Association of genomic imbalances with drug resistance and thermoresistance in human gastric carcinoma cells

Therapy resistance is the major obstacle to advances in successful cancer treatment. To characterize chromosomal alterations associated with different types of acquired MDR and thermoresistance, we applied CGH to compare a unique panel of human gastric carcinoma cells consisting of the parental, drug-sensitive and thermosensitive cancer cell line EPG85-257P, the atypical MDR variant EPG85-257RNOV, the classical MDR subline EPG85-257RDB and their thermoresistant counterparts EPG85-257P-TR, EPG85-257RNOV-TR and EPG85-257RDB-TR. CGH with genomic DNA prepared from these cell lines as probes successfully identified genomic gains and/or losses in chromosomal regions encoding putative genes associated with drug resistance and/or thermoresistance. These genes included various members of the families of ABC transporters and molecular chaperones. The importance of these cell variant-specific genomic imbalances in the development of MDR and thermoresistance is discussed and remains to be elucidated.     

High antineoplastic activity of new heterocyclic compounds in cancer cells with resistance against classical DNA topoisomerase II-targeting drugs

Twenty previously synthesized fused heterocyclic DNA-topoisomerase II (Topo II)-inhibiting compounds were investigated for their potential efficacy in various human cancer cell lines that were derived from different tumor entities. Moreover, different multidrug-resistant variants of these cancer cell lines with decreased Topo II expression were investigated. In parental, drug-sensitive cells merely the compounds BD3 and G35 showed efficacies, in terms of microM, which were similar to that of the classical Topo II inhibitor etoposide. On the other hand, most of the tested heterocyclic compounds were found more effective in drug-resistant cells than in the parental, drug-sensitive ones, and some of the compounds showed high antineoplastic efficacy in several drug-resistant cell models. Compounds BD13, BD14 and BD16 exhibited high antineoplastic activities against the drug-resistant sublines EPG85-257RNOV and EPG85-257RDB derived from gastric carcinoma, EPP85-181RNOV and EPP85-181RDB derived from pancreatic carcinoma, MCF-7/Adr derived from breast cancer, D79/86RNOV derived from fibrosarcoma, and MeWoETO1 derived from melanoma. Furthermore, compound D23 was found highly efficient in the multidrug-resistant variants HT-29RNOV and HT-29RDB derived from colon carcinoma, and compound D24 exhibited the highest antineoplastic activity among the tested compounds in the drug-resistant subline MDA-MB-231ROV derived from breast cancer. In conclusion, compounds BD 13, BD 14, BD 16, D 23 and D 24 may be useful for the treatment of different multidrug-resistant cancer cells with cross resistance against "classical" Topo II-targeting drugs.     

Modulation of the atypical multidrug-resistant phenotype by a hammerhead ribozyme directed against the ABC transporter BCRP/MXR/ABCG2

The phenomenon of multidrug resistance (MDR) in human cancers is one of the major causes of failure of chemotherapy. A recently identified new member of the superfamily of ATP-binding cassette transporters, breast cancer resistance protein (BCRP), was demonstrated to confer an atypical multidrug-resistant phenotype to tumor cells. To overcome the BCRP-mediated drug resistance, a specific anti-BCRP hammerhead ribozyme was introduced into the human gastric carcinoma cell line, EPG85-257RNOV, exhibiting an atypical MDR phenotype. By this approach, the expression levels of the targeted BCRP-encoding mRNA and the BCRP transport protein were decreased to the low constitutive expression level that was observed in highly drug-sensitive parental gastric carcinoma cells. In addition, in the anti-BCRP ribozyme-treated cells, the cellular drug accumulation was dramatically increased to the level measured in drug-sensitive cells. These effects were accompanied by an extensive reversal of the drug-resistant phenotype of more than 80%. Because additional mechanisms contribute to the multimodal-mediated MDR phenotype exhibited by this gastric carcinoma cell line, the data suggest that the BCRP-mediated contingent to the drug resistance was overcome nearly completely. Moreover, the data indicate that ribozyme-based gene therapy may be clinically applicable in preventing and reversing BCRP-mediated atypical MDR.     

Crocin Increases Gastric Cancer Cells’ Sensitivity to Doxorubicin

Background: Crocin is one of the substantial constituents of saffron extract. It has multiple clinical effects including anti-cancer effects. The development of the multidrug resistance (MDR) phenotype is one of the principal causes of cancer chemotherapy failure. The multidrug resistance protein 1 (MDR1) is one of the MDR-related protein and is often overexpressed in different cancers. In the present study, we aimed to evaluate the influence of crocin on the expression and function of MDR1 protein in EPG85-257 and EPG85-257RDB gastric cancer cell lines. Methods: The cytotoxicity effect of crocin was evaluated by the MTT assay. The impacts of crocin on the expression and function of MDR1 were assessed by Real-time RT-PCR and MTT assay, respectively. Results: The results demonstrated that crocin decreased cell viability in a dose-dependent manner with higher intensity on the EPG85-257 than the EPG85-257RDB cells. Crocin did not make any significant changes in the MDR1 gene expression level in EPG85-257 and EPG85-257RDB cell lines. In contrast, crocin increased doxorubicin cytotoxicity in drug-resistant cells, which might be induced by reduced MDR1 activity. Conclusion: In summary, although crocin did not affect mRNA expression of MDR1, results of MTT assay suggest that it might inhibit the MDR1 function.     

Reversal of breast cancer resistance protein-mediated drug resistance by tryprostatin A

MDR in human cancers is one of the major causes of failure of chemotherapy. A member of the superfamily of ABC transporters, BCRP, was demonstrated to confer an atypical MDR phenotype to tumor cells. To overcome the BCRP-mediated drug resistance, the fungal secondary metabolite TPS-A, a diketopiperazine, was analyzed with regard to its potency to reverse the BCRP-mediated drug-resistant phenotype. At concentrations of 10-50 microM, TPS-A reversed a mitoxantrone-resistant phenotype and inhibited the cellular BCRP-dependent mitoxantrone accumulation in the human gastric carcinoma cell line EPG85-257RNOV, the human breast cancer cell line MCF7/AdrVp (both exhibiting acquired BCRP-mediated MDR) and the BCRP cDNA-transfected breast cancer cell line MCF-7/BCRP clone 8. No cytotoxicity was seen at effective concentrations. These data indicate that TPS-A is a novel BCRP inhibitor.     

Stable and complete overcoming of MDR1/P-glycoprotein-mediated multidrug resistance in human gastric carcinoma cells by RNA interference

Multidrug resistance (MDR) is the major cause of failure of effective chemotherapeutic treatment of disseminated neoplasms. The "classical" MDR phenotype of human malignancies is mediated by drug extrusion by the adenosine triphosphate binding cassette (ABC)-transporter P-glycoprotein (MDR1/P-gp). For stable reversal of "classical" MDR by RNA interference (RNAi) technology, an H1-RNA gene promoter-driven expression vector encoding anti-MDR1/P-gp short hairpin RNA (shRNA) molecules was constructed. By introduction of anti-MDR1/P-gp shRNA expression vectors into the extremely high drug-resistant human gastric carcinoma cell line EPG85-257RDB, the MDR phenotype was completely reversed. The reversal of MDR was accompanied by a complete suppression of MDR1/P-gp expression on mRNA and protein level, and by a considerable increased intracellular anthracyline accumulation in the anti-MDR1/P-gp shRNA-treated cells. The data indicate that stable shRNA-mediated RNAi can be tremendously effective in reversing MDR1/P-gp-mediated MDR and is therefore a promising strategy for overcoming MDR by gene therapeutic applications.     

Increased expression of the breast cancer resistance protein (BCRP) in relapsed or refractory acute myeloid leukemia (AML).

Expression of the multidrug resistance proteins P-glycoprotein, encoded by the MDR1 gene, multidrug resistance-associated protein (MRP1) and the lung resistance-related protein or major vault protein (LRP/MVP) is associated with clinical resistance to chemotherapy in acute myeloid leukemia (AML). Recently, the breast cancer-resistant protein (BCRP), the equivalent of mitoxantrone-resistant protein (MXR) or placental ABC transporter (ABCP), was described in AML. We investigated MDR1, MRP1, LRP/MVP and BCRP mRNA expression simultaneously in 20 paired clinical AML samples from diagnosis and relapse or refractory disease, using quantitative Taqman analysis. In addition, standard assays for P-glycoprotein expression and function were performed. BCRP was the only resistance protein that was expressed at a significantly higher RNA level (median 1.7-fold, P = 0.04) at relapsed/refractory state as compared to diagnosis. In contrast, LRP/MVP mRNA expression decreased as disease evolved (P = 0.02), whereas MDR1 and MRP1 mRNA levels were not different at relapse as compared to diagnosis. Also, at the protein level no difference of MDR1 between diagnosis and relapse was found. A significant co-expression of BCRP and MDR1 was found at diagnosis (r = 0.47, P = 0.04). The present results suggest that BCRP, but not MDR1, MRP1 or LRP/MVP is associated with clinical resistant disease in AML.     

Glypican-3 is involved in cellular protection against mitoxantrone in gastric carcinoma cells

Elevated expression of the heparan sulphate proteoglycan glypican-3 (GPC3) was found on mRNA and protein levels in the atypical multidrug-resistant gastric carcinoma cell line EPG85-257RNOV, which was established by in vitro selection against mitoxantrone. In order to elucidate a putative role of GPC3 in the drug-resistant phenotype, the mitoxantrone-resistant cell line EPG85-257RNOV was transfected with an expression vector construct carrying an anti-GPC3 hammerhead ribozyme. It could be demonstrated that in anti-GPC3 ribozyme-transfected cell clones, the GPC3-specific mRNA and corresponding protein expression levels were decreased to levels that are similar to those observed in nonresistant, parental cells. The anti-GPC3 ribozyme-containing clones reduced the mitoxantrone resistance level up to 21% of the original resistance and the crossresistance against etoposide to 33% of the original value. This reversal of drug resistance was accompanied by an increased cellular mitoxantrone accumulation in the anti-GPC3 ribozyme-expressing cells. In conclusion, it was verified that GPC3 is involved in the cellular protection against mitoxantrone in the atypical multidrug-resistant gastric carcinoma cell line EPG85-257RNOV.     

Membrane vesicle formation due to acquired mitoxantrone resistance in human gastric carcinoma cell line EPG85-257

A newly established gastric carcinoma cell line (EPG85-257P) exhibited a high sensitivity to mitoxantrone (DHAD) as determined by a monolayer proliferation assay. The concentration to inhibit cell growth to 50% of controls (IC50) was 0.0022 micrograms/ml culture medium. The cells were continuously incubated for more than 4 months in the presence of stepwise increased concentrations of DHAD, and the IC50 was increased to 0.41 micrograms/ml, i.e., 186.4-fold. This resistant variant was named EPG85-257RNOV. The EPG85-257RNOV cells became cross-resistant to Adriamycin with enhanced IC50 by 10.5-fold and to daunomycin with enhanced IC50 by 3.9-fold. No distinct resistance was observed to vinblastine, vincristine, and colchicine. Verapamil (10(-6), 4 X 10(-6) and 10(-5) M) and cyclosporin A (10(-6), 3 X 10(-6) and 10(-5) M) did not reverse DHAD resistance. As shown by immunocytochemistry (monoclonal antibodies: C219 and JSB-1) and Northern blot analysis, DHAD resistance was not associated with the appearance of the multidrug resistance (MDR)-associated (Mr 170,000) P-glycoprotein or the overexpression of P-glycoprotein mRNA. The data indicate a chemoresistance pattern unlike typical MDR (often called "atypical" MDR). The phenotypes of parent and resistant EPG85-257 cells were compared using interference contrast microscopy, electron microscopy, and immunocytochemistry. After DHAD application the following structural characteristics were found to be associated with emergence of resistance: (a) intensive formation of surface vesicles in the resistant variant. Such vesicles were almost absent in sensitive cells; (b) the vesicles contained the selecting DHAD which was visualized by its blue color; and (c) in electron microscopy the vesicles were formed by an inner and an outer double membrane, presumably derived from the plasmalemma. These observations suggest a complex cellular mechanism responsible for DHAD resistance which includes formation of membrane vesicles, vesicular drug binding, and drug compartmentalization.     

Induction of broad drug resistance in small cell lung cancer cells and its reversal by paclitaxel

The H82 “variant” and the H69 “classic” small cell lung cancer (SCLC) cell lines were treated with low levels of epirubicin (69 and 14 nM) which caused little cell death but produced the H82/E8 and H69/E8 extended-multidrug resistant sublines. Both were resistant to drugs associated with multidrug resistance (MDR), and to chlorambucil (9.5- and 5.6-fold, respectively) and cisplatin (2.3- and 8.5-fold, respectively). There was increased expression of the multidrug resistance-associated protein (MRP1) in the H82/E8 subline while P-glycoprotein expression was not detected in any cells or sublines. Treatment of the H82 cells for 1 hr with 69 nM epirubicin increased MRP1-mRNA expression within 4 hr and this was associated with an increase in the resistance to epirubicin, chlorambucil, cisplatin and paclitaxel. Further, a 1 hr treatment with non-cytotoxic doses of chlorambucil (2.5 μM), cisplatin (1.3 μM) or paclitaxel (13 nM), drugs not normally associated with MRP1-mediated MDR, also increased MRP1-mRNA expression in the H82 cells with paclitaxel causing the highest increase (4.5-fold). For chlorambucil treatment, this increased MRP1-mRNA expression was accompanied by increased drug resistance while paclitaxel treatment had no effect on drug resistance in the H82 cells. For the drug resistant H82/E8 subline, these drug treatments had no effect on the MRP1-mRNA expression and little effect on increasing the subline drug resistance. However, pre-treatment with paclitaxel sensitised the H82/E8 subline to chlorambucil and cisplatin returning the subline to the sensitivity of the H82 cell line. We conclude that treatment with low levels of MDR and non-MDR drugs can induce extended-multidrug resistance in SCLC cells, a process that probably involves the co-ordinate upregulation of MRP1 and other resistance mechanisms. The results also suggest paclitaxel may have a role as a response modifier in the treatment of refractory SCLC. Int. J. Cancer 76:702–708, 1998.© 1998 Wiley-Liss, Inc.     

Atypical multidrug resistance: breast cancer resistance protein messenger RNA expression in mitoxantrone-selected cell lines

BACKGROUND: Human cancer cell lines grown in the presence of the cytotoxic agent mitoxantrone frequently develop resistance associated with a reduction in intracellular drug accumulation without increased expression of the known drug resistance transporters P-glycoprotein and multidrug resistance protein (also known as multidrug resistance-associated protein). Breast cancer resistance protein (BCRP) is a recently described adenosine triphosphate-binding cassette transporter associated with resistance to mitoxantrone and anthracyclines. This study was undertaken to test the prevalence of BCRP overexpression in cell lines selected for growth in the presence of mitoxantrone. METHODS: Total cellular RNA or poly A+ RNA and genomic DNA were isolated from parental and drug-selected cell lines. Expression of BCRP messenger RNA (mRNA) and amplification of the BCRP gene were analyzed by northern and Southern blot hybridization, respectively. RESULTS: A variety of drug-resistant human cancer cell lines derived by selection with mitoxantrone markedly overexpressed BCRP mRNA; these cell lines included sublines of human breast carcinoma (MCF-7), colon carcinoma (S1 and HT29), gastric carcinoma (EPG85-257), fibrosarcoma (EPF86-079), and myeloma (8226) origins. Analysis of genomic DNA from BCRP-overexpressing MCF-7/MX cells demonstrated that the BCRP gene was also amplified in these cells. CONCLUSIONS: Overexpression of BCRP mRNA is frequently observed in multidrug-resistant cell lines selected with mitoxantrone, suggesting that BCRP is likely to be a major cellular defense mechanism elicited in response to exposure to this drug. It is likely that BCRP is the putative "mitoxantrone transporter" hypothesized to be present in these cell lines.     

ABC 转运蛋白在肝细胞癌中的表达及意义*

目的:探讨P-gp、MRP1、BCRP 等ABC 转运蛋白在肝细胞癌中的表达及其与临床病理特征的关系。方法:应用RT-PCR 和免疫组织化学方法检测P-gp/MDR1、MRP1、BCRP等mRNA 及蛋白在34例的肝细胞癌、19例癌旁肝组织中的表达。结果:MDR1、MRP1、BCRP等mRNA 在肝癌组的相对表达水平分别为1.15± 0.24、0.64± 0.33、1.07± 0.32,在癌旁肝组织组的相对表达水平分别为0.36± 0.14、0.19± 0.06、0.31± 0.09。MDR1、MRP1、BCRP 在肝细胞癌中低分化组（Ⅲ、Ⅳ级）为1.38± 0.26、0.73± 0.35、1.34± 0.21,在高分化组（Ⅰ、Ⅱ级）分别为0.74± 0.32、0.30± 0.11、0.45± 0.13。P-gp、MRP1、BCRP等的阳性反应产物主要分布于细胞膜和胞浆内;在肝癌组和癌旁肝组织组的阳性表达率分别为82.35% 、58.82% 、79.41% 和42.11% 、26.32% 、36.84% 。P-gp、MRP1、BCRP在肝细胞癌中低分化组（Ⅲ、Ⅳ级）的阳性表达率分别为100% 、81.25% 、100% ,在高分化组（Ⅰ、Ⅱ级）的阳性表达率分别为66.67% 、38.89% 、61.11% 。RT-PCR 及免疫组织化学均显示,P-gp、MDR1、MRP1、BCRP mRNA和蛋白在肝癌组的表达均高于癌旁肝组织组,且在低分化（Ⅲ、Ⅳ级）肝癌组织的表达高于高分化者（Ⅰ、Ⅱ级）,差异有统计学意义（P<0.05）。 MDR1、MRP1、BCRP之间的表达无线性相关。结论:在肝细胞癌中存在原发性多药耐药现象,且多种耐药机制并存。P-gp、MDR1、MRP1、BCRP等与肝细胞癌的耐药有关,在肝癌组的表达高于癌旁肝组织组,且在肝细胞癌中的表达随着肿瘤分化程度的增高而降低,可作为肝细胞癌多药耐药性作用的靶点。      

HDAC inhibitors downregulate MRP2 expression in multidrug resistant cancer cells: implication for chemosensitization

Although histone deacetylase (HDAC) inhibitors are emerging as a promising class of cancer chemotherapeutic agents, their effects on multidrug resistance (MDR) are poorly understood. In this study, we investigated whether HDAC inhibitors overcome MDR phenotype. HDAC inhibitors suppress the growth of both MDR positive cancer cells KBV20C and its parental cells KB with similar potencies. In parallel, histone acetylation and p21WAF1 expression by the HDAC inhibitors were similarly increased in both cell types, indicating that these HDAC inhibitors are poor substrates of ABC drug transporters and effective in MDR cancer cells. In addition, multidrug resistance protein 2 (MRP2) expression is selectively attenuated by HDAC inhibitors, especially SAHA and TSA, in KBV20C cells, whereas MDR1 and BCRP expressions are not affected. This downregulation of MRP2 contributes to increase in paclitaxel-induced G2/M arrest and apoptosis, which might be due to intracellular accumulation of paclitaxel. Collectively, our data provide a molecular rationale for the application of HDAC inhibitors to overcome MDR in cancer cells.     

多药耐药相关蛋白7及其抑制剂

多药耐药(MDR)的机制与转运蛋白有关,现在研究最多的为P-糖蛋白(P-gp)、多药耐药相关蛋白(MRP)1、乳腺癌耐药相关蛋白(BCRP)等的抑制剂.MRP7可介导对紫杉醇、长春新碱和长春碱等的耐药.MRP7抑制剂近年研究主要包括千斤藤素、酪氨酸酶抑制剂、环孢素A等,MDR是多种机制共同作用的结果,对其他转运体的研究会提供更全面、更广泛的MDR逆转途径.     

ABCG2/BCRP expression modulates D-Luciferin based bioluminescence imaging

Bioluminescence imaging (BLI) is becoming indispensable to the study of transgene expression during development and, in many in vivo models of disease such as cancer, for high throughput drug screening in vitro. Because reaction of d-luciferin with firefly luciferase (fLuc) produces photons of sufficiently long wavelength to permit imaging in intact animals, use of this substrate and enzyme pair has become the method of choice for performing BLI in vivo. We now show that expression of the ATP-binding cassette (ABC) family transporter ABCG2/BCRP affects BLI signal output from the substrate d-luciferin. In vitro studies show that d-luciferin is a substrate for ABCG2/BCRP but not for the MDR1 P-glycoprotein (ABCB1/Pgp), multidrug resistance protein 1 (MRP1/ABCC1), or multidrug resistance protein 2 (MRP2/ABCC2). d-Luciferin uptake within cells is shown to be modulated by ABC transporter inhibitors, including the potent and selective ABCG2/BCRP inhibitor fumitremorgin C. Images of xenografts engineered to express transgenic ABCG2/BCRP, as well as xenografts derived from the human prostate cancer cell line 22Rv1 that naturally express ABCG2/BCRP, show that ABCG2/BCRP expression and function within regions of interest substantially influence d-luciferin-dependent bioluminescent output in vivo. These findings highlight the need to consider ABCG2/BCRP effects during d-luciferin-based BLI and suggest novel high throughput methods for identifying new ABCG2/BCRP inhibitors.     

Overexpression of the ATP-binding cassette half-transporter, ABCG2 (Mxr/BCrp/ABCP1), in flavopiridol-resistant human breast cancer cells.

We sought to characterize the interactions of flavopiridol with members of the ATP-binding cassette (ABC) transporter family. Cells overexpressing multidrug resistance-1 (MDR-1) and multidrug resistance-associated protein (MRP) did not exhibit appreciable flavopiridol resistance, whereas cell lines overexpressing the ABC half-transporter, ABCG2 (MXR/BCRP/ABCP1), were found to be resistant to flavopiridol. Flavopiridol at a concentration of 10 microM was able to prevent MRP-mediated calcein efflux, whereas Pgp-mediated transport of rhodamine 123 was unaffected at flavopiridol concentrations of up to 100 microM. To determine putative mechanisms of resistance to flavopiridol, we exposed the human breast cancer cell line MCF-7 to incrementally increasing concentrations of flavopiridol. The resulting resistant subline, MCF-7 FLV1000, is maintained in 1,000 nM flavopiridol and was found to be 24-fold resistant to flavopiridol, as well as highly cross-resistant to mitoxantrone (675-fold), topotecan (423-fold), and SN-38 (950-fold), the active metabolite of irinotecan. Because this cross-resistance pattern is consistent with that reported for ABCG2-overexpressing cells, cytotoxicity studies were repeated in the presence of 5 microM of the ABCG2 inhibitor fumitremorgin C (FTC), and sensitivity of MCF-7 FLV1000 cells to flavopiridol, mitoxantrone, SN-38, and topotecan was restored. Mitoxantrone efflux studies were performed, and high levels of FTC-reversible mitoxantrone efflux were found. Northern blot and PCR analysis revealed overexpression of the ABCG2 gene. Western blot confirmed overexpression of ABCG2; neither P-glycoprotein nor MRP overexpression was detected. These results suggest that ABCG2 plays a role in resistance to flavopiridol.