The relationship among amyloid-βdeposition,sphingomyelin level,and the expression and function of P-glycoprotein in Alzheimer’s disease pathological process

In Alzheimer’s disease,the transporter P-glycoprotein is responsible for the clearance of amyloid-βin the brain.Amyloid-βcorrelates with the sphingomyelin metabolism,and sphingomyelin participates in the regulation of P-glycoprotein.The amyloid cascade hypothesis describes amyloid-βas the central cause of Alzheimer’s disease neuropathology.Better understanding of the change of P-glycoprotein and sphingomyelin along with amyloid-βand their potential association in the pathological process of Alzheimer’s disease is critical.Herein,we found that the expression of P-glycoprotein in APP/PS1 mice tended to increase with age and was significantly higher at 9 and 12 months of age than that in wild-type mice at comparable age.The functionality of P-glycoprotein of APP/PS1 mice did not change with age but was significantly lower than that of wild-type mice at 12 months of age.Decreased sphingomyelin levels,increased ceramide levels,and the increased expression and activity of neutral sphingomyelinase 1 were observed in APP/PS1 mice at 9 and 12 months of age compared with the levels in wild-type mice.Similar results were observed in the Alzheimer’s disease mouse model induced by intracerebroventricular injection of amyloid-β1-42 and human cerebral microvascular endothelial cells treated with amyloid-β1-42.In human cerebral microvascular endothelial cells,neutral sphingomyelinase 1 inhibitor interfered with the changes of sphingomyelin metabolism and P-glycoprotein expression and functionality caused by amyloid-β1-42 treatment.Neutral sphingomyelinase 1 regulated the expression and functionality of P-glycoprotein and the levels of sphingomyelin and ceramide.Together,these findings indicate that neutral sphingomyelinase 1 regulates the expression and function of P-glycoprotein via the sphingomyelin/ceramide pathway.These studies may serve as new pursuits for the development of anti-Alzheimer’s disease drugs.

Effect of Cyclooxygenase Inhibition on P-Glycoprotein Expression and Phenytoin Level in Brain Tissue of Pilocarpine Induced Epilepsy in Rats

Background: Increased brain P-glycoprotein (P-gp) expression may play important role in resistance to antiseizure drugs. The present work aimed to overcome the drug resistance that develop due to overexpression of P-gp with subsequent increase in brain phenytoin level in epileptic rats, using either non-selective (indomethacin) or selective (celecoxib) cyclooxygenase inhibitors. Methods: Fifty-six adult male albino rats were randomly divided into seven groups. Epilepsy was induced using the lithium pilocarpine model. Rats received indomethacin (2.5 mg/kg) or celecoxib (20 mg/kg), either alone or combined with phenytoin (50 mg/kg). Seizures were evaluated using Racine score. Motor coordination was assessed using open field and rotarod tests. Phenytoin brain level was measured using High Performance Liquid Chromatography (HPLC), glutamate expression was measured using Enzyme Linked Immunosorbent Assay (ELISA), ATP Binding Cassette Subfamily B Member 1 (ABCB1) gene expression was assessed using Real Time-Polymerase Chain Reaction (RT-PCR), and immunohistochemical analysis was done for P-gp expression. Results: Phenytoin combination with either indomethacin or celecoxib had improved the Racine score, motor coordination on rotarod apparatus, and open field test results. Also, phenytoin combination with either indomethacin or celecoxib decreased brain glutamate level, ABCB1 gene and P-gp expression, and increased brain phenytoin level compared to treatment with phenytoin alone. This indicated that both P-gp inhibitors indomethacin and celecoxib, increased the level of phenytoin that reached the brain of rats. However, brain uptake of phenytoin was significantly enhanced using celecoxib rather than indomethacin (CI 95%, 17.092: 32.808, P-value Conclusion: Cyclooxygenase inhibition using either celecoxib or indomethacin resulted in downregulation of P-gp expression, with subsequent increase in brain phenytoin level in epileptic rats.

