Synergistic Effect of Hyperthermia and Neferine on Reverse Multidrug Resistance in Adriamycin-resistant SGC7901/ADM Gastric Cancer Cells

Multidrug resistance（MDR） plays a major obstacle to successful gastric cancer chemotherapy.The purpose of this study was to investigate the MDR reversal effect and mechanisms of hyperthermia in combination with neferine（Nef） in adriamycin（ADM） resistant human SGC7901/ADM gastric cancer cells.The MDR cells were heated at 42℃ and 45℃ for 30 min alone or combined with 10 μg/mL Nef.The cytotoxic effect of ADM was evaluated by MTT assay.Cellular plasma membrane lipid fluidity was detected by fluorescence polarization technique.Intracellular accumulation of ADM was monitored with high performance liquid chromatography.Mdr-1 mRNA,P-glycoprotein（P-gp）,γH2AX expression and γH2AX foci formation were determined by real-time PCR,Western blot and immunocytochemical staining respectively.It was found that different heating methods induced different cytotoxic effects.Water submerged hyperthermia had the strongest cytotoxicity of ADM and Nef combined with hyperthermia had a synergistic cytotoxicity of ADM in the MDR cells.The water submerged hyperthermia increased the cell membrane fluidity.Both water submerged hyperthermia and Nef increased the intracellular accumulation of ADM.The water submerged hyperthermia and Nef down-regulated the expression of mdr-1 mRNA and P-gp.The water submerged hyperthermia could damage DNA and increase the γH2AX expression of SGC7901/ADM cells.The higher temperature was,the worse effect was.Our results show that combined treatment of hyperthermia with Nef can synergistically reverse MDR in human SGC7901/ADM gastric cancer cells.

Breast cancer resistance protein(BCRP/ABCG2):its role in multidrug resistance and regulation of its gene expression

Breast cancer resistance protein(BCRP)/ATP-binding cassette subfamily G member 2(ABCG2) is an ATP-binding cassette(ABC) transporter identified as a molecular cause of multidrug resistance(MDR) in diverse cancer cells.BCRP physiologically functions as a part of a self-defense mechanism for the organism;it enhances elimination of toxic xenobiotic substances and harmful agents in the gut and biliary tract,as well as through the blood-brain,placental,and possibly blood-testis barriers.BCRP recognizes and transports numerous anticancer drugs including conventional chemotherapeutic and targeted small therapeutic molecules relatively new in clinical use.Thus,BCRP expression in cancer cells directly causes MDR by active efflux of anticancer drugs.Because BCRP is also known to be a stem cell marker,its expression in cancer cells could be a manifestation of metabolic and signaling pathways that confer multiple mechanisms of drug resistance,self-renewal(stemness),and invasiveness(aggressiveness),and thereby impart a poor prognosis.Therefore,blocking BCRP-mediated active efflux may provide a therapeutic benefit for cancers.Delineating the precise molecular mechanisms for BCRP gene expression may lead to identification of a novel molecular target to modulate BCRP-mediated MDR.Current evidence suggests that BCRP gene transcription is regulated by a number of trans-acting elements including hypoxia inducible factor 1α,estrogen receptor,and peroxisome proliferator-activated receptor.Furthermore,alternative promoter usage,demethylation of the BCRP promoter,and histone modification are likely associated with drug-induced BCRP overexpression in cancer cells.Finally,PI3K/AKT signaling may play a critical role in modulating BCRP function under a variety of conditions.These biological events seem involved in a complicated manner.Untangling the events would be an essential first step to developing a method to modulate BCRP function to aid patients with cancer.This review will present a synopsis of the impact of BCRP-mediated MDR in cancer cells,and the molecular mechanisms of acquired MDR currently postulated in a variety of human cancers.

