The Activity of Erianin and Chrysotoxine from Dendrobium chrysotoxum to Reverse Multidrug Resistance in B16/h MDR-1 Cells

The ability of two dihydrostilbene derivatives erianin and chrysotoxine from Dendrobium chrysotoxum to reverse multidrug resistant (MDR) cells was investigated using murine B16 melanoma cells transfected with the human MDR 1 gene and crossresistant to vinblastine and adriamycin (B16/h MDR 1 cells). Both of the two compounds were shown to increase the accumulation of adriamycin, the P glycoprotein (P gp) substrate, in B16/h MDR 1 transfectants.

Reversing multidrug resistance by RNA interference through the suppression of MDR1 gene in human hepatoma cells

AIM： To reverse the multidrug resistance （MDR） by RNA interference （RNAi）-mediated MDRI suppression in heparoma cells.METHODS： For reversing MDR by RNAi technology, two different short hairpin RNAs （shRNAs） were designed and constructed into pGenSil-1 plasmid, respectively. They were then transfected into a highly adriarnycin-resistant HepG2 hepatorna cell line （HepG2/ADM）. The RNAi effect on MDR was evaluated by real-time PCR, cell cytotoxicity assay and rhodarnine 123 （Rh123） efflux assy. RESULTS： The stably-transfected clones showed various degrees of reversal of MDR phenotype. Surprisingly, the MDR phenotype was completely reversed in two transfected clones. CONCLUSION： MDR can be reversed by the shRNAmediated MDRI suppression in HepG2/ADM cells, which provides a valuable clue to make multidrug-resistant hepatoma cells sensitive to anti-cancer drugs.

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.

Association of single nucleotide polymorphisms of brain-derived neurotrophic factor gene and multidrug resistance 1 gene to refractory epilepsy in Chinese Han children

BACKGROUND： There are two hypotheses for the underlying cause of refractory epilepsy： ＂target＂ and ＂transport＂. Studies have shown that brain-derived neurotrophic factor （BDNF） is over-expressed in refractory epilepsy. Multidrug resistance 1 （MDR1） gene encodes for P-glycoprotein, the primary ATP-binding cassette transporter in the human body. Some single nucleotide polymorphisms of the MDR1 gene have been associated with refractory epilepsy. OBJECTIVE： To investigate the association between BDNF gene C270T polymorphism and MDR1 T-129C polymorphism with refractory epilepsy in Chinese Han children through the use of polymerase chain reaction （PCR）-restriction fragment length polymorphism analysis. DESIGN, TIME AND SETTING： A case-control, genetic association study was performed at the Central Laboratory, Third Xiangya Hospital of Central South University from June 2005 to November 2007. PARTICIPANTS： A total of 84 cases of unrelated children with epilepsy, including 41 cases of refractory epilepsy and 43 cases of drug-responsive epilepsy, were enrolled. An additional 30 healthy, Chinese Han children, whose ages and gender matched the refractory epilepsy patients, were selected as normal controls. METHODS： Venous blood was collected and genomic DNA was extracted from the blood specimens. C270T polymorphism in BDNF gene and T-129C polymorphism in MDR1 gene were genotyped using PCR-restriction fragment length polymorphism analysis. Association analysis using the Ftest and Chi-square test was statistically performed between C270T polymorphism in BDNF gene and T-129C polymorphism in MDR1 gene and refractory epilepsy. MAIN OUTCOME MEASURES： The distribution of genotypes and allele frequencies of C270T polymorphism in BDNF gene and T-129C polymorphism in MDR1 gene. RESULTS： The distribution of CC, CT, and TT genotypes, as well as C and T allele frequencies, in the BDNF gene was not significantly different between the refractory epilepsy group, drug-responsive epilepsy group, or the normal control group （P 〉 0.05）. The distribution of TT genotype and T allele frequencies of the MDR1 gene was significantly different in the refractory epilepsy group compared with the drug-responsive epilepsy and normal control groups （P 〈 0.05）. Comparison of haplotype combinations demonstrated that there were no significant differences in combinations of TT＋CC, -FI-＋CT, TC＋CC, and TC＋CT among the three groups （P 〉 0.05）. CONCLUSION： C270T polymorphism of the BDNF gene was not associated with refractory epilepsy in Chinese Han children, but T-129C polymorphism in the MDR1 gene was associated with refractory epilepsy in Chinese Han children. The TT genotype and T allele frequencies could serve as susceptibility loci for refractory epilepsy. Interactions between C270T in BDNF gene and T-129C in MDR1 gene were not observed in refractory epilepsy in Chinese Han children.

