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

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

EXPRESSION OF MULTIDRUG RESISTANCE-ASSOCIATED PROTEIN IN HUMAN GASTRIC AND RENAL CARCINOMAS

Objective The clinical signilicance of exPression of multidrug resistance- associated protein (MRP) in gastric and renal carcinoma was investigated. Methods LSAB immunohistochemistry was performed to detect eopression of MRP in the carcinoma tissues of 52 patients with gastric carcinoma and 20 cases with renal cell carcinoma. Results The positive expression rate of MRP was 38.5% (20/52) in gastric carcinoma tissues, and 60% (12/20) in renal carcinoma tissues. The expression of MRP both on cellular membrane and in cytoplasm was observed, but the expression in cytoplasm (thick granule) was more obvious. The positive expression rates of MRP in advanced gastric and renal carcinoma (Ⅲ orⅣ stage) were 60% (15/25) and 88.90% (8/9) reSPectively, which were higher than those in early lesion (Ⅰ or Ⅱ stage, 18.5% and 36.4% respectively). Furthermore, the patients with positive expression of MRP in gastric carcinoma tissues had shorter mean survival time and lower 5-year survival rate than that with negative eopression of MRP. Conclusion MRP plays an important role in the infiltration and metastasis of gastric and renal carcinoma and might contribute to the intrinsic drug - resistance in both carcinomas.

Effect of Histone Deacetylase Inhibition on the Expression of Multidrug Resistance-associated Protein 2 in a Human Placental Trophoblast Cell Line

Background： Placental multidrug resistance-associated protein 2 （MRP2）, encoded by ABCC2 gene in human, plays a significant role in regulating drugs＇ transplacental transfer rates. Studies o11 placental MRP2 regulation could provide more therapeutic targets for individualized and safe pharmacotherapy during pregnancy. Currently, the roles of epigenetic mechanisms in regulating placental drug transporters are still unclear. This study aimed to investigate the effect of histone deacetylases （HDACs） inhibition on MRP2 expression in the placental trophoblast cell line and to explore whether HDAC 1/2/3 are preliminarily involved in this process. Methods： The human choriocarcinoma-derived trophoblast cell line （Bewo cells） was treated with the HDAC inhibitors-trichostatin A （TSA） at different concentration gradients of 0.5, 1.0, 3.0, and 5.0 μmol/L. Cells were harvested after 24 and 48 h treatment. Small interfering RNA （siRNA） specific for HDACI/HDAC2/HDAC3 or control siRNA was transfected into cells. Total HDAC activity was detected by colorimetric assay kits. HDAC 1/2/3/ABCC2 messenger RNA （mRNA） and protein expressions were determined by real-time quantitative polymerase chain reaction and Western-blot analysis, respectively. Immunofluorescence for MRP2 protein expression was visualized and assessed using an immunofluorescence microscopy and ImageJ software, respectively. Results： TSA could inhibit total HDAC activity and HDAC 1/2/3 expression in company with increase ofM RP2 expression in Bewo cells. Reduction of HDAC 1 protein level was noted after 24 h of TSA incubation at 1.0, 3.0, and 5.0 μmol/L （vs. vehicle group, all P 〈 0.001 ）, accompanied with dose-dependent induction of MRP2 expression （P = 0.045 for 1.0 μmol/L, P = 0.001 for 3.0 μmol/L, and P 〈 0.001 for 5.0 μmol/L）, whereas no significant diferences in MRP2 expression were noted after HDAC2/3 silencing. Fluorescent micrograph images of MRP2 protein were expressed on the cell membrane. The fluorescent intensities of MRP2 in the control, HDAC2, and HDAC3 siRNA-transfected cells weir week, and no significant differences were noticed among these three groups （all P 〉 0.05）. However, MRP2 expression was remarkably elevated in H DAC1 siRNA-transfected cells, which displayed an almost 3.19-fold changes in comparison with the control siRNA-transfected cells （P 〈 0.001 ）. Conclusions： HDACs inhibition could up-regulate placental MRP2 expression in ritzy, and HDAC 1 was probably to be involved in this process.

