Synergistic effects of the purine analog sulfinosine and curcumin on the multidrug resistant human non-small cell lung carcinoma cell line (NCI-H460/R)

Multidrug resistance (MDR) is the main obstacle to a successful chemotherapy of lung cancer. We tested the potential of sulfinosine and curcumin, alone and in combination, for modulating MDR in the human resistant, non-small cell lung carcinoma cell line (NCI-H460/R). First, we determined the mutational status of the p53 gene in NCI-H460/R cells by PCR-SSCP and DNA sequencing and identified mutations which could at least partially contribute to the development of the MDR phenotype. The effects of sulfinosine and curcumin were studied, both separately and in combination, at the level of cytotoxicity, cell cycle distribution and gene expression. Sulfinosine displayed dose-dependent growth inhibition in both resistant and control sensitive cell lines, whereas curcumin considerably inhibited their growth only at relatively high doses. When sulfinosine was combined with a low dose of curcumin the drugs exerted a synergistic cytotoxic effect in NCI-H460/R cells. The expression of MDR-related genes mdr1, gst-pi and topo IIalpha, was altered by sulfinosine and curcumin. The most pronounced effect was observed when the agents were applied together. Sulfinosine and curcumin caused perturbations in cell cycle distribution in the NCI-H460/R cell line. The combination of the two drugs induced a more pronounced cell cycle arrest in S and G(2)/M in NCI-H460/R cells. Our results show that sulfinosine and curcumin overcome MDR in non-small cell lung carcinoma cell line (NSCLC), especially in combination despite the presence of a mutated p53 gene.     

吉西他滨耐药细胞系H460/Gem及其亲代细胞NCI-H460之间的不同

Objective: To discuss the difference between multi-drug resistant cell line H460/Gem and its parental cell NCI-H460 on the basis of establishment of human gemcitabine-resistant cell line H460/Gem so as to elaborate the possible mech-anisms of gemcitabine resistance. Methods: Human gemcitabine-resistant non-small cell lung cancer cell line H460/Gem was established by 2/3 clinical serous peak concentration gemcitabine intermittent selection from its parental cell human large cell lung carcinoma cell line NCI-H460 which was sensitive to gemcitabine. During the course of inducement, we had monitored their morphology, checked their resistance indexes and resistant pedigree by MTT method, gathered their growth curves and calculated their doubling time, examined their DNA contents and cell cycles by FCM; at the same time, we had measured its expressions of P53, EGFR, c-erb-B-2, PTEN, PCNA, c-myc, VEGF, MDR-1, Bcl-2, nm23, MMP-9, TIMP-1, CD44v6 proteins via immunocytochemistry staining, RRM1 and ERCC1 mRNA by real-time fluorescent quantitative-PCR. Results: The resis-tance index of H460/Gem' cells (the deputy of cells in the process of inducement) to gemcitabine was 1.201, and the cell line also exhibited cross-resistance to paclitaxol, fluorouraci, etoposide, cisplatin and oxaliplatin, but kept sensitivity to vinorelbine and taxotere. The doubling time of H460/Gem' cells was longer and figures in G0-G1 phase was decreased than that of NCI-H460 cells. Compared with NCI-H460 cells, H460/Gem' cells had achieved TIMP-1 protein expression emerged, nm23 protein expression enhanced, VEGF and MMP-9 protein expressions reduced, and CD44v6, P53 protein expressions van-ished, but expressions of EGFR, c-erb-B-2, PTEN, PCNA, c-myc, MDR-1, Bcl-2 proteins and RRM1, ERCC1 mRNA changed trivially. The resistance index of H460/Gem cells to gemcitabine was 1.644, and the cell line also exhibited cross-resistance to fluorouraci, cisplatin and oxaliplatin, but kept sensitivity to paclitaxol, vinorelbine, taxotere, and etoposide. The doubling time of H460/Gem cells was longer and figures in G0-G1 phase was decreased than those of NCI-H460 cells. The farther studies indicated that, compared with NCI-H460 cells, the expressions of MDR-1, nm23 and Bcl-2 proteins in H460/Gem cells had been enhanced, c-erb-B-2 protein expression emerged, P53, MMP-9 and VEGR protein expression had been weakened, but the changes of PTEN, PCNA, c-myc, TIMP-1, EGFR, CD44v6 protein, RRM1 mRNA and ERCC1 mRNA expressions were trivial. Furthermore, compared with its parental cells, H460/Gem cells were mixed with giant cells of different sizes that were larger and more irregular. Conclusion: The human gemcitabine-resistant non-small cell lung cancer cell line H460/Gem had achieved multi-drug resistance and great changes of biological characters compared with its parental cells. And these changes possibly participated in the formation of multidrug resistance.     