局灶性脑缺血大鼠脑内mdr1／P-glycoprotein表达的变化

目的观察大鼠局灶性脑缺血损害后脑内mdr1／P—glycoprotein的表达变化。方法大鼠大脑中动脉栓塞法(MCAO法)制作局灶性脑缺血模型,脑切片免疫组织化学染色检测mdr-1／P—glycoprotein在脑内的表达部位及表达时程的变化。结果 mdr-1／P—glycoprootein在缺血侧皮层和纹状体的血管内皮细胞表达增多,并出现在同侧损伤部位的神经元,其在损伤后2h开始出现,6h达到高峰,之后开始下降,到24h不能被检测到。结论大脑中动脉阻塞后可以诱导缺血损伤侧的血管内皮细胞P—glycoprotein过量表达,而同侧的神经元短暂表达P-glyco- protein．

核偏最小二乘法及其在P-glycoprotein抑制剂设计中应用

介绍了一个新的基于优化推导出的核偏最小二乘(kernel partial least squares,K-PLS)的算法原理和实现步骤,并且给出了利用K-PLS法构建P-糖蛋白(P-glycoprotein,P-gp)黄酮类抑制剂的定量构效关系(QSAR)模型.利用该方法结合几个简单的分子拓扑参数,构建了具有高准确率的预测模型.该模型将有助于P-gp黄酮类抑制剂的虚拟筛选和理性设计.结果证明K-PLS是一个十分稳定可靠的方法,将会在化学计量学领域得到较好的应用和推广.

P-glycoprotein的新功能在肿瘤研究中的进展

肿瘤多药耐药性(multiple drug resistance,MDR)的发生往往伴随着多药耐药基因如MDR1、MRP1和BCRP等高表达,其中MDR1基因编码的P-糖蛋白(P-glycoprotein,P-gp)是目前公认可以诱发癌细胞发生MDR的重要分子。传统研究认为P-gp主要是作为一个药物泵将化疗药物从细胞内排出从而导致MDR。然而系列研究发现,除了介导MDR以外,P-gp还能够调节癌细胞的生长、增殖、凋亡、迁移和侵袭等其他生物学行为;而且研究表明P-gp的这些作用可以依赖,也可以不依赖于其药物泵的功能。这些结果表明P-gp能够通过一些新的机制促进肿瘤的进展。本文主要针对P-gp在促进肿瘤进展中的作用进行综述。

多药耐药糖蛋白p-glycoprotein及其抑制剂的研究进展

多药耐药是肿瘤化疗失败的主要原因之一,以p-glycoprotein(p-gp)的过度表达为主要特征,可将肿瘤细胞内的化疗药物排出胞外,导致化疗效果降低,从而使肿瘤细胞产生耐药性。抑制p-gp外排药物可以提高化疗药物杀伤肿瘤细胞的作用,对提高化疗效果具有重要意义。多药耐药糖蛋白抑制剂的发展经历了三代,并日趋完善,在化疗中起着重要作用,但仍需改进。本文对多药耐药糖蛋白p-gp及其抑制剂的研究进展作一综述。

Using ^(99m)Tc-MIBI to Evaluate the Effects of Chemosensitizer on P-glycoprotein in Multidrug-resistant Carcinoma Cells

To establish a method to evaluate the effects of chemosensitizer onP-glycoprotein using ^(99m)Tc-MIBI, and observe the changes of ^(99m)Tc-MIBI uptake kinetics andP-glycoprotein levels after using verapamil in MDR human breast cells MCF-7/Adr. Methods: MDR breastcarcinoma cells, MCF-7/Adr, were incubated and different protocols were performed. Protocol Ⅰ: achemosensitizer, verapamil (10 μmol/L), was added into cell culture medium, while in control group,the same volume of DMEM was given. Cells were harvested after 2 h incubation with ^(99m)Tc-MIBI.Protocol Ⅱ: Verapamil (10 μmol/L) was added into cell culture medium and incubated for 20 min, 40min, 60 min, 80 min, 8 h, 24 h, 48 h and 72 h respectively. Cells were harvested after 2 hincubation with ^(99m)Tc-MIBI. The radioactivity of the cells was measured and P-glycoproteinexpression levels were determined with immunohistochemical stain. Results: Protocol Ⅰ: After 2hincubation with verapamil the cellular uptake of ^(99m)Tc-MIBI was remarkably higher than controlgroup (t=2.33, P 【 0.05), but there was no difference in P-glycoprotein expression levels betweentwo groups (P 】 0.05). Protocol Ⅱ: In verapamil group, ^(99m)Tc-MIBI uptake was increased withincubation time prolonging (F=58.2, P 【 0.05). When verapamil incubation time surpassed 8 h the^(99m)Tc-MIBI uptake negatively correlated to the P-glycoprotein expression levels (r=-0.73, P 【0.01). However, when incubation time was less than 80 min, there was no correlation between^(99m)Tc-MIBI accumulation and P-glycoprotein levels (r=0.16, P 】 0.05). Conclusion: ^(99m)Tc-MIBImay be used to evaluate the qualitative as well as quantitative change of P-glycoprotein expressionlevels induced by the chemosensitizer, verapamil.