REVERSAL EFFECTS OF MIFEPRISTONE ON MULTIDRUG RESISTANCE(MDR) IN DRUG-RESISTANT BREAST CANCER CELL LINE MCF7/ADR IN VITRO AND IN VIVO

To explore the reversal effect of mifepristone on multidrug resistance (MDR) in drug-resistant human breast cancer cell line MCF7/ADR and its mechanisms. Methods: Expression of MDR1 and MDR-associated protein(MRP) mRNA in MCF7/ADR cells was detected using reverse transcription- polymerase chain reaction(RT-PCR). Western blotting was used to assay the protein levels of P-glycoprotein (P-gp) and MRP. Intracellular rhodamine 123 retention and [3H]vincristine (VCR) accumulation were measured by flow cytometry and liquid scintillation counter, respectively. MTT reduction assay was used to determine the sensitivity of cells to the anticancer agent, adriamycin (ADR). Additionally, a MCF7/ADR cell xenograft model was established to assess the reversal effect of mifeprisone on MDR in MCF7/ADR cells in vivo. Results: Miferpristone dose-dependently down- regulated the expression of MDR1 and MRP mRNA in MCF7/ADR cells, accompanied by a significant decrease in the protein levels of P-gp and MRP. After exposure to 5, 10, and 20 mmol/L mifepristone, MCF7/ADR cells showed a 3.87-, 5.81-, and 7.40-fold increase in the accumulation of intracellular VCR(a known substrate of MRP), and a 2.14-, 4.39-, and 5.53-fold increase in the retention of intracellular rhodamine 123(an indicator of P-gp function), respectively. MTT analysis showed that the sensitivity of MCF7/ADR cells to ADR was enhanced by 7.23-, 13.62-, and 20.96-fold after incubation with mifepristone as above-mentioned doses for 96 h. In vivo, mifepristone effectively restored the chemosensitivity of MCF7/ADR cells to ADR. After 8 weeks of administration with ADR(2 mg穔g-1穌-1) alone or in combination with mifepristone(50 mg穔g-1穌-1), the growth inhibitory rate of xenografted tumors in nude mice was 8.08% and 37.25%, respectively. Conclusion: Mifepristone exerts potent reversal effects on MDR in MCF7/ADR cells in vitro and in vivo through down- regulation of MDR1/P-gp and MRP expression and inhibition of P-gp- and MRP-dependent drug efflux, thus increasing the sensitivity to anticancer drug.

Expression of multidrug resistance 1 gene and C3435T genetic polymorphism in peripheral blood of patients with intractable epilepsy

BACKGROUND： Increased expression of multidrug resistance 1 （MDR1） mRNA in peripheral blood of patients with intractable epilepsy is not due to epilepsy drugs, but epilepsy behavior. Monitoring MDR1 expression in peripheral blood is a target for MDR1 gene evaluation. OBJECTIVE： To investigate the influence of antiepileptic drugs and seizures on MDR expression in intractable epilepsy, and to analyze the genetic polymorphisms of C3435T in the MDRl gene. DESIGN, TIME AND SETTING： Factorial designs and comparative observations at the experimental center of the Affiliated Hospital of Qingdao Medical College, Qingdao University between October 2003 and October 2004. PARTICIPANTS： A total of 120 subjects were recruited from the epilepsy clinical department of the Affiliated Hospital of Qingdao Medical College. Four groups （n = 30） were classified according to statistical factorial design： intractable epilepsy, treatment response, no treatment, and normal control groups. METHODS： One-step semi-quantitative reverse-transcription polymerase chain reaction technology was used to test expressions of the MDR1 gene in 120 subjects. C3435T polymorphisms in intractable epilepsy group and normal control groups were analyzed by polymerase chain reaction-restriction fragment length polymorphism. MAIN OUTCOME MEASURES： Expression of MDR1 mRNA in the four groups, and C3435T genetic polymorphisms in intractable epilepsy and normal control groups. RESULTS： MDRl gene expression was increased in the intractable epilepsy group, due to the factor seizures, but not the antiepileptic drugs. However, the interaction between the two factors was not statistically significant. Of the 30 subjects in the intractable epilepsy group, the following genotypes were exhibited： 3 （10%） C/C genotype, 9 （30%） C/T genotype, and 18 （60%） T/T genotype at the site of C3435T, while 4 （13%）, 10 （33%）, and 16 （53%） subjects were determined to express these genotypes in the normal control group, respectively. C and T allele frequency were 25% and 75% in the intractable epilepsy group, and 30% and 70% in the normal control group, respectively. However, there was no statistical difference between the groups. CONCLUSION： Results demonstrated that seizures, not antiepileptic drugs, induced MDR1 gene expression in intractable epilepsy. Genetic polymorphisms of C3435T in the MDR1 gene did not contribute to the development of multidrug resistance in patients with intractable epilepsy.

