β-榄香烯乳剂逆转多药耐药细胞株MCF-7/ADM对阿霉素耐药性研究

目的：测定中药β-榄香烯乳剂对MCF-7/ADM细胞的无毒剂量,并检测此无毒剂量是否有逆转MCF-7/ADM细胞对化疗药物阿霉素（ADM）的多药耐药（multidrug resistance,MDR）性。方法：采用四甲基偶氮唑蓝（MTT）法测定药物的细胞毒性及耐药细胞逆转倍数;荧光分光光度法测定细胞内药物浓度。结果：无毒剂量的β-榄香烯乳剂(6μg/ml）能显著降低化疗药物ADM对乳腺癌耐药细胞株MCF-7/ADM细胞的IC50,明显增加耐药细胞内药物浓度。结论：初步研究表明β-榄香烯乳剂具有逆转MCF-7/ADM细胞MDR的作用。     

shRNA抑制c-fos表达对P-gp介导的乳腺癌多药耐药的影响

多药耐药(multidrug resistance,MDR)是导致化疗失败的重要原因,多药耐药基因(multidrug resistance gene,mdr1)产物P-糖蛋白(P-glycoprotein,P-gp)过表达是最主要的耐药机制。原癌基因c-fos在肿瘤MDR中的作用渐受重视。主要选用人乳腺癌敏感株MCF-7和阿霉素(adriamycin,ADR)筛选的、mdr1/P-gp高表达的耐药株MCF-7/ADR,探讨c-fos在P-gp介导的乳腺癌MDR中的作用。相对于MCF-7,c-fos在MCF-7/ADR高表达。采用shRNA法下调c-fos表达后,MCF-7/ADR对ADR的敏感性大大增强,且mdr1/P-gp表达减少、P-gp外排功能降低。c-fos表达下调可逆转对P-gp介导的乳腺癌MDR的实验结果,为c-fos成为逆转肿瘤耐药诊断和治疗的新靶标,对实现耐药乳腺癌的分子靶向治疗提供了理论基础。     

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。     

两种不同来源的绿色木霉降解木质纤维素研究

利用纤维素酶高产菌绿色木霉Trichoderma viride降解木质纤维素是实现废料资源化的重要手段。本研究选取来自不同生境的两株T. viride,分别以玉米秸秆和甘草药渣为基质,测定两者滤纸纤维素酶（filter paper cellulase,FPase）活性和还原糖产量。从时间、温度、水分、pH 4个方面比较两株T. viride的环境适应性和不同基质的差异性。结果表明,以玉米秸秆为基质,T. viride XJ最适初始料液比为1:4-1:5.5,T. viride AG最适初始料液比为1:5-1:5.5。初始料液比1:5.5时,T. viride AG产FPase活性显著高于T. viride XJ。两株T. viride最适发酵温度均为28℃,各温度处理下不同菌株间无显著差异。两株T. viride均表现为还原糖消耗。以甘草药渣为基质,T. viride XJ最适初始料液比为1:2-1:2.5,T. viride AG最适初始料液比为1:3-1:3.5。料液比高于1:3,T. viride AG产FPase活性显著高于T. viride XJ。T. viride AG最适发酵温度为28℃,T. viride XJ最适发酵温度为23-28℃。温度低于28℃,T. viride XJ产FPase活性显著高于T. viride AG。两株T. viride均表现为还原糖积累。两株T. viride最适初始pH均为6-7,最适发酵时间均为3d。最优发酵条件下FPase活性：T. viride AG>T. viride XJ。对T. viride产FPase诱导能力：甘草药渣>玉米秸秆。变差分解表明两株T. viride产FPase活性差异主要源于菌株对生境的生态适应。比较分析菌种来源、基质类型、环境条件对T. viride发酵效果的影响,将有助于该菌大规模应用性研究。     

