转染肿瘤坏死因子及反向多药耐药基因对乳腺癌细胞耐药基因表达的影响

目的构建反向pEGFP-MDR1重组表达载体和pDsRed2-TNF-α重组表达载体,在乳腺癌耐药细胞株MCF-7/ADR中进行表达,并观察它们对多药耐药(MDR)基因的影响。方法应用RT-PCR和DNA重组技术构建反向绿色荧光蛋白pEGFP-MDR1融合蛋白表达载体和红色荧光蛋白pDsRed2-TNF-α融合蛋白表达载体,分别和同时导入乳腺癌耐药细胞株MCF-7/ADR中进行表达,应用荧光显微镜直接观察融合蛋白的表达情况,RT-PCR和免疫细胞化学染色法分别检测转染前后MDR1-mRNA和P糖蛋白表达情况。结果转染了反向pEGFP-MDR1载体的细胞可见到绿色荧光,转染了pDsRed2-TNF-α载体的细胞可见到红色荧光,而同时转染了反向pEGFP-MDR1载体和pDsRed2-TNF-α载体的细胞可见到红色及绿色荧光。转染后的细胞在mRNA水平及蛋白水平明显降低了耐药细胞MCF-7/ADR的MDR1基因的表达。结论反向pEGFP-MDR1融合蛋白和pDsRed2-TNF-α融合蛋白能在乳腺癌耐药细胞MCF-7/ADR中分别及同时获得表达,并能抑制MDR1基因在MCF-7/ADR细胞中的表达,为进一步研究基因治疗联同免疫治疗逆转乳腺癌耐药建立了很好的基础。     

MDR1 基因单靶点双荧光素酶报告基因系统的建立

目的通过构建以MDR1启动子为启动序列的双荧光素酶报告基因系统并进行活性分析，为MDR1基因表达的单靶点调控研究和逆转剂的筛选提供一种有效的方法。方法从HCT-8细胞中提取DNA并克隆含有MDR1基因启动子中Y—box序列。将该序列重组到萤光素酶报告基因载体pGL-3．Basic的启动区域中，从而构建报告基因载体pGL-MDR1。将pGL-MDR1和pRL-TK载体共转染到HCT-8和HCT-8／VCR细胞中。通过调节不同载体的比例来优化转染效率。利用MDRI基因激活剂（热诱导）和抑制剂（EGCG）等处理来分析其启动转录活性受外界因素的影响。结果通过直接测序法验证了pGL-MDR1含有MDR1基因启动子Y—box序列且没有出现碱基突变。在pGL-MDR1和pRL-TK的转染比例为5：5时，转染效率最高并具有最高的萤光素酶活性。通过MDR1基因激活处理后表现为时间依赖性地激活MDR1基因的表达，而MDR1基因抑制剂的作用则相反。结论MDR1启动子为启动序列的双荧光素酶报告基因系统建立成功。该系统不但可以用于研究活体生物发光成像和MDRI基因表达的机理，而且可用于单靶点的多药耐药抑制剂的筛选。     

多药耐药基因介导的骨髓保护在肝癌小鼠化疗时的富集效应

目的 探讨多药耐药基因转染小鼠骨髓单个核细胞移植后,化疗时其在体内的表达、分布以及在骨髓和外周血的富集效应.方法 骨髓造血细胞转染外源性多药耐药基因后移植入荷瘤Balb/c小鼠,免疫组化和RT-PCR观察mdr1基因在骨髓造血细胞、外周血单个核细胞及重要脏器的表达和分布;监测外周血白细胞变化及肿瘤组织P-糖蛋白表达.结果 外源性多药耐药基因在重要脏器和肿瘤组织无表达;化疗前骨髓细胞和外周血的P-糖蛋白表达阳性率分别为(9.36±1.84)%、(8.52±1.26)%,化疗药物剂量递增时,P-糖蛋白表达阳性率增高;移植未转染组与移植转染组外周血白细胞计数差异有统计学意义(P＜0.01).结论 外源性多药耐药基因转染在骨髓造血细胞和外周血单个核细胞有持续较高表达,在重要脏器无表达;随化疗药物剂量递增时骨髓和外周血有明显的富集效应;多药耐药基因转染介导保护骨髓在超剂量化疗中获得显著效果.     

P-Glycoprotein Is Positively Correlated with p53 Protein Accumulation in Human Colorectal Cancers

To explore the relationship between mutant p53 and Pgp expression, we have examined the levels of both proteins in human colorectal adenocarcinomas. Serial frozen sections of 40 surgical samples were stained with an anti-Pgp (MRK16) and two different anti-p53 protein antibodies (Abs), PAb421 and Pabl80l. Nineteen (47.5%) of 40 samples examined were positive for Pgp, and 18 (45%) of 40 were positive for p53. The samples that stained positively with PAb421 also stained positively with Pahl80l. Pgp expression was detected in 13 (76.5%) of 17 samples that were positive for p53 using PAb421 and in 15 (83.3%) of 18 samples that were positive for p53 using Pabl80. Thus, we found that p53 and Pgp were co-expressed in a significant number of samples ( P < 0.002). There was no relationship between Pgp or p53 protein accumulation and histologic grade or stage. The present results demonstrate that Pgp expression is closely associated with p53 protein accumulation in human colorectal cancers. These data provide evidence to support the idea that mutant p53 activates the MDR1 gene in vivo .     