Correlation between c-erbB-2 and P-glycoprotein Expression in Esophageal Carcinoma

Objective： To investigate the correlation between c-erbB-2 and multidrug resistance （MDR） and its clinical significance, Methods： Immunohistochemistry stain was used to examine the expression of c-erbB-2 and flow cytometry was used to detect the expression of P-glycoprotein （P-gp） in samples from 46 patients with esophageal carcinoma. Results： The positive expression rate of c-erbB-2 was 26.1% （12/46） in the 46 cases of esophageal carcinoma, of which 4 cases being low expression and 8 cases mediumhigh expression. The positive expression rate of P-gp was 60.9% （28/46） in the 46 cases of esophageal carcinoma, of which 6 cases being low expression, 13 cases medium expression and 9 cases high expression. Comparing c-erbB-2 with P-gp expression in different lymph node metastasis statuses showed that there was significant difference （P〈0.01） between P-gp expressions with lymph node metastasis （31.09%±5.33%） and without lymph node metastasis （8.04%±3.03%） when c-erbB-2 expression was positive. Comparing c-erbB-2 with P-gp expression in different TNM stages of esophageal carcinoma showed that there was significant difference （P〈0.01） between P-gp expressions in HI Ⅳ stage （33.68%±5.51%）and in Ⅱ stage patients （9.30%±2.78%） when c-erbB-2 expression was positive. The tumor＇s size and differentiation degree were not related to c-erbB-2 and P-gp expression. Conclusion： The high level of P-gp expression was related to the positive expression of c-erbB-2 with the lymph node metastasis in clinical Ⅲ-Ⅳ stage patients of esophageal carcinoma, suggesting that the double positive might lead to a poor prognosis. However, when the c-erbB-2 expression was negative, the lymph node metastasis and clinical staging were not related to the P-gp expression in esophageal carcinoma patients.

Some substrates of P-glycoprotein targeting <i>β</i>-amyloid clearance by quantitative structure-activity relationship (QSAR)/membrane-interaction (MI)-QSAR analysis

The pathogenesis of Alzheimer’s disease (AD) putatively involves a compromised blood-brain barrier (BBB). In particular, the importance of brain-to-blood transport of brain-derived metabolites across the BBB has gained increasing attention as a potential mechanism in the pathogenesis of neurodegenerative disorders such as AD, which is characterized by the aberrant polymerization and accumulation of specific misfolded proteins, particularly β-amyloid (Aβ), a neuropathological hallmark of AD. P-glycoprotein (P-gp), a major component of the BBB, plays a role in the etiology of AD through Aβ clearance from the brain. Our QSAR models on a series of purine-type and propafenone-type substrates of P-gp showed that the interaction between P-gp and its modulators depended on Molar Refractivity, LogP, and Shape Attribute of drugs it transports. Meanwhile, another model on BBB partitioning of some compounds revealed that BBB partitioning relied upon the polar surface area, LogP, Balaban Index, the strength of a molecule combined with the membrane-water complex, and the changeability of the structure of a solute-membrane-water complex. The predictive model on BBB partitioning contributes to the discovery of some molecules through BBB as potential AD therapeutic drugs. Moreover, the interaction model of P-gp and modulators for treatment of multidrug resistance (MDR) indicates the discovery of some molecules to increase Aβ clearance from the brain and reduce Aβ brain accumulation by regulating BBB P-gp in the early stages of AD. The mechanism provides a new insight into the therapeutic strategy for AD.

