In vitro inhibition of CSFV replication by multiple siRNA expression

Classical swine fever (CSF) is a highly contagious viral disease of pigs which causes major economic losses worldwide. No specific drug is currently available for the effective treatment of CSFV infection; however, RNA interference (RNAi) has been applied successfully to inhibit the replication of human and other animal viruses. In this study, three effective siRNAs targeting NS3 of CSFV were selected. siNS3-2 targeting NS3 gene was chosen for further experimentation, while siN1 and siN2 targeting N^pro gene, and siNS5B targeting NS5B gene describe previously. Single, double and quadruple anti-CSFV siRNA expression plasmids, with loxp sites at each end of the selectable marker genes, were constructed and analyzed using the same promoters or four different promoters, targeting N^pro, NS3 and NS5B genes of CSFV. Results indicate that single or multiple siRNA expression plasmids can efficiently inhibit CSFV replication and that inhibition was markedly stronger when multiple siRNAs were expressed targeting different genes of CSFV. Since RNAi applied to anti-CSFV research, this study provides anti-CSFV methods by single and multiple siRNA expression which can target most viral isolates of different subtypes and prevent viral escape. It also provides a basis for development of CSFV-resistant transgenic pigs.     

小干扰RNA逆转人乳腺癌细胞MCF-7多药耐药的体外研究

目的研究以多药耐药相关蛋白(MRP)为靶标的小干扰RNA(siRNA)抑制相应蛋白表达,对人乳腺癌细胞MCF-7药物敏感性的影响。方法以MRP基因为靶标的siRNA转入MCF-7细胞,检测对MRP mRNA和蛋白表达水平的影响及其对抗肿瘤药物IC50的影响。结果经siRNA干扰后,MRP基因的mR-NA和蛋白的表达均有明显降低,肿瘤细胞对相关化疗药物的敏感性明显增加。结论以MRP基因为靶标的siRNA一定程度上逆转了肿瘤细胞的多药耐药性。     

In vitro andin vivo circumvention of multidrug resistance by Servier 9788, a novel triazinoaminopiperidine derivative

Summary S 9788 is a novel triazinoaminopiperidine derivative which does not belong to any of the classes of compounds known to reverse multidrug resistance (MDR). S 9788 was far more potent than verapamil (VRP) in reversing resistance to adriamycin (ADR) in the ADR-selected murine leukaemia cell lines P388/ADR-1 and P388/ADR-10, and the human chronic myelogenous leukaemia K562/R. Fold reversion with S 9788 (5M was, respectively, 3.5, 5.4 and 11.3 times greater than that with VRP (5M). S 9788 was also a more potent reversant of ADR resistance in the intrinsically resistant human colon adenocarcinoma COLO 320DM (2.3 fold), and of vincristine (VCR) resistance in the human MDR1 gene-transfected squamous lung carcinoma line S1/tMDR1 (5.6 fold). The activity of S 9788 depended on both the MDR cell line and the cytotoxic agent. S 9788 (50–100 mg/kg/d) administered IP once a day on days 1–4 resulted in a dose-dependent increase in the chemotherapeutic effect of VCR (0.25 mg/kg/d) in P388/VCR-bearing mice and ADR (4 mg/kg/d) in P388/ADR-bearing mice. Increases in antitumor activity were (% T/C) of +20–34% in the P388/ADR model and +50–78% in the P388/VCR model with respect to cytotoxic agent treatment alone. S 9788 appeared to be devoid of toxicity at its effective doses. The mechanism of action of S 9788 is unknown but S 9788 (0.5–10M) induced a dose-dependent increase in ADR accumulation in KB-Al cells and compared to verapamil its effect was twice as active and approximately seven times more potent. We conclude that S 9788 is a novel agent capable of reversing MDRin vitro andin vivo, and whose pharmacological profile warrants its selection as a candidate drug for eventual assessment in the clinic.     

Cytotoxicity and reversal of multidrug resistance by tryptanthrin-derived indoloquinazolines

Aim:

To evaluate the effects and elucidate the mechanisms of a series of indoloquinazolines as novel anticancer agents.