EXPRESSION AND CLINICAL SIGNIFICANCE OF MULTIDRUG RESISTANCE GENE AND MULTIDRUG RESISTANCE-ASSOCIATEDPROTEIN GENE IN ACUTE LEUKEMIA

Objective: To evaluate the expression and clinical significance of multidrug resistance gene (mdr1) and multidrug resistance-associated protein (MRP) gene in acute leukemia. Methods: The expression of mdr1 and MRP assay in 55 patients with acute leukemia (AL) by reverse transcription polymerase chain reaction (RT-PCR). Results: The mdr1 and MRP gene expression levels in the relapsed AL and the blastic plastic phases of CML were significantly higher than those in the newly diagnostic AL and controls. The mdr1 and MRP gene expression levels in the clinical drug-resistant group were significantly higher than those in the non-drug-resistant group. The complete remission (CR) rate in patients with high mdr1 expression (14.3%) was significantly lower than that with low mdr1 expression (57.5%); similarly the CR rate in patients with high MRP level was also lower than that with low MRP level. Using both high expression of mdr1 and MRP gene as the indicator for evaluating multidrug resistance (MDR), the positive predictive value and accuracy increased in comparison with single gene high expression. Conclusion: Elevated level of mdr1 or MRP gene expression might be unfavorable prognostic factors for AL patient and may be used as an important index for predicting drug-resistance and relapse in AL patient. Measuring both mdr1 and MRP gene expression would increase accuracy and sensibility of evaluating MDR in acute leukemia.

Expression and significance of multi-drug resistance-associated protein 3 in different tumor cell lines

Objective To investigate the expression and meaning of MRP3 in different tumor cells. MethodsThe monoclonal antibody against MRP3 was used to identify the expression of MRP3 by flow cytometer in seven tumor cells and human embryo kidney cell lines 293T.And RT-PCR was used to detect the mRNA of MRP3 in eight cell lines. ResultsThe mRNA of MRP3 was expressed in three pancreatic carcinoma cell lines.MRP3 protein was observed in BxPC-3 and AsPC-1 cells. ConclusionMRP3 may express in different tumor in tissue-specific manner.BxPC-3 and AsPC-1 may serve as cellular models for in vitro studies on multidrug resistance of pancreatic carcinoma.

JNK1,JNK2,and JNK3 are involved in P-glycoprotein-mediated multidrug resistance of hepatocellular carcinoma cells

BACKGROUND:Multidrug resistance(MDR)is extremely common in hepatocellular carcinoma(HCC)and is a major problem in cancer eradication by limiting the efficacy of chemotherapy.Modulation of c-Jun NH2-terminal kinase(JNK)activation could be a new method to reverse MDR.However,the relationship between JNK activity and MDR in HCC cells is unknown.This study aimed to explore the relationship between MDR and JNK in HCC cell lines with different degrees of MDR.METHODS:A MDR human HCC cell line,SMMC-7721/ ADM,was developed by exposing parental cells to gradually increasing concentrations of adriamycin.The MTT assay was used to determine drug sensitivity.Flow cytometry was used to analyze the cell cycle distribution and to measure the expression levels of P-glycoprotein(P-gp)and MDR-related protein(MRP)-1 in these cells.JNK1,JNK2 and JNK3 mRNA expression levels were quantified by real-time PCR.Expression and phosphorylation of JNK1,JNK2,and JNK3 were analyzed by Western blotting.RESULTS:The MDR of SMMC-7721/ADM cells resistant to 0.05 mg/L adriamycin was mainly attributed to the overexpression of P-gp but not MRP1.In addition,these cells had a significant increase in percentage in the S phase,accompanied by a decrease in percentage in the G0/G1 phase,which is likely associated with a reduced ability for cell proliferation and MDR generation.We found that JNK1,JNK2,and JNK3 activities were negatively correlated with the degree of MDR in HCC cells.CONCLUSION:This study suggests that JNK1,JNK2,and JNK3 activities are negatively correlated with the degree of MDR in HCC cells.

