P388/ADR). Lectin-induced agglutination was used as a probe. Agglutination was studied using two plant lectins, wheat germ agglutinin (WGA) and Ricinus communis agglutinin-I (RCA-I). A 7-fold higher amount of WGA and 14-fold higher amount of RCA-I were required to bring about minimum agglutination of P388/S as compared to P388/ADR. The present studies clearly indicate a change in the plasma membrane of P388/ADR cells.     

P388 leukaemia cells resistant to the anthracycline menogaril lack multidrug resistant phenotype

Menogaril is an anthracycline presently in Phase II clinical trials. Menogaril-resistant mouse leukaemia P388 cells were developed in vitro by 4 months of exposure to step-wise increasing concentrations of menogaril after which resistant cells (P388/MEN) were cloned in 320 ng ml-1 menogaril. P388/MEN cells were 40-fold more resistant to menogaril in vitro compared to P388/O and were also resistant in vivo. Resistance to menogaril was stable for at least 2 months in the absence of the drug. The results indicate that P388/MEN, although resistant to an anthracycline, did not display the typical multidrug resistant phenotype. It was not cross-resistant to several structurally unrelated drugs such as actinomycin D, cisplatin, or vinblastine, but it was cross-resistant to the anthracycline, adriamycin. Uptake and efflux of menogaril was similar in sensitive and resistant cell lines. Also, resistance was not reversed by verapamil. No major karyotypic difference was noted between P388/O and P388/MEN. There was no significant amplification or overexpression of the mdr gene in P388/MEN compared to P388/O. In contrast to P388/MEN, P388 cells resistant to adriamycin displayed the typical multidrug resistant phenotype. Glutathione content of P388/MEN cells was similar to that of P388/O and depletion of glutathione did not potentiate menogaril cytotoxicity. Therefore, we conclude that glutathione is not likely to be involved in menogaril resistance to P388/MEN cells.     

Direct correlation between DNA topoisomerase II activity and cytotoxicity in adriamycin-sensitive and -resistant P388 leukemia cell lines

The relationship between DNA topoisomerase II activity and drug resistance was studied in cloned cell lines of Adriamycin (ADR)-sensitive and -resistant P388 leukemia; drug resistant P388/ADR/3 (clone 3) and P388/ADR/7 (clone 7) cells are 5- and 10-fold more resistant to ADR than the sensitive cell line P388/4 (Cancer Res., 46: 2978, 1986). Topoisomerase II catalytic activity in crude nuclear extracts was reduced in drug-resistant cells as determined qualitatively by decatenation of kDNA. Using the centrifugal method fo quantitative analysis, topoisomerase II catalytic activity (mean +/- SE) was 81 +/- 10 units/mg total nuclear protein in sensitive cells, 29 +/- 2 units/mg total nuclear protein in resistant clone 3 cells, and 16 +/- 2 units/mg total nuclear protein in resistant clone 7 cells; these differences were highly significant (P less than 0.005). Similarly, quantitative analysis of DNA cleavage activity using 3' 32P-end-labeled pBR322 restriction fragments showed that drug-stimulated topoisomerase II cleavage activity in nuclear extracts from sensitive cells was approximately 1.7- and 2.9-fold greater than that from resistant clone 3 and 7 cells, respectively. Western blot analysis of nuclear extracts from the three cell lines using antibody against the C-terminal half of recombinant-prepared human topoisomerase II polypeptide revealed reduced immunoreactivity of topoisomerase II protein in the drug-resistant cells. These data suggest that reduced topoisomerase II activity in resistant cells, which may represent quantitative reduction of the enzyme, may be another property contributing to multifactorial drug resistance in these cells.     

Membrane transport of 1-beta-D-arabinofuranosylcytosine and accumulation of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate in P388 murine leukemic cells resistant to vincristine

The membrane transport of ara-C and intracellular ara-CTP accumulation were investigated in P388 murine leukemic cells resistant to vincristine (P388/VCR) and its parent cell line. The transport of ara-C in P388/VCR cell line was a 1.4-fold increase at 30 sec compared to that in P388 parent cell line (P less than 0.01). The increase of the transport of ara-C in P388/VCR cell line, however, was not completely abolished by the nucleoside transport inhibitor, nitrobenzylthioinosine (NBTI) to the level in parent cell line. Scatchard analyses revealed that the resistant cells had significantly less NBTI binding sites than the parent cells had. These results suggested that the changes in ara-C transport in P388/VCR cells were due, in part, to increase of NBTI-insensitive transport sites in the membrane. The measurement of the intracellular ara-CTP concentration by high-performance liquid chromatography revealed that the intracellular ara-CTP level in P388/VCR cells was also significantly higher than that in parent cells (1.4-fold, P less than 0.01). As the transport of ara-C is rate limiting at a concentration of 1 microM in the both cell lines, we concluded that the accumulation of ara-CTP in P388/VCR cells might have partially resulted from the enhancement of the ara-C transport.     