Methods:

Condensation of the substituted isatoic anhydride with the substituted isatin was performed to prepare compounds 1–4, followed by adding malononitrile to prepare compounds 5–7. Cytotoxicity was measured by MTT assays. Apoptosis induction was evaluated using DNA fragmentation, cell cycle assay, caspase 3/7 activity and Western blot.

Results:

Compounds 3, 4, and 5 display cytotoxicity against MCF-7, HeLa, SKOV3, and A498 cancer cells. DNA ladders appear in cells treated with compounds 3, 4, and 5. Within those, compound 4 exhibits the greatest activity in regards to sub-G₁ accumulations in the cell cycle and the activation of caspase-3/7. Furthermore, Fas and Fas ligand levels are elevated by compound 4, implying that the apoptosis is in part mediated through the signals. On the other hand, compounds 1 and 7 display chemosensitizing activity since cytotoxicity of doxorubicine and etoposide is enhanced in combination with compound 1 and 7, respectively, in MCF-7/adr (doxorubicin-resistant) and MCF-7/vp (etoposide-resistant).

Conclusion:

The cytotoxicity of indoloquinazolines is structure-dependent rather than cell type-dependent due to the similar degree of cytotoxicity induced by the individual compounds in all four cell lines. Further modification of the tryptanthrin skeleton is important to develop novel anticancer agents bearing either cytotoxicity against MCF-7 cells or drug resistance reversal in MCF-7/adr and MCF-7/vp.     

多药耐药基因与体外药敏检测在急性白血病中的临床意义

目的：研究急性白血病（ＡＬ）多药耐药－１（ＭＤＲ１）基因表达与临床疗效的关系，提高对肿瘤细胞耐药情况预测的准确性。方法：采用逆转录敏－多聚酶链反应（ＲＴ－ＰＣＲ）检测了３０例ＡＬ患者骨髓中ＭＤＲ１基因的表达，同时对每例均进行体外化疗药物敏感性（ＴＭＭ）检测。结果：３０例ＡＬ ＭＤＲ１基因过度表达占４０％，ＭＴＴ检出耐药为３０％（１０／３０），即有ＭＤＲ１基因过量表达又显示耐药者２７％（８／３０）；     

Lapatinib and erlotinib are potent reversal agents for MRP7 (ABCC10)-mediated multidrug resistance

In recent years, a number of TKIs (tyrosine kinase inhibitors) targeting epidermal growth factor receptor (EGFR) family have been synthesized and some have been approved for clinical treatment of cancer by the FDA. We recently reported a new pharmacological action of the 4-anilinoquinazoline derived EGFR TKIs, such as lapatinib (Tykerb^®) and erlotinib (Tarceva^®), which significantly affect the drug resistance patterns in cells expressing the multidrug resistance (MDR) phenotype. Previously, we showed that lapatinib and erlotinib could inhibit the drug efflux function of P-glycoprotein (P-gp, ABCB1) and ABCG2 transporters. In this study, we determined if these TKIs have the potential to reverse MDR due to the presence of the multidrug resistance protein 7 (MRP7, ABCC10). Our results showed that lapatinib and erlotinib dose-dependently enhanced the sensitivity of MRP7-transfected HEK293 cells to several established MRP7 substrates, specifically docetaxel, paclitaxel, vinblastine and vinorelbine, whereas there was no or a less effect on the control vector transfected HEK293 cells. [³H]-paclitaxel accumulation and efflux studies demonstrated that lapatinib and erlotinib increased the intracellular accumulation of [³H]-paclitaxel and inhibited the efflux of [³H]-paclitaxel from MRP7-transfected cells but not in the control cell line. Lapatinib is a more potent inhibitor of MRP7 than erlotinib. In addition, the Western blot analysis revealed that both lapatinib and erlotinib did not significantly affect MRP7 expression. We conclude that the EGFR TKIs, lapatinib and erlotinib reverse MRP7-mediated MDR through inhibition of the drug efflux function, suggesting that an EGFR TKI based combinational therapy may be applicable for chemotherapeutic practice clinically.     