Correlative Expression of Glutathion S-Transferase-π and Multidrug Resistance Associated Protein in Bladder Transitional Cell Carcinoma

In order to elucidate the mechanisms of multidrug resistance (MDR) in bladder cancer, the expression of glutathione S-transferase-π (GST-π) and multidrug resistance associated protein (MRP) in tissue samples resected from 44 patients and 6 normal bladder mucosa as control was de- tected by using immunohistochemical method, and the results were analyzed by computer-assisted im- age analyzing system (IAS) to achieve semi-quantitative data. In addition, correlation between the expression of both factors was studied. The results showed that the positive expression rate of GST- π and MRP in bladder cancer was 72. 7 % (32/44) and 68. 2 % (30/44) respectively, significantly higher than those in normal bladder mucosa, being 16. 7% and 33. 3% respectively. The rate of GST-πpositive staining was increased correspondingly with tumor grade and stage elevated, being higher in recurrent tumors treated by chemotherapy, but not significantly (P>0. 05). There was no significant differences between the expression of MRP and tumors' behaviors and clinical characters. However, the results demonstrated that the correlation between the expression of both resistant fac- tors was very evident (r=0. 695, P<0. 0025). It was suggested that the activation of GST-π and MRP might occur during malignant transformation of normal mucosa, but tumors' differentiation and progression could not be the unique factors that influenced both overexpression. Chemotherapy might be another important reason. The correlation of both indicated that there was a common mech- anism regulating their expression probably, which made them play a pivotal role in chemotherapy drug resistance of bladder cancers.

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.

Down-regulation of extracellular signal-regulated kinase 1/2 activity in P-glycoprotein-mediated multidrug resistant hepatocellular carcinoma cells

AIM:To study the expression and phosphorylation of extracellular signal-regulated kinase(ERK)1 and ERK2 in multidrug resistant(MDR)hepatocellular carcinoma(HCC)cells.METHODS:MDR HCC cell lines,HepG2/adriamycin(ADM)and SMMC7721/ADM,were developed by exposing parental cells to stepwise increasing concentrations of ADM.MTT assay was used to determine drug sensitivity.Flow cytometry was employed to analyze cell cycle distribution and measure cell P-glycoprotein(P-gp)and multidrug resistant protein 1(MRP1)expression levels.ERK1 and ERK2 mRNA expression levels were measured by quantitative real-time PCR(QRTPCR).Expression and phosphorylation of ERK1 and ERK2 were analyzed by Western blot.SMMC7721/ADM were resistant not only to ADM,but also to multiple anticancer drugs.The P-gp expression was over 10-fold higher in HepG2/ADM cells than in HepG2 cells(8.92%±0.22%vs 0.88%±0.05%,P<0.001)and over 4-fold higher in SMMC7721/ADM cells than in SMMC7721 cells(7.37%±0.26%vs 1.74%±0.25%,P<0.001).However,the MRP1 expression was not significantly higher in HepG2/ADM and SMMC7721/ADM cells than in parental cells.In addition,the percentage of MDR HepG2/ADM and SMMC7721/ADM cells was significantly decreased in the G0/G1 phase and increased in the the S phase or G2/M phase.QRT-PCR analysis demonstrated that the ERK1 and ERK2 mRNA expression increased apparently in HepG2/ADM cells and decreased significantly in SMMC7721/ADM cells.Compared with the expression of parental cells,ERK1 and ERK2 protein expressions were markedly decreased in SMMC7721/ADM cells.However,ERK2 protein expression was markedly increased while ERK1 protein expression had no significant change in HepG2/ADM cells.Phosphorylation of ERK1 and ERK2 was markedly decreased in both HepG2/ADM and SMMC7721/ADM MDR cells.CONCLUSION:ERK1 and ERK2 activities are downregulated in P-gp-mediated MDR HCC cells.ERK1 or ERK2 might be a potential drug target for circumventing MDR HCC cells.

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.

Multidrug resistance protein 3 R652G may reduce susceptibility to idiopathic infant cholestasis

AIM:To evaluate the role of genetic factors in the pathogenesis of idiopathic infant cholestasis.METHODS:We performed a case-control study,in-cluding 78 infants with idiopathic infant cholestasis and 113 healthy infants as controls.Genomic DNA was extracted from peripheral venous blood leukocytes us-ing phenol chloroform methodology.Polymerase chain reaction was used to amplify the multidrug resistance protein 3(MDR3)R652G fragment,and products were sequenced using the ABI 3100 Sequencer.RESULTS:The R652G single nucleotide polymorphism(SNP)was significantly more frequent in healthy infants(allele frequency 8.0%)than in patients(allele frequency 2.60%)(P < 0.05),odds ratio,0.29;95% confidence interval,0.12-0.84.The conjugated bilirubin in patients with the AG genotype was significantly lower than in those with the AA genotype(44.70 ± 6.15 μmol/L vs 95.52 ± 5.93 μmol/L,P < 0.05).CONCLUSION:MDR3 R652G is negatively correlated with idiopathic infant cholestasis.Children with the R652G SNP in Guangxi of China may have reduced susceptibility to infant intrahepatic cholestasis.