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.

Roles of sulfonylurea receptor 1 and multidrug resistance protein 1 in modulating insulin secretion in human insulinoma

BACKGROUND:Sulfonylurea receptor 1(SUR1)and multidrug resistance protein 1(MRP1)are two prominent members of multidrug resistance proteins associated with insulin secretion. The aims of this study were to investigate their expression in insulinomas and their sole and synergistic effects in modulating abnormal insulin secretion. METHODS:Fasting glucose,insulin and C-peptide were measured in 11 insulinoma patients and 11 healthy controls. Prolonged oral glucose tolerance tests were performed in 6 insulinoma patients.Insulin content,SUR1 and MRP1 were detected in 11 insulinoma patients by immunohistochemistry. SUR1 and MRP1 were also detected in 6 insulinoma patients by immunofluorescence. RESULTS:Insulinoma patients presented the typical demons-trations of Whipple’s triad.Fasting glucose of each insulinoma patient was lower than 2.8 mmol/L,and simultaneous insulin and C-peptide were increased in insulinoma patients. Prolonged oral glucose tolerance tests showed that insulin secretion in insulinoma patients were also stimulated by high glucose.Immunohistochemistry and immunofluorescence staining showed that SUR1 increased,but MRP1 decreased in insulinoma compared with the adjacent islets. CONCLUSIONS:The hypersecretion of insulin in insulinomas might be,at least partially,due to the enrichment of SUR1. In contrast,MRP1,which is down-regulated in insulinomas, might reflect a negative feedback in insulin secretion.

Chitosan/pshRNA Plasmid Nanoparticles Targeting MDR1 Gene Reverse Paclitaxel Resistance in Ovarian Cancer Cells

In order to investigate the effect of chitosan/pshRNA plasmid nanoparticles targeting MDR1 genes on the resistance of A2780/TS cells to paclitaxel, chitosan/pshRNA plasmid nanoparti- cles were synthesized by means of a complex coacervation technique and transfected into A2780/TS cells. The cells transfected with MDRl-targeted chitosan/pshRNA plasmid nanoparticles were experimental cells and the cells transfected with chitosan/pGPU6/GFP/Neo no-load plasmid nanoparticles served as negative control cells. Morphological features of the nanoparticles were observed under transmission electron microscope （TEM）. MDR1 mRNA expression was assessed by RT-PCR. Half-inhibitory concentration （IC50） ofpaclitaxel for A2780/TS cells was determined by MTT method. TEM showed that the nanoparticles were round-shaped, smooth in surface and the diameters varied from 80 to 120 nm. The MDR1 mRNA in the transfected cells was significantly decreased by 17.6%, 27.8% and 52.6% on the post-transfection day 2, 4 and 7 when compared with that in A2780/TS cells control （P〈0.05）. MTT assay revealed that the relative reversal efficiency was increased over time and was 29.6%, 51.2% and 61.3% respectively in the transfected cells 2, 4, 7 days after transfection and IC_50 （0.197±0.003, 0.144±0.001, 0.120±0.004） were decreased with difference being significant when compared with that in A2780/TS （0.269±0.003） cells control （P〈0.05）. It was concluded that chitosan/pshRNA plasmid nanoparticles targeting MDR1 can effectively reverse the paclitaxel resistance in A2780/TS cells in a time-dependent manner.