Inhibitory effect of the reversal agents V-104, GF120918 and Pluronic L61 on MDR1 Pgp-, MRP1- and MRP2-mediated transport

The human multidrug transporter MDR1 P-glycoprotein and the multidrug resistance proteins MRP1 and MRP2 transport a range of cytotoxic drugs, resulting in multidrug resistance in tumour cells. To overcome this form of drug resistance in patients, several inhibitors (reversal agents) of these transporters have been isolated. Using polarized cell lines stably expressing human MDR1, MRP1 or MRP2cDNA, and 2008 ovarian carcinoma cells stably expressing MRP1 cDNA, we have investigated in this study the specificity of the reversal agents V-104 (a pipecolinate derivative), GF120918 (an acridone carboxamide derivative also known as GG918), and Pluronic L61 (a (poly)oxypropethylene and (poly)oxypropylene block copolymer). Transport experiments with cytotoxic drugs with polarized cell lines indicate that all three compounds efficiently inhibit MDR1 Pgp. Furthermore, V-104 partially inhibits daunorubicin transport by MRP1 but not vinblastine transport by MRP2. V-104 reverses etoposide resistance of 2008/MRP1 cells, whereas GF120918 does not reverse resistance due to MRP1. V-104 partially inhibits the export of the organic anion dinitrophenyl S-glutathione by MDCKII-MRP1 but not by MDCKII-MRP2 cells. Unexpectedly, export of the organic anion calcein by MDCKII-MRP1 and MDCKII-MRP2 cells is stimulated by Pluronic L61, probably because it relieves the block on entry of calcein AM into the cell by endogenous MDR1 Pgp.     

Selective modulation of P-glycoprotein's ATPase and anion efflux regulation activities with PKC α and PKC ɛ in Sf9 cells

The modulation of P-glycoprotein's (Pgp) ATPase activity and its ability to regulate swelling-activated ¹²⁵I efflux, by PKC α and PKC ɛ, was examined in insect cells. Recombinant baculovirus was used to express human Pgp in Sf9 cells and Pgp was also co-expressed with either PKC α or PKC ɛ. ATPase assays showed the enzyme activity of Pgp to be elevated during co-expression with the Ca²⁺ dependent isoform PKC α, but not with the Ca²⁺ independent variant PKC ɛ. Furthermore, neither isoform, when co-expressed with Pgp, altered the swelling-activated efflux of ¹²⁵I from Sf9 cells. However, in cells co-expressing Pgp/PKC (α or ɛ), pre-treatment with the phorbol ester TPA significantly reduced the swelling-activated ¹²⁵I efflux with both PKC isoforms. Our results suggest that phosphorylation with the Ca²⁺ independent variant PKC ɛ does not regulate the ATPase activity of Pgp and that stimulation of PKC with TPA alters the swelling-activated efflux of anions from insect cells expressing Pgp. Received: 8 March 2000 / Accepted: 5 June 2000     

多药耐药基因在慢性癫癎大鼠中的表达及托吡酯对其表达的影响

目的探讨多药耐药基因（mdr）在慢性大鼠中的表达及托吡酯（TPM）对其表达的影响。方法将生后28d的SD大鼠给予海人酸致,对照组给予相同的方法注射生理盐水。待自发性形成后,将癫痫组分为持续状态并发自发性（简称SE）组、持续状态并发自发性治疗（简称SE＋TPM）组、非癫痫持续状态并发自发性癫痫（简称N—SE）组和非持续状态并发自发性治疗（简称N—SE＋TPM）组;将生理盐水对照组分为正常生理盐水对照组和正常生理盐水对照治疗（对照＋TPM）组。治疗组均给予TPM治疗,治疗6周后,将所有大鼠断头取海马,RT—PCR检测mdr1α和mdr1b mRNA的表达。结果SE组、SE＋TPM组和N—SE＋TPM组的mdr1α和mdr1b mRNA表达均比对照组高（P〈0．001或〈0．05）,SE＋TPM组的mdr1α和mdr1b mRNA表达也比SE组高（P〈0．001）,其他治疗组（N—SE＋TPM,对照＋TPM）mdr1α和mdr1b mRNA表达较相对应的未治疗（N—SE,对照）组相比高,但无统计学意义（P〉0．05）。结论反复癫痫发作,特别是持续状态可使大鼠海马中mdr1α和mdr1b mRNA表达增加,颞叶的耐药可能与mdr1α和mdr1b mRNA高表达有关。TPM可增加大鼠海马中mdr1α和mdr1b mRNA的表达,尤其mdr1α mRNA的表达更明显。mdr1α 和mdr1b mRNA高表达可能与癫痫和TPM均有关。     