吉西他滨耐药细胞系H460/Gem的建立及其生物学特性研究

目的:建立吉西他滨耐药细胞系H460/Gem,通过研究其生物学特性,初步从细胞水平分析其获得性耐药的可能机制。方法:以人肺大细胞癌细胞系NCI-H460为亲代细胞,采用"2/3临床血浆峰浓度间歇诱导"法,用吉西他滨进行诱导,建立耐吉西他滨的细胞亚系H460/Gem,把诱导过程中的细胞命名为H460/Gem。分别在诱导前、诱导过程中和诱导成功后的三个不同时间点,采用MTT法检测其耐药指数和对其他化疗药物的敏感性,使用倒置光学显微镜观察形态学特征,通过绘制生长曲线计算倍增时间,以流式细胞术分析细胞周期分布,以免疫细胞化学染色检测P53、EGFR、C-erbB-2、PTEN、PCNA、c-myc、VEGF、MDR-1、Bcl-2、nm23、MMP-9、TIMP-1和CD44v6蛋白的表达,采用实时荧光定量PCR法检测RRM1mRNA表达。结果:H460/Gem细胞对吉西他滨耐药指数为1.201时,对紫杉醇、氟尿嘧啶、依托泊甙、顺铂、奥沙利铂耐药,对长春瑞滨、多西他赛敏感;它的倍增时间(18.611小时)比NCI-H460细胞(16.731小时)稍延长,G0~G1期细胞减少(分别为51.56%和68.06%),VEGF、MMP-9表达减弱,失去CD44v6和P53表达,nm23表达增强,出现TIMP-1表达,EGFR、C-erbB-2、PTEN、PC-NA、c-myc、MDR-1、Bcl-2表达无变化,RRM1 mRNA的相对表达量有所减少(分别为0.1589和0.4510)。H460/Gem细胞对吉西他滨的耐药指数为1.644时,同时对氟尿嘧啶、顺铂和奥沙利铂耐药,而对紫杉醇、长春瑞滨、多西他赛和依托泊甙敏感,倍增时间(51.539小时)比NCI-H460细胞明显延长,G0~G1期细胞(57.23%)有所减少,MDR-1、nm23、Bcl-2表达增强,出现C-erbB-2表达,P53、MMP-9和VEGR表达减弱,PTEN、PCNA、c-myc、TIMP-1、EGFR和CD44v6表达无变化,RRM1 mRNA的相对表达量(0.3389)变化不大。与NCI-H460细胞相比,H460/Gem细胞逐渐呈现出如下形态学特征:形态不规则,大小不一,形态各异,且透光性减弱。结论:H460/Gem细胞的生物学特性较NCI-H460细胞发生了较大变化,其多药耐药性的发生与多种基因表达有关。     

Cytogenetic and phenotypic analysis of a human colon carcinoma cell line resistant to mitoxantrone