Expression of multidrug-resistance associated proteins in human retinoblastoma treated by primary enucleation

AIM： To reveal the expression of multidrug-resistance associated proteins： glutathione-S-transferase π（GSTπ）, P-glycoprotein（P-gp） and vault protein lung resistance protein（LRP） in retinoblastoma（RB） without any conservative treatment before primary enucleation and to correlate this expression with histopathological tumor features. METHODS： A total of 42 specimens of RB undergone primary enucleation were selected for the research. Sections from the formalin-fixed, paraffin-embedded specimens were stained with HE and immunohistochemistry to detect the expression of GSTπ, P-gp and LRP.RESULTS： GSTπ was expressed in 39/42（92.86%） RBs and in 9/9（100%） well-differentiated RBs. P-gp/GSTπ was found in 30（71.42%） of 42 RBs. Totally 9（21.43%） tumors were well differentiated and 33（78.57%） were poorly differentiated. Totally 15（35.71%） eyes had optic nerve（ON） tumor invasion, 36（85.71%） had choroidal tumor invasion, and 14（33.33%） had simultaneous choroidal and ON invasion. There was no statistically significant relationship between P-gp, GSTπ, LRP positivity and the degree of ocular layer tumor invasion and ON tumor invasion（P〉0.05）. CONCLUSION： RB intrinsically expresses GSTπ, P-gp and LRP. GSTπ expression is positive in 100% welldifferentiation ones, so in which way it is correlated with differentiation. But the other two proteins expressions are not related to tumor differentiation and to the degree of tumor invasion. GSTπ may be a new target of chemotherapy in RB.

Expression of multidrug resistance proteins in retinoblastoma

AIM： To elucidate the mechanism of multidrug resistance in retinoblastoma, and to acquire more insights into in vivo drug resistance.METHODS： Three anticancer drug resistant Y79 human RB cells were generated against vincristine, etoposide or carboplatin, which are used for conventional chemotherapy in RB. Primary cultures from enucleated eyes after chemotherapy（PCNC） were also prepared. Their chemosensitivity to chemotherapeutic agents（vincristine, etoposide and carboplatin） were measured using MTT assay. Western blot analysis was performed to evaluate the expression of p53, Bcl-2 and various multidrug resistant proteins in retinoblastoma cells.RESULTS： Following exposure to chemotherapeutic drugs, PCNC showed less sensitivity to drugs. No significant changes observed in the p53 expression, whereas Bcl-2 expression was found to be increased in the drug resistant cells as well as in PCNC. Increased expression of P-glycoprotein（P-gp） was observed in drug resistant Y79 cells; however there was no significant change in the expression of P-gp found between primary cultures of primarily enucleated eyes and PCNC. Multidrug resistance protein 1（Mrp-1） expression was found to be elevated in the drug resistant Y79 cells as well as in PCNC. No significant change in the expression of lung resistance associatedprotein（Lrp） was observed in the drug resistant Y79 cells as well as in PCNC.CONCLUSION： Our results suggest that multidrug resistant proteins are intrinsically present in retinoblastoma which causes treatment failure in managing retinoblastoma with chemotherapy.

Molecular Modelling of Human Multidrug Resistance Protein 5 (ABCC5)

