P-gp、MRP、LRP、GSTπ和TOPOII在胃癌表达的趋势

多药耐药(multidrugresistance,MDR)是严重影响肿瘤病人化疗效果及生存的主要原因之一,是指肿瘤细胞对某一化疗药物产生耐药性后,对其他化学结构及机理不同的化疗药物也产生交叉耐药性[1]。在1970年,Biedler和Riehm首次注意到多药耐药现象[2]。目前认为多药耐药有关主要分子包括转运蛋白如P糖蛋白(P gp)、多药耐药相关蛋白(MRP)、肺耐药蛋白(LRP)、乳腺癌耐药蛋白(BCRP)和抗原过程相关转运泵(TAP),细胞解毒系统如谷胱甘肽转移酶(GST)和DNA修复系统,药物靶点如拓扑异构酶Ⅱ(TOPOⅡ),参与细胞调亡的分子如Bcl2、Bcl XL和p53等。…     

P-gp、MRP、LRP、GSTπ和TOPOⅡ在胃癌表达的趋势

多药耐药（muhidrug resistance，MDR）是严重影响肿瘤病人化疗效果及生存的主要原因之一，是指肿瘤细胞对某一化疗药物产生耐药性后，对其他化学结构及机理不同的化疗药物也产生交叉耐药性。在1970年，Biedler和Riehm首次注意到多药耐药现象。目前认为多药耐药有关主要分子包括转运蛋白如P糖蛋白（P-gP）、多药耐药相关蛋白（MRP）、     

难治及复发性急性白血病多药耐药及其逆转剂的应用

多药耐药是白血病难治和复发的主要原因。所谓多药耐药性 ( MDR) ,即在化疗初期效果好 ,但经过几个疗程治疗后 ,肿瘤细胞不但对所用药 ,而且对其他结构和作用机理不同的多种来源的药物也产生交叉耐药性。1　 MDR产生的主要机制1.1　膜转运蛋白介导的药物外排泵机制　膜转运蛋白 P-糖蛋白 ( P- gp)、多药耐药相关蛋白 ( MRP)、肺耐药蛋白( L RP)和乳癌耐药蛋白 ( BCRP)可通过改变药物的转运 ,降低白血病细胞内药物浓度 ,使细胞对多种药物耐药。此类蛋白中除 L RP外均属 ATP结合盒 ( ABC)转运蛋白超家族成员 ,可作为能量依赖性外排…     

至真方调控Hedgehog/ABCG2信号途径改善大肠癌细胞的多药耐药性

[目的]探讨至真方醇提物(ZZR)对大肠癌多药耐药细胞HCT-8/5-FU细胞耐药性的改善作用,并从Hedgehog/ABCG2信号途径探讨至真方改善大肠癌多药耐药的可能作用机制。[方法]高效液相色谱法鉴定至真方醇提物中的5种主要成分;CCK-8法检测大肠癌多药耐药细胞HCT-8/5-FU的多药耐药性及至真方对其耐药性的改善作用;应用Real-Time PCR和western blot方法分别从基因和蛋白水平检测至真方对Hedghog/ABCG2信号途径的调节作用。[结果]HCT-8/5-FU细胞有明显多药耐药性,至真方醇提物干预HCT-8/5-FU细胞48h后,能增加其对不同化疗药物(5-FU、L-OHP、Taxol)的敏感性,且Hedgehog通路上关键因子-Gli1与ABCG2的mRNA相对表达量均明显下调(P0.05),蛋白表达下降(P0.05)。[结论]至真方醇提物能够有效改善HCT8/5-FU细胞多药耐药,其机制可能与抑制Hedgehog信号通路活性从而降低ABCG2蛋白表达有关。     

乳腺癌耐药蛋白在消化道肿瘤中的作用研究

乳腺癌耐药蛋白属于三磷酸腺苷结合转运蛋白G超家族成员2(ATP-binding cassette superfamily G member 2, ABCG2),其作为药物排出泵,可以降低细胞内药物的浓度,保护细胞免受有毒物质的侵害.它保护正常细胞,但同时使肿瘤细胞对各种抗肿瘤药物产生耐药性,影响化疗效果.本文综述ABCG2的生理功能、表达影响因素以及与消化道肿瘤的关系与作用,为消化道肿瘤的临床基础研究提供参考.     

