The dMRP/CG6214 gene of Drosophila is evolutionarily and functionally related to the human multidrug resistance-associated protein family

ATP-binding cassette (ABC) transporters are involved in the transport of substrates across biological membranes and are essential for many cellular processes. Of the fifty-six Drosophila ABC transporter genes only white, brown, scarlet, E23 and Atet have been studied in detail. Phylogenetic analyses identify the Drosophila gene dMRP/CG6214 as an orthologue to the human multidrug-resistance associated proteins MRP1, MRP2, MRP3 and MRP6. To study evolutionarily conserved roles of MRPs we have initiated a characterization of dMRP. In situ hybridization and Northern analysis indicate that dMRP is expressed throughout development and appears to be head enriched in adults. Functional studies indicate that DMRP is capable of transporting a known MRP1 substrate and establishes DMRP as a high capacity ATP-dependent, vanadate-sensitive organic anion transporter.     

Immunophenotyping as a guide for targeted therapy

Immunophenotyping of acute and chronic leukaemias has revealed many lineage- and differentiation-specific antigens. It has now become possible to classify leukaemias according to their unique antigenic expression pattern. Among many lineage- and differentiation-specific antigens, disease-specific antigens are increasingly recognized because of their specific prognostic or therapeutic relevance. Expression of the multidrug resistance proteins of the ABC transporter family is associated with a poor response to treatment and a grave clinical prognosis. Recently, attempts to reverse refractory disease by using P-glycoprotein inhibitors have been performed in acute myeloid leukaemia, so far without evidence of clinical benefit.Other new leads to use antigen expression as a way of designing tumour-specific therapy have resulted in imatinib and Flt3 inhibitors which target tyrosine kinases in the leukaemic cell. Clinical trials are underway to investigate the effect of these new agents. The development of an antibody-calicheamycin complex directed against the myeloid-specific antigen CD33 has shown clinical activity in patients with relapsed acute myeloid leukaemia. The further development of these approaches is discussed.     

梗阻性黄疸大鼠肝细胞MRP2和FXR蛋白表达变化及意义分析

目的通过建立梗阻性黄疸动物模型，在蛋白水平观察多耐药相关蛋白MRP2（muhidrug resistance-associated protein2，MRP2）和类法尼醇X受体FXR（farnesoid X receptor）表达变化并分析二者之间的关系。方法用胆总管结扎术方法制备大鼠梗阻性黄疸模型，检测肝功能；提取大鼠肝细胞膜蛋白与核蛋白，测定提取液蛋白浓度；采用Westernblot技术检测MRP2和FXR蛋白表达。结果梗阻性黄疸大鼠总胆红素、直接胆红素显著升高；与假手术对照组相比，梗阻性黄疸组大鼠肝细胞MRP2蛋白表达明显降低（P=0．041），FXR蛋白无表达，差异均有统计学意义。结论MRP2表达下调可能与FXR表达抑制有关，FXR蛋白可能对MRP2蛋白表达有正性调控作用。     

Expression and localization of ATP binding cassette (ABC) family of drug transporters in gastric hepatoid adenocarcinomas

Aims:  Hepatoid adenocarcinomas are clinically chemoresistant; however, data concerning the mechanisms of chemoresistance are lacking. ATP-binding cassette (ABC) transporters play a role in the ATP-dependent outward efflux of drugs, and their function renders tumour cells multidrug resistant. We assumed that the expression of ABC transporters may be accompanied by hepatic differentiation because most ABC transporters are dominantly expressed in hepatocytes. The aim of this study was to investigate the expression of ABC transporters in hepatoid adenocarcinomas.
Methods and results:  The expression of P-glycoprotein, multidrug resistant-associated protein (MRP) 1, MRP2, MRP3 and MRP6 was investigated using immunohistochemistry in 13 cases of gastric hepatoid adenocarcinoma and 32 cases of control adenocarcinoma. P-glycoprotein was expressed in all cases examined. The positive rates of MRP1 (84.6% versus 21.9%), MRP2 (100% versus 43.8%) and MRP6 (61.5% versus 15.6%) were significantly higher in hepatoid than in control adenocarcinoma. MRP3 was negative in all hepatoid adenocarcinomas. Immunohistochemistry by polyclonal anti-carcinoembryonic antigen antibody, which detects bile canaliculi, suggested that MRP2 and MRP6 are located on bile canalicular-like structures in sheet or trabecular nests.
Conclusions:  These results support the hypothesis that ABC transporters participate in the mechanisms of multidrug resistance in hepatoid adenocarcinomas.     

