基因逆转肿瘤多药耐药的研究进展

化疗在恶性肿瘤的综合治疗中占有非常重要的地位,而耐药性是严重影响肿瘤病人化疗效果及生存的主要原因之一,其中多药耐药(multi-drug resistance,MDR)最具临床意义。多药耐药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。研究表明MDR是一个多阶段发展、多因素参与的复杂事件。逆转肿瘤多药耐药是目前肿瘤化疗的研究热点之一。近年随着基础科学研究的不断深入,基因逆转肿瘤多药耐药的研究已从分子水平上,定点、多位点阻断多药耐药基因的表达,已取得一些显著的进展。本文对肿瘤多药耐药机制以及逆转肿瘤多药耐药性的相关基因做一简要综述。     

新辅助化疗对骨肉瘤多药耐药相关蛋白表达的影响

目的:探讨不同新辅助化疗方案对多药耐药相关蛋白在骨肉瘤组织中表达的影响。方法:采用RP-PCR技术以及免疫组化技术检测48例骨肉瘤患者在不同新辅助化疗方案实施前后多药耐药相关蛋白在mRNA以及蛋白水平的表达变化。结果:在同一新辅助化疗方案实施前后以及不同新辅助化疗方案之间,肿瘤组织的多药耐药蛋白的mRNA及蛋白表达均无显著性差异。结论:不同新辅助化疗方案的实施对骨肉瘤多药耐药蛋白表达的影响有限,其多药耐药性可能主要决定于肿瘤本身,检测多药耐药蛋白的表达有利于制定个体化化疗方案。     

肿瘤多药耐药:机制及逆转剂

肿瘤细胞多药耐药性(multidrug resistance,MDR)的产生是临床上导致肿瘤化疗失败的主要原因之一,因此寻找高效低毒的MDR逆转剂已成为肿瘤药物开发领域的热点。MDR的作用机制主要包括P-糖蛋白、多药耐药相关蛋白、乳腺癌耐药蛋白、肺耐药相关蛋白等等。多药耐药逆转剂包括钙离子通道阻滞剂、维拉帕米及其衍生物等等。本文主要介绍了MDR的作用机制以及肿瘤多药耐药逆转剂的研究进展。     

骨肉瘤化疗多药耐药的分子机制及其逆转

目的：总结国内外对骨肉瘤化疗多药耐药的分子机制及相应逆转措施的研究进展;方法：应用PubMed及CNKI期刊全文数据库检索系统,以＂骨肉瘤、化疗多药耐药、机制、逆转＂等为关键词,检索2000-2011年的相关文献。纳入标准：1）骨肉瘤耐药相关的蛋白质、酶类及相关基因;2）各因素发挥作用的机制;3）相关的逆转措施。结果：骨肉瘤多药耐药是当今骨肉瘤化疗治疗的一大难题,多药耐药性即肿瘤细胞对一种抗肿瘤药物产生耐药性的同时,对其他结构和作用机制不同的多种药物产生交叉耐药性。其作用的发生是多种因素共同作用的结果。结论：与骨肉瘤化疗多药耐药相关的主要有P-糖蛋白,多药耐药相关蛋白,肺耐药蛋白,谷胱甘肽,拓扑异构酶,蛋白激酶C以及DNA损伤修复和细胞凋亡抑制等相关机制。而逆转措施主要通过抑制剂和基因疗法。     

质膜蛋白与肿瘤多药耐药现象

多药耐药(MDR)是影响肿瘤化疗效果的主要障碍,是由于在耐药细胞质膜上的一系列蛋白是使细胞免受有害因素的攻击。通过30年的研究．证实了肿瘤细胞逃逸化疗药物攻击的许多途径．很显然,多药耐药已经成为肿瘤阻碍各种化疗药物有效治疗的途径。因此．评价肿瘤多药耐药机制及其耐药程度,探讨新的逆转肿瘤多药耐药方法有助于提高化疗效果。本文就MDR中质膜蛋白的分子结构和表型、耐药机制及其逆转方法的研究进展进行综述。     

多药耐药基因与子宫颈癌化疗

肿瘤细胞对化疗药物产生多药耐药性是化疗失败的主要原因之一,肿瘤多药耐药的机制十分广泛,其中P-gp/mdrl介导的多药耐药是最经典的耐药机制.故本文就MDR1与宫颈癌化疗的关系进行回顾和总结.     