Effects of Jianpi Jiedu Recipe (健脾解毒方)on Reversion of P-Glycoprotein-Mediated Multidrug Resistance through COX-2 Pathway in Colorectal Cancer

Objective： To evaluate the underlying mechanism of Jianpi Jiedu Recipe （健脾解毒方, JJR） in the reversion of multidrug resistance concerning colorectal cancer in vitro and in vivo. Methods： Mice were treated orally with JJR at a daily 4.25 g/（kg.day） or injected with vinblastine （VCR） 2.5 mg/（kg day） for 3 weeks after having been inoculated with HCT8N cells; tumor tissues were assayed by hematoxylin and eosin staining. Firstly, the effects of JJR on the expression of cyclooxygenase-2 （COX-2） were tested by real-time polymerase chain reaction （PCR） technique and COX-2 gene silenced by siRNA. Secondly, the variation of intracellular concentration of oxaliplatin （L-OHP） was evaluated by the inductively coupled plasma mass spectroscopy （ICP- MS） in HCT8N and its COX-2 siRNA cells; the concentration of J JR combined with chemotherapeutic drugs and the reverse effect of multidrug resistance （MDR） in HCT8N cells was evaluated by the MTT assay. Thirdly, real-time quantitative PCR and Western blot analysis were used to detect the multidrug resistance gene 1 （MDR1） mRNA and P-gp expression. Results： JJR had an inhibitory effect on the growth of tumors in vivo, and it, in combination with chemotherapeutic drugs, could reverse the drug-resistance of HCT8N cells and increase the sensitivity of HCT8N cells to VCR, DDP, 5-Fu, and THP. ICP-MS results showed that JJR could increase the concentration of drugs in HCT8/V cells （P〈0.01）. Furthermore, it was shown that JJR could reverse drug resistance of colorectal cancer cells by decreasing MDR1 expression and P-gp level via downregulation of COX-2, which has been represented as one of the major mechanisms that contributes to the MDR phenotype （P〈0.01）. Conclusion： JJR reversed multidrug resistance and enhanced the sensitivity to chemotherapy, which could be attributed to the down-regulation of COX-2 in MDRl/P-gp-mediated MDR colorectal cancer after chemotherapy.

The roles of the human ATP-binding cassette transporters P-glycoprotein and ABCG2 in multidrug resistance in cancer and at endogenous sites: future opportunities for structure-based drug design of inhibitors

The ATP-binding cassette(ABC)transporters P-glycoprotein(P-gp)and ABCG2 are multidrug transporters that confer drug resistance to numerous anti-cancer therapeutics in cell culture.These findings initially created great excitement in the medical oncology community,as inhibitors of these transporters held the promise of overcoming clinical multidrug resistance in cancer patients.However,clinical trials of P-gp and ABCG2 inhibitors in combination with cancer chemotherapeutics have not been successful due,in part,to flawed clinical trial designs resulting from an incomplete molecular understanding of the multifactorial basis of multidrug resistance(MDR)in the cancers examined.The field was also stymied by the lack of high-resolution structural information for P-gp and ABCG2 for use in the rational structure-based drug design of inhibitors.Recent advances in structural biology have led to numerous structures of both ABCG2 and P-gp that elucidated more clearly the mechanism of transport and the polyspecific nature of their substrate and inhibitor binding sites.These data should prove useful helpful for developing even more potent and specific inhibitors of both transporters.As such,although possible pharmacokinetic interactions would need to be evaluated,these inhibitors may show greater effectiveness in overcoming ABC-dependent multidrug resistance in combination with chemotherapeutics in carefully selected subsets of cancers.Another perhaps even more compelling use of these inhibitors may be in reversibly inhibiting endogenously expressed P-gp and ABCG2,which serve a protective role at various blood-tissue barriers.Inhibition of these transporters at sanctuary sites such as the brain and gut could lead to increased penetration by chemotherapeutics used to treat brain cancers or other brain disorders and increased oral bioavailability of these agents,respectively.