A human colon carcinoma cell line selected for a 21-fold resistance to mitoxantrone was cross-resistant to the anthracycline, doxorubicin, but not to the anthracene, bisantrene. A 2-fold resistance was observed with vinblastine, another drug associated with multidrug resistance. Net intracellular mitoxantrone and doxorubicin accumulation were decreased at 1 h for all dose levels in the resistant cell line compared to the sensitive cell line. Although the resistant cells were more resistant to mitoxantrone than doxorubicin, the net accumulation of mitoxantrone was only 19% less than the sensitive cell line; whereas doxorubicin accumulation was decreased by 49%. No significant difference between the sensitive and resistant cell lines was observed in the initial accumulation of mitoxantrone; however, the efflux of mitoxantrone was increased in the resistant cell line. Verapamil did not overcome the resistance to mitoxantrone and did not increase the net accumulation of drug. No alterations in the electrophoretic mobility of membrane proteins were observed. Using immunoblotting techniques, the resistant cell line did not express P-glycoprotein which is frequently observed for cells resistant to anthracycline antibiotics. Cytogenetic analysis showed a putative homogenously staining region on the short arm of chromosome 7 in the resistant cell line. The limited cross-resistant phenotype, lack of verapamil reversal, nondetection of P-glycoprotein, and cytogenetic evidence of gene amplification suggests the involvement of a novel drug-resistant gene associated with resistance to mitoxantrone.     

吉西他滨耐药的A549和NCI-H460细胞中耐药相关基因的表达和RRMl(-)37A/C基因多态性

目的 研究吉西他滨(Gem)耐药的A549和NCI-H460细胞中胞啶脱酰氨酶(CDA)、核糖核苷酸还原酶M1亚单位(RRMl)、10q丢失的与张力蛋白同源的磷酸酶基因(PTEN)、切除修复交叉互补基因1(ERCC1)和脱氧胞苷酸酶(dCK)的表达以及RRMl(-)37A/C基因多态性.方法 采用药物临床血浆峰浓度冲击与逐步增加剂量相结合的诱导方法,成功诱导抗Gem的细胞系A549/Gem和NCI-H460/Gem.在药物诱导前、诱导过程中和诱导成功后,采用实时荧光定量PCR法检测其CDA、RRM1、PTEN、ERCC1和dCKmRNA的表达,并对其RRM1(-)37位点进行基因分型.结果 A549/Gem和NCI-H460/Gem细胞在药物诱导过程中,耐药指数(RI)随诱导时间的延长分别升至163.228和181.684.但达到一定峰值后逐渐降低,直至产生稳定的耐药性,RI分别为115.297和129.783.RRM1、PTEN、ERCC1和CDA mRNA表达量随着对Gem耐受程度的变化增高和降低,而dCK mRNA表达变化不明显.RRM1(-)37等位基因野生型引物能扩增出诱导各阶段A549/Gem和NCI-H460/Gem细胞的基因组DNA,而突变型引物则不能,说明A549/Gem和NCI-H460/Gem细胞目前的基因型与其亲代细胞一样,仍均为野生型.结论 与亲代细胞比较,A549/Gem和NCI-H460/Gem细胞的CDA、RRM1、PTEN和ERCC1表达升高,dCK表达变化不明显;RRM1(-)37位点单核苷酸无突变,其基因型与亲代细胞一样为野生型.     

P-glycoprotein overexpression cannot explain the complete doxorubicin-resistance phenotype in rat glioblastoma cell lines.