肿瘤多药耐药中的细胞色素P450

肿瘤化学治疗是目前抗肿瘤治疗最常用且最有效的方法,而在肿瘤化疗过程中出现的多药耐药现象,是导致治疗失败的主要原因.肿瘤多药耐药由多种机制共同作用而成,其中由酶类介导的多药耐药愈显重要.目前的研究发现,有多类细胞色素P450酶与肿瘤多药耐药的发生密切相关.本文着重对近年来有关细胞色素P450与肿瘤多药耐药的相关研究进行阐述,以期为肿瘤治疗提供一个新的方向.     

肿瘤耐药相关信号传导通路研究进展

<正>临床上,化疗在肿瘤治疗中占有重要地位,但化疗也易出现肿瘤细胞耐药现象。耐药分为原药耐药(PDR)和多药耐药(MDR),原药耐药为肿瘤细胞对已使用过的药物产生了耐药作用;而多药耐药是指肿瘤细胞在对一种化疗药物产生耐药后,出现对其他不同作用机制的药物也产生耐药。肿瘤细胞多药耐药是决定肿瘤患者化疗成功与否的关键。多药耐药已出现在多种肿瘤疾病,如乳腺癌、食管癌、鼻咽癌、     

纳米载药系统在肿瘤多药耐药中的应用

当今世界,肿瘤已经成为威胁人类健康的重大疾病。在肿瘤疾病中,化疗可控制肿瘤的生长和转移,增强放疗的疗效,是治疗肿瘤疾病的主要手段之一。而肿瘤多药耐药是影响化疗药物疗效、引起化疗失败的重要原因,影响肿瘤患者的治愈效果,降低生存率。如何提高化疗的疗效,延长肿瘤患者的寿命成为医学界的难题。纳米载药系统是生物医学领域研究的热点,相对于单一药物,纳米载药体现了许多优越性,具有良好的应用前景。纳米级颗粒更有利于药代动力学,这些纳米载药颗粒通过被动和主动的机制表现出在全身血液循环寿命延长,持续的药物释放动力,使其能更好的在肿瘤细胞中积累而发挥作用,提高化疗的疗效。本文综述了肿瘤多药耐药研究中主要的纳米载体以及它们在逆转多药耐药方面的应用,并展望载药系统的有更多更好的发展趋势。     

以P-糖蛋白为靶点的肿瘤多药耐药逆转剂

肿瘤的多药耐药性(multidrug resistance,MDR)是导致化疗失败的主要原因,因此寻找高效低毒的MDR逆转剂已成为肿瘤药物开发领域的热点。P-糖蛋白是引起多药耐药性产生的重要因素之一,也是目前肿瘤多药耐药逆转剂最重要的药物靶点。本文介绍了P-糖蛋白的结构、功能和作用机制,以及以P-糖蛋白为靶标的肿瘤多药耐药逆转剂的开发现状。     

The Involvement of Sphingolipids in Multidrug Resistance

Administration of most chemotherapeutic agents eventually results in the onset of apoptosis, despite the agents' variety in structure and molecular targets. Ceramide, the central molecule in cellular glycosphingolipid metabolism, has recently been identified as an important mediator of this process. Indeed, one of the events elicited by application of many cytotoxic drugs is an accumulation of this lipid. Treatment failure in cancer chemotherapy is largely attributable to multidrug resistance, in which tumor cells are typically cross-resistant to multiple chemotherapeutic agents. Different cellular mechanisms underlying this phenomenon have been described. Of these the drug efflux pump activity of P-glycoprotein and the multidrug resistance-associated proteins are the most extensively studied examples. Recently, an increased cellular capacity for ceramide glycosylation has been recognized as a novel multidrug resistance mechanism. Indeed, virtually all multidrug-resistant cells exhibit a deviating sphingolipid composition, most typically, increased levels of glucosylceramide. On the other hand, several direct molecular interactions between sphingolipids and drug efflux proteins have been described. Therefore, in addition to a role in the multidrug resistance phenotype by which ceramide accumulation and, thus, the onset of apoptosis are prevented, an indirect role for sphingolipids might be envisaged, by which the activity of these efflux proteins is modulated. In this review, we present an overview of the current understanding of the interesting relations that exist between sphingolipid metabolism and multidrug resistance. Received: 16 June 2000/Revised: 16 August 2000     

Modulation of Multidrug Resistance in Cancer Cells by Liposome Encapsulated Doxorubicin

Abstract

A major problem in the chemotherapy of solid tumors and hematologic malignancies is the intrinsic as well as acquired cross resistance to multiple chemotherapeutic agents. Recently, this type of multidrug resistance has been related to a gene, MDR1, and its gene product, p-glycoprotein, which functions as the efflux pump, prevents accumulation of drugs and alters their cytotoxicity. Many drug-resistant human tumors express the MDR1 gene and MDR1 RNA levels are elevated in many cancers that have not responded to chemotherapy. The same persistent observation has been made in recurrent tumors who have responded initially to chemotherapy.