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。     

核酸适配体介导的多药耐药性肿瘤的治疗

化疗是目前肿瘤治疗最常见的方法。然而,肿瘤细胞的多药耐药（multidrug resistance,MDR）常导致临床化疗失败及患者的死亡。因此,干预和逆转肿瘤多药耐药,提高化疗效果,对于肿瘤的治疗具有重要的意义。核酸适配体是一种短的单链寡核苷酸,通过折叠形成特定空间结构从而与靶标特异性结合。靶向肿瘤的核酸适配体可以选择性地将治疗性物质（抗癌药物,siRNA,miRNA）和药物载体递送至肿瘤中,对肿瘤进行靶向杀伤。利用核酸适配体靶向多药耐药性肿瘤,能够特异性干预甚至逆转肿瘤的多药耐药性。本文概述了核酸适配体介导的干预与逆转肿瘤多药耐药性的研究进展。     

HepG2/mdr1稳定细胞系的建立及特性研究

将已构建好的含有人多药耐药（multidrug resistance, MDR）全长基因的真核表达质粒pCI-neo-mdr1,应用脂质体导入人肝癌HepG2细胞,应用G418筛选出人肝癌多药耐药细胞株HepG2/mdr1。通过对HepG2/mdr1细胞形态学的观察和生物学特性的研究,成功地建立了高效、稳定的HepG2/mdr1细胞系;为深入研究肝癌的MDR及其逆转提供了理想的细胞模型,并为探索建立肝癌MDR细胞株提供新的方法和思路,同时为研究肝癌细胞胰岛素抵抗与MDR的关系提供了模型细胞。 将已构建好的含有人多药耐药（multidrug resistance, MDR）全长基因的真核表达质粒pCI-neo-mdr1,应用脂质体导入人肝癌HepG2细胞,应用G418筛选出人肝癌多药耐药细胞株HepG2/mdr1。通过对HepG2/mdr1细胞形态学的观察和生物学特性的研究,成功地建立了高效、稳定的HepG2/mdr1细胞系;为深入研究肝癌的MDR及其逆转提供了理想的细胞模型,并为探索建立肝癌MDR细胞株提供新的方法和思路,同时为研究肝癌细胞胰岛素抵抗与MDR的关系提供了模型细胞。     

低频脉冲电场逆转MCF-7/ADR对高三尖杉酯碱和长春新碱的耐药性

为了探讨低频脉冲电场对人乳腺癌多药耐药细胞系MCF-7/ADR耐药性的逆转作用及机制,采用MTT比色法检测MCF-7/ADR的耐药指数和耐药性的逆转倍数,荧光显微镜观察脉冲电场对MCF-7/ADR细胞内DiOC2(3)(P-gp的特异性荧光底物)积累和外排的影响。结果发现,在低频脉冲电场不影响MCF-7/ADR细胞生长的情况下,不同时间的电场作用均能逆转MCF-7/A的多药耐药,对高三尖杉酯碱(HHT)耐药性的逆转倍数在1.429～1.848之间,对长春新碱(VCR)耐药性的逆转倍数在1.473～2.090之间,45min电场作用的逆转效果最好,其次是30min电场作用。药物积累和外排实验结果表明,脉冲电场作用45min能使细胞内的DiOC2(3)积累明显增加,而30min电场作用能显著抑制DiOC2(3)的外排。促进药物积累和抑制其外排可能是脉冲电场逆转多药耐药的机制之一。     

