Detection of C1236T,G2677T/A,and C3435T polymorphism of MDR1 by amplification refractory mutation system PCR

C1236T, G2677T/A, and C3435T polymorphism of the multidrug resistance (MDR1) gene have substantial impact on expression or activity of P‐glycoprotein (P‐gp). We developed new methods based on amplification refractory mutation system (ARMS) to detect these polymorphisms. Tetra‐primers amplification in a single tube was established to detect C1236T and C3435T polymorphism. For G2677T/A polymorphism, a two‐step allele‐specific amplification method was used. MDR1 genotypes of 177 Chinese subjects were determined by the methods we established. The methods we established were verified with gene sequencing. Gene frequencies of 1236C and 1236T were 37.8 and 62.2%, respectively; gene frequencies of 2677G, 2677T and 2677A were 44.1, 38.4 and 17.5%, respectively; the gene frequencies of 3435C and 3435T were 65.0 and 35.0%, respectively. The results were similar with other studies on Oriental subjects. The methods we established are simple, accurate, and economical, and can provide reliable approaches for determining MDR1 polymorphism. J. Clin. Lab. Anal. 23:110–116, 2009. © 2009 Wiley‐Liss, Inc.     

Synergism between Gamma Interferon and Doxorubicin in a Human MDR Colon Adenocarcinoma Cell Line

Summary

Recent interest in cancer therapy derives from the ability of interferons to synergistically increase the activity of chemotherapeutic agents. To understand the biological basis of this synergism we evaluated the effects of human recombinant IFN-γ on the expression of the mdrl gene and on the cellular growth of a human colon adenocarcinoma cell line (LoVo) and its MDR subline (LoVo/Dx) after coincubation with doxorubicin. Treatment with IFN-γ showed unchanged levels of MDR 1-glycoprotein, no perturbation on cell cycle distribution and a significant reduction of colony formation in both lines (P<0.05) starting from 100 U/ml. A synergistic effect was observed in the LoVo/Dx cell line when doxorubicin was added after exposure to 0.1-10 U/ml of IFN-γ. Our data indicate that the effects of IFN-γ, independent from action on cell proliferation and from modulation of p-glycoprotein expression, are a cause of the synergistic activity between this lymphokine and conventional chemotherapeutic agents such as doxorubicin.     

Molecular characterization of CTX‐M‐15‐producing clinical isolates of Escherichia coli reveals the spread of multidrug‐resistant ST131 (O25:H4) and ST964 (O102:H6) strains in Norway

Nationwide, CTX‐M‐producing clinical Escherichia coli isolates from the Norwegian ESBL study in 2003 (n=45) were characterized on strain and plasmid levels. Bla_CTX‐M allele typing, characterization of the genetic environment, phylogenetic groups, pulsed field gel electrophoresis (PFGE), serotyping and multilocus sequence typing were performed. Plasmid analysis included S1‐nuclease‐PFGE, polymerase chain reaction‐based replicon typing, plasmid transfer and multidrug resistance profiling. Bla_CTX‐M‐15 (n=23; 51%) and bla_CTX‐M‐14 (n=11; 24%) were the major alleles of which 18 (78%) and 6 (55%), respectively, were linked to ISEcp1. Thirty‐two isolates were of phylogenetic groups B2 and D. Isolates were of 29 different XbaI‐PFGE‐types including six regional clusters. Twenty‐three different O:H serotypes were found, dominated by O25:H4 (n=9, 20%) and O102:H6 (n=9, 20%). Nineteen different STs were identified, where ST131 (n=9, 20%) and ST964 (n=7, 16%) were dominant. Bla_CTX‐M was found on ≥100 kb plasmids (39/45) of 10 different replicons dominated by IncFII (n=39, 87%), FIB (n=20, 44%) and FIA (n=19, 42%). Thirty‐nine isolates (87%) displayed co‐resistance to other classes of antibiotics. A transferable CTX‐M phenotype was observed in 9/14 isolates. This study reveals that the majority of CTX‐M‐15‐expressing strains in Norway are part of the global spread of multidrug‐resistant ST131 and ST‐complex 405, associated with ISEcp1 on transferrable IncFII plasmids.     