Doxorubicin is one of the most important anticancer agent having significant single agent activity in a variety of cancer types and is now the cornerstone of some widely used combination regimens. Despite the clinical effectiveness of the drug, doxorubicin resistance that arises in malignant cells following repeated courses of treatment is the major problem in the clinical management of neoplastic diseases. Recently, extensive studies have demonstrated that liposome encapsulated doxorubicin effectively modulates the multidrug resistance phenotype in cancer cells by altering the function of p-glycoprotein. This modulation of MDR phenotype by liposomes has been demonstrated in vitro in human breast cancer cells, ovarian cancer cells, human promyelocytic leukemia cells and in human colon cancer cells and in vivo in transgenic mice transfected with a functional MDR1 gene. It appears liposomes can play an effective role as a new modality of treatment for human cancers which have become refractory to chemotherapy. An exciting area of research which soon will emerge will exploit the different binding sites on p-glycoprotein by using combination of liposomes with other pharmacological modulators of MDR to impart maximal overcoming of multidrug resistance in cancer patients.     

A multiple-targets alkaloid nuciferine overcomes paclitaxel-induced drug resistance in vitro and in vivo

ObjectiveMultidrug resistance (MDR) is the major barrier to the successful treatment of chemotherapy. Compounds from nature products working as MDR sensitizers provided new treatment strategies for chemo-resistant cancers patients.MethodsWe investigated the reversal effects of nuciferine (NF), an alkaloid from Nelumbo nucifera and Nymphaea caerulea, on the paclitaxel (PTX) resistance ABCB1-overexpressing cancer in vitro and in vivo, and explored the underlying mechanism by evaluating drug sensitivity, cell cycle perturbations, intracellular accumulation, function and protein expression of efflux transporters as well as molecular signaling involved in governing transporters expression and development of MDR in cancer.ResultsNF overcomes the resistance of chemotherapeutic agents included PTX, doxorubicin (DOX), docetaxel, and daunorubicin to HCT-8/T and A549/T cancer cells. Notably, NF suppressed the colony formation of MDR cells in vitro and the tumor growth in A549/T xenograft mice in vivo, which demonstrated a very strong synergetic cytotoxic effect between NF and PTX as combination index (CI) (CI<0.1) indicated. Furthermore, NF increased the intracellular accumulation of P-gp substrates included DOX and Rho123 in the MDR cells and inhibited verapamil-stimulated ATPase activity. Mechanistically, inhibition of PI3K/AKT/ERK pathways by NF suppressed the activation of Nrf2 and HIF-1α, and further reduced the expression of P-gp and BCRP, contributing to the sensitizing effects of NF against MDR in cancer.ConclusionThis novel finding provides a promising treatment strategy for overcoming MDR and improving the efficiency of chemotherapy by using a multiple-targets MDR sensitizer NF.     

Ascorbate promotes the cellular accumulation of doxorubicin and reverses the multidrug resistance in breast cancer cells by inducing ROS-dependent ATP depletion

Chemotherapy is the most effective strategy for the treatment of metastatic breast cancer. However, P-glycoprotein (P-gp)-mediated multidrug resistance severely limits the efficacy of chemotherapy and is a major cause of the failure during chemotherapeutic treatment. In this study, we investigated the anticancer effects of combining chemotherapeutic drugs with ascorbate (AA) in human breast cancer cells. We found that combined administration of AA can improve the sensitivity of both MCF-7 and doxorubicin (Dox)-resistant MCF-7/Adr cells to Dox in vitro and in vivo by a reactive oxygen species (ROS)-dependent mechanism. Further studies proved that AA can promote the accumulation of Dox in MCF-7/Adr cells when combined with doxorubicin. AA had no effect on the expression of P-gp at the mRNA and protein levels, but could decrease its activity as demonstrated by an obvious inhibition of efflux of P-gp substrate Rh 123. AA reduced ATP levels in both MCF-7 and MCF-7/Adr cells, and pretreating AA-stimulating cells with catalase completely rescued ATP levels. With ATP reduction, we observed an increased cellular calcium and the appearance of vacuoles and micropores on the cell surface, indicating the increased cell membrane permeability in AA-treated MCF-7/Adr cells. The above results suggest that AA could promote the cellular accumulation of doxorubicin by inducing ROS-dependent ATP depletion. Clinically, a combination of AA with doxorubicin would be a novel strategy for reversal of the multidrug resistance in human breast cancer cells during chemotherapy.     