Expression profile of early lung adenocarcinoma: identification of MRP3 as a molecular marker for early progression

Early lung adenocarcinoma is well-recognized as a small-sized non-invasive adenocarcinoma or localized non-mucinous bronchioloalveolar carcinoma (LNMBAC); however, the molecular events associated with these early lesions are not clear. To determine the genes involved in tumorigenesis at the early stage of lung adenocarcinoma, we compared the mRNA expression profiles of LNMBAC and normal lungs with an oligonucleotide array. Immunohistochemical analyses were performed to confirm the expression of detected genes. We identified 183 differentially expressed genes, of which 15 were up-regulated and 168 down-regulated. Among them, most up-regulated genes, such as AQP3 and Claudin-4, were expressed in both adenocarcinoma cells and type II alveolar pneumocytes, corresponding to the histological similarity between these cell types. However, multidrug resistant protein 3 (MRP3) was only expressed on tumour cell membranes and not in type II alveolar pneumocytes, as confirmed by immunohistochemistry. Moreover, the number of MRP3-positive cells significantly increased from AAH (the precursor lesion of lung adenocarcinoma) to LNMBAC. We conclude that MRP3 could be a novel molecular marker for LNMBAC, whose expression increases during the early progression of tumourigenesis.     

多药耐药性相关蛋白在乳腺癌组织中的表达及其与预后关系

目的:研究多药耐药相关蛋白（Multidrug　resistance-associated　protein　1,MRP1）在乳腺癌组织中的表达,评估其在乳腺癌预后中的作用。方法:采用免疫组织化学方法（IHC）检测47例手术切除的乳腺癌组织中MRP1的表达,并分析其与临床、病理特征的关系及对预后的影响。结果:（1）MRP1在乳腺癌组织中的阳性表达率为85.1％（40/47例）,其中高表达者占53.2％（25/47例）;（2）腋淋巴结阳性者MRP1表达水平明显高于腋淋巴结阴性者（P<0.05）,MRP1表达与月经状况、肿瘤大小、组织分级和激素受体状况均无关（P>0.05）;（3）Kaplan-Meier生存分析结果表明MRP1表达与无病生存期明显相关（P<0.05）,但和总生存期无关（P>0.05）;（4）Cox单因素分析显示肿瘤大小和MRP1表达与无病生存期明显相关（P<0.05）,但仅有肿瘤大小和总生存期明显相关（P<0.05）;而多因素分析却显示只有腋淋巴结转移和无病生存期（P<0.01）和总生存期（P<0.05）明显相关。结论:MRP1在乳腺癌组织中具有较高的表达水平,与乳腺癌患者的无病生存期有关,而与总生存期无关。     

非小细胞肺癌细胞MRP基因表达及意义

研究多药耐药性相关蛋白基因－ＭＲＰ基因（ｍｕｌｔｉ－ｄｒｕｇ ｒｅｓｉｓｔａｎｃｅ ａｓｓｏｃｉａｔｅｄ ｐｒｏｔｅｉｎ ｇｅｎｅ ,ＭＲＰ ｇｅｎｅ）对非小细胞肺癌（ｎｏｎ－ｓｍａｌｌ ｃｅｌｌ ｌｕｎｇ ｃａｎｃｅｒ,ＮＳＣＬＣ）患者预后的影响。方法应用地高辛标记探针原位发子杂交结合免疫组化技术检测４７例ＮＳＣＬＣ患得根治术后石蜡组织标本中癌细胞ＭＲＰ基因ｍＲＮＡ＃牵? ＤＰ ＣＦ ＫＫＨＮＦ     

Computational and structural insights into the pre- and post-hydrolysis states of bovine multidrug resistance-associated protein 1

ATP-binding cassette C-family drug membrane transporters play an important role in local pharmacokinetics, that is, drug concentration in cellular compartments. From the structural point of view, only the bovine ortholog of the multidrug resistance-associated protein 1 (bMRP1) has been resolved. We here used μs-scaled molecular dynamics simulations to investigate the structure and dynamics of the bovine multidrug resistance-associated protein 1 in pre- and post-hydrolysis functional states. The present work aims to examine the slight but likely relevant structural differences between pre- and post-hydrolysis states of outward-facing conformations as well as the interactions between the multidrug resistance-associated protein 1 and the surrounding lipid bilayer. Global conformational dynamics show unfavourable extracellular opening associated with nucleotide-binding domain dimerization indicating that the post-hydrolysis state adopts a close-cleft conformation rather than an outward-open conformation. Our present simulations also highlight persistent interactions with annular cholesterol molecules and the expected active role of lipid bilayer in the allosteric communication between distant domains of the transporter.