THE CORRELATION BETWEEN THE EXPRESSION OF MULTIDRUG RESISTANCE RELATED GENE AND CELL APOPTOSIS AND CLINICAL SIGNIFICANCE IN NON-SMALL CELL LUNG CANCER

Objective: To explore the correlation and clinical significance between expression of MDR (multidrug resistance) related gene MRP, MDR1, C-erbB-2 and cell apoptosis in non-small cell lung cancer (NSCLC). Methods: RT-PCR, Immunohistochemistry were used to examine the expression of mRNA and protein in the MDR and apoptosis related gene. Apoptosis cells were assayed by Terminal deoxynucleotidyl transferase (TdT)- mediated biotin dUTP nick end-labeling (TUNEL). Results: The positive rates of MRP, MDR1, C-erbB-2, bc1-2, C-myc mRNA in 63 cases NSCLC were 81.0% (51/63), 38.1%(24/63), 47.6%(30/63), 65.1%(41/63), 76.2%(48/63) respectively. Their levels were higher than those of corresponding proteins (74.6%, 34.9%, 46.0%, 61.9%, 71.4%, respectively). The significant association was found between the mRNA level and the protein expression (r =+0.764, P<0.02). The C-myc expression in 2 cases adjacent and benign lung tissue were light positive, and another 3 cases were negative. The positive correlation were demonstrated between C-myc and C-erbB-2 (r=+0.547, p=0.001) as well as bcl-2 and C-erbB-2 (r =+0.486, p=0.023) in NSCLC. There is no any correlation among bcl-2, C-myc and MRP or MDR1. There exists inverse correlation between apoptotic index and bcl-2 (r = -0.587, p = 0.017), and no any correlation among apoptotic index and MRP or MDR1 or C-erbB-2 or C-myc. The average apoptotic index were higher in the effective chemotherapy group (27.2( 2.1, 30.5(1.8) than that in the non-effective chemotherapy group (9.4( 1.3, 12.6( 2.4) with adenocarcinoma and squamous cell carcinoma (p =0.01, p=0.004). The positive rates of bcl-2, MRP, C-erbB-2 expression in the effective chemotherapy group (31.8%, 40.9%, 22.7%, respectively) were lower than those in the non-effective chemotherapy group (77.4%, 90.3%, 67.7%, respectively) (p=0.036, p=0.012, p=0.01), but MDR1 and C-myc expression have no any significant difference (p=0.067, p=0.282). The median survival time in the patients with coexpression of more than three MDR and/or apoptosis related genes are shorter (8.6 months) than that in those patients with coexpression of less than three MDR and/or apoptosis related genes (15.5 months)(p=0.01). Conclusion: The multidrug resistance in NSCLC is not only related to many drug resistance genes, but also involved in cell apoptosis and apoptosis related gene expression. The coexpression of MDR and apoptosis related gene is related to the survival time.

Differential expression of breast cancer-resistance protein,lung resistance protein,and multidrug resistance protein 1 in retinas of streptozotocin-induced diabetic mice

AIM：To investigate the altering expression profiles of efflux transporters such as breast cancer-resistance protein（BCRP）,lung resistance protein（LRP）,and multidrug resistance protein 1（MDR1） at the inner blood-retinal barrier（BRB） during the development of early diabetic retinopathy（DR） and/or aging in mice.METHODS：Relative m RNA and protein expression profiles of these three efflux transporters in the retina during the development of early DR and/or aging in mice were examined.The differing expression profiles of Zonula occludens 1（ ZO-1） and vascular endothelial growth factor-A（ VEGFA） in the retina as well as the perfusion characterization of fluorescein isothiocyanate（FITC）-dextran and Evans blue were examined to evaluate the integrity of the inner BRB.RESULTS：There were significant alterations in these three efflux transporters＇ expression profiles in the m RNA and protein levels of the retina during the development of diabetes mellitus and/or aging.The development of early DR was confirmed by the expression profiles of ZO-1 and VEGFA in the retina as well as the compromised integrity of the inner BRB.CONCLUSION：The expression profiles of some efflux transporters such as BCRP,LRP,and MDR1 in mice retina during diabetic and/or aging conditions are tested,and the attenuated expression of BCRP,LRP,and MDR1 along with the breakdown of the inner BRB is found,which may be linked to the pathogenesis of early DR.