高效木质素降解菌的筛选及其对玉米秸秆的降解效果

本研究利用愈创木酚和苯胺蓝固体培养基对菌株进行初筛,利用形态学和分子生物学对筛选出的菌株进行鉴定,以黄孢原毛平革菌Phanerochaete chrysosporium CGMCC 5.0776为对照,利用其对玉米秸秆进行预处理并测定木质素和纤维素的降解率,测定筛选菌株在预处理玉米秸秆过程中漆酶、锰过氧化物酶（manganese peroxidase,MnP）和木质素过氧化物酶（lignin peroxidase,LiP）活性。结果表明:利用愈创木酚和苯胺蓝固体培养基,从16株白腐真菌菌株中筛选出2株具有较高漆酶或MnP活性的菌株,鉴定其为桦栓孔菌Trametes betulina (L.) Pilát（ZT-153）和亚黑管孔菌Bjerkandera fumosa (Pers.) P. Karst.（ZT-307）,测定T. betulina ZT-153和B. fumosa ZT-307对玉米秸秆酸不溶木质素降解效率分别为13.60%和21.87%,较对照P. chrysosporium CGMCC 5.0776高1.58%和9.85%,对纤维素的降解率较低,分别为4.10%和4.50%。2株菌株在预处理玉米秸秆过程中,T. betulina ZT-153表现出漆酶和MnP活性,B. fumosa ZT-307只表现出LiP活性。其中B. fumosa ZT-307对玉米秸秆酸不溶木质素的降解效率最高,在秸秆资源的综合利用方面具有较好的潜力和应用前景。     

上皮细胞黏附分子增强细胞间紧密连接促进乳腺癌细胞耐药

乳腺癌是致死率很高的恶性肿瘤,由ABCG2 (ATP-binding cassette G2)介导的多药耐药(multidrug resistance,MDR)是导致其化疗失败的重要原因,探讨ABCG2介导的耐药机制并探寻其关键分子是当前亟待解决的难题。上皮细胞黏附分子(epithelial cell adhesion molecule,EpCAM)参与多种肿瘤耐药,且与乳腺癌MDR密切相关,但它在ABCG2介导的乳腺癌耐药中的作用尚未阐明。本研究目的在于探究EpCAM对于ABCG2介导的乳腺癌细胞的多药耐药的调节作用及其机制。CCK8细胞毒性结果证实,相对于人乳腺癌药物敏感株MCF-7,耐药株MCF-7/MX对米托蒽醌(mitoxantrone,MX)的耐药性显著增强;Western 印迹结果显示,与MCF-7相比,MCF-7/MX细胞中ABCG2高表达,EpCAM表达上调。siRNA法敲低MCF-7/MX细胞中EpCAM可下调其ABCG2表达,并恢复对MX的敏感性。倒置显微镜观察细胞形态,发现敲低EpCAM可减少MCF-7/MX细胞间连接。免疫荧光双染法观察到EpCAM与密封蛋白1(claudin 1)在MCF-7/MX细胞共定位;进一步Western 印迹结果表明,敲低EpCAM减少MCF-7/MX细胞中密封蛋白1表达。综上所述,EpCAM可能通过与密封蛋白1相互作用,增强细胞间紧密连接,促进ABCG2介导的乳腺癌多药耐药。     

Chloride channel-3 mediates multidrug resistance of cancer by upregulating P-glycoprotein expression

Chloride channel-3 (ClC-3), a member of the ClC family of voltage-gated Cl⁻ channels, is involved in the resistance of tumor cells to chemotherapeutic drugs. Here, we report a new mechanism for ClC-3 in mediating multidrug resistance (MDR). ClC-3 was highly expressed in the P-glycoprotein (P-gp)-dependent human lung adenocarcinoma cell line (A549)/paclitaxel (PTX) and the human breast carcinoma cell line (MCF-7)/doxorubicin (DOX) resistant cells. Changes in the ClC-3 expression resulted in the development of drug resistance in formerly drug-sensitive A549 or MCF-7 cells, and drug sensitivity in formerly drug-resistant A549/Taxol and MCF-7/DOX cells. Double transgenic MMTV-PyMT/CLCN3 mice with spontaneous mammary cancer and ClC-3 overexpression demonstrated drug resistance to PTX and DOX. ClC-3 expression upregulated the expression of MDR1 messenger RNA and P-gp by activating the nuclear factor-κB (NF-κB)-signaling pathway. These data suggest that ClC-3 expression in cancer cells induces MDR by upregulating NF-κB-signaling-dependent P-gp expression involving another new mechanism for ClC-3 in the development of drug resistance of cancers.     