Detection and clinical significance of multidrug resistance-1 mRNA in bone marrow cells in children with acute lymphoblastic leukemia by real-time fluorescence quantitative RT-PCR

Objective： Multidrug resistance（MDR） is one of the most important reasons for treatment failure and recurrence of acute leukemia. Its manifestations are different in children with acute lymphoblastic leukemia（ALL） which may be due to different detection methods. This study was to detect the expression of MDR1 mRNA in bone marrow cells of children with ALL by real-time fluorescence- quantitative reverse transcription polymerase-chain reaction（FQ-RT-PCR）, and combine minimal residual desease（MRD） detection by flow cytometry（FCM） and to study their relationship with treatment response and prognosis of ALL. Methods：The MDR1 mRNA levels in bone marrow cells from 67 children with ALL[28 had newly diagnosed disease, 27 had achieved complete remission（CR）, 12 recurrent] and 22 children without leukemia were detected by FQ-RT-PCR. MRD was detected by FCM. The patients were observed for 9-101 months, with a median of 64 months. Results：Standard curves of human MDR1 and GAPDH genes were constructed successfully. MDR1 mRNA was detected in all children with a positive rate of 100%. The mRNA level of MDR1 was similar among the newly diagnosed ALL group, CR group, and control group（P 〉 0.05）, but significantly higher in the recurrence group than that in newly diagnosed disease group and control group（0.50 ± 0.55 vs. 0.09 ± 0.26 and 0.12 ± 0.23, P〈 0.05）. 54 ALL patients were followed up, and it was found that MDR1 mRNA level was significantly higher in ALL patients within 3 years duration than that of ALL patients with 3-6 years and over 6 years duration（0.63 ± 0.56 vs. 0.11 ± 0.12 and 0.04 ± 0.06, P〈 0.01）. For the 28 children with newly diagnosed disease, the MDR1 mRNA level was similar between WBC 〉 50 ~ 109 group and WBC〈50 × 10^9 group（P〉 0.05）. In the 33 CR patients, the MDR1 mRNA level was significantly higher in MRD〉10a group than that in MRD〈10a group（0.39 ± 0.47 vs. 0.03 ± 0.03, P 〈 0.05）. Conclusion：The sensitivity and specificity of FQ-RT-PCR in detecting MDR1 mRNA in bone marrowy cells of children with ALL patients are high. MDR1 mRNA is expressed in children with and without leukemia. MDR1 mRNA is highly expressed in the CR ALL patients with high MRD, recurrence and short duration（within 3 years）. Monitoring MRD and the MDR1 mRNA level might be helpful for individual treatment.

Reversal of Adriamycin Resistance of Hepatocellular Carcinoma by Targeting with Recombined Adenovirus Caning Antisense mdr1 RNA

OBJECTIVE Chemotherapy is an important therapy for hepatocellular carcinoma （HCC）. However, it is not effective in many cases due to recurrence and metastasis even if the initial treatment produces a response. Multidrug resistance （MDR） is considered to be one of the considerable causes. The aim of this study was to reverse MDR of HepG2/ADM cells by blocking mdr1 with an adenovirus vector carrying antisense mdr1 in a tumor transplantated in athymic mice. METHODS PCMV IE was removed from the pshuttle vector. A 0.3 kb AFP promoter was inserted into the pshuttle vector and pCMV changed into pAFP. The pAFP and asmdr1 PCR products were doubly digested with Kpnl and Apal, the digested products were ligated by T4 ligase, the asmdr1 gene was inserted into pAFP and a newly plasmid pAFP-asmdr1 was constructed. Following digestion with PI-SceI/I-Ceu I, pAFP-asmdr1 was ligated with Adeno-X genome DNA and amplified in E.coli XL1-Blue. The HEK293 cells were transfected and virus collected. The HepG2 MDR cells （HepG2/ADM） were induced by graded resistance to ADM and were inoculated into athymic mice. After adeno-asmdr1 was injected, the expression of mdr1-mRNA and the volume of the transplantated tumor and its cells were observed. RESULTS Following injection with Adeno-asmdr1, the tumor volume in the ADM＋Adeno-asmdr1 group did not increase. However the tumor volume in the PBS plus ADM group did significantly increase （P〈0.05）. In the tumor xenograft cells, mdr1 mRNA in the xenografts was assessed by RT-PCR and was found to be reduced at 1 week and 4 weeks in the ADM＋asmdr1 group, but it was stable in the ADM group. It was only 20% in the ADM＋asmdr1 group compared to the ADM group at the 4th week （P〈0.05）. Evidence of apoptosis was observed in the tumor xenograft cells treated with Adeno-asmdr1, but there was rare or no apoptosis in the group treated with ADM and PBS. CONCLUSION Adenovirus carrying antisense mdr1 RNA can partially reverse the MDR of HepG2/ADM cells and inhibit tumor growth by down-regulating mdr1 mRNA resulting in tumor cell apoptosis.