The role of structural factors in the kinetics of cellular uptake of pyrazoloacridines and pyrazolopyrimidoacridines: implications for overcoming multidrug resistance towards leukaemia K562/DOX cells

The appearance of multidrug resistance (MDR) of tumour cells to a wide array of antitumour drugs, structurally diverse and having different mechanisms of action, constitutes the major obstacle to the successful treatment of cancer. Our approach to search for non-cross resistant antitumour agents is based on the rational design of derivatives, which have a high kinetics of passive cellular uptake rendering their active efflux by MDR exporting pumps inefficient. Recently, two families of acridine cytotoxic agents were obtained, pyrazoloacridines (PACs) and pyrazolopyrimidoacridines (PPACs). The aim of this study was to examine molecular basis of the reported differences in retaining cytotoxic activity of these derivatives at cellular level against resistant erythroleukaemia K562/DOX (overexpressing P-glycoprotein) cell line. The study was performed using a spectrofluorometric method, which allows continuous monitoring of the uptake and efflux of fluorescent molecules by living cells. It was demonstrated that the presence of two additional rings, pyrazole and pyrimidine, fused to the acridine chromophore structure (PPAC) favoured more rapid cellular diffusion than the presence of only one additional pyrazole ring (PAC). The presence of hydrophobic substituent OCH3 markedly favoured the cellular uptake of pyrazoloacridines and pyrazolopyrimidoacridines while compounds having hydrophilic substituent OH exhibited very low kinetics of cellular uptake. In contrast, it was found that neither structure of the ring system nor the hydrophobic/hydrophilic character of examined substituents determined the rate of active efflux of these compounds by P-glycoprotein. Our data showed that a nearly linear relation exists between the resistance factor (RF) and lnV+ reflecting the impact of the cellular uptake rate (V+) on the ability of these compounds to overcome MDR.     

Effect of acetaminophen on expression and activity of rat liver multidrug resistance-associated protein 2 and P-glycoprotein

We evaluated the effect of acetaminophen (APAP), given as a single, 1g/kg body weight dose, on expression and activity of rat liver multidrug resistance-associated protein 2 (Mrp2) and P-glycoprotein (P-gp), two major canalicular drug transporters. The studies were performed 24h after administration of the drug. APAP induced an increase in plasma membrane content of Mrp2 detected by western blotting, consistent with increased detection of the protein at the canalicular level by immunoflourescence microscopy. In vivo biliary excretion of dinitrophenyl-S-glutathione, a well known Mrp2 substrate, was slightly but significantly increased by APAP, agreeing well with upregulation of the transporter. Basal biliary excretion of oxidized glutathione, an endogenous Mrp2 substrate, was also increased by APAP, likely indicating increased hepatic synthesis as a result of APAP-induced oxidative stress followed by accelerated canalicular secretion mediated by Mrp2. APAP also increased the expression of P-gp detected by western blotting and immunofluorescence microscopy as well as the in vivo biliary secretory rate of digoxin, a model P-gp substrate. Because specific APAP-conjugated metabolites are Mrp2 substrates, we postulate that induction of Mrp2 by APAP may represent an adaptive mechanism to accelerate liver disposition of the drug. In addition, increased Mrp2-mediated elimination of oxidized glutathione may be essential in maintaining the redox equilibrium in the hepatocyte under conditions of APAP-induced oxidative stress.     

Selenite-induced apoptosis in doxorubicin-resistant cells and effects on the thioredoxin system

Selenium treatment of the doxorubicin-resistant cell line, U-1285dox, derived from human small cell carcinoma of the lung, resulted in massive apoptosis. This effect appeared maximal at 2 days after addition of selenite. The apoptosis was caspase-3 independent as revealed by Western blot analysis, activity measurement and by using caspase inhibitors. Induction of apoptosis was significantly more pronounced and occurred after addition of lower concentrations of selenite in the doxorubicin-resistant cells compared to the parental doxorubicin-sensitive cells. High levels of selenite caused necrosis in the doxorubicin-sensitive cells. Analysis of enzymatic activity (insulin reduction) of thioredoxin reductase (TrxR) and TrxR protein concentration, measured by ELISA, revealed increasing activity and protein levels after treatment with increasing concentrations of selenium. Maximum relative increase was induced up to 1 μM in both sublines and at this selenium level the concentrations of TrxR measured as insulin reducing activity or ELISA immunoreactivity were nearly identical. Increasing concentrations of selenite up to 10 μM resulted in increased activity and concentration of TrxR in the sensitive subline but decreasing levels in the resistant subline. The level of truncated Trx (tTrx) was higher in the resistant U-1285dox cells but the level did not change with increasing selenite concentrations. Our results demonstrate pronounced selective selenium-mediated apoptosis in therapy-resistant cells and suggest that redox regulation through the thioredoxin system is an important target for cancer therapy.