Multidrug resistance protein 5 (MRP5/ABCC5) is a 161 kDa member of the super family of ATP-binding cassette (ABC) superfamily of transmembrane transporters that is clinically relevant for its ability to confer multidrug resistance by actively e?uxing anticancer drugs. ABCC5 has also been identified as an efflux transporter of cGMP (cyclic guanosine monophosphate). Elevated intracellular levels of cGMP in cancer cells have been implicated in several clinical studies, that may induce apoptosis, and as a result many different cancer cells seem to overcome this deleterious effect by increased efflux of cGMP through ABCC5. Thus inhibition of ABCC5 may have cytotoxic effects mediated through cGMP and it will also increase the intracellular concentration of other drugs that are aimed for the treatment of cancer which are otherwise exported out of the cells. Considering the functional importance and lack of X-ray crystal structure of ABCC5, present work was undertaken to construct 3D structure of protein using homology modeling protocol of YASARA structure (V. 16.3.28). In this study, five different ABC templates (PDB ID’s: 4F4C, 4Q9H, 4M1M, 4M2T and 4KSD) were used for homology modeling. Five models were constructed on each template and a hybrid model was built using all five templates. All models were refined and ranked as per their overall Z-score. The top ranked ABBC5 model was based on template 4Q9H that had 91.2% of residues in allowed regions as revealed by PROCHECK-NMR and the QMEAN score was 0.54 which indicated a reliable model. The results of the study and the proposed model can be further used for elucidating the structural and functional aspects of ABCC5 and to gain more insights to the molecular basis of ABCC5 inhibition through docking studies.

多药耐药相关蛋白转运体在药物性肝损伤中的作用研究进展

肝脏是人体新陈代谢最旺盛的器官,也是体内多种药物的解毒器官。当长期或过量使用药物时会增加药物性肝损伤(DILI)的风险。多药耐药相关蛋白(MRPs)是位于细胞膜上的功能蛋白,可转运多种药物,在DILI中发挥重要作用。MRPs功能的抑制、缺失是药物肝毒性产生的重要原因。本文对MRPs的结构、表达部位及功能进行归纳,并对MRPs与DILI的关系及其改善DILI的机制进行总结,期望更好地了解MRPs转运体与DILI的关系,为后续防治DILI提供参考。

蛋白质糖基化修饰在结直肠癌中的研究进展

结直肠癌作为中国最常见的恶性肿瘤之一,涉及多种复杂的病理生理过程。随着糖组学的深入研究,揭露了蛋白质糖基化修饰与结直肠癌的发生、进展、转移及多药耐药的密切关系,糖基化的改变作为重要的生物标志物,为早期诊断及干预治疗提供了新的靶点。本文综述了蛋白质糖基化修饰在结直肠癌中最新研究进展,希望可以通过靶向相关糖基化修饰位点,改善患者预后及耐药性。

ATP结合盒亚家族B成员4(ABCB4)基因突变相关性肝硬化合并胆囊结石1例报告

ATP结合盒亚家族B成员4(ABCB4)基因突变疾病谱涉及进行性家族性肝内胆汁淤积3型、胆石症、妊娠期肝内胆汁淤积症、门静脉高压、肝硬化,甚至原发性肝脏、胆道恶性肿瘤等多种疾病。本院肝胆内科收治1例青年男性患者,入院初步诊断为胆囊结石,计划腹腔镜胆囊切除术,术前检查发现该患者肝功能异常、肝硬化、脾大、食管静脉轻度曲张,后进一步行二代测序明确诊断为ABCB4基因突变相关性肝硬化合并胆囊结石,给予熊去氧胆酸胶囊利胆治疗后,肝功能逐渐恢复正常。

Effects of Hypoxia on Expression of P-gp and Mutltidrug Resistance Protein in Human Lung Adenocarcinoma A549 Cell Line

To study the effects of hypoxia on the expression of P-gp and mutltidrug resistance protein in human lung adenocarcinoma A549 cell line, and to explore the probable mechanism of hypoxia in tumor cell of MDR. The expression of hypoxia inducible factor-1α, P-gp and mutltidrug resistance protein was immunohistochemically detected by culturing human lung adenocarcinoma A549 cell under hypoxia (2 % O_2) for 24 h. After interaction with adriamycin or cisplatin under hypoxia (2 % O_2) for 24 h, the cell survival rate was detected by MTT. Our results showed that the expression of hypoxia inducible factor-1α, P-gp and mutltidrug resistance protein under hypoxia were higher than the expression under normoxia, and correlations between the expression of HIF-1α and P-gp or multidrug resistance-associated protein was observed (P<0.05). The resistance of adriamycin of A549 cell was enhanced under hypoxia. It is concluded that the resistance of tumor chemotherapy is enhanced in hypoxia. The expression of HIF-1α is obviously correlated with the expression of P-gp and mutltidrug resistance protein.

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

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