Reversal Effect of BM-cyclin 1 on Multidrug Resistance by Down-regulating MRP2 in BALB/C Nude Mice Bearing C-A120 Cells

Our previous study demonstrated that BM-cyclin 1, a traditional anti-mycoplasma drug, could effectively reverse the multidrug resistance （MDR） of C-A120 cells. The present study aims to explore the reversal effect of BM-cyclin 1 on MDR and its mechanisms in BALB/C nude mice bearing C-A120 cells. Irnmunoblotting analysis and reverse transcription-polymerase chain reaction （RT-PCR） were used to study the change in multidrug resistance-associated protein 2 （MRP2） induced by BM-cyclin 1. We found that the expression levels of MRP2 protein and mRNA in C-A120 cells treated with BM-cyclin 1 were reduced significantly. Chemical colorimetry revealed no significant change in the level of glutathione （GSH）. In the xenografl model, the inhibitory rate of C-A120 cells growth in BM-cyclin 1 plus adriamycin （ADM） group was 52%, which was significantly higher than in control group （P〈0.01）. The immunoblotting and RT-PCR results conclusively demonstrated that BM-cycin 1 could significantly reduce the expression of MRP2 in transplanted tumor. In conclusion, BM-cyclin 1 could effectively reverse the MDR of C-A 120 cells in vivo by suppressing the expression of MRP2.

In Vitro Study of Ultrasound on Multidrug Resistance in MDR Human Hepatoma HepG_2 Cells

OBJECTIVE The aim of the study was to examine the reversal effects of ultrasound （US） on the MDR in HepG2/ADM, a HepG2 cell line resistant to Adriamycin （ADM）, and to study the mechanism of US action.METHODS Using the MTT assay, the effects of US on MDR in HepG2/ADR cells were studied. Before and after the treatment with 0.5 W/cm^2 low intensity ultrasound （LIUS）, the expression of the MDR-related genes, mdrl, mrp and lrp was assayed with the reverse transcriptase polymerase chain reaction （RT-PCR） and the levels of their respective protein expression determined by flow cytometry. By using confocal laser scanning microscopy （CLSM）, we examined the intracellular daunorubicin （DNR） distribution, and the effects on the cells of treatment with US or DNR.RESULTS LIUS significantly reversed MDR in HepG2/ADR cells. After treatment with LIUS at 0.5 W/cm^2, chemosensitivity to ADM and DNR increased 3.35-fold and 2.81-fold, respectively. The reversal activity by LIUS plus verapamil （VER） was stronger than with either US or VER alone. After treatment with 0.5 W/cm^2, the expression of both the MDR1 and the MRP mRNA genes began to decline （P 〈 0.01 and P 〈 0.05, respectively）; the expression of LRP showed no significant changes. Changes in the expression of the P-glycoprotein （P-gp） and MRP were similar to those of their mRNA expressions. Results of the CLSM showed that administration of US （0. 5 W/cm^2） or VER （15.7 uM） with DNR to HepGa/ADM cells showed a significant change in the distribution of DNR in the cells.CONCLUSION Our results show that LIUS can reverse MDR. The reversal effects are stronger than those of either US or VER alone, when combined with VER administration. As LIUS is noninvasive causing no toxicity, it might have potential for clinical application. The reversal mechanism needs further study.