We have associated pharmacological studies to a semi-quantitative evaluation of P-glycoprotein(s) expression, to establish if classical multidrug resistance (MDR) could account for the complete resistance phenotype exhibited by progressively doxorubicin-resistant rat glioblastoma cells. Three resistant variants (C6 0.001, C6 0.1 and C6 0.5) of the C6 glioblastoma cell line (C6 S) were selected by long-term culture in the presence of three concentrations of doxorubicin (0.001, 0.1 and 0.5 microgram.ml-1 respectively). The degree of doxorubicin resistance was respectively 7, 33 and 400, and all the cell variants were cross-resistant to m-AMSA, etoposide and vincristine. Doxorubicin incorporation was reduced similarly in all resistant cells, irrespective of the level of resistance. When exposed to their respective doxorubicin IC50, the 7-fold resistant cells had the same intracellular drug incorporation as the sensitive cells, whereas the 33-fold and 400-fold resistant cells could incorporate respectively 3.7 and 17 times more drug. The ratio of doxorubicin exposures required for 50% DNA synthesis inhibition and 50% growth inhibition was dependent on the degree of resistance; this ratio was 12.8 in C6 S, 11.6 in C6 0.001, 6.3 in C6 0.1 and 1.8 in C6 0.5. P-glycoprotein(s) overexpression was of the same magnitude as the resistance factor in variants C6 0.001 and C6 0.1, but was lower than resistance factor in variant C6 0.5. Reversal of drug incorporation by verapamil was complete in all resistant cell lines; however, reversal of doxorubicin cytotoxicity was complete only in the 7-fold resistant line and was only partial in the most resistant lines, which remained 10-fold and 20-fold resistant to doxorubicin. These results suggest that classical MDR was the first phenotype selected by doxorubicin in C6 0.001, whereas mechanism(s) of doxorubicin resistance other than classical MDR are added in the most resistant lines.     

肺癌细胞株APC基因启动子甲基化对其转录的影响

背景与目的:抑癌基因家族性腺瘤样结肠息肉病易感基因(adenomatous polyposis coli,APC)启动子区的高甲基化在很多肿瘤中被发现,与这些肿瘤的发生发展相关.本实验室在肺癌患者肿瘤组织中检测到APC甲基化率达47%,为了研究其在肺癌细胞株中的甲基化情况,并进一步了解甲基化对其转录的影响,本研究检测了3株肺癌细胞的抑癌基因APC启动子甲基化状态及其对该基因转录水平的影响.方法:提取3株肺癌细胞株(肺腺癌细胞株SPC-A1、小细胞肺癌细胞株NCI-H446、大细胞肺癌细胞株NCI-H460)的DNA,以经转甲基处理和未做处理的脐带血DNA为阳性、阴性对照,亚硫酸氢盐化学修饰后,用甲基化特异性基因扩增(methylation specific-polymerase chain reaction,MSP)和甲基化基因芯片对APC基因启动子1A CpG岛甲基化进行研究,并用实时荧光定量PCR(real time-polymerase chain reaction)技术,以Sybr-GreenⅠ为荧光染料,β-actin基因为内参照,检测mRNA转录;对甲基化阳性的NCI-H460细胞,分别用1、5、10、15 μmol/L的5'-杂氮-2'-脱氧胞嘧啶(5-aza-2-deoxycytidine,5-aza-dC)试剂进行脱甲基化,提取RNA,荧光定量检测其转录变化.结果:SPC-A1和NCI-H446细胞APC甲基化阴性,NCI-H460细胞APC甲基化阳性;甲基化芯片检测NCI-H460细胞在APC启动子1A 5个CpG位点均存在甲基化(687、707、714、719、726),SPC-A1和NCI-H446甲基化阴性,荧光定量结果NCI-H460的APC转录较SPC-A1和NCI-H446有明显的下降,仅为二者平均的30.04%;经5-aza-dC脱甲基化作用后,NCI-H460细胞的APC表达增加了约5～10倍,其中10 μmol/L浓度作用下,APC表达增加最多.结论:肺癌细胞株NCI-H460中存在APC基因高甲基化,5-aza-dC脱甲基化试剂可以激活其转录.     

Doxorubicin retention and chemoresistance in human mesothelioma cell lines

Eight cell lines were established from the pleural effusion of 4 patients with malignant mesothelioma. The most sensitive (FCCMES-4) and the most resistant (FCCMES-2) mesothelioma cell lines had IC₅₀ of 0.66 and 1.85 μM for doxorubicin in clonogenic assays, respectively. In comparison with murine leukemic P388 cells, mesothelioma cell lines were 7.5- to 21 -fold more resistant to doxorubicin. Co-incubation with verapamil significantly increased doxorubicin retention in one of the cell lines (FCCMES-2) expressing P-glycoprotein in 16.8% of the cells. These results indicate that doxorubicin resistance may be intrinsic in refractory mesothelioma patients and P-glycoprotein-mediated drug efflux may be involved in resistance of some of the mesotheliomas. © 1994 Wiley-Liss, Inc.     