Cepharanthine is a potent reversal agent for MRP7(ABCC10)-mediated multidrug resistance

Multidrug resistance protein 7 (MRP7; ABCC10) is an ABC transporter that confers resistance to anticancer agents such as the taxanes. We previously reported that several inhibitors of P-gp and MRP1 were able to inhibit the in vitro transport of E₂17βG by MRP7 in membrane vesicles transport assays. However, compounds that are able to reverse MRP7-mediated cellular resistance have not been identified. In this study, we examined the effects of cepharanthine (6′,12′-dimethoxy-2,2′-dimethyl-6,7-[methylenebis(oxy)]oxyacanthan), an herbal extract isolated from Stephania cepharantha Hayata, to reverse paclitaxel resistance in MRP7-transfected HEK293 cells. Cepharanthine, at 2 μM, completely reversed paclitaxel resistance in MRP7-transfected cells. In contrast, the effect of cepharanthine on the parental transfected cells was significantly less than that on the MRP7-transfected cells. In addition, cepharanthine significantly increased the accumulation of paclitaxel in MRP7-transfected cells almost to the level of control cells in the absence of cepharanthine. The efflux of paclitaxel from MRP7-transfected cells was also significantly inhibited by cepharanthine. The ability of cepharanthine to inhibit MRP7 was analyzed in membrane vesicle assays using E₂17βG, an established substrate of MRP7, as a probe. E₂17βG transport was competitively inhibited by cepharanthine with a K_i value of 4.86 μM. These findings indicate that cepharanthine reverses MRP7-mediated resistance to paclitaxel in a competitive manner.     

In vitro - in vivo correlation of gene expression alterations induced by liver carcinogens

Although cultivated hepatocytes are widely used in the studies of drug metabolism, their application in toxicogenomics is considered as problematic, because previous studies have reported only little overlap between chemically induced gene expression alterations in liver in vivo and in cultivated hepatocytes. Here, we identified 22 genes that were altered in livers of rats after oral administration of the liver carcinogens aflatoxin B1 (AB1), 2-nitrofluorene (2-NF), methapyrilene (MP) or piperonyl-butoxide (PBO). The functions of the 22 genes have been classified into two groups. Genes related to stress response, DNA repair or metabolism and genes associated with cell proliferation, respectively. Next, rat hepatocyte sandwich cultures were exposed to AB1, 2-NF, MP or PBO for 24h and expression of the above mentioned genes was determined by RT-qPCR. Significant correlations between the degree of gene expression alterations in vivo and in vitro were obtained for the stress, DNA repair and metabolism associated genes at concentrations covering a range from cytotoxic concentrations to non-toxic/in vivo relevant concentrations. In contrast to the stress associated genes, no significant in vivo/in vitro correlation was obtained for the genes associated with cell proliferation. To understand the reason of this discrepancy, we compared replacement proliferation in vivo and in vitro. While hepatocytes in vivo, killed after administration of hepatotoxic compounds, are rapidly replaced by proliferating surviving cells, in vitro no replacement proliferation as evidenced by BrdU incorporation was observed after washing out hepatotoxic concentrations of MP. In conclusion, there is a good correlation between gene expression alterations induced by liver carcinogens in vivo and in cultivated hepatocytes. However, it should be considered that cultivated primary hepatocytes do not show replacement proliferation explaining the in vivo/in vitro discrepancy concerning proliferation associated genes.     

肿瘤多药耐药逆转剂研究进展

化疗是治疗肿瘤的主要手段之一，多药耐药性的产生是肿瘤化疗中存在的主要问题。开发多药耐药逆转剂，逆转现有化疗药物的耐药性将是一种有效的治疗方法。目前已有多种多药耐药逆转剂处于基础和临床试验阶段。本文对近年来多药耐药逆转剂的研究概况做了简要阐述。     

In vitro and in vivo inhibition of lysyl oxidase by aminopropionitriles.