Environmentally responsive dual-targeting nanotheranostics for overcoming cancer multidrug resistance

The development of multiple drug resistance(MDR) to chemotherapy and subsequent treatment failures are major obstacles in cancer therapy. An attractive option for combating MDR is inhibiting the expression of P-glycoprotein(P-gp) in tumor cells. Here, we report a novel chemosensitizing agent, XMD8-92,which can down-regulate P-gp. To enhance the specificity of MDR chemotherapy, a promising nanotheranostic micelle system based on poly(ethylene glycol)-blocked-poly(L-leucine)(PEG-b-Leu) was developed to simultaneously carry the anticancer drug doxorubicin, chemosensitizing agent XMD8-92, and superparamagnetic iron oxide nanoparticles(SPIOs). Featured with MDR environmentally responsive dual-targeting capability, controllable drug delivery, and efficient magnetic resonance(MR) imaging characteristics, the prepared nanotheranostics(DXS@NPs) showed outstanding in vitro cytotoxicity on MDR cells(SCG 7901/VCR) with only 53% of cells surviving compared to 90% of DOX-treated cells.Furthermore, efficient tumor inhibition and highly reduced systemic toxicity were exhibited by MDR tumor-bearing mice treated with DXS@NPs. Overall, the environmentally responsive dual-targeting nanotheranostics represent a promising approach for overcoming cancer MDR.

Recent advances in the search of BCRP- and dual P-gp/BCRP-based multidrug resistance modulators

The development of multidrug resistance (MDR) is one of the major challenges to the success of chemotherapy treatment of cancer. This phenomenon is often associated with the overexpression of the ATP-binding cassette (ABC) transporters P-gp (P-glycoprotein, ABCB1), multidrug resistance-associated protein 1, ABCC1 and breast cancer resistance protein, ABCG2 (BCRP). These transporters are constitutively expressed in many tissues playing relevant protective roles by the regulation of the permeability of biological membranes, but they are also overexpressed in malignant tissues. P-gp is the first efflux transporter discovered to be involved in cancer drug resistance, and over the years, inhibitors of this pump have been disclosed to administer them in combination with chemotherapeutic agents. Three generations of inhibitors of P-gp have been examined in preclinical and clinical studies;however, these trials have largely failed to demonstrate that coadministration of pump inhibitors elicits an improvement in therapeutic efficacy of antitumor agents, although some of the latest compounds show better results. Therefore, new and innovative strategies, such as the fallback to natural products and the discover of dual activity ligands emerged as new perspectives. BCRP is the most recently ABC protein identified to be involved in multidrug resistance. It is overexpressed in several haematological and solid tumours together with P-gp, threatening the therapeutic effectiveness of different chemotherapeutic drugs. The chemistry of recently described BCRP inhibitors and dual P-gp/BCRP inhibitors, as well as their preliminary pharmacological evaluation are discussed, and the most recent advances concerning these kinds of MDR modulators are reviewed.

Screening potential P-glycoprotein inhibitors by combination of a detergent-free membrane protein extraction with surface plasmon resonance biosensor

P-glycoprotein(P-gp)highly expressed in cancer cells can lead to multidrug resistance(MDR)and the combination of anti-cancer drugs with P-gp inhibitor has been a promising strategy to reverse MDR in cancer treatment.In this study,we established a label-free and detergent-free system combining surface plasmon resonance(SPR)biosensor with styrene maleic acid(SMA)polymer membrane proteins(MPs)stabilization technology to screen potential P-gp inhibitors.First,P-gp was extracted from MCF-7/ADR cells using SMA polymer to form SMA liposomes(SMALPs).Following that,SMALPs were immobilized on an SPR biosensor chip to establish a P-gp inhibitor screening system,and the affinity between P-gp and small molecule ligand was determined.The methodological investigation proved that the screening system had good specificity and stability.Nine P-gp ligands were screened out from 50 natural products,and their affinity constants with P-gp were also determined.The in vitro cell verification experiments demonstrated that tetrandrine,fangchinoline,praeruptorin B,neobaicalein,and icariin could significantly increase the sensitivity of MCF-7/ADR cells to Adriamycin(Adr).Moreover,tetrandrine,praeruptorin B,and neobaicalein could reverse MDR in MCF-7/ADR cells by inhibiting the function of P-gp.This is the first time that SMALPs-based stabilization strategy was applied to SPR analysis system.SMA polymer can retain P-gp in the environment of natural lipid bilayer and thus maintain the correct conformation and physiological functions of P-gp.The developed system can quickly and accurately screen small molecule ligands of complex MPs and obtain affinity between complex MPs and small molecule ligands without protein purification.