ATP结合盒式蛋白转运蛋白在结直肠腺癌中表达及其临床意义

目的探讨多药耐药基因(MDR)1、多药耐药相关蛋白(MRP)1及乳腺癌耐药蛋白(ABCG2)在结直肠腺癌中的表达及其与临床病理特征的关系。方法采用增强型二步法免疫组织化学方法检测MDR1、MRP1及ABCG2三个基因在116例结直肠腺癌组织中的表达,并分析其可能的临床预后价值。结果 MDR1、MRP1及ABCG2在结直肠腺癌的阳性表达率显著高于切端正常组织(P<0.05)。MDR1、MRP1及ABCG2的表达与病理学分级、淋巴结转移及Duke分期密切相关(P<0.05),而与年龄、性别及肿瘤发生部位无关(P>0.05)。在结直肠腺癌中MDR1、MRP1及ABCG2的表达呈显著正相关(P<0.05)。结论结直肠腺癌中存在原发性耐药现象,MDR1、MRP1及ABCG2可能在结直肠癌侵袭转移中存在协同作用。联合检测MDR1、MRP1及ABCG2在结直肠腺癌组织中的表达对化疗药物的选择、化疗方案优化及估计患者预后具有重要指导意义。     

肺耐药蛋白与肺癌

肺耐药蛋白(LRP)是新近发现的一种与多药耐药性(MDR)相关的蛋白,被认为是人的穹窿体主蛋白(MVP),它可以阻止以胞核为效应点的药物通过核孔进入细胞核,并将进入细胞核的药物转运到胞浆中和/或将进入胞浆的药物转运到运输囊泡中,隔绝药物作用,并以胞吐的方式将其排出细胞外,从而介导P-gp阴性的肿瘤耐药。本文复习近年文献,对LEP的作用机制及其研究进展,LRP在肺癌中的表达对于肺癌化疗药物的选择、化疗方案的制定、新型化疗药物的研制开发以及LRP与肺癌的预后进行了综述。     

041 肺耐药蛋白与肺癌

肺耐药蛋白(LRP)是新近发现的一种与多药耐药性(MDR)相关的蛋白.被认为是人的穹窿体主蛋白(MVP),它可以阻止以胞核为效应点的药物通过核孔进入细胞核,并将进入细胞核的药物转运到胞浆中和/或将进人胞浆的药物转运到运输囊泡中,隔绝药物作用,并以胞吐的方式将其排出细胞外,从而介导P-gp,阴性的肿瘤耐药.本文复习近年文献,对LRP的作用机制及其研究进展,LRP在肺癌中的表达对于肺癌化疗药物的选择、化疗方案的制定、新型化疗药物的研制开发以及LRP与肺癌的预后进行了综述.     

铜离子转运蛋白家族与肺癌顺铂耐药的研究进展

铂类药作为化疗一种关键药之一,被广泛用于治疗各种恶性肿瘤,如卵巢、膀胱、头颈部肿瘤及肺癌.但铂类耐药的发生限制了化疗反应,影响了患者的预后.目前在铂类耐药的机制方面已经有一些重要的发展,其中之一是肿瘤铂类耐药与细胞内浓度的蓄积之间的相关性,摄入的减少和泵出过多均可减少药物在细胞内的聚积,导致耐药.但是具体耐药机制尚不清楚.铜离子动态平衡是由铜离子转运蛋白及其分子伴侣来维持.铜离子转运蛋白家族包括铜离子转运蛋白和铜离子转运磷酸化ATP酶.本文将就铜离子转运蛋白家族与肺癌顺铂耐药作一综述.     