EXPRESSION OF MULTIDRUG RESISTANCE-ASSOCIATED PROTEIN (MRP) AND ITS RELATIONSHIP WITH CLINICOPATHOLOGICAL FACTORS IN NON-SMALL CELL LUNG CANCER

Objective: To investigate the relationship between the expression of multidrug resistance-associated protein (MRP) and clinicopathological factors and prognosis. Methods: The expression of MRP in 62 cases with non-small cell lung cancer (NSCLC) was detected using immunohistochemistry method. The expression of MRP in 30 cases of NSCLC and corresponding normal lung tissues were detected using immunohistochemistry and Western Blot. Results: this study of tumor tissues confirmed the plasma membrane and/or cytoplasm locations of MRP. There was apparent difference between normal lung tissues and NSCLC in MRP. The survival analysis of 62 NSCLC showed that the mean survival time of the patients with negative MRP expression was 69.8117.41 months and that of patients with positive MRP expression, 25.384.46 months. Log-rank test suggested that the difference between them was significant (P=0.0156). It was also found that in squamous cell lung cancer the statistically significant difference between the mean survival time of patients with positive MRP expression and those with negative MRP expression (P=0.0153). Multivariate Cox model analysis suggested that the survival time was significantly related to expression of MRP (P=0.035) and lymphatic metastasis (P=0.038). Conclusion: MRP expression in NSCLC is significantly higher compared with normal lung tissues. The mean survival time of patients with negative MRP was relative longer and expression of MRP was an independent factor for prognosis.

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.

Mechanism of Drug Resistance Identified in Human Lung Adenocarcinoma Cell Line SPC-A1 Selected for Resistance to Docetaxel

Objective： To investigate the mechanism of resistance to docetaxel in human lung cancer. Methods： Human lung carcinoma SPC-A1/Docetaxel cells were derived from parental SPC-A1 cells by continuous exposure to increasing concentration of docetaxel. The drug sensitivity was measured by MTT assay in vitro. The cDNA microarray identified a set of differentially expressed genes, and some genes were confirmed by RT-PCR. P-glycoprotein level was measured by flow cytometry analysis. Results： The results of drug sensitivity measured by MTT assay showed that SPC-A1/Docetaxel cells were 13.2-fold resistant to docetaxel and cross-resistant at varying levels to other drugs. The cDNA microarray results identified a set of differentially expressed genes, which showed 428 genes that were up-regulated and 506 genes that were down-regulated in SPC-A1/Docetaxel ceils, and some genes were confirmed by RT-PCR. Flow cytometry analysis suggests expression of P-glycoprotein （P-gp） was more abundant in SPC-A1/Docetaxel cells than in the parental cells and docetaxel selection reduces the apoptotic response. Conclusion： The results suggest that docetaxel selection led to changes in gene expression that contribute to the multidrug resistance phenotype.

Effects of arsenic trioxide on drug transporting molecules in multidrug resistance malignant neoplasma MR2 cell line

Objective： To study the effect of arsenic trioxide （As203） on the expression of drug transporting molecules in multidrug resistance malignant neoplasma acute promyelocytic leukemia （APL） MR2 cell line. Methods： MR2 resistant to alltrans retinoic acid （ATRA） and non-ATRA resistant APL cell line NB4 were used. Expressions of P-glycoprotein （Pgp）, multidrug resistance protein （MRP） and lung resistance-related protein （LRP） were detected by immunocytochemical assay. Results： The expression of Pgp was significantly higher in MR2（30%-40%） than that in NB4（10%-20%） （P 〈 0.001）, and the expression of MRP was also higher in MR2 （56.9 ± 3.4 - 21.2 ± 1.1） than that in NB4 （20.6 ± 5.3 - 16.7 ± 1.2） （P 〈 0.001）. As2O3 ranging from 0.5-2.0 μmol/L, could significantly decrease the expressions of Pgp and MRP. The expression of Pgp and MRP in MR.2 cell line were negatively correlated with the dose and duration of action of As2O3. Conclusion： Pgp and MRP may be the sensitive targets of As2O3 to overcome drug-resistance. ATRA might be the substrates of Pgp and MRP.