Modulation of multidrug resistance-associated protein 1 (MRP1) by p53 mutant in Saos-2 cells

The p53 tumor suppressor gene is one of the most frequently mutated genes in human cancer and the mutation is correlated with a poor prognosis in cancer therapy. Upregulation of multidrug resistance-associated protein 1 (MRP1) and increase in drug resistance have been found to be induced by p53 mutation. Human osteosarcoma Saos-2 cells, a p53-null cell line, was transfected with p53 with mutations at codon 143 (V to A), 175 (R to H), 248 (R to W), 273 (R to H) and 281 (D to G). Among the different transfectants, overexpression (about 42-fold) of MRP1 was detected in p53-R175H cells. Furthermore, the p53-R175H cells were 2.5-fold more resistant to doxorubicin (DOX) and had a 4-fold greater DOX efflux rate than the control cells 1 h after DOX treatment. Transfection with antisense MRP1 oligonucleotides demonstrated a DOX sensitization effect (about 2-fold) in p53-R175H transfectants but not in control cells. In addition, transfection with antisense p53 oligonucleotides greatly suppressed MRP1 expression and reversed DOX resistance in p53-R175H cells but had no effect in control cells. The results suggested that p53-R175H might induce MRP1 expression and DOX resistance in cells.     

An increase in the expression of ribonucleotide reductase large subunit 1 is associated with gemcitabine resistance in non-small cell lung cancer cell lines

The mechanisms of resistance to the antimetabolite gemcitabine in non-small cell lung cancer have not been extensively evaluated. In this study, we report the generation of two gemcitabine-selected non-small cell lung cancer cell lines, H358-G200 and H460-G400. Expression profiling results indicated that there was evidence for changes in the expression of 134 genes in H358-G200 cells compared with its parental line, whereas H460-G400 cells exhibited 233 genes that appeared to be under- or overexpressed compared with H460 cells. However, only the increased expression of ribonucleotide reductase subunit 1 (RRM1), which appeared in both resistant cell lines, met predefined analysis criteria for genes to investigate further. Quantitative PCR analysis demonstrated H358-G200 cells had a greater than 125-fold increase in RRM1 RNA expression. Western blot analysis confirmed high levels of RRM1 protein in this line compared with the gemcitabine-sensitive parent. No significant change in the expression of RRM2 was observed in either cell line, although both gemcitabine-resistant cell lines had an approximate 3-fold increase in p53R2 protein. A partial revertant of H358-G200 cells had reduced levels of RRM1 protein (compared with G200 cells), without observed changes in RRM2 or p53R2. In vitro analyses of ribonucleotide reductase activity demonstrated that despite high levels of RRM1 protein, ribonucleotide reductase activity was not increased in H358-G200 cells when compared with parental cells. The cDNA encoding RRM1 from H358-G200 cells was cloned and sequenced but did not reveal the presence of any mutations. The results from this study indicate that the level of RRM1 may affect gemcitabine response. Furthermore, RRM1 may serve as a biomarker for gemcitabine response.     

Establishment and characterization of acquired resistance to the farnesyl protein transferase inhibitor R115777 in a human colon cancer cell line.