ABCG2、MDR1基因表达水平与5-氟尿嘧啶耐药的CD44+SGC-7901/5-Fu多药耐药关系

目的探讨乳腺癌耐药蛋白(ABCG2)、P-糖蛋白(MDR1)基因表达水平与5-氟尿嘧啶(5-Fu)耐药的CD44+SGC-7901/5-Fu多药耐药关系。方法采用反复短期暴露并逐步递增药物浓度法建立5-Fu耐药胃癌细胞株SGC7901/5-Fu,鼠抗人CD44抗体,流式细胞术(FACS)检测分选CD44+SGC-7901/5-Fu。四甲基偶氮唑蓝(MTT)比色法测定SGC-7901/5-Fu、CD44+SGC-7901/5-Fu、CD44-SGC-7901/5-Fu细胞5-Fu耐药指数及交叉耐药性。RT-PCR方法分别检测对数期生长的SGC-7901、SGC-7901/5-Fu、CD44+SGC-7901/5-Fu、CD44-SGC-7901/5-Fu细胞ABCG2、MDR1 mRNA表达。结果 CD44+SGC-7901/5-Fu相对于SGC-7901细胞的耐药指数为12.5(P<0.05),但CD44-SGC-7901/5-Fu相对于SGC-7901细胞的耐药指数为1.2(P>0.05)。CD44+SGC-7901/5-Fu对ADM、MMC和DDP也有交叉耐药性,CD44-SGC-7901/5-Fu对ADM、MMC和DDP无交叉耐药性。与对照组(正常SGC-790)细胞比较,ABCG2、MDR1在5-Fu耐药的SGC-7901细胞株中表达明显增强(P<0.05)。与5-Fu耐药的SGC-7901细胞株比较,CD44+SGC-7901/5-Fu细胞株ABCG2、MDR1表达继续增加(P<0.05);。与5-Fu耐药的SGC-7901细胞株比较,CD44-SGC-7901/5-Fu细胞ABCG2、MDR1表达差别无统计学意义(P>0.05)。结论 CD44+SGC-7901/5-Fu细胞株对5-Fu耐药性明显增强,其多药耐药机制可能与ABCG2、MDR1mRNA表达增加相关。     

ABC of oral bioavailability: transporters as gatekeepers in the gut

MDR1 (ABCB1), MRP2 (ABCC2), and BCRP (ABCG2) are members of the family of ATP binding cassette (ABC) transporters. These are plasma membrane transporters that are expressed in various organs. The role of MDR1 and MRP2 in the hepatobiliary system is well defined; both contribute to bile formation by transport of drugs, toxins, and waste products across the canalicular membrane. As they transport exogenous and endogenous substances, they reduce the body load of potentially harmful compounds. The role of ABCG2, which is also expressed in the canalicular membrane of hepatocytes, has not yet been fully characterised. All three proteins are also expressed in the apical membrane of enterocytes where they probably control oral availability of many substances. This important "gatekeeper" function of ABC transporters has been recognised recently and is currently under further investigation. Expression and activity of these transporters in the gut may differ between individuals, due to genetic polymorphisms or pathological conditions. This will lead to individual differences in bioavailability of different drugs, toxins, and (food derived) carcinogens. Recent information on substrates, transport mechanisms, function, and regulation of expression of MDR1, MRP2, and BCRP in different species is summarised in this review.     

Potential role of cyclooxygenase-2 on the regulation of the drug efflux transporter ABCG2 in breast cancer cell lines

Purpose  

ABCG2 (BCRP) implicated as a member of the multidrug resistance (MDR) proteins in tumors, mediating efflux of a wide spectrum of anticancer drugs. In recent years, there has been an increasing tendency toward the exploring of the potential link between cyclooxygenase-2 (COX-2) expression and development of multidrug resistance phenotype in patients with cancer. The aim of this study was to investigate the role of the COX-2 in modulating drug efflux by ABCG2 in a group of breast cancer cell lines.     