CYP3A5、MDR1基因多态性对他克莫司治疗后膜性肾病患者临床疗效和感染并发症的影响

目的 分析细胞色素P450酶3A5(CYP3A5)、多药耐药基因1(MDR1)基因多态性对他克莫司治疗后原发性膜性肾病(PMN)患者临床疗效和感染并发症的影响。方法 选择2020年10月至2022年10月郑州市第七人民医院收治的PMN患者75例,采用限制性片段长度多态性聚合酶链反应(PCR-RFLP)方法检测CYP3A5*3、MDR1 C1236T、MDR1 G2677T、MDR1 C3435T基因多态性,并比较不同基因型他克莫司C/D值(他克莫司血药浓度/剂量×体质量)差异以及对PMN患者临床疗效和感染并发症发生情况的影响。结果 CYP3A5*3中*3/*3基因型、G等位基因突变频率分别为54.67%和75.33%,MDR1 C1236T中CT基因型突变频率为57.33%,MDR1 G2677T中GT基因型突变频率为49.33%,MDR1 C3435T中CT基因型突变频率高达57.33%;CYP3A5*3中AA+AG基因型他克莫司C/D值低于GG基因型,差异有统计学意义(P<0.05),MDR1 C3435T中CC基因型他克莫司C/D值低于CT+TT基因型,差异有统计学意义(P<0.05);CYP3A5*3、MDR1 C1236T/A、MDR1 G2677T不同基因型使用的他克莫司剂量对PMN患者临床疗效的影响差异无统计学意义(P>0.05),MDR1 C3435T中CT+TT基因型他克莫司治疗缓解率高于CC基因型(71.70%比45.45%,P<0.05),差异有统计学意义;CYP3A5、MDR1不同基因型使用的他克莫司剂量对PMN患者感染并发症发生率,差异无统计学意义(P>0.05)。结论CYP3A5*3 GG基因型和MDR1 C3435T CT+TT基因型可升高他克莫司C/D值,且MDR1 C3435T CT+TT基因型患者他克莫司临床疗效较好。

Role of Hypoxia-inducible Factor-1α in Formation of Muttidrug Resistance Induced by Microenvironment in Hepatocellular Carcinoma

Objective： To explore the role of hypoxia-inducible factor-1α （HIF-1α） in formation of multidrug resistance （MDR） induced by microenvironment and to find a new and effective molecular target on preventing and reversing chemoresistance in hepatocellular carcinoma （HCC）. Methods： In HepG2 cells exposed to hypoxia, low glucose or transfected by plasmid pcDNA3/HBX, the expression of HIF-1α mRNA and protein was respectively detected using real-time fluorescent quantitative PCR and Westernblot technique and its expression localization was investigated by immunocytochemical technique. Plasmid pcDNA3/HIF-1α was transfected into HepG2 cells and then the expression of multidrug resistance related genes mdrl, multidrug resistance-associated protein 1 （MRP1） and lung resistance protein （LRP） in transfected cells was determined by the same methods. Results： In HepG2 cells respectively exposed to hypoxia, low glucose or transfected by plasmid pcDNA3/HBX, HIF-1α was overexpressed at mRNA and protein levels to varying degrees and translocated into nucleus. The gene expression levels of mdrl, MRP1 and LRP in HepG2 cells transfected by plasmid pcDNA3/HIF-1α were respectively increased by 2.4±0.2, 2.2±0.3 and 2.3±0.4 folds as compared with those in non-transfected HepG2 cells （all P〈0.01） and similar changes were observed in protein level. Conclusion： Microenvironmental factors around HCC could modulate the transcription of the MDR related genes by nuclear transcript factor HIF-1α, thereby conferred MDR of HCC. Up-regulation of HIF-1α expression could hold a central position in the formation of MDR of HCC induced by microenvironment. HIF-1α probably becomes a new and effective molecular target on preventing and reversing MDR in HCC.

Multidrug resistance associated proteins in multidrug resistance

Multidrug resistance proteins(MRPs) are members of the C family of a group of proteins named ATP-binding cassette(ABC) transporters.These ABC transporters together form the largest branch of proteins within the human body.The MRP family comprises of 13 members,of which MRP1 to MRP9 are the major transporters indicated to cause multidrug resistance in tumor cells by extruding anticancer drugs out of the cell.They are mainly lipophilic anionic transporters and are reported to transport free or conjugates of glutathione(GSH),glucuronate,or sulphate.In addition,MRP1 to MRP3 can transport neutral organic drugs in free form in the presence of free GSH.Collectively,MRPs can transport drugs that differ structurally and mechanistically,including natural anticancer drugs,nucleoside analogs,antimetabolites,and tyrosine kinase inhibitors.Many of these MRPs transport physiologically important anions such as leukotriene C4,bilirubin glucuronide,and cyclic nucleotides.This review focuses mainly on the physiological functions,cellular resistance characteristics,and probable in vivo role of MRP1 to MRP9.

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.