Evaluating the regulation of transporter proteins and P-glycoprotein in rats with cholestasis and its implication for digoxin clearance

BACKGROUND Cardiac and hepatic functionality are intertwined in a multifaceted relationship.Pathologic processes involving one may affect the other through a variety of mechanisms,including hemodynamic and membrane transport effects.AIM To better understand the effect of extrahepatic cholestasis on regulations of membrane transporters involving digoxin and its implication for digoxin clearance.METHODS Twelve adult rats were included in this study;baseline hepatic and renal laboratory values and digoxin pharmacokinetic(PK)studies were established before evenly dividing them into two groups to undergo bile duct ligation(BDL)or a sham procedure.After 7 d repeat digoxin PK studies were completed and tissue samples were taken to determine the expressions of cell membrane transport proteins by quantitative western blot and real-time polymerase chain reaction.Data were analyzed using SigmaStat 3.5.Means between pre-surgery and post-surgery in the same experimental group were compared by paired t-test,while independent t-test was employed to compare the means between sham and BDL groups.RESULTS Digoxin clearance was decreased and liver function,but not renal function,was impaired in BDL rats.BDL resulted in significant up-regulation of multidrug resistance 1 expression in the liver and kidney and its down-regulation in the small intestine.Organic anion transporting polypeptides(OATP)1A4 was up-regulated in the liver but down-regulated in intestine after BDL.OATP4C1 expression was markedly increased in the kidney following BDL.CONCLUSION The results suggest that cell membrane transporters of digoxin are regulated during extrahepatic cholestasis.These regulations are favorable for increasing digoxin excretion in the kidney and decreasing its absorption from the intestine to compensate for reduced digoxin clearance due to cholestasis.

Astragalus polysaccharides can regulate cytokine and P-glycoprotein expression in H22 tumor-bearing mice

AIM:To investigate the adjunct anticancer effect of Astragalus polysaccharides in H22 tumor-bearing mice.METHODS:To establish a solid tumor model,5.0 × 10 6 /mL H22 hepatoma cells were inoculated subcutaneously into the right armpit region of Kunming mice(6-12 wk old,18-22 g).When the tumors reached a size of 100 mm 3,the animals were treated as indicated,and the mice were randomly assigned to seven groups(n = 10 each).After ten days of treatment,blood samples were collected from mouse eyes,and serum was harvested by centrifugation.Mice were sacrificed,and the whole body,tumor,spleen and thymus were weighed immediately.The rate of tumor inhibition and organ indexes were calculated.The expression levels of serum cytokines,P-glycoprotein(P-GP) and multidrug resistance(MDR) 1 mRNA in tumor tissues were detected using enzyme-linked immunosorbent assay,Western blotting,and quantitative myeloid-derived suppressor cells reverse transcription-polymerase chain reaction,respectively.RESULTS:The tumor inhibition rates in the treatment groups of Adriamycin(ADM) + Astragalus polysaccharides(APS)(50 mg/kg),ADM + APS(100 mg/kg),and ADM + APS(200 mg/kg) were significantly higher than in the ADM group(72.88% vs 60.36%,P = 0.013;73.40% vs 60.36%,P = 0.010;77.57% vs 60.36%,P = 0.001).The spleen indexes of the above groups were also significantly higher than in the ADM group(0.65 ± 0.22 vs 0.39 ± 0.17,P = 0.023;0.62 ± 0.34 vs 0.39 ± 0.17,P = 0.022;0.67 ± 0.20 vs 0.39 ± 0.17,P = 0.012),and the thymus indexes of the ADM + APS(100 mg/kg) and ADM + APS(200 mg/kg) groups were significantly higher than in the ADM group(0.20 ± 0.06 vs 0.13 ± 0.04,P = 0.029;0.47 ± 0.12 vs 0.13 ± 0.04,P = 0.000).APS was found to exert a synergistic antitumor effect with ADM and to alleviate the decrease in the sizes of the spleen and thymus induced by AMD.The expression of interleukin-1α(IL-1α),IL-2,IL-6,and tumor necrosis factor-α(TNF-α) was significantly higher in the ADM + APS(50 mg/kg),ADM + APS(100 mg/kg) and ADM + APS(200 mg/kg) groups than in the ADM group;and IL-10 was significantly lower in the above groups than in the ADM group.APS could increase IL-1α,IL-2,IL-6,and TNF-α expression and decrease IL-10 levels.Compared with the ADM group,APS treatment at a dose of 50-200 mg/kg could downregulate MDR1 mRNA expression in a dose-dependent manner(0.48 ± 0.13 vs 4.26 ± 1.51,P = 0.000;0.36 ± 0.03 vs 4.26 ± 1.51,P = 0.000;0.21 ± 0.04 vs 4.26 ± 1.51,P = 0.000).The expression level of P-GP was significantly lower in the ADM + APS(200 mg/kg) group than in the ADM group(137.35 ± 9.20 mg/kg vs 282.19 ± 20.54 mg/kg,P = 0.023).CONCLUSION:APS exerts a synergistic anti-tumor effect with ADM in H22 tumor-bearing mice.This may be related to its ability to enhance the expression of IL1α,IL-2,IL-6,and TNF-α,decrease IL-10,and downregulate MDR1 mRNA and P-GP expression levels.