Inhibition of lysyl oxidase (protein-lysine 6-oxidase, EC 1.4.3.13) decreases the rate of collagen and elastin cross-link formation and produces osteolathyrism in animals. Organic nitriles, including beta-aminopropionitrile (BAPN), have been shown to irreversibly inhibit lysyl oxidase in vitro. Both BAPN and 3,3'-iminodipropionitrile (IDPN) have been shown to produce osteolathyric changes when administered to animals. To date compounds that have been reported to inhibit this enzyme possess a primary amine functional group. In this study a series of primary and substituted aminopropionitriles was studied for their ability to inhibit lysyl oxidase activity both in vitro and in vivo. Our results show that of the compounds tested, BAPN was the most potent inhibitor of the enzyme. Reversible inhibition of lysyl oxidase in vitro was found with two secondary aminonitriles, IDPN and monomethylaminopropionitrile (MMAPN). There was no inhibition of enzyme activity associated with the tertiary compound 3,3'-dimethylaminopropionitrile (DMAPN) or propionitrile, a compound lacking an amine functional group. IDPN was found to produce a slight irreversible inhibition of the enzyme both in vitro and in vivo. Pretreatment of rats with pargyline, an inhibitor of monoamine oxidase, was found to increase the inhibitory potential of BAPN (p < or = .1). Pargyline pretreatment did not alter the inhibitory potential for any of the other aminonitriles tested. These results suggest that the presence of a primary amino functional group is not a strict requirement for inhibition of lysyl oxidase. In addition, reversible and irreversible mechanisms of inhibition may be involved in the production of osteolathyric changes associated with IDPN exposure.     

吗丙嗪逆转多药抗药性作用及其分子机制的探讨

目的：探讨吗丙嗪逆转肿瘤多药抗药性（ＭＤＲ）的作用及其机制。方法：以ＭＴＴ与Ｆｕｒａ－２－ＡＭ法进行吗丙嗪逆转ＭＤＲ活性测定；以ＤＰＨ荧光测定法探讨吗丙嗪对膜脂流动性的影响；以荧光分光光度计法测定吗丙嗪与高钙或低钙对细胞内阿霉素（Ｄｏｘ）积累的影响及Ｆｕｒａ－２－ＡＭ法测定吗丙嗪对细胞内游离钙离子浓度的影响。结果：在浓度２．５μｍｏｌ·Ｌ－１时，吗丙嗪能显著增加ＭＣＦ－７／ＡＤＲ细胞内Ｆｕｒａ－２的积累和降低ＭＣＦ－７／ＡＤＲ对Ｄｏｘ的ＩＣ５０而对敏感株ＭＣＦ－７无明显影响，表明吗丙嗪具有逆转ＭＤＲ的作用。吗丙嗪能显著增加ＭＤＲ细胞内Ｄｏｘ积累和降低ＭＤＲ细胞的膜脂流动性。高钙或低钙对ＭＤＲ细胞内Ｄｏｘ积累无影响，吗丙嗪也不能改变１９９７－０４－１１收稿１中山医科大学中心实验室，广州５１００８９作者简介：符立梧，男，３２岁，博士，讲师，主要从事逆转多药抗药性的研究；潘启超，男，６７岁，教授，博士生导师，主要从事肿瘤药理与化疗方面的研究ＭＤＲ细胞内游离钙离子浓度。结论：吗丙嗪有逆转ＭＤＲ作用。其逆转机制与降低膜脂流动性增加细胞内ＤＯＸ积累有关，与钙离子浓度无关     

The role of multidrug resistance proteins MRP1, MRP2 and MRP3 in cellular folate homeostasis