Multifactorial resistance to adriamycin: relationship of DNA repair, glutathione transferase activity, drug efflux, and P-glycoprotein in cloned cell lines of adriamycin-sensitive and -resistant P388 leukemia

Cloned lines of Adriamycin (ADR)-sensitive and -resistant P388 leukemia have been established, including P388/ADR/3 and P388/ADR/7 that are 5- and 10-fold more resistant than the cloned sensitive cell line P388/4 (Cancer Res., 46: 2978, 1986). A time course of ADR-induced DNA double-strand breaks revealed that in sensitive P388/4 cells, evidence of DNA repair was noted 4 h after removal of drug, whereas in resistant clone 3 and 7 cells repair was observed 1 h after drug removal. The earlier onset of DNA repair was statistically significant (p = 0.0154 for clone 3 cells, and p = 0.0009 for clone 7 cells). By contrast, once the repair process was initiated, the rate of repair was similar for all three cell lines. The level of glutathione transferase activity was determined in whole cell extracts. Enzyme activity (mean +/- SE) in sensitive cells was 9.49 +/- 1.00 nmol/min/mg protein, that in resistant clone 3 cells was 13.36 +/- 1.03 nmol/min/mg, and that in clone 7 cells was 13.96 +/- 1.44 nmol/min/mg; the 1.44-fold increase in enzyme activity in resistant cells was statistically significant (p = 0.01). Further evidence of induction of glutathione transferase was provided by Northern blot analysis using a 32P-labeled cDNA for an anionic glutathione transferase, which demonstrated approximately a twofold increase in mRNA in resistant clone 7 cells. Western blot analysis with a polyvalent antibody against anionic glutathione transferase also revealed a proportionate increase in gene product in resistant cells. Dose-survival studies showed that ADR-resistant cells were cross-resistant to actinomycin D, daunorubicin, mitoxantrone, colchicine, and etoposide, but not to the alkylating agent melphalan; this finding provided evidence that these cells are multidrug resistant. Using a cDNA probe for P-glycoprotein, a phenotypic marker for multidrug resistance, Northern blot analysis showed an increase in the steady state level of mRNA of approximately twofold in resistant clone 3 and 7 cells. Southern analysis with the same cDNA probe showed no evidence of gene amplification or rearrangement. Western blot analysis with monoclonal C219 antibody demonstrated a distinct increase in P-glycoprotein in resistant cells. Efflux of Adriamycin as measured by the efflux rate constant was identical in all three cell lines. Furthermore, the metabolic inhibitors azide and dinitrophenol did not augment drug uptake in either sensitive or resistant cells. These findings suggest that despite the increase in P-glycoprotein, an active extrusion pump was not operational in these cells.(ABSTRACT TRUNCATED AT 400 WORDS)     

Increased sensitivity to 1-beta-D-arabinofuranosylcytosine in P388 murine leukemic cells resistant to etoposide

A variant P388 murine leukemic cell resistant to 4'-demethylepipodophyllotoxin-9-(4,6-O-ethylidine)-beta-D-gl ucopyranoside (etoposide) (VP-16-213) was cloned. The variant P388/VP-16 cell line was 159-fold resistant to VP-16. We found that this variant P388/VP-16 cell line showed collateral drug sensitivity to 1-beta-D-arabinofuranosylcytosine(Ara-C), determined by comparing the 50% inhibitory concentrations in 48-h growth inhibition assay. To clarify the mechanism of this increased sensitivity to Ara-C, we quantified the deoxyribonucleoside triphosphate pools and 1-beta-D-arabinofuranosylcytosine triphosphate(Ara-CTP) using high-performance liquid chromatography in the parent and drug-resistant sublines of P388 cells. The analysis of deoxyribonucleoside triphosphate pools revealed that the pyrimidine triphosphate pools were significantly decreased in the P388/VP-16 cell line and the Ara-CTP concentration of two variant cell lines were not significantly different. The Ara-CTP/dCTP ratio was significantly increased in P388/VP-16 cells. These data suggest that the inhibition of the dCTP de-novo pathway and the preservation of the dCTP salvage pathway in P388/VP-16 cells might correlate with the increased sensitivity to Ara-C.     

Reversal of vinblastine resistance by a new staurosporine derivative, NA-382, in P388/ADR cells.

Activities of a newly synthesized compound, N-ethoxycarbonyl-7-oxo-staurosporine (NA-382), on cyclic AMP-dependent protein kinase (A-kinase), Ca2+/phospholipid dependent protein kinase (C-kinase), and drug resistance were investigated and compared with those of staurosporine. Protein kinase-inhibitory activity of NA-382 was lower but more selective to C-kinase than that of staurosporine. NA-382 was less toxic to P388 cells and at a non-cytotoxic concentration completely reversed the vinblastine (VBL) resistance of Adriamycin-resistant P388 (P388/ADR) cells without influence on the effect of VBL on the parental P388/S cells. However, the cytotoxicity of staurosporine was too high to give the combination effect with VBL. NA-382 dose-dependently increased VBL-accumulation and inhibited VBL-efflux in P388/ADR with higher potency than staurosporine. Both compounds inhibited the photolabeling of [3H]azidopine on 140-kDa P-glycoprotein in the plasma membrane from the resistant cells. These results suggest that a staurosporine analog, NA-382, reverses multidrug resistance by inhibiting the drug-efflux system or P-glycoprotein.