Hepatic expression of ABC transporters G5 and G8 does not correlate with biliary cholesterol secretion in liver transplant patients

The adenosine triphosphate (ATP)-binding cassette (ABC)-transporters ABCG5 and ABCG8 have been shown to mediate hepatic and intestinal excretion of cholesterol. In various (genetically modified) murine models, a strong relationship was found between hepatic expression of ABCG5/ABCG8 and biliary cholesterol content. Our study aimed to relate levels of hepatic expression of ABCG5 and ABCG8 to biliary excretion of cholesterol in man. From 24 patients who had received a liver transplant, bile samples were collected daily after transplantation over a 2-week period to determine biliary composition. Expression of ABCG5, ABCG8, MDR3, and BSEP was assessed by real-time polymerase chain reaction (PCR) in liver biopsy specimens collected before and after transplantation. Levels of hepatic ABCG5, ABCG8, and MDR3 messenger RNA (mRNA) were strongly correlated. After transplantation, the biliary secretion rate of cholesterol continuously increased, coinciding with gradual increases in bile salt and phospholipid secretion. In contrast, hepatic levels of ABCG5 and ABCG8 mRNA remained unchanged. Surprisingly, no correlation was found between the hepatic expression of ABCG5 and ABCG8 and rates of biliary cholesterol secretion, normalized for biliary phospholipid secretion. As expected, the concentration of biliary phospholipids correlated well with MDR3 expression. In conclusion, the strong relationship between ABCG5 and ABCG8 gene expression is consistent with the coordinate regulation of both genes, and in line with heterodimerization of both proteins into a functional transporter. Hepatic ABCG5/ABCG8 expression, at least during the early phase after transplantation, is not directly related to biliary cholesterol secretion in humans. This finding suggests the existence of alternative pathways for the hepatobiliary transport of cholesterol that are not controlled by ABCG5/ABCG8.     

Up‐regulation of breast cancer resistance protein expression in hepatoblastoma following chemotherapy: A study in patients and in vitro

Aim: Hepatoblastoma (HB), the most common pediatric malignant liver tumor, is treated with chemotherapy to facilitate surgical resection. Previous studies suggest that HB acquires chemoresistance via increased expression of multidrug resistance protein 1 (MDR1, ABCC1). There is no well established evidence that this also occurs in the clinical setting and little is known about the effects of chemotherapeutic treatments on HB in situ. Methods: Clinical and histopathological features and expression patterns of ABC transporters in diagnostic needle biopsies from 7 HBs taken before chemotherapy were compared with those in surgically resected tumors. To understand the mechanism s leading to chemoresistance we also investigated the involvement of hypoxia on protein expression and functional activity of drug transporters (BCRP and MDR1) in cultures of HepG2 human HB cells. Results: We found that chemotherapeutical treatment of HBs led to an increased expression of the breast cancer resistance protein (BCRP, ABCG2) in all patients studied. There was no change in the expression pattern of MDR1 or other ABC transporters. Chemotherapy‐induced specific vascular abnormalities associated with areas of necrosis and fibrosis were seen in all cases, suggesting tumor hypoxia. The observations of increased BCRP expression in hypoxic areas of three‐dimensional HepG2 aggregates and the enhanced BCRP function in monolayer cultures of HepG2 cells under hypoxic conditions, support a role for hypoxia in enhanced BCRP expression. Conclusions: Chemotherapeutical treatment of HB leads to vascular alterations that modify the tumor microenvironment, and increased BCRP expression in which hypoxia might play a role. No evidence was found for upregulation of MDR1 in HBs as suggested from previous experimental studies.     

Efflux transporters in ulcerative colitis: decreased expression of BCRP (ABCG2) and Pgp (ABCB1)