EXPRESSION OF BCRP GENE IN THE NORMAL LUNG TISSUE AND LUNG CANCER

Objective: To investigate the expression of novel multidrug resistance transporter (BCRP gene) from human MCF-7/AdrVp breast cancer cells in normal lung tissue and non-small lung cancer tissue. Methods: RNA was extracted immediately from fresh normal lung tissue and viable tumor tissue harvested from surgically resected specimens of non-small cell lung cancer patients. cDNA of BCRP gene was prepared by RT-PCR and was then amplified by PCR. cDNA products from those specimens were transferred to blotting membrane through electrophoresis and transferring technique and southern blot hybridization was eventually performed to detect the expression of BCRP gene. Results: RNA were extracted from 8 tumor tissue alone and 12 pairs of tumor tissue and normal lung tissue harvested from the same lung. Four patients’ RNA samples with poor quality due to degrading were discarded. cDNA products of BCRP gene were obtained by RT-PCR and were then amplified by PCR in the remain 16 patients’ RNA samples. Through southern blot hybridization, BCRP gene was found to be slightly expressed in various amounts in all normal lung tissue (10/10) and only in a half of tumor tissue samples (8/16). Conclusion: BCRP gene is slightly expressed in different amount in all normal lung tissue and only in a half of tumor tissue of non-small cell lung cancer patients. It is possible to induce it’s overexpression and to develop multidrug resistance during chemotherapy if using anthracycline anticancer drugs.

EXPRESSION AND SIGNIFICANCE OF C-erbB-2 IN THE TISSUES OF LUNG CANCER

Objective To elucidate the expression and clinical significance or C-erbB-2 in the tissue of lung cancer. Method Immunohistochemistry method was used to detect the protein expression or C-erbB-2 in lung can- cer tissue. Results The positive expression rate of C-erbB-2 protein in 38 cases or lung cancer was 53. 3% (21/38), which was higher than those in lung benign control group (P<0.001). The significant correlation were found between the protein level and tumor stage(r= +0. 64,P<0.02). The order was stage IV>stage Ⅲ>stage,Ⅱ>stage I. There was no correlation among protein expression or C-erhB-2 in various histological types of lung cancer (P>0.05 for all). Conclusion The positive expression rates of C-erbB-2 were significantly higher in lung cancer group than those in benign control group. There is significant correlation between C-erbB-2 expression and lung cancer stage. There is no correlation among protein expression of C-erbB-2 and histological types or lung cancer.

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.

Mechanism of multidrug resistance of human small cell lung cancer cell line H446/VP

Background Small cell lung cancer （SCLC） is the most aggressive form of lung cancer. This study aimed to investigate the mechanism of human small cell lung cancer cell line resistance to etoposide （VP-16）, H446NP. Methods The cell viability was measured by MTT assay. Immunocytochemistry, reverse transcription-polymerase chain reaction （RT-PCR） and Western blotting methods were used to detect the multidrug resistance gene （MDR1）, bcl-2, bax and the topoisomerase Ⅱ （TopoⅡ） expressions in H446 and H446NP cells after treated with or without VP-16. Results The 50% inhibition concentration （IC50） of VP-16 on H446 cells was 49 mg/L, and 836 mg/L was for H446NP cells. The expressions of MDR1 and bcl-2 were up-regulated, while the amounts of bax and Topo II were reduced in H446NP cells. After treated with 49 mg/L of VP-16, it showed that the drug could significantly inhibit bcl-2 and Topo fl expressions, and increase bax expression in H446 cells compared with that of H446NP cells. Conclusions The H446NP cell was stably resistant to VP-16. The decreased expression of Topo II was correlated with the H446NP multidrug resistance. The elevated expressions of MDR1, and the altered apoptotic pathways also played an important role in VP-16 induced multidrug resistance of SCLC.

Reversal of drug resistance of multidrug-resistant human lung cancer cells by an MDR1 ribozyme

MALIGNANT tumor is very harmful to human health, and the mortality is very high. About 50% of the patients with malignancy can be operated on, and the other 50% patients have to be treated with chemotherapy. Because tumors are mostly chemoresistant, chemotherapy for these patients often has no effect. The overexpression of MDR1 gene is very common in hu man malignant tumors, about 50% in previously untreated patients and more than 50% in previously treated patients for whom the tumor is resistant to the previous sensitive

小细胞肺癌耐药细胞的建立及生物学特性和多药耐药性鉴定

目的建立对顺铂与依托泊苷抵抗的小细胞肺癌(small cell lung cancer,SCLC)耐药细胞NCI-H446/EP,对其生物学特性和多药耐药性进行评价。方法裸鼠皮下接种SCLC NCI-H446细胞构建异种移植瘤体内模型,给予SCLC一线EP方案治疗,诱导体内耐药,剥离瘤组织体外培养获得耐药细胞。体外实验检测其耐药系数,细胞倍增时间,细胞周期分布,多药耐药基因(MDR1)、耐药相关蛋白的表达,体内验证其耐药性。结果NCI-H446成瘤裸鼠给予EP治疗,8周后产生获得性耐药,经分离培养获得耐药细胞株NCI-H446/EP。该细胞株对顺铂、依托泊苷、SN38和阿霉素的耐药系数分别是12.01、18.36、65.4和10.12。与亲本细胞相比,耐药细胞G 0/G 1期比例明显增加,G 2/M期细胞比例减少,倍增时间延长。耐药细胞MDR1在mRNA及蛋白水平均高于亲本细胞,在体内也具有耐药性。结论成功构建了SCLC耐药细胞株NCI-H446/EP,该细胞具有多药耐药的基本特征,可用于抗SCLC药物筛选及耐药机制的研究。