The 150 most important questions in cancer research and clinical oncology series: questions 94-101

Since the beginning of 2017,Cancer Communications(former title:Chinese Journal of Cancer)has published a series of important questions regarding cancer research and clinical oncology,to provide an enhanced stimulus for can-cer research,and to accelerate collaborations between institutions and investigators.In this edition,the following 8 valuable questions are presented.Question 94.The origin of tumors:time for a new paradigm?Question 95.How can we accelerate the identification of biomarkers for the early detection of pancreatic ductal adenocarcinoma?Question 96.Can we improve the treatment outcomes of metastatic pancreatic ductal adenocarcinoma through precision medicine guided by a combination of the genetic and proteomic information of the tumor?Question 97.What are the parameters that determine a competent immune system that gives a complete response to cancers after immune induction?Question 98.Is high local concentration of metformin essential for its anti-cancer activity?Question 99.How can we monitor the emergence of cancer cells anywhere in the body through plasma testing?Question 100.Can phytochemicals be more specific and efficient at targeting P-glycoproteins to overcome multi-drug resistance in cancer cells?Question 101.Is cell migration a selectable trait in the natural evolution of carcinoma?

Overexpression of glucosylceramide synthase and its significance in the clinical outcome of non-small cell lung cancer

Background Glucosylceramide synthase （GCS）,an enzyme responsible for ceramide glycosylation,plays an important role in multidrug resistance （MDR） in some tumors in vitro; however,its expression and clinicopathological significance in non-small cell lung cancer （NSCLC） remains unclear.Methods We evaluated GCS expression in 116 paired tumor and adjacent non-cancerous tissues and 50 frozen tissues from patients with NSCLC using immunohistochemistry and western blotting,and explored the correlation between GCS and NSCLC clinicopathological characteristics and prognosis.We observed the association between GCS and the MDR proteins P-glycoprotein （P-gp） and lung resistance-related protein （LRP） to determine the link between GCS and MDR at the histological level.Results GCS expression was significantly upregulated in NSCLC tumors compared with non-cancerous tissue.There was high GCS expression in 75/116 tumor specimens （64.7％） and 16/116 non-cancerous specimens （13.8％）.High GCS expression was significantly associated with poor differentiation （P=0.01）,lymph node metastasis （P=0.004）,recurrence/ distant metastasis （P=0.006）,and chemotherapy resistance （P=0.025）.Multivariate analysis demonstrated that GCS immunopositivity was an independent risk factor for survival （P=0.018）.P-gp was expressed in 80/116 tumors （69.0％） and in 12/116 non-cancerous tissue specimens （10.3％; P=0.001）; LRP was expressed in 85/116 tumors （73.3％） and 19/116 non-cancerous tissue specimens （16.4％; P=0.001）.Importantly,the results demonstrated that increased GCS expression in NSCLC cancer specimens correlated with increased expression of P-gp and LRP,molecules known to stimulate cancer cell MDR （r=0.612 and 0.503,P=0.01 and 0.035,respectively）.Conclusion GCS upregulation might contribute to the development of NSCLC and could be a useful prognostic indicator and chemoresistance predictor for NSCLC patients.