Previously, we reported that the multidrug resistance proteins MRP1, MRP2 and MRP3 confer resistance to therapeutic antifolates by mediating their cellular extrusion. We now determined whether MRPs also play a role in controlling cellular homeostasis of natural folates. In MRP1, MRP2 and MRP3-transfected 2008 human ovarian carcinoma cells total cellular folate content was 32-38% lower than in 2008 cells (105+/-14pmolfolate/mgprotein) when grown in medium containing 2.3 microM folic acid (FA). Under these conditions cellular growth rates were not compromised. However, when cells were challenged under folate-depleted conditions with a short exposure (4 hr) to FA or leucovorin, MRP1 and MRP3 overexpressing cells were impaired in their growth. In contrast to wild-type cells, MRP1 transfected cells retained only 60% of the maximum growth when exposed to 500 nM leucovorin or 500 microM FA. For 2008/MRP1 and 2008/MRP3 cells FA growth stimulation capacity was dramatically decreased when, during a 4 hr exposure, metabolism into rapidly polyglutamatable and retainable dihydrofolate was blocked by the dihydrofolate reductase inhibitor trimetrexate. To retain growth under such conditions MRP1 overexpressing cells required much higher concentrations of FA (EC(50) > 500 microM) compared to 2008 cells (EC(50): 12 microM). These results suggest that down- and up-regulation of MRP1 (and MRP3) expression can influence cellular folate homeostasis, in particular when cellular retention by polyglutamylation of folates is attenuated.     

黄酮类化合物逆转肿瘤多药耐药作用的研究进展

肿瘤多药耐药是肿瘤治疗过程中一个亟待解决的难题,其表现为肿瘤细胞对单一或多种化疗药物同时出现耐药性,从而导致治疗失败,与药物的化学结构和作用机制无关。将化疗药物与肿瘤多药耐药逆转剂联合应用是目前公认的治疗方案之一。黄酮类化合物由于其低毒、高效,具有多种药理作用等优点而受到广泛的关注。在肿瘤治疗期间,黄酮类化合物能通过抑制ABC转运体、诱导凋亡、调节氧化应激等作用逆转肿瘤多药耐药。归纳总结了黄酮类化合物逆转肿瘤多药耐药的主要机制、应用及其纳米剂型改造的进展,为进一步的临床研究提供参考。     

Comparison of hyaluronic acid-based micelles and polyethylene glycol-based micelles on reversal of multidrug resistance and enhanced anticancer efficacy in vitro and in vivo

Polyethylene glycol (PEG)-based block copolymer micelles and hyaluronic acid (HA)-based grafted copolymer micelles have been widely investigated in chemotherapy. In this study, to evaluate the differences among HA-based grafted polymer micelles, PEG-based block polymer micelles and the mixed of these two micelles in enhancing antitumor effects and overcoming MDR, two amphiphilic vitamin E succinate (VES) derivatives, HA VES (HA-g-VES) and PEG 2000 VES (TPGS2k), were applied as nanocarriers to prepare HA-VES micelles (HA-PMs), TPGS2k micelles (TPGS2k-PMs) and the mixed micelles (HA/TPGS2k-PMs) for the co-delivery of doxorubicin (DOX) and curcumin (Cur). With the addition of TPGS2k, the particle size of HA/TPGS2k-PMs (153.37?±?1.00?nm) was smaller than that of HA-PMs (223.83?±?1.84) but significantly larger than that of TPGS2k-PMs (about 20?nm). The loading efficiency of HA/TPGS2k-PMs was 7.10%, which was lower than HA-PMs (8.31?±?0.15%) but higher than TPGS2k-PMs (4.38?±?0.24%). In vitro, HA/TPGS2k-PMs and TPGS2k-PMs exhibited higher cytotoxicity and reversal MDR effects than HA-PMs in MCF-7/Adr cells. However, HA/TPGS2k-PMs, HA-PMs and TPGS2k-PMs all significantly improved the tumor biodistribution, the antitumor effects and reduced the side effects of DOX in 4T1-tumor-bearing mice, but these three micelles displayed no differences in vivo. Therefore, EPR passive targeting effects caused by PEGylated micelles and CD44 active targeting effects caused by HA-based micelles have no significant variance in the delivery of antitumor drugs by i.v.     