Plasmid mediated antibiotic resistance of Vibrio cholerae Ol biotype E1 Tor serotype Ogawa associated with an outbreak in Kolkata,India

Objective:To determine the antibiotic resistance of Vibrio choleras(V.cholerae) O1 biotype El Tor serotype Ogawa isolates involved in an outbreak of watery diarrhea in Kolkata,and to explore the role of plasmid in mediating antibiotic resistance.Methods:Antibiotic susceptibility and minimum inhibitory concentration(MIC) values of antibiotics for the isolated V.cholerae 01 Ogawa(n=12) were determined by disk diffusion and agar dilution methods,respectively,using ampicillin(Am),chloramphenicol(C),trimethoprim(Tm),tetracycline(T).erythromycine(Er), nalidixic acid(Nx).ciprofloxacin(Cp),amikacin(Ak) and cefotaxime(Cf).Plasmid curing of multidrug resistant(MDR) V.cholerae 01 Ogawa strains was done following ethidium bromide treatment.Following electrophoresis,the plasmid DNAs,extracted from the isolated MDR V. cholerae O1 Ogawa strains and their cured derivatives,were visualized and documented in ’gel doc’ system.Results:The outbreak causing V.cholerae O1 Ogawa isolates were MDR as determined by disk diffusion susceptibility test,and MIC determination.The isolates showed three different drug resistance patterns:AmTmTErNx(for 6 isolates).TmTErCp(for 5 isolates), and AmTniNx(for one isolate),and showed uniform sensitivity to C,Ak and Cf.The loss of plasmids with the concomitant loss of resistance to Am,Tm,T and Er of the isolates occurred following ethidium bromide treatment.Conclusions:The current findings suggest that the V. cholerae O1 Ogawa associated with the cholera outbreak were MDR,and resistance to Am,Tm,T and Er among the isolates were plasmid mediated.

The expression and significance of the multidrug resistance-related proteins P-gp, MRP and LRP in human non-small cell lung cancer tissues

Objective: To explore the expression and significance of the multidrug resistance-related proteins P-glycopro-tein (P-gp), multidrug resistance-related protein (MRP), lung resistance protein (LRP) in human non-small cell lung cancer (NSCLC) tissues and paratumor tissues. Methods: Immunohistochemistry (IHC) was used to examine the expression level of proteins P-gp, MRP and LRP in 43 samples of NSCLC and 15 samples of paratumor tissues. Results: The expression rates of P-gp, MRP and LRP in 43 tumor tissues were 74.42% (32/43), 67.44% (29/43) and 88.37% (38/43), respectively, while in 15 paratumor tissues were 13.33% (2/15), 20.00% (3/15) and 6.67% (1/15), respectively. There was significant difference in the expression of proteins (P-gp, MRP and LRP) between lung cancer tissues and paratumor tissues (P < 0.05). The expres-sion of proteins P-gp, LRP in lung adenocarcinoma were higher than that in other pathological carcinomas (P < 0.05). The expression of protein MRP was not related to pathological type, clinical stage and classification of histodifferentiation (P > 0.05). Conclusion: Multidrug resistance is more common in NSCLC. The proteins of P-gp, MRP and LRP participated in the formation of multidrug resistance in lung cancer. Detection of multidrug resistance-related proteins in lung cancer tissues may be useful to choice drugs.

Natural Products Modulate the Multifactorial Multidrug Resistance of Cancer

Multidrug resistance (MDR) is a critical problem in cancer chemotherapy. Cancer cells can develop resistance not only to a single cytotoxic drug, but also to entire classes of structurally and functionally unrelated compounds. Several mechanisms can mediate the development of MDR, including increased drug efflux from the cells by ABC-transporters (ABCT), activation of metabolic enzymes, and defective pathways towards apoptosis. Many plant secondary metabolites (SMs) can potentially increase sensitivity of drug-resistant cancer cells to chemotherapeutical agents. The present thesis investigates the modulation of MDR by certain medicinal plants and their active compounds. The inhibition of ABCTs (P-gp/MDR1, MRP1, BCRP) and metabolic enzymes (GST and CYP3A4), and the induction of apoptosis are useful indicators of the efficacy of a potential medicinal drug. The focus of this study was the possible mechanisms of drug resistance including: expression of resistance proteins, activation of metabolic enzymes, and alteration of the apoptosis and how to overcome their resistance effect on cancer cells. The overall goal of this review was to evaluate how commonly used medicinal plants and their main active secondary metabolites modulate multidrug resistance in cancer cells in order to validate their uses as anticancer drugs, introduce new therapeutic options for resistant cancer, and facilitate the development of their anticancer strategies and/or combination therapies. In conclusion, SMs from medicinal plants exhibit multitarget activity against MDR-related proteins, metabolic enzymes, and apoptotic signaling, this may help to overcome resistance towards chemotherapeutic drugs.