Genomic stability at the coding regions of the multidrug transporter gene ABCB1: insights into the development of alternative drug resistance mechanisms in human leukemia cells

Aim:Despite considerable efforts to reverse clinical multidrug resistance(MDR),targeting the predominant multidrug transporter ABCB1/P-glycoprotein(P-gp)using small molecule inhibitors has been unsuccessful,possibly due to the emergence of alternative drug resistance mechanisms.However,the non-specific P-gp inhibitor cyclosporine(CsA)showed significant clinical benefits in patients with acute myeloid leukemia(AML),which likely represents the only proof-of-principle clinical trial using several generations of MDR inhibitors.Nevertheless,the mutational mechanisms that may underlie unsuccessful MDR modulation by CsA are not elucidated because of the absence of CsA-relevant cellular models.In this study,our aims were to establish CsA-resistant leukemia models and to examine the presence or absence of ABCB1 exonic mutations in these models as well as in diverse types of human cancer samples including AMLs.Methods:Drug-resistant lines were established by stepwise drug co-selection and characterized by drug sensitivity assay,rhodamine-123 accumulation,[3H]-labeled drug export,ABCB1 cDNA sequencing,and RNase protection assay.The genomic stability of the ABCB1 coding regions was evaluated by exome sequencing analysis of variant allele frequencies in human populations.Moreover,the mutational spectrum of ABCB1 was further assessed in diverse types of cancer samples including AMLs in the Cancer Genome Atlas(TCGA)at the National Cancer Institute.Results:We report the development of two erythroleukemia variants,RVC and RDC,which were derived by stepwise co-selection of K562/R7 drug-resistant leukemia cells with the etoposide-CsA and doxorubicin-CsA drug combinations,respectively.Interestingly,both RVC and RDC cell lines,which retained P-gp expression,showed altered multidrug-resistant phenotypes that were resistant to CsA modulation.Strikingly,no mutations were found in the ABCB1 coding regions in these variant cells even under long-term stringent drug selection.Genomically,ABCB1 displayed relatively low variant allele frequencies in human populations when compared with several ABC superfamily members.Moreover,ABCB1 also exhibited a very low mutational frequency in AMLs compared with all types of human cancer.In addition,we found that CsA played a role in undermining the selection of highly drug-resistant cells via induction of low-level and unstable drug resistance.Conclusion:Our data indicate that ABCB1 coding regions are genomically stable and relatively resistant to drug-induced mutations.Non-ABCB1 mutational mechanisms are responsible for the drug-resistant phenotypes in both RVC and RDC cell lines,which are also prevalent in clinical AML patients.Accordingly,we propose several relevant models that account for the development of alternative drug resistance mechanisms in the absence of ABCB1 mutations.

Bromocriptine enhances the uptake of^(99m)Tc-MIBI in patients with hepatocellular carcinoma

99mTc-methoxyisobutyl isonitrile （MIBI） is a suitable transport substrate for the multidrug resistance gene prod- uct P-glycoprotein （P-gp） and widely used for tumor imaging. Bromocriptine has been shown to inhibit the ATPase activity and the function of P-gp. We hypothesized that bromocriptine could promote the accumulation of MIBI by inhibiting P-gp activities, a feature that can be taken advantage of for enhancing 99mTc-MIBI imaging. In the cur- rent study, we sought to investigate whether bromocriptine enhanced the uptake of 99mTc-MIBI in hepatocellular carcinoma patients. Sixty primary hepatocellular carcinoma patients received 99mTc-MIBI single photon emission computer tomgraphy （SPECT） prior to surgery. 99mTc-MIBI SPECT was performed 15 and 120 min after injec- tion of 20 mCi 99mTc-MIBI, and early uptake, delayed uptake （L/Nd）, and washout rate （L/Nwr） of 99mTc-MIBI were obtained. In addition, a second 99mTc-MIBI SPECT was performed according to the same method 48 h after bromocriptine administration. We found that, prior to bromocriptine administration, significant MIBI uptake in tumor lesions was noted in only 10 （16.7%, 10/60） patients with hepatocellular carcinoma. No significant MIBI uptake was observed in the tumor lesions of the remaining 50 （83.3%, 50/60） hepatocellular carcinoma patients. Following bromocriptine administration, all the patients without apparent MIBI uptake demonstrated significant MIBI uptake on 99mTc-MIBI SPECT （P 〈 0.05）. Our findings indicate that bromocriptine enhances the uptake of 99mTc-MIBI in patients with hepatocellular carcinoma.

