以膜转运蛋白为靶点的胃癌多药耐药研究进展

胃癌是我国病死率最高的常见恶性肿瘤,肿瘤多药耐药（MDR）严重影响临床化疗的效果,而膜转运蛋白如P－糖蛋白（P－gp）、MDR相关蛋白（MRP）、乳腺癌耐药蛋白(BCRP)和肺耐药相关蛋白(LRP)的异常表达是引起肿瘤多药耐药的重要机制之一. 简述上述4种膜转运蛋白在胃癌中的异常表达、耐药机制、临床意义及其逆转药.     

肝豆状核变性基因与肿瘤耐药的研究进展

肝豆状核变性基因(ATP7B)定位于13q14．3区，编码一种铜转运P型ATP酶。ATP7B的突变使其蛋白缺乏或丧失转运肝铜的功能，导致肝、肾和脑等组织铜累积过多，表现为慢性肝病和(或)神经损害，ATP7B蛋白对铜的转运机制尚未明了。ATP7B在多种肿瘤细胞中表达对顺铂耐药，研究表明ATP7B除了是铜的转运蛋白外，还可能转运顺铂，但转运位点不清楚。ATP7B可能是一个新的肿瘤化疗耐药指标。     

黄酮类化合物对肿瘤多药耐药调节作用的研究进展

多药耐药是临床上化疗失败的重要原因之一。黄酮类化合物存在于多种植物中,具有广泛的药理活性,对P-糖蛋白(P-gp)、多药耐药相关蛋白(MRP)、乳腺癌耐药蛋白(BCRP)等外向转运蛋白的抑制作用使其可能成为肿瘤多药耐药调节剂。文中分别对黄酮类化合物对ABC家族转运蛋白抑制作用的研究概况、作用机制以及构效关系进行综述,为肿瘤多药耐药抑制剂的开发和应用提供重要信息。     

原花青素二聚体B_2对大鼠滑膜细胞NF-κB核转运及炎症因子表达的影响

目的通过观察原花青素二聚体B2(procyanidins di-mer B2,PCB2)对大鼠滑膜细胞NF-κB核转运及相关炎症因子表达的影响,探讨其抗炎的分子机制。方法免疫荧光法观察NF-κB/p65在细胞中的定位,RT-PCR检测PCB2对诱导细胞的COX-2 mRNA表达,Western blot分析COX-2蛋白含量变化,ELISA测定各处理组细胞上清液中IL-1β、VEGF的含量变化。结果 TNF-α(10μg.L-1)诱导RSC-364细胞NF-κB从细胞质转运至细胞核,50μmol.L-1 PCB2明显抑制NF-κB/P65核转运;PCB2剂量依赖性抑制COX-2基因和蛋白的表达;PCB2下调了TNF-α诱导的IL-1β、VEGF的水平。结论 PCB2能有效抑制COX-2、IL-1β及VEGF的表达,其机制可能与抑制TNF-α诱导的NF-κB核转运,抑制NF-κB活化有关。     

有机阴离子转运蛋白在外源化学物毒性中的作用

机体接触各种潜在毒性有机阴离子,包括内源性物质如激素、神经递质和细胞代谢产物;外源性化学物质如多种药物、农药和动植物毒素等。快速有效地清除其中的毒性物质是机体最好的防御方式。有机阴离子转运蛋白介导的跨上皮主动转运通常是其中的限速过程。因此,研究有机阴离子转运蛋白的种类、分布及其转运与表达调控机制具有重要的毒理学意义。     

药物转运蛋白功能及应用

细胞膜转运蛋白是一些药物的吸收、分布和消除的决定因素，具有重要的药剂学意义。作为异生物质排出细胞的通道，ABC转运蛋白对大多数现在使用的药物的体内行为产生重要影响，包括治疗肿瘤、艾滋病和微生物感染用药。小肽转运蛋白具有广谱的底物特异性．能够转运大量的口服的结构类似于小肽的药物。由于新的小肽和多肽模拟物类药物的迅速增加，小肽转运蛋白因可能成为药物转运系统而倍受关注。在分子水平加深对药物转运蛋白的理解势必促进药物设计与生物药剂学的发展。     

ABC转运蛋白与肿瘤多药耐药

目的 :介绍ABC转运蛋白与肿瘤多药耐药的研究进展 ,阐述ABC转运蛋白高表达是多药耐药的重要机制之一。方法 :检索国内外大量文献资料进行汇总、综述。结果 :ABC转运蛋白是具有ATP结合区的单向底物外排泵。P -糖蛋白高表达是肿瘤细胞产生多药耐药的经典路径 ,多药耐药相关蛋白高表达能导致非P -糖蛋白介导的多药耐药。结论 :开发多药耐药蛋白抑制剂有广阔的应用价值 ,但注重其药理作用的同时还应对其潜在的毒副作用保持高度警惕     