BACKGROUND: Efflux transport proteins are important components of the intestinal barrier against bacterial toxins, carcinogens, and drugs. This investigation was conducted to determine the expression of Breast Cancer Resistance Protein (BCRP/ABCG2), P-glycoprotein (Pgp/MDR1/ABCB1), and Multidrug Resistance Protein 2 (MRP2/ABCC2) in the gut mucosa of patients with ulcerative colitis (UC). METHODS: Patients were thoroughly diagnosed according to well-established clinical, endoscopic, and histologic criteria to be included in the group of patients with active UC (n = 16) or UC in remission (n = 17). Colonic and rectal mucosa from patients with UC were compared with tissues from control subjects (n = 15). The mRNA expression (TaqMan) of the efflux transporters and the proinflammatory cytokines interleukin (IL)-1beta and IL-6 was determined. Western blot was used in the analysis of protein expression and the tissue localization of BCRP was determined with confocal microscopy. RESULTS: BCRP and Pgp expression was strongly reduced in individuals with active inflammation compared with controls and was negatively correlated with the levels of IL-6 mRNA. The BCRP staining of colonic epithelium seen in healthy mucosa was diminished in inflamed tissues, with concurrent disruption of epithelial F-actin structure. CONCLUSIONS: Two of the efflux transporters of importance for the barrier function of the gut mucosa, Pgp and BCRP, are expressed at strongly reduced levels during active inflammation in patients with UC. Investigations are warranted to determine whether the low levels of efflux transporters during active UC contribute to altered transport and tissue exposure of carcinogens, bacterial toxins, and drugs.     

Cyclooxygenase-2 inhibitors prevent the development of chemoresistance phenotype in a breast cancer cell line by inhibiting glycoprotein p-170 expression

Breast cancer cells are usually sensitive to several chemotherapeutic regimens, but they can develop chemoresistance after prolonged exposure to cytotoxic drugs, acquiring a more aggressive phenotype. Drug resistance might involve the multi-drug resistance (MDR) 1 gene, encoding a transmembrane glycoprotein p-170 (P-gp), which antagonizes intracellular accumulation of cytotoxic agents, such as doxorubicin. We previously demonstrated that type 2 cyclooxygenase (COX-2) inhibitors can reverse the chemoresistance phenotype of a medullary thyroid carcinoma cell line by inhibiting P-gp expression and function. The aim of our study was to investigate the role of COX-2 inhibitors in modulating chemoresistance in a human breast cancer cell line, MCF7. MCF7 cells, expressing COX-2 but not MDR1, were treated with increasing doses of doxorubicin, and they became chemoresistant after 10 days of treatment, in association with MDR1 expression induction. This effect was reversed by doxorubicin withdrawal and prevented by co-incubation with N-[2-(cyclohexyloxy)4-nitrophenyl]-methanesulfonamide (NS-398), a selective COX-2 inhibitor. Treatment with NS-398 alone did not influence cell viability of a resistant MCF7 cell clone (rMCF7), but sensitized rMCF7 cells to the cytotoxic effects of doxorubicin. Moreover, treatment with NS-398 significantly reduced MDR1 expression in rMCF7 cells. Doxorubicin-induced membrane P-gp expression and function was also greatly impaired. Our data therefore support the hypothesis that COX-2 inhibitors can prevent or reduce the development of the chemoresistance phenotype in breast cancer cells by inhibiting P-gp expression and function.     

ATP binding cassette transporter G1 (ABCG1) is an intracellular sterol transporter

Four members of the mammalian ATP binding cassette (ABC) transporter G subfamily are thought to be involved in transmembrane (TM) transport of sterols. The residues responsible for this transport are unknown. The mechanism of action of ABCG1 is controversial and it has been proposed to act at the plasma membrane to facilitate the efflux of cellular sterols to exogenous high-density lipoprotein (HDL). Here we show that ABCG1 function is dependent on localization to intracellular endosomes. Importantly, localization to the endosome pathway distinguishes ABCG1 and/or ABCG4 from all other mammalian members of this superfamily, including other sterol transporters. We have identified critical residues within the TM domains of ABCG1 that are both essential for sterol transport and conserved in some other members of the ABCG subfamily and/or the insulin-induced gene 2 (INSIG-2). Our conclusions are based on studies in which (i) biotinylation of peritoneal macrophages showed that endogenous ABCG1 is intracellular and undetectable at the cell surface, (ii) a chimeric protein containing the TM of ABCG1 and the cytoplasmic domains of the nonsterol transporter ABCG2 is both targeted to endosomes and functional, and (iii) ABCG1 colocalizes with multiple proteins that mark late endosomes and recycling endosomes. Mutagenesis studies identify critical residues in the TM domains that are important for ABCG1 to alter sterol efflux, induce sterol regulatory element binding protein-2 (SREBP-2) processing, and selectively attenuate the oxysterol-mediated repression of SREBP-2 processing. Our data demonstrate that ABCG1 is an intracellular sterol transporter that localizes to endocytic vesicles to facilitate the redistribution of specific intracellular sterols away from the endoplasmic reticulum (ER).     