Preclinical studies of the triazolo[1,5-a]pyrimidine derivative WS-716 as a highly potent,specific and orally active P-glycoprotein(P-gp)inhibitor

Multidrug resistance(MDR) is the main cause of clinical treatment failure and poor prognosis in cancer. Targeting P-glycoprotein(P-gp) has been regarded as an effective strategy to overcome MDR. In this work, we reported our preclinical studies of the triazolo[1,5-a]pyrimidine-based compound WS-716 as a highly potent, specific, and orally active P-gp inhibitor. Through direct binding to P-gp,WS-716 inhibited efflux function of P-gp and specifically reversed P-gp-mediated MDR to paclitaxel(PTX) in multiple resistant cell lines, without changing its expression or subcellular localization. WS-716 and PTX synergistically inhibited formation of colony and 3D spheroid, induced apoptosis and cell cycle arrest at G2/M phase in resistant SW620/Ad300 cells. In addition, WS-716 displayed minimal effect on the drug-metabolizing enzyme cytochrome P4503A4(CYP3A4). Importantly, WS-716 increased sensitivity of both pre-clinically and clinically derived MDR tumors to PTX in vivo with the T/C value of 29.7% in patient-derived xenograft(PDX) models. Relative to PTX treatment alone, combination of WS-716 and PTX caused no obvious adverse reactions. Taken together, our preclinical studies revealed therapeutic promise of WS-716 against MDR cancer, the promising data warrant its further development for cancer therapy.

P-糖蛋白抑制剂的研究进展

介绍P 糖蛋白抑制剂的发展、P 糖蛋白抑制剂的特性及第二代和第三代抑制剂的临床应用现状。多药耐药是肿瘤化疗失败原因之一 ,其以P 糖蛋白的过度表达为特征 ,导致化疗药物从癌细胞中的外排增加 ,使疗效降低。因此有效抑制P 糖蛋白的活性可逆转肿瘤的多药耐药性。

PPIs抑制空泡型质子泵逆转胃癌化疗多药耐药

肿瘤多药耐药性影响着胃癌化疗的效果,肿瘤微环境变化与多药耐药密切相关,而酸化与缺氧是微环境的两大特征.肿瘤细胞内无氧酵解生成大量H+,但却仍能维持胞内中性pH环境,推测与调节肿瘤泌酸功能的空泡型质子泵密切相关.胞外pH值的酸化可活化胞内PI3K/Akt信号通路,活化mTOR,上调HIF-1α,进而促进P-gp及MRP1的表达产生胃癌化疗耐药.PPIs可能是通过抑制空泡型质子泵的表达,改变肿瘤微环境,影响PI3K/Akt/mTOR/HIF-1α信号通路而逆转胃癌化疗多药耐药.