白介素37下调多药耐药基因-1逆转肺腺癌紫杉醇耐药的研究

目的 本研究旨在探究白介素37(IL-37)在抑制肺腺癌细胞多药耐药性方面的潜在作用,及其对于耐紫杉醇的A549/TAX细胞的影响。方法 通过细胞培养、处理程序、实时荧光定量PCR、Western blot分析和统计学分析等实验方法,系统研究了IL-37对耐紫杉醇A549/TAX细胞的影响。结果 紫杉醇明显抑制了A549和A549/TAX细胞的增殖,其中A549/TAX的耐药指数RI为16.88。100ng/mL的rhIL-37显著抑制了A549/TAX细胞的增殖。在紫杉醇和rhIL-37联合处理组,细胞增殖的抑制率显著高于仅用紫杉醇处理组(P<0.05)。此外,rhIL-37在24小时后显著抑制了A549/TAX细胞的迁移和侵袭。非细胞毒性浓度的rhIL-37也能显著抑制A549/TAX细胞的集落形成。经rhIL-37作用48小时后,A549/TAX细胞中MDR1的表达水平比对照组下降了约66%(P<0.05)。结论 IL-37与紫杉醇联合处理可有效抑制A549/TAX细胞的增殖、迁移和侵袭,同时通过降低MDR1基因的表达水平可能逆转细胞的耐药性,为IL-37在肺腺癌治疗中的潜在应用提供了实验依据。

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.

基于OCT2、MRP2探讨加味生脉饮对Lewis肺癌小鼠顺铂化疗的增效减毒机制

【目的】观察加味生脉饮对顺铂化疗Lewis肺癌小鼠有机阳离子转运体2(OCT2)、多药耐药相关蛋白2(MRP2)的影响,探讨其对Lewis肺癌小鼠顺铂化疗的增效减毒机制。【方法】采用腋窝皮下接种Lewis肺癌细胞(LLC)构建肺癌移植瘤小鼠模型,造模成功后随机分为对照组、顺铂组、联合组(顺铂联合加味生脉饮)和生脉饮组,每组7只小鼠,给药14 d。观察4组小鼠一般状态、肿瘤生长情况,肿瘤、肾脏组织病理学以及血清尿素氮(BUN)、肌酐(Cr)浓度。通过免疫组织化学染色(IHC)和Western Blot的方法检测OCT2、MRP2蛋白表达情况,并使用高效液相色谱串联质谱(HPLC-MS/MS)法测定肾脏和肿瘤组织中顺铂含量。【结果】(1)给药结束后,各组小鼠体质量均有下降,顺铂组下降幅度最大,顺铂组体质量变化显著高于联合组、生脉饮组(P<0.05),生脉饮组和联合组小鼠一般状态均优于对照组和顺铂组。(2)干预结束时,顺铂组肿瘤体积和质量小于生脉饮组和对照组,联合组肿瘤体积和质量显著小于顺铂组(P<0.05)。(3)组织病理学结果显示:生脉饮组、对照组肿瘤细胞结构清晰,细胞形态正常;顺铂组与联合组可见肿瘤细胞坏死,肿瘤细胞边缘模糊,联合组肿瘤细胞坏死面积更大。生脉饮组、对照组肾脏细胞形态正常;联合组肾脏细胞损伤较轻,无明显病变;顺铂组肾组织明显病变,肾小管上皮细胞边缘模糊。(4)顺铂组小鼠血清BUN、Cr水平显著高于其他3组(P<0.05)。(5)顺铂组肾脏组织OCT2表达相比对照组显著增加,联合组OCT2表达相比顺铂组显著降低(均P<0.05);顺铂组肿瘤组织MRP2表达相比对照组显著增加,联合组MRP2表达相比顺铂组显著降低(均P<0.05)。(6)联合组肿瘤组织中顺铂含量显著高于顺铂组,联合组肾脏组织中顺铂含量显著低于顺铂组(均P<0.05)。【结论】OCT2、MRP2在顺铂肾脏毒性与耐药性中起重要的调控作用,加味生脉饮可能通过抑制肾脏中OCT2与肿瘤细胞中MRP2的蛋白表达,降低了顺铂治疗的肾脏毒性,提高了顺铂的抗肿瘤效果。