R115777 (Zarnestra) is a farnesyl protein transferase inhibitor currently undergoing worldwide clinical trials. As acquired drug resistance may limit the efficacy of the drug, a model of acquired resistance has been established in vitro by continuous drug exposure of the human colon cancer cell line KM12. A stably resistant cell line possessing 13-fold resistance to R115777 was generated. The resistant cells showed cross-resistance to another, structurally different farnesyl transferase inhibitor-277, but not to GGTI-298. A lack of cross-resistance was observed to a variety of other agents, which included clinically used drugs, such as doxorubicin, etoposide, cisplatin, and paclitaxel, as well as signal transduction blockers, such as the mitogen-activated protein/extracellular signal-regulated kinase kinase inhibitor UO126, the phosphatidylinositol 3'-kinase inhibitor LY294002, and the epidermal growth factor receptor tyrosine kinase inhibitor PD153035. Resistance did not appear to be related to differences in drug efflux pumps, such as P-glycoprotein or in drug accumulation. Total levels of farnesyl transferase protein subunits were similar in the parent and resistant cells, but, notably, the enzyme activity was markedly reduced in the resistant cell line compared with the parent cells. This was not because of a mutation in the enzyme or a difference in activation of the alpha-subunit of farnesyl transferase by phosphorylation. Hence, resistance to R115777 was generated; the mechanism of resistance in this model may be associated with the enzyme target of the inhibitor. The results suggest that the development of clinical resistance may occur with farnesyl protein transferase inhibitors.     

Reduced intracellular drug accumulation in the absence of P-glycoprotein (mdr1) overexpression in mitoxantrone-resistant human MCF-7 breast cancer cells.

A mitoxantrone-resistant human MCF-7 breast cancer subline (MCF/MX) which is approximately 4000-fold resistant to mitoxantrone was isolated by serial passage of the parental wild-type MCF-7 cells (MCF/WT) in stepwise increasing concentrations of drug. MCF/MX cells were also approximately 10-fold cross-resistant to doxorubicin and etoposide but were not cross-resistant to vinblastine. Intracellular accumulation of radiolabeled mitoxantrone was markedly reduced in MCF/MX cells relative to that in the drug-sensitive MCF/WT cells. This decrease in intracellular drug accumulation into MCF/MX cells was associated with enhanced drug efflux, which was reversed when cells were incubated in the presence of sodium azide and 2, 4-dinitrophenol, suggesting an energy-dependent process. Incubation of MCF/MX cells with verapamil did not affect either the accumulation of mitoxantrone or the level of resistance in these cells. Furthermore, RNase protection and Western blot analyses failed to detect the expression of the mdr1 RNA or P-glycoprotein, a drug efflux pump known to be associated with the development of multidrug resistance in vitro. However, a polyclonal antibody directed against a synthetic peptide corresponding to the putative ATP binding domain of P-glycoprotein reacted with two (M(r) 42,000 and 85,000) membrane proteins from MCF/MX cells which were not found in MCF/WT. Functional assays and Western blot analysis for topoisomerase II revealed no differences in topoisomerase II activity or protein levels in MCF/MX cells. Thus, resistance in this cell line is apparently associated with enhanced drug efflux involving a pathway distinct from the mdr1-encoded multidrug transporter P-glycoprotein.     

Cyclosporin A is a broad-spectrum multidrug resistance modulator.

PURPOSE: Overexpression of the multidrug resistance proteins P-glycoprotein (Pgp), multidrug resistance protein (MRP-1), breast cancer resistance protein (BCRP), and lung resistance protein (LRP) is associated with treatment failure in acute myeloid leukemia (AML) and other malignancies. The Pgp modulator cyclosporin A has shown clinical efficacy in AML, whereas its analogue PSC-833 has not. Cyclosporin A is known to also modulate MRP-1, and we hypothesized that broad-spectrum multidrug resistance modulation might contribute to its clinical efficacy. EXPERIMENTAL DESIGN: We studied the effects of cyclosporin A and PSC-833 on in vitro drug retention and cytotoxicity in resistant cell lines overexpressing Pgp, MRP-1, and BCRP and on nuclear-cytoplasmic drug distribution and cytotoxicity in cells overexpressing LRP. Cellular drug content was assessed by flow cytometry and nuclear-cytoplasmic drug distribution by confocal microscopy. RESULTS: Cyclosporin A enhanced retention of the substrate drug mitoxantrone in cells overexpressing Pgp (HL60/VCR), MRP-1 (HL60/ADR), and BCRP (8226/MR20, HEK-293 482R) and increased cytotoxicity 6-, 4-, 4-, and 3-fold, respectively. Moreover, cyclosporin A enhanced nuclear distribution of doxorubicin in 8226/MR20 cells, which also express LRP, and increased doxorubicin cytotoxicity 12-fold without an effect on cellular doxorubicin content, consistent with expression of wild-type BCRP, which does not efflux doxorubicin. Cyclosporin A also enhanced nuclear doxorubicin distribution in a second cell line with LRP overexpression, HT1080/DR4. PSC-833 enhanced mitoxantrone retention and cytotoxicity in cells overexpressing Pgp, but had no effect in cells overexpressing MRP-1, BCRP, or LRP. CONCLUSIONS: Cyclosporin A modulates Pgp, MRP-1, BCRP, and LRP, and this broad-spectrum activity may contribute to its clinical efficacy.     