Overexpression of P-glycoprotein in hepatocellular carcinoma and its clinical implication

INTRODUCTIONMost advanced hepatocellular garcinoma (HCC) isinsensitive to most anticancer drugs which might berelated to the high frequency of expression of themultidrug resistance-1(MDR1) gene and itsproduct,P-glycoprotein (p-gp).p-gp expressionmay also be concerned with tumor progression anddifferentiation.In the present study。

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.

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） i 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 lev-ls were measured by quantitative real-time PCR （QRTPCR）. Expression and phosphorylation of ERK1 and ERK2 were analyzed by Western blot.RESULTS： MTT assay showed that HepG2/ADM andSMMC7721/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,

Potential synergic mechanism of Wutou-Gancao herb-pair by inhibiting efflux transporter P-glycoprotein

Wutou-Gancao herb-pair is extensively used to attenuate the toxicity and enhance the efficacy of aconite.In this study,potential synergic mechanism of the herb pair was investigated by utilizing multiple ap-proaches.In silico and in vitro Caco-2 cell models were applied to study the potential binding mode of bioactive ingredients existing in liquorice with P-glycoprotein(P-gp),as well as the inhibition effects on P-gp.Additionally,anti-inflammatory activity of aconitine(AC)combined with active ingredients of liquorice,as well as pharmacokinetic patterns of AC after co-administration was investigated.Anti-inflammatory effect of AC(1 mg/kg)in rats was enhanced in combination with bioactive ingredients of liquorice(10 mg/kg).In the meanwhile,the exposure of AC in vivo was altered,in terms of Cmax and AUC.For instance,the Cmax and AUC were increased to 1.9 and 1.3 folds,respectively,when used in combination with liquiritigenin.The in silico study revealed the potential binding mode with outward facing conformation of P-gp.The resulting data obtained from transport of rhodamine-123(Rh-123)across Caco-2 cell monolayer further indicated that the function of P-gp was inhibited by chemicals in liquorice.The synergic effect was therefore proposed to be attributed to inhibition of P-gp by liquorice since AC has been demonstrated to be the substrate of P-gp.The resuls revealed that potential synergic mechanism of Wutou-Gancao herb-pair by inhibiting function of key efflux transporter P-gp to enhance the exposure of AC in systematic circulation,and further the anti-inflammatory effect,which helps clarify the compatibility rationale of these two herbs.

Relationship between therapeutic efficacy of arterial infusion chemotherapy and expression of P-glycoprotein and p53 protein in advanced hepatocellular carcinoma

AIM： To investigate the relationship between the chemotherapeutic drug efficacy and the expression of P-glycoprotein （PGP） and p53 protein in advanced hepatocellular carcinoma （HCC）. METHODS： The study was conducted on 41 patients with advanced HCC who were treated by repeated arterial infusion chemotherapy. Biopsy specimens from the tumor were collected before the start of treatment in all the patients, and the specimens were stored frozen until immunohistochemical staining, which was performed after the start of treatment, to detect PGP and p53 protein expressions. Twenty of the fortyone patients were treated