抗肿瘤多药耐药纳米粒的制备及其对MCF-7/ADR 细胞的体外评价

目的:肿瘤的多药耐药现象会显著降低肿瘤细胞内药物浓度,本研究通过制备抗肿瘤多药耐药的靶向给药系统来逆转肿瘤的耐药性以提升细胞对药物的敏感性,从而降低该现象对癌症治疗的阻碍。方法:本文使用乳化溶剂挥发法制备以含姜黄素两亲性嵌段共聚物载体、以紫杉醇和磁性粒为核心的抗肿瘤多药耐药纳米粒,使用透射电镜和动态粒径散射仪等对纳米粒进行表征和磁响应性测试后,使用MTT法测定纳米粒对肿瘤耐药细胞MCF-7/ADR的抑制率以探究给药系统的耐药逆转性能。结果:制备的抗肿瘤多耐药纳米粒粒径为105 nm左右,磁响应性良好。所制得载紫杉醇纳米粒包封率为74.74%,载药率为12.40%。纳米粒可以通过磁场和生物素受体介导作用促进肿瘤细胞对粒子的内化,以增加抗癌药物的蓄积。与游离紫杉醇相比,逆转细胞耐药指数达8.5。结论:纳米系统在维持自身稳定性同时,能够凭借协同作用和靶向作用较大程度提升药物对耐药肿瘤细胞的杀伤效果。     

Functionalized Graphene Oxide Mediated Adriamycin Delivery and miR-21 Gene Silencing to Overcome Tumor Multidrug Resistance In Vitro

Multidrug resistance (MDR) is a major impediment to successful cancer chemotherapy. Co-delivery of novel MDR-reversing agents and anticancer drugs to cancer cells holds great promise for cancer treatment. MicroRNA-21 (miR-21) overexpression is associated with the development and progression of MDR in breast cancer, and it is emerging as a novel and promising MDR-reversing target. In this study, a multifunctional nanocomplex, composed of polyethylenimine (PEI)/poly(sodium 4-styrenesulfonates) (PSS)/graphene oxide (GO) and termed PPG, was prepared using the layer-by-layer assembly method to evaluate the reversal effects of PPG as a carrier for adriamycin (ADR) along with miR-21 targeted siRNA (anti-miR-21) in cancer drug resistance. ADR was firstly loaded onto the PPG surface (PPG_ADR) by physical mixing and anti-miR-21 was sequentially loaded onto PPG_ADR through electric absorption to form ^anti-miR-21PPG_ADR. Cell experiments showed that PPG significantly enhanced the accumulation of ADR in MCF-7/ADR cells (an ADR resistant breast cancer cell line) and exhibited much higher cytotoxicity than free ADR, suggesting that PPG could effectively reverse ADR resistance of MCF-7/ADR. Furthermore, the enhanced therapeutic efficacy of PPG could be correlated with effective silencing of miR-21 and with increased accumulation of ADR in drug-resistant tumor cells. The endocytosis study confirmed that PPG could effectively carry drug molecules into cells via the caveolae and clathrin-mediated endocytosis pathways. These results suggest that this PPG could be a potential and efficient non-viral vector for reversing MDR, and the strategy of combining anticancer drugs with miRNA therapy to overcome MDR could be an attractive approach in cancer treatment.     