Dipyridamole-mediated reversal of multidrug resistance in MRP over-expressing human lung carcinoma cells in vitro

Expression of the multidrug resistance-associated protein (MRP) is widespread in human malignancies, high levels are associated with poor prognosis and may be responsible for intrinsic and radiotherapy-induced chemoresistance. In this study, the nucleoside transport inhibitor, dipyridamole (DP), was investigated as a chemosensitiser of MRP. In growth inhibition assays MRP-overexpressing COR L23/R cells were 20 times more resistant to VP16 and doxorubicin compared with the parental COR L23/R human lung carcinoma cells. DP caused an approximately 8-fold sensitisation of the resistant cells and a 2-fold sensitisation of the parental cells. DP enhanced the accumulation of VP16 1.5 to 2-fold in the parental cells, but had only a modest effect on VP16 accumulation in the resistant cells. VP16 efflux was rapid in both cell lines. DP caused a modest and transient inhibition of the initial efflux in the resistant cells but not the parental cells. Incubation with DP caused a progressive decrease in GSH levels which was more rapid and profound in COR L23/R cells than in COR L23/P cells. Thus, chemosensitisation to VP16 by DP in MRP-overexpressing COR L23/R cells appears to be caused by depletion of cellular GSH rather than a direct effect of DP on MRP-mediated drug accumulation and efflux.     

Retention of activity by selected anthracyclines in a multidrug resistant human large cell lung carcinoma line without P-glycoprotein hyperexpression.

A subline (COR-L23/R) of the human large cell lung line [corrected] COR-L23, derived by in vivo exposure to doxorubicin, exhibits an unusual multidrug resistant (MDR) phenotype. This subline shows cross-resistance to daunorubicin, vincristine, colchicine and etoposide but does not express P-glycoprotein. Interestingly, COR-L23/R [corrected] shows little or no resistance to a range of structurally-modified analogues of doxorubicin comprising 9-alkyl and/or sugar modified anthracyclines. We have previously identified these same compounds as effective agents against P-glycoprotein-positive MDR cell lines. In contrast to typical MDR cell lines, COR-L23/R [corrected] shows only minimal chemosensitisation by verapamil and no collateral sensitivity to verapamil. Compared to the parental cell line, COR-L23/R [corrected] displays reduced accumulation of doxorubicin and daunorubicin. Accumulation defects were apparent only after 0.5-1 h of incubation of cells with these agents. The rate of daunorubicin efflux was shown to be enhanced by COR-L23/R [corrected] and this efflux was demonstrated to be energy-dependent. The use of anthracyclines which retain activity in MDR cells thus appears to be a valid approach for the circumvention of MDR, not only in cells which express P-glycoprotein, but also where defective drug accumulation is due to other mechanisms possibly involving an alternative multidrug transporter.     