Hsp90抑制剂WH-4对肝癌细胞株SK-HEP-1增殖、凋亡及耐药基因表达的影响观察

目的探讨Hsp90抑制剂WH-4对肝癌细胞SK-HEP-1增殖、凋亡及耐药基因表达的影响。方法将肝癌细胞SK-HEP-1随机分为A、B、C组,A组分别加入0.625、1.25、2.5、5、10μmol/L WH-4,B组分别加入0.625、1.25、2.5、5、10μmol/L 17-AAG,C组加入等量生理盐水,培养48 h后,采用MTT法测算各组肝癌细胞SK-HEP-1增殖抑制率,并计算IC 50。将肝癌细胞SK-HEP-1随机分为A1、B1、C1组,分别加入2.3μmol/L WH-4、2.6μmol/L 17-AAG及生理盐水,培养48 h后,采用BrdU法观察肝癌细胞SK-HEP-1增殖活性。将肝癌细胞SK-HEP-1随机分为A2、B2、C2组,分别加入2.25μmol/L WH-4、2.80μmol/L 17-AAG、生理盐水,培养48 h后,采用软琼脂平板实验检测肝癌细胞SK-HEP-1克隆形成率,流式细胞术检测肝癌细胞SK-HEP-1凋亡率,采用Western blotting法检测肝癌细胞SK-HEP-1凋亡蛋白Bcl2、Bax、Bcl-xL。将肝癌细胞SK-HEP-1随机分为A3、B3、C3组,分别加入2.30μmol/L WH-4、2.65μmol/L 17-AAG及生理盐水。培养48 h后,采用qPCR法检测耐药基因ABCB1、ABCG2。结果WH-4对肝癌细胞SK-HEP-1有抑制作用,且呈浓度依赖性(R 2=0.647(48h),P均<0.05),IC 50为(2.35±0.25)μmol/L。与C1组相比,A1、B1组SK-HEP-1绿色荧光减弱。A2、B2组克隆形成率相比,P<0.05。与B2组比较,A2组细胞凋亡率升高(t=0.342,P<0.05),Bax蛋白相对表达量升高,B淋巴细胞瘤-2基因及Bcl-xL蛋白相对表达量降低。A3组ABCB1、ABCG2基因相对表达量低于B3组(t分别为-8.88、-13.00,P均<0.05)。结论Hsp90抑制剂WH-4对肝癌细胞SK-HEP-1具有增殖抑制、诱导凋亡作用,同时可降低耐药基因的表达。

PI3K抑制剂对三阴性人乳腺癌细胞株MBA-MB-231/ADR的多药耐药逆转作用

目的探讨PI3K抑制剂对三阴性人乳腺癌细胞多药耐药的逆转作用及其与PI3K/Akt信号转导关系。方法采用MTT法测定三阴性乳腺癌细胞系MBA-MB-231及其多药耐药细胞株MBA-MB-231/ADR对经典化疗药物阿霉素的半数抑制浓度(IC50),以及MBA-MB-231/ADR细胞株在PI3K抑制剂LY294002给药前后对阿霉素的敏感性差异。Western Blot检测MDA-MB-231/ADR细胞株LY294002给药前后,P-Akt、Akt、IκBα、NF-κB、P-gp和cleaved-caspase-3表达水平差异。结果 1MBA-MB-231和耐药细胞株MBA-MB-231/ADR对阿霉素的IC50分别为(0.36±0.03)μmol/L和(16.77±1.57)μmol/L,耐药倍数为46.58倍。2LY294002给药后,耐药细胞株MBAMB-231/ADR对阿霉素的IC50降至(2.59±0.07)μmol/L,耐药倍数降至6.475,对药物敏感性显著增加。3耐药细胞株MBA-MB-231/ADR中PI3K/Akt和NF-κB通路被激活,细胞耐药相关蛋白P-gp处于高表达水平;LY294002处理之后,MBA-MB-231/ADR细胞中PI3K/Akt和NF-κB通路被抑制,P-gp表达水平下调,细胞凋亡相关的cleaved-caspase-3表达上调。结论 PI3K抑制剂LY294002能有效逆转耐药细胞株MBA-MB-231/ADR的耐药性,从而增强耐药细胞MBA-MB-231/ADR对化疗药物阿霉素的敏感性。该研究结果提示LY294002通过阻断PI3K/Akt通路抑制下游NF-κB通路的活化和P-gp表达上调,从而参与MBA-MB-231/ADR耐药性的逆转。

胃癌细胞多药耐药机制及耐药性逆转

中国胃癌的发病例数占全球总数的1／3。化疗是治疗胃癌的有效手段，但由于肿瘤细胞多药耐药性（MDR）的产生，化疗疗效往往不佳。深入探讨胃癌MDR产生机制，寻找有效低毒的多药耐药逆转剂，对提高化疗的有效性，延长患者的生存期有着重要的意义。从转运蛋白有关的耐药机制、酶系统有关的耐药机制、细胞凋亡与耐药、细胞因子等四方面肿瘤细胞MDR产生的机制做一简要综述。