Specific reversal of multidrug resistance to colchicine in CEM/VLB100 cells by Gynostemma pentaphyllum extract

P-glycoprotein (P-gp)-mediated multiple drug resistance (MDR) is perhaps the most thoroughly studied cellular mechanism of cytotoxic drug resistance. Its efflux function can be circumvented by a wide range of pharmacological agents in vitro and in vivo. Most of these agents are pharmaceuticals used clinically for conditions other than cancer. However, their use in alleviating MDR is limited because the concentrations required for inhibition of the pump surpass their dose-limiting toxicity. The aim of this research is to study the role of gypenosides, isolated from Gynostemma pentaphyllum, as modulators of P-gp-mediated MDR in tumor cells, at both cellular and plasma membrane level. In the presence of total gypenoside preparation (0.1 mg/ml), an approximately 15-fold reversal of colchicine (COL) resistance was observed in P-gp-overexpressed CEM/VLB₁₀₀ cells. However, the gypenoside sample showed no reversal effect in cells treated with vinblastine and taxol. A purified gypenoside sample (gypenoside fraction 100) exhibited even more significant reversal of COL resistance (42-fold) in the CEM/VLB₁₀₀ cells. Further examination of the reversal effect of fraction 100 in membrane vesicles derived from CEM/VLB₁₀₀ cells using the continuous fluorescence method found that gypenoside fraction 100 at 0.1 mg/ml completely abolished the transport of fluorescein–COL.     

Systematic expression analysis of genes related to multidrug-resistance in isogenic docetaxel- and adriamycin-resistant breast cancer cell lines

Docetaxel (Doc) and adriamycin (Adr) are two of the most effective chemotherapeutic agents in the treatment of breast cancer. However, their efficacy is often limited by the emergence of multidrug resistance (MDR). The purpose of this study was to investigate MDR mechanisms through analyzing systematically the expression changes of genes related to MDR in the induction process of isogenic drug resistant MCF-7 cell lines. Isogenic resistant sublines selected at 100 and 200 nM Doc (MCF-7/100 nM Doc and MCF-7/200 nM Doc) or at 500 and 1,500 nM Adr (MCF-7/500 nM Adr and MCF-7/1,500 nM) were developed from human breast cancer parental cell line MCF-7, by exposing MCF-7 to gradually increasing concentrations of Doc or Adr in vitro. Cell growth curve, flow cytometry and MTT cytotoxicity assay were preformed to evaluate the MDR characteristics developed in the sublines. Some key genes on the pathways related to drug resistance (including drug-transporters: MDR1, MRP1 and BCRP; drug metabolizing-enzymes: CYP3A4 and glutathione S-transferases (GST) pi; target genes: topoisomerase II (TopoIIα) and Tubb3; apoptosis genes: Bcl-2 and Bax) were analyzed at RNA and protein expression levels by real time RT-qPCR and western blot, respectively. Compared to MCF-7/S (30.6 h), cell doubling time of MCF-7/Doc (41.6 h) and MCF-7/Adr (33.8 h) were both prolonged, and the cell proportion of resistant sublines in G1/G2 phase increased while that in S-phase decreased. MCF-7/100 nM Doc and MCF-7/200 nM Doc was 22- and 37-fold resistant to Doc, 18- and 32-fold to Adr, respectively. MCF-7/500 nM Adr and MCF-7/1,500 nM Adr was 61- and 274-fold resistant to Adr, three and 12-fold to Doc, respectively. Meantime, they also showed cross-resistance to the other anticancer drugs in different degrees. Compared to MCF-7/S, RT-qPCR and Western blot results revealed that the expression of MDR1, MRP1, BCRP, Tubb3 and Bcl-2 were elevated in both MCF-7/Doc and MCF-7/Adr, and TopoIIα, Bax were down-regulated in both the sublines, while CYP3A4, GST pi were increased only in MCF-7/Doc and MCF-7/Adr respectively. Furthermore, the changes above were dose-dependent. The established MCF-7/Doc or MCF-7/Adr has the typical MDR characteristics, which can be used as the models for resistance mechanism study. The acquired process of MCF-7/S resistance to Doc or Adr is gradual, and is complicated with the various pathways involved in. There are some common resistant mechanisms as well as own drug-specific changes between both the sublines.