青藤碱诱导肺癌NCI-H460细胞凋亡及其机制的实验研究

目的:探究青藤碱(SIN)诱导肺癌NCI-H460细胞凋亡的作用机制。方法:四甲基偶氮唑蓝(MTT)法测定SIN对肺癌NCI-H460细胞生长的影响;Western blot测定Bcl-2,Bax蛋白的表达;用SIN、PI3K/Akt和MAPK/ERK信号通路抑制剂干预NCI-H460细胞,流式细胞术检测细胞的凋亡率。结果:SIN对肺癌NCI-H460细胞生长有抑制作用,呈时间、浓度依赖性;SIN可以使NCI-H460细胞Bcl-2表达减低,Bax增强;SIN与PI3K/Akt和MAPK/ERK信号通路抑制剂联用后可协同增加NCI-H460细胞凋亡(P<0.05)。结论:SIN可以抑制肺癌NCI-H460细胞的生长,能改变其Bax,Bcl-2蛋白的表达,与PI3K/Akt和MAPK/ERK信号通路抑制剂联用可协同发挥促进肺癌细胞凋亡作用,可望成为新的肺癌治疗药物。     

Constitutive expression of the c-H-ras oncogene inhibits doxorubicin-induced apoptosis and promotes cell survival in a rhabdomyosarcoma cell line.

Drugs used in anti-cancer chemotherapy are thought to exert their cytotoxic action by induction of apoptosis. Genes have been identified which can mediate or modulate this drug-induced apoptosis, among which are c-myc, p53 and bcl-2. Since expression of oncogenic ras genes is a frequent observation in human cancer, we investigated the effects of the c-H-ras oncogene on anti-cancer drug-induced apoptosis. Apoptosis induced by a 2 h doxorubicin exposure was measured by in situ nick translation and flow cytometry in a rat cell line (R2T24) stably transfected with the c-H-ras oncogene and in a control cell line (R2NEO) transfected only with the antibiotic resistance gene neo. Both cell lines (R2T24 and R2NEO) had nearly identical growth characteristics, including cell doubling time, distribution over the cell cycle phases and plating efficiency in soft agar. Doxorubicin exposure of the R2NEO cells led to massive induction of apoptosis. In contrast, R2T24 cells, expressing the c-H-ras oncogene, showed significantly less apoptosis after doxorubicin incubation. Doxorubicin induced approximately 3- to 5-fold less cytotoxicity in the R2T24 cells than in the R2NEO cells, as determined by clonogenic assay in soft agar. No difference was observed in intracellular doxorubicin accumulation between the two cell lines, indicating that the classical, P-glycoprotein-mediated multidrug resistance phenotype is not involved in the observed differences in drug sensitivity. In conclusion, our data show that constitutive expression of the c-H-ras oncogene suppresses doxorubicin-induced apoptosis and promotes cell survival, suggesting that human tumours with ras oncogene expression might be less susceptible to doxorubicin treatment.     

体内培育S-180R阿霉素抗药细胞株遗传稳定性分子生物学证据

目的从分子水平阐明ＢＡＬＢ／ｃ小鼠体内阿霉素抗药细胞株Ｓ－１８０Ｒ遗传稳定性证据。方法采用流式细胞技术,ＤＮＡ、ＲＮＡ分子杂交和ＲＴ－ＰＣＲ对Ｓ－１８０Ｒ进行分析。结果Ｓ－１８０Ｒ抗药细胞排药能力比亲本细胞提高近１００倍,抗药细胞峰半峰宽与峰高比值由０．５６变为０．２３。Ｓ－１８０Ｒ抗药细胞ＤＮＡ出现多药耐药基因的显著扩增和转录,并可见拓扑异构酶基因的转录降低,但多药耐药相关蛋白基因转录未见增强。结论与两年前建系时相比,Ｓ－１８０Ｒ抗药细胞抗药倍数提高,抗药性更加均一,抗药机理是以多药耐药为主,拓扑异构酶Ⅱ为辅。Ｓ－１８０Ｒ小鼠腹水瘤抗阿霉素细胞株是理想的研究阿霉素抗药和抗药逆转剂的体内动物实验模型。