多药耐药性相关ATP结合盒转运蛋白

ATP结合盒（ABC）转运蛋白超家族是一大类以ATP水解为动力的转运蛋白，在肿瘤细胞和正常组织都有分布，有多种重要功能。ABC转运蛋白家族中与多药耐药性相关的转运蛋白有P-糖蛋白、多药耐药性相关蛋白、乳腺癌耐药蛋白。本文对这些多药耐药性ABC转运蛋白的生理、生化特性进行综述。     

ATP结合盒转运蛋白介导的MDR逆转剂的实验研究现况

多药耐药性(mu ltidrug resistance,MDR)是指人肿瘤细胞对结构各异的化疗药物产生交叉耐药,是肿瘤化疗失败的主要原因之一。为了增强肿瘤细胞对化疗药物的敏感性,积极寻求有效逆转MDR的药物已成为研究重点。体外被证实具有逆转耐药活性的化合物很多,但由于体内要达到体外逆转试验的有效浓度所需剂量过大,毒副作用大,因此限制了临床应用。ATP结合盒转运蛋白家族(ATP-b ind ing cassette,ABC)介导的药物外排机制是目前MDR的主要机制,ABC转运蛋白家族中与多药耐药性相关的转运蛋有P-糖蛋白(P-gp)、多药耐药相关蛋白(MRP)和乳腺癌耐药蛋白(BCRP)。本文对ABC转运蛋白介导的MDR逆转剂的研究进展做一综述。     

单胺转运蛋白与单胺重摄取抑制剂研究进展

5-羟色胺转运蛋白(serotonin transporter,SERT)和去甲肾上腺素转运蛋白(norepinephrine transporter,NET)是单胺类神经递质转运体,其功能是将释放到突触间隙的5-羟色胺(serotonin,5-HT)和去甲肾上腺素(norepinephrine,NE)分别转运入突触前神经细胞,以终止相应的突触信号传递。SERT、NET抑制剂可阻断5-HT和NE的重摄取,提高突触间隙单胺递质水平,从而发挥抗抑郁效应。SERT、NET作为主流抗抑郁药物的作用靶标,了解其分布与功能、分子结构和活性调节因素,以及单胺重摄取抑制剂的作用机制对抗抑郁药物研发及应用具有重要意义。     

Nucleo-cytoplasmic transport of proteins as a target for therapeutic drugs

Recruitment of cytoplasmic signaling proteins into the nucleus is an essential step in the activation of gene expression in response to an extracellular signal. Nucleo-cytoplasmic transport of macromolecules is mediated by the transport receptors of an importin beta family. Post-translational modifications and masking/unmasking of specific signal sequences responsible for nuclear import and export are important for the coordinated control of the nucleo-cytoplasmic transport. Malfunctioning of the nucleo-cytoplasmic transport is profoundly involved in a number of diseases including cancer. Leptomycin B (LMB) is a Streptomyces metabolite that causes specific inhibition of the cell cycle of fission yeast and mammalian cells. The target molecule of LMB has been shown by genetic and biochemical analyses to be CRM1, a highly conserved protein in eukaryotes. CRM1 was shown to be a member of the importin beta family and a receptor for the nuclear export signal (NES) of proteins in both yeast and mammalian cells. LMB binds directly to CRM1, which results in dissociation of the NES from the nuclear export machinery containing CRM1. Thus, LMB serves as a potent tool for understanding the molecular mechanisms of nucleo-cytoplasmic transport of proteins and a potential therapeutic drug for diseases caused by mislocalization of regulatory proteins.     

Nuclear targeting of viral and non-viral DNA

The nuclear envelope presents a major barrier to transgene delivery and expression using a non-viral vector. Virus is capable of overcoming the barrier to deliver their genetic materials efficiently into the nucleus by virtue of the specialized protein components with the unique amino acid sequences recognizing cellular nuclear transport machinery. However, considering the safety issues in the clinical gene therapy for treating critical human diseases, non-viral systems are highly promising compared with their viral counterparts. This review summarizes the progress on exploring the nuclear traffic mechanisms for the prominent viral vectors and the technological innovations for the nuclear delivery of non-viral DNA by mimicking those natural processes evolved for the viruses as well as for many cellular proteins.     

Nuclear targeting of DNA.