Pharmacogenomics of MDR1/ABCB1 gene: the influence on risk and clinical outcome of haematological malignancies

Pharmacogenomics is a rapidly developing field of biomedical research, which investigates phenotypic and pharmacodynamic consequences of the genetic variations among individuals. The multi-drug resistance-1, MDR1 (ABCB1) gene belongs to ATP-binding cassette (ABC) family and encodes for membrane transporter P-glycoprotein (P-gp). A wide array of P-gp substrates comprises toxic xenobiotics and numerous commonly used medications including anti-cancer drugs. Under physiological conditions P-gp protects cells against toxins, whereas in malignant cells P-gp confers multi-drug resistance phenotype. Moreover, characteristic tissue localisation enables P-gp to influence the uptake, tissue distribution and elimination of P-gp transported drugs. A number of recent studies identified variety of single nucleotide polymorphisms (SNPs) in the MDR1 gene and demonstrated significant ethnic differences in their allelic frequency distribution. Furthermore, it was shown that some of these SNPs, especially silent C3435T polymorphism in exon 26, may alter P-gp expression and transport activity. Consequently, it is likely that specific functional MDR1 haplotypes may result with altered exposure to toxins and drugs, thus influencing predisposition to certain diseases as well as efficacy or toxicity of pharmacotherapy. In this paper, we focus on the available data concerning the impact of MDR1 polymorphism on the risk and clinical outcome of haematological malignancies. The structure and function of P-gp as well as results of studies addressing the relevance of MDR1 polymorphism in non-haematological disorders are also briefly discussed.     

Modulation of drug resistance transporters as a strategy for treating myelodysplastic syndrome

Resistance to chemotherapy is an obstacle to the successful treatment of acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). The failure of therapeutic treatment may be due to the development of multidrug resistance (MDR), mechanisms of which include upregulation of membrane-resident transporters which efflux chemotherapeutic drugs from tumor cells, and failure of the cancer cell to undergo apoptosis in response to chemotherapy. Membrane transporter-based drug efflux transporters have been extensively studied, and agents that block drug efflux have been found and investigated. Presence of P-glycoprotein (Pgp, MDR1, ABCB1), a member of the ATP-binding cassette (ABC) transporter family, has been reported to correlate with poor prognosis in AML and MDS. In MDS, Pgp expression increases as the disease progresses. Overexpression of other transporters, such as the multidrug resistance protein (MRP1, ABCC1), and the vault-associated transporter lung resistance protein have been shown as well in both MDS and AML, but their prognostic relevance is not clear. Recently, a novel ABC half-transporter, the breast cancer resistance protein (ABCG2) has been found in approximately 30% of AML cases, and may play a role in resistance to chemotherapy. In clinical trials in MDS, first-generation Pgp blockers, such as cyclosporin-A and verapamil, were minimally effective, non-specific, and toxic. However, another first-generation blocker, quinine, was used in MDS and may specifically benefit MDS patients overexpressing Pgp. A second-generation drug, the non-immunosuppressive cyclosporine analog valspodar (PSC833), was studied in AML and MDS, and was highly toxic, resulting in the need to reduce the dosage of the chemotherapeutic drugs as a result of valspodar reducing the clearance of the chemotherapeutic agents. Third-generation drugs, which are highly specific for Pgp and which seem to have only modest effects on drug clearance, include tariquidar, zosuquidar, laniquidar, and ONT-093. These are all in phase I/II trials and show promise for future treatment.