Circulating MiR-125b as a marker predicting chemoresistance in breast cancer

Background

Chemotherapy is an important component in the treatment paradigm for breast cancers. However, the resistance of cancer cells to chemotherapeutic agents frequently results in the subsequent recurrence and metastasis. Identification of molecular markers to predict treatment outcome is therefore warranted. The aim of the present study was to evaluate whether expression of circulating microRNAs (miRNAs) can predict clinical outcome in breast cancer patients treated with adjuvant chemotherapy.

Methodology/Principal Findings

Circulating miRNAs in blood serum prior to treatment were determined by quantitative Real-Time PCR in 56 breast cancer patients with invasive ductal carcinoma and pre-operative neoadjuvant chemotherapy. Proliferating cell nuclear antigen (PCNA) immunostaining and TUNEL were performed in surgical samples to determine the effects of chemotherapy on cancer cell proliferation and apoptosis, respectively. Among the miRNAs tested, only miR-125b was significantly associated with therapeutic response, exhibiting higher expression level in non-responsive patients (n = 26, 46%; p = 0.008). In addition, breast cancers with high miR-125b expression had higher percentage of proliferating cells and lower percentage of apoptotic cells in the corresponding surgical specimens obtained after neoadjuvant chemotherapy. Increased resistance to anticancer drug was observed in vitro in breast cancer cells with ectopic miR-125b expression; conversely, reducing miR-125b level sensitized breast cancer cells to chemotherapy. Moreover, we demonstrated that the E2F3 was a direct target of miR-125b in breast cancer cells.

Conclusions/Significance

These data suggest that circulating miR-125b expression is associated with chemotherapeutic resistance of breast cancer. This finding has important implications in the development of targeted therapeutics for overcoming chemotherapeutic resistance in novel anti-cancer strategies.     

EGFR-mediated G1/S transition contributes to the multidrug resistance in breast cancer cells

Despite the improvement of strategies against cancer therapy, the multidrug resistance (MDR)is the critical problem for successful cancer therapy. Recurrent cancers after initial treatment with chemotherapy are generally refractory to second treatments with these anticancer therapies. Therefore, it is necessary to elucidate the therapy-resistant mechanism for development of effective therapeutic modalities against tumors. Here we demonstrate a phase-specific chemotherapy resistance due to epidermal growth factor receptor (EGFR) in human breast cancer cells. Thymidine-induced G1-arrested cultures showed upregulated chemosensitivity, whereas S-phase arrested cells were more resistant to chemotherapeutic agents. Overexpression of EGFR promoted the MDR phenotypes in breast cancer cells via accelerating the G1/S phase transition, whereas depletion of EGFR exerted the opposite effects. Furthermore, CyclinD1, a protein related to cell cycle, was demonstrated to be involved in above EGFR-mediated effects since EGFR increased the expression of CyclinD1, and the specific RNA interference against CyclinD1 could primarily abolish the EGFR-induced MDR phenotypes. These data provide new insights into the mode by which MDR breast cancers evade cytoxic attacks from chemotherapeutic agents and also suggest a role for EGFR-CyclinD1 axis in this process.     

Multidrug resistance in fungi

Antibiotic and synthetic chemotherapeutic resistance in pathogenic yeast becomes one of the biggest challenges for the modern chemotherapy. An increasing number of pathogenic yeast and filamentous fungi resistant to the action of the majority of currently used drugs is isolated in clinics nowadays. Among variety of the resistance mechanisms, the most dangerous grows to be the multidrug resistance. The most important mechanism of the multidrug resistance is the overexpression of membrane proteins participating in the active efflux of drugs out of the cells subjected to chemotherapy. Representatives of two classes of multidrug efflux transporters, ABC and MFS, have been identified in fungi. One of the most important strategies for overcome the phenomenon of multidrug resistance in pathogenic fungi, is the use of chemical compounds co-administrated with chemotherapeutics which are able to restore drug susceptibility in multidrug resistant cells. Mode of action of these chemical compounds may be very diverse, from the substrate competition, through the influence on the membrane fluidity, to the multidrug transporters activity modulation. This paper presents a review of the current knowledge on proteins contributing to fungal multidrug resistance and strategies for overcoming multidrug resistance by pharmacological intervention.     