The nuclear membrane is a tight barrier for cytoplasmic proteins, but nuclear proteins have the intrinsic ability to overcome this barrier by an active signal-mediated process. Specific cytoplasmic carrier proteins have the responsibility to escort these proteins into the nucleus through the nuclear pore. The nuclear membrane is also a tight barrier for exogenous DNA delivered by synthetic vehicles, while many of the karyophilic viruses have a mechanism to actively deliver their genome through the nuclear pore. Virus DNA and RNA cannot move into the nucleus by themselves and require the viral structural proteins for efficient nuclear transport. In this article, we review the recent progress in understanding the mechanism of the nuclear transport of proteins and the virus genome, and discuss the possibility of developing synthetic gene-delivery systems based on these outcomes.     

Controlling protein transport by small molecules

Many proteins are transported from the nucleus to the cytoplasm by the exportin CRM1, which recognizes cargo proteins through a leucine rich nuclear export signal (NES). This nuclear export process can be inhibited by several small molecules, both natural products and fully synthetic compounds. The structural basis for the inhibition of nuclear export by leptomycin (LMB) based on disruption of the protein/protein interaction between CRM1 and cargo proteins is discussed. The chemistry and inhibition of nucleocytoplasmic transport of leptomycin, anguinomycin and derivatives, goniothalamin, JBIR-02, valtrate, dihydrovaltrate, ACA, peumusolide A and several synthetic compounds is presented. Consequences for the design of nuclear export inhibitors are discussed, and the potential of these compounds as anticancer agents is evaluated.     

The kinetics of methotrexate distribution in spontaneous canine lymphosarcoma

A mathematical model is presented to simulate the time-dependent uptake of methotrexate in spontaneous canine lymphosarcomas in vivo.Blood flow rates in these tumors are high so that transport to the tumor is limited by cell membrane resistance. A significant amount of rapidly exchangeable methotrexate appears to exist in extracellular space loosely bound to proteins or cell membranes. Transmembrane drug transport follows Michaelis-Menten kinetics, with the maximum facilitated transport ranging from 0.002 to 0.007 g/min/ml for the separate tumors studied and a Michaelis constant for transport equal to 0.2 g/ml. This is in the range of Michaelis constants reported for normal tissues in rats in vivoand in several cell lines in vitro.     

The Complexities of Hepatic Drug Transport: Current Knowledge and Emerging Concepts

Recently, hepatic transport processes have been recognized as important determinants of drug disposition. Therefore, it is not surprising that characterization of the hepatic transport and biliary excretion properties of potential drug candidates is an important part of the drug development process. Such information also is useful in understanding alterations in the hepatobiliary disposition of compounds due to drug interactions or disease states. Basolateral transport systems are responsible for translocating molecules across the sinusoidal membrane, whereas active canalicular transport systems are responsible for the biliary excretion of drugs and metabolites. Several transport proteins involved in basolateral transport have been identified including the Na(+)-taurocholate co-transporting polypeptide [NTCP (SLC10A1)], organic anion transporting polypeptides [OATPs (SLCO family)], multidrug resistance-associated proteins [MRPs (ABCC family)], and organic anion and cation transporters [OATs, OCTs (SLC22A family)]. Canalicular transport is mediated predominantly via P-glycoprotein (ABCB1), MRP2 (ABCC2), the bile salt export pump [BSEP (ABCB11)], and the breast cancer resistance protein [BCRP (ABCG2)]. This review summarizes current knowledge regarding these hepatic basolateral and apical transport proteins in terms of substrate specificity, regulation by nuclear hormone receptors and intracellular signaling pathways, genetic differences, and role in drug interactions. Transport knockout models and other systems available for hepatobiliary transport studies also are discussed. This overview of hepatobiliary drug transport summarizes knowledge to date in this rapidly growing field and emphasizes the importance of understanding these fundamental processes in hepatic drug disposition.     

Drug Delivery and Transport to Solid Tumors

Purpose. The purpose of this review is to provide an overview of the principles of and barriers to drug transport and delivery to solid tumors. Methods. This review consists of four parts. Part I provides an overview of the differences in the vasculature in normal and tumor tissues, and the relationship between tumor vasculature and drug transport. Part II describes the determinants of transport of drugs and particles across tumor vasculature into surrounding tumor tissues. Part III discusses the determinants and barriers of drug transport, accumulation, and retention in tumors. Part IV summarizes the experimental approaches used to enhance drug delivery and transport in solid tumors. Results. Drug delivery to solid tumors consists of multiple processes, including transport via blood vessels, transvascular transport, and transport through interstitial spaces. These processes are dynamic and change with time and tumor properties and are affected by multiple physicochemical factors of a drug, multiple tumor biologic factors, and as a consequence of drug treatments. The biologic factors, in turn, have opposing effects on one or more processes in the delivery of drugs to solid tumors. Conclusion. The effectiveness of cancer therapy depends in part on adequate delivery of the therapeutic agents to tumor cells. A better understanding of the processes and contribution of these factors governing drug delivery may lead to new cancer therapeutic strategies.