Newer Options for Treating Drug-Resistant (MDR+) Cancer Cells using Photoradiation Therapy

Emergence of drug resistance with conventional cytotoxic therapy is a major challenge towards the curability of many cancers, especially in patients undergoing autologous BMT with ex-vivo purged hematopoietic support. We have explored the potential role of photoradiation therapy in purging hematopoietic stem cells of various hematological malignancies. Benzoporphyrin derivative, monoacid ring A (BPD-MA), dihematoporphyrin ether (DHE), and MC-540 were evaluated for the “ex-vivo” purging of residual tumor cells from autologous bone marrow (BM) grafts. BPD-MA and DHE photosensitizing activity was tested against two human large cell lymphoma cell lines and colony forming-unit leukemia (CFU-L) derived from patients with acute myelogenous leukemia (AML). In mixing experiments four log elimination of tumor cell lines was observed after 1 hr of incubation with BPD-MA or DHE followed by white light exposure. By comparison, using the same concentration of BPD-MA or DHE, the mean recovery of normal BM progenitors was 4-5.2% for granulocyte-macrophage colony forming unit (CFU-GM) and 5-9.8% for burst forming unit erythroid (BFUE).

The T lymphoblastic leukemia cell line CEM and its vinblastine (VBL)-resistant subline CEM/VBL₁₀₀. along with the acute promyelocyte leukemia cell line HL-60 and its vincristine (VCR)-resistant subline HL-60/VCR, were also tested. Our results demonstrated the preferential cytotoxicity of BPD-MA and DHE toward neoplastic cell lines and CFU-L from AML patients. In addition, DHE was slightly more effective in purging tumor cells expressing the p-170 glycoprotein. These results suggest that photoradiation would be useful for “ex-vivo” purging of malignant cells. Other methods to deal with decreasing drug resistance are also detailed.     

A phase I trial of high-dose oral tamoxifen and CHOPE

Drug resistance is a common phenomenon in clinical oncology. In vitro, tamoxifen has been shown to be an effective inhibitor of P-glycoprotein and a modulator of the multidrug resistance phenotype. We have previously shown that vinblastine can be given safely in combination with tamoxifen at doses that may modulate P-glycoprotein activity. In this phase I trial, tamoxifen (150 mg/m² twice a day) was given with CHOPE (cyclophosphamide/doxorubicin/vincristine/prednisone/etoposide) in order to assess the toxicities of the combination. Resistance to three of these cytotoxic agents (doxorubicin, vincristine, and etoposide) may be mediated by P-glycoprotein. A total of 13 patients were evaluable on this trial, which showed that the maximum tolerated doses of cyclophosphamide and etoposide were 750 and 80 mg/m², respectively. The dose-limiting toxicity was myelosuppression with 50% of the patients (3/6) treated at this dose level developing febrile neutropenia and 85% (6/7) developing grade 4 neutropenia. Tamoxifen at a dose of 150 mg/m² twice a day can be given safely with the lymphoma regimen CHOPE at standard doses, but his combination may result in increased myelosuppression.Supported in part by grants 5T32-CA-09307 and P30-A-14236-18 from the National Institutes of Healthand the National Cancer Institute, the P. B. Cohen Memorial Fund, and ICI Pharmaceuticals, Inc.     

Multidrug Resistance in Leukemias and its Reversal

Drug resistance often results in failure of anticancer chemotherapy in leukemias. Several mechanisms of drug resistance are known with multidrug resistance (MDR) being the best characterized one. MDR can be due to enhanced expression of certain genes (MDR1, MRP or LRP). alterations in glutathione-S-transferase activity or GSH levels and to reduction of the amount or the activity of topoisomerase II. Here we review the current status of the clinical significance of the various mechanisms of MDR in leukemias and also discuss possibilities for the reversal of MDR, MDR1 gene expression has been seen in many leukemias, notably in acute myeloid leukemia (AML) and blast crisis of chronic myeloid leukemia. Both MDR1 RNA and P-glycoprotein expression of the leukemic cells have been shown to correlate with poor clinical outcome in AML. However, preliminary results indicate that the MRP gene as well as the LRP gene can be expressed in AML. Thus, drug resistance in leukemias appears to be multifactorial. P-glycoprotein-mediated MDR can be reversed by several drugs. These resistance modifiers are currently evaluated with regard to their clinical efficacy. Despite some encouraging results, reversal of drug resistance and subsequent improvement in clinical outcome remains to be shown.     