Genes of multidrug resistance in haematological malignancies

Since the early 1970s, multiple drug resistance has been known to exist in cancer cells and is thought to be attributable to a membrane-bound, energy-dependent pump protein (P-glycoprotein [P-gp]) capable of extruding various related and unrelated chemotherapeutic drugs. The development of refractory disease in haematological malignancies is frequently associated with the expression of one or several multidrug resistance (MDR) genes. MDR1, multidrug resistance-associated protein (MRP) and lung-resistance protein (LRP) have been identified as important adverse prognostic factors. Recently it has become possible to reverse clinical MDR by blocking P-gp-mediated drug efflux. The potential relevance of these reversal agents of MDR as well as the potential new approaches to treat the refractory disease are discussed in this article. In addition, an array of different molecules and mechanisms by which resistant cells can escape the cytotoxic effect of anticancer drugs has now been identified. These molecules and mechanisms include apoptosis-related proteins and drug inactivation enzymes. Resistance to chemotherapy is believed to cause treatment failure in more than 50% patients. Clearly, if drug resistance could be overcome, the impact on survival would be highly significant. This review focuses on molecular mechanism of drug resistance in haematological malignancies with emphasis on molecules involved in MDR. In addition, it brings the survey of methods involved in determination of MDR, in particular P-gp/MDR1, MRP and LRP.     

Epigenetic Regulation of RIP3 Suppresses Necroptosis and Increases Resistance to Chemotherapy in NonSmall Cell Lung Cancer

INTRODUCTION: The efficacy of chemotherapeutic agents in killing cancer cells is mainly attributed to the induction of apoptosis. However, the tremendous efforts on enhancing apoptosis-related mechanisms have only moderately improved lung cancer chemotherapy, suggesting that other cell death mechanisms such as necroptosis could be involved. In this study, we investigated the role of the necroptosis pathway in the responsiveness of nonsmall cell lung cancer (NSCLC) to chemotherapy. METHODS: In vitro cell culture and in vivo xenograft tumor therapy models and clinical sample studies are combined in studying the role of necroptosis in chemotherapy and mechanism of necroptosis suppression involving RIP3 expression regulation. RESULTS: While chemotherapeutic drugs were able to induce necroptotic cell death, this pathway was suppressed in lung cancer cells at least partly through downregulation of RIP3 expression. Ectopic RIP3 expression significantly sensitized lung cancer cells to the cytotoxicity of anticancer drugs such as cisplatin, etoposide, vincristine, and adriamycin. In addition, RIP3 suppression was associated with RIP3 promoter methylation, and demethylation partly restored RIP3 expression and increased chemotherapeutic-induced necroptotic cell death. In a xenograft tumor therapy model, ectopic RIP3 expression significantly sensitized anticancer activity of cisplatin in vivo. Furthermore, lower RIP3 expression was associated with worse chemotherapy response in NSCLC patients. CONCLUSION: Our results indicate that the necroptosis pathway is suppressed in lung cancer through RIP3 promoter methylation, and reactivating this pathway should be exploited for improving lung cancer chemotherapy.     

Antitumor effects of MutT homolog 1 inhibitors in human bladder cancer cells

ABSTRACT

As standard second-line regimen has not been established for patients who are refractory to or relapse with cisplatin-based chemotherapy, an effective class of novel chemotherapeutic agents is needed for cisplatin-resistant bladder cancer. Recent publications reported that MutT homolog 1 (MTH1) inhibitors suppress tumor growth and induce impressive therapeutic responses in a variety of human cancer cells. Few studies investigated the cytotoxic effects of MTH1 inhibitors in human bladder cancer. Accordingly, we investigated the antitumor effects and the possible molecular mechanisms of MTH1 inhibitors in cisplatin-sensitive (T24) and – resistant (T24R2) human bladder cancer cell lines. These results suggest that TH588 or TH287 may induce cancer cell suppression by off-target effects such as alterations in the expression of apoptosis- and cell cycle-related proteins rather than MTH1 inhibition in cisplatin-sensitive and – resistant bladder cancer cells.

Abbreviations: MTH: MutT homolog; ROS: reactive oxygen species; CCK-8: cell counting kit-8; DCFH-DA: dichlorofluorescein diacetate; PARP: poly (ADP-ribose) polymerase