Recent advances in P-glycoprotein-mediated multidrug resistance reversal mechanisms

Expression of the multidrug resistance (MDR) phenotype is responsible for chemotherapy failure in numerous cancers. Overexpression of mdr1 gene-encoded permeability glycoprotein (P-gp) is known to play a pivotal role in the development of this phenotype. The role of P-gp has been proposed as an important goal in the design of chemotherapy strategies. However, modulation of P-gp activity by chemotherapy has limited possibilities because of toxicity and poor specificity. In this article, we review the latest advancements in different potential P-gp-mediated MDR reversal mechanisms as well as the methods of evaluating MDR reversal activity, which would be helpful in finding novel MDR reversal agents (or chemosensitizers).     

The role of the MDR1 (P-glycoprotein) gene in multidrug resistance in vitro and in vivo.

This review describes the studies that address the role of the MDR1 (P-glycoprotein) gene in multidrug resistance in cell lines selected in vitro and in clinical cancer. Molecular genetic studies have demonstrated that expression of P-glycoprotein, an efflux pump acting at diverse lipophilic compounds, is sufficient to provide resistance to a large number of lipophilic drugs in tissue culture. The MDR1 gene is expressed in several normal human tissues associated with secretory or barrier functions and in some bone marrow and blood cells, including hematopoietic progenitor cells. MDR1 expression in clinical cancer is often found in untreated tumors of different types. Several studies showed a correlation between MDR1 expression and tumor resistance to combination chemotherapy. MDR1 expression in untreated tumors may reflect their origin from MDR1-positive normal cells or cellular changes associated with neoplastic transformation or progression. MDR1 expression in some types of cancer may be a marker of a more aggressive subpopulation of tumor cells, possessing multiple mechanisms for resistance to treatment.     

In vitro evaluation of nucleoside transport inhibition in vivo

A method is described which permits rapid evaluation of the effects of nucleoside transport inhibitors on [³H]thymidine uptake into mouse whole blood cells. The uptake is measured after 15–20 sec by withdrawing 100 μl of blood from the orbital sinus into microcapillary pipets that have been prelabeled with [³H]thymidine. Blood cells are rapidly separated from plasma by centrifugation through a layer of dibutyl phthalate using an Eppendorf microcentrifuge. The acid-soluble radioactivity associated with the cell pellet is then determined. Treatment of mice with the nucleoside transport inhibitors dipyridamole or p-nitrobenzylthioinosine 5'-monophosphate reduces uptake of the radioisotope into the cells. The assay allows for estimation of the dose- and time-effect relationships for inhibition of nucleoside transport by these agents. Advantages of the method are its simplicity, its speed, and the fact that the biological sample and drug are not diluted before measurement of the drug effect.     

托吡酯对大鼠星形细胞内谷胱甘肽硫转移酶及多药耐受基因的影响

目的 :探讨托吡酯的药物耐受性及其机制。方法 :不同浓度托吡酯持续作用于培养的新生大鼠大脑皮质星形胶质细胞 ,对照组不加药。分别在给药后 5 ,10 ,15和 2 0d ,测定细胞内谷胱甘肽硫转移酶 (GST)的活性 ,在加药后 10和 15d用流式细胞术检测多药耐受基因 (MDR1)标志物P 糖蛋白(Pgp)的表达率 ,并与对照组比较。结果 :对照组细胞内GST的活性在各时间点无差异 (P >0 .0 5 )。加托吡酯 5d时 ,4 0 ,80 ,16 0mg·L- 1组GST活性明显升高 ;加药 10d时 ,各浓度组细胞内GST活性均明显升高 ;10d后GST活性变化无显著意义(P >0 .0 5 ) ,细胞内GST活性随托吡酯浓度的增加有上升趋势。各浓度组在 15d以内Pgp的表达率与对照组比较差异无显著意义 (P >0 .0 5 )。结论 :托吡酯可使GST活性升高 ,且与剂量和时间有关 ,提示其可能有代谢性药物耐受性存在 ,托吡酯对MDR1基因表达无影响 ,表明其与其他抗癫痫药能诱导MDR1表达的作用不同。