Expression of multidrug resistance-related markers in primary neuroblastoma

Background Multidrug resistance is associated with a poor prognosis in various human cancers. However, the clinical significance of the expression of multidrug resistance-related markers in neuroblastoma is still on debate. In this study, the effect of the expression of p-glycoprotein (P-gp), multidrug resistance-associated protein (MRP), and lung resistance protein (LRP) in neuroblastoma was evaluated. Methods The streptavidin-biotin immunoperoxidase (SP) technique was used to evaluate the expression of P-gp, MRP, and LRP in 70 cases of untreated primary neuroblastoma. Results The frequencies of the expression of P-gp, MRP, and LRP were 61.4%, 38.6%, and 24.3%, respectively. A significant positive correlation was observed between P-gp and MRP expression (P=0.001), as well as between LRP and MRP expression (P=0.01). The rates of expression of P-gp and MRP were higher in tumors from patients aged greater than one year old than in tumors from patients aged less than 1 year old at time of diagnosis (P=0.01 and 0.018, respectively). MRP expression in tumors that had metastasized was significantly more frequent than in tumors that had not metastasized (P=0.015). The expression of all tested proteins showed a significant relationship with whether or not the tumor had differentiated (P=0.006, 0.000 or 0.001, respectively). MRP expression was significantly associated with a reduction in both median survival time and 2-year cumulative survival (P=0.02). By contrast, P-gp and MRP expression did not correlate with survival. According to Cox regression analysis, only the co-expression of P-gp and MRP had significant prognostic value (relative hazard, 3.513, P=0.033). Conclusions The intrinsic, multidrug resistance of neuroblastoma involves the combined effects of P-gp, MRP, and LRP. MRP expression may be an important factor determining prognosis in neuroblastoma.

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.

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.

大剂量三苯氧胺逆转对EP方案耐药的非小细胞肺癌

目的 研究大剂量三苯氧胺 (tamoxifen ,TAM)逆转治疗对鬼臼乙叉甙 顺铂 (EP)方案耐药 ,且P gp表达阳性的非小细胞肺癌。方法 41例对EP方案耐药 ,且P gp阳性的NSCLC患者随机分为二组 ,逆转组应用TAM 10 0mg ,2次 /日 ,第 1～ 5天 ,然后采用EP方案 ;对照组仅采用EP方案治疗。结果 逆转组CR 1例 ,PR 5例 ,NC 11例 ,PD 4例 ,有效率为 2 8.6% (6/2 1) ,中位生存期为 8.4月 ,1年生存率为 3 8.1% ;对照组NC 9例 ,PD 11例 ,有效率为 0 ,中位生存期为 4.6月 ,1年生存率为 3 5 .0 %。逆转组有效率明显高于对照组 (P =0 .0 12 1) ,中位生存期明显长于对照组 (P <0 .0 1)。逆转组P gp阴转率为 3 3 .3 % (7/2 1) ,对照组无阴转者。主要毒副反应为Ⅱ～Ⅲ度血液学毒性 ,Ⅳ度少见。消化道反应均为Ⅰ～Ⅱ度。两组间毒副反应比较均无显著差异 (P >0 .0 5 )。结论 大剂量三苯氧胺能逆转对EP方案耐药 ,且P gp表达阳性的非小细胞肺癌。

三氧化二砷逆转人肺腺癌A549/R细胞耐药及对GSTs表达的影响

目的探讨三氧化二砷(As2O3)对人肺腺癌A549/R细胞耐药的逆转及谷胱甘肽S-转移酶(GSTs)表达的变化。方法分别采用生化方法及RT-PCR方法检测GSTs活性及GST-πmRNA表达水平的变化。结果0.15μmol/LAs2O3可使A549/R细胞内阿霉素(ADM)浓度增加,其IC50值由原来的0.495μmol/L降低至0.217μmol/L,逆转倍数为2.3倍。耐药细胞中GSTs活性增高,GST-πmRNA呈过表达状态。不同浓度的As2O3作用后,GSTs活性下降(P<0.05),GST-πmRNA表达水平下调,呈浓度依赖性变化。结论As2O3可部分逆转A549/R细胞对ADM的耐药性,GST-π的改变参与其耐药机制。