Inhibition of transport across the hepatocyte canalicular membrane by the antibiotic fusidate

Hyperbilirubinemia is a frequent side effect induced by long-term therapy with the antibiotic fusidate. The aim of this study was to elucidate the molecular mechanisms of fusidate-induced hyperbilirubinemia by investigating its influence on hepatic transport systems in the canalicular membrane. Using canalicular membrane vesicles from rat liver, we determined the effect of fusidate on the adenosine 5'-triphosphate (ATP)-dependent transport of substrates of the apical conjugate export pump, multi-drug resistance protein 2 (Mrp2, symbol Abcc2) and the bile salt export pump (Bsep, symbol Abcb11). Fusidate inhibited the ATP-dependent transport of the Mrp2 substrates 17beta-glucuronosyl estradiol and leukotriene C4, and the transport of cholyltaurine by Bsep with Ki values of 2.2+/-0.3, 7.6+/-1.3, and 5.5+/-0.8 microM, respectively. To elucidate the in vivo implication of these findings, the effect of fusidate treatment on the elimination of intravenously administered tracer doses of 17beta-glucuronosyl estradiol and cholyltaurine into bile was studied in rats. Treatment with fusidate (100 micromol/kg body weight) reduced the biliary excretion rate of 17beta-glucuronosyl [3H]estradiol and [3H]cholyltaurine by 75 and 80%, respectively. Extended treatment of rats with fusidate (100 micromol/kg body weight, three times daily i.p. for 3 days) reduced hepatic Mrp2 protein levels by 61% (P<0.001). Our data suggest that there are at least two different mechanisms involved in the impairment of transport processes and hepatobiliary elimination by fusidate, direct inhibition of transport of Mrp2 and Bsep substrates by competitive interaction and impairment by a decreased level of hepatic Mrp2.     

电穿孔法介导醛脱氢酶基因与多药耐药基因的转移和表达

背景与目的：将不同类型的耐药基因同时导入造血细胞,以扩大耐药范围和进行体内选择是基因治疗的重要策略,这类载体基因片段较长,进行基因转移有一定的难度。本研究旨在寻找安全有效的长片段基因转移G1Na-AIM以NdeⅠ酶切线性化,电穿孔法转导PA317细胞,经长春新碱（VCR）和4－氢过氧化环磷酰胺（4－HC）选择后,应用Southern blot法确定原病毒的整合,逆转录聚合酶链反应（RT－PCR）和流式细胞术（FCM）分析转移基因的表达,筑巢式聚合酶链反应（nested PCR)检验转移系统的安全性。结果：电穿孔法有效介导了ALDH1与MDR1基因的同时转移,Southern blot法证实ALDH1与MDR1基因稳定整合至宿主细胞基因组,RT－PCR检测到转移基因的转录,FCM测定下游基因MDR1蛋白表达增高4倍,转导率达98％。nested PCR未检测到辅助病毒（env)。结论：电穿孔法安全有效地介导了ALDH1与MDR1基因的共移和高表达。     

初发及复发转移大肠癌患者外周血MDR-1基因表达的研究

目的：检测初发及复发转移大肠癌患外周血中多药耐药基因(MDR—1)的表达,探讨其与病理类型及化疗疗效的关系。方法：应用逆转录多聚酶链反应(RT—PcR)法对56例初发大肠癌及40例经术后辅助化疗后复发、转移大肠癌患的外周血进行检测,并与其病理类型及化疗疗效作对比研究。结果：56例初发大肠癌患外周血中MDR—1阳性表达率为27．2％,与病理类型无显相关(P＞0．05);但与肠系膜淋巴结转移密切相关,有淋巴结转移阳性表达率显高于无淋巴结转移(P＜0．05);40例化疗后复发、转移患外周血MDR—1阳性表达率为72．5％,与初发大肠癌患的MDR—1阳性表达宰相比差异有显性(P＜0．05),且MDR－1的表达与化疗疗效呈负相关,MDR—1阳性表达化疗疗效明显低于阴性表达(P＜0．05)。结论：大肠癌存在先天性和获得性多药耐药性;检测外周血MDR—1表达情况可以帮助预测化疗疗效,对制定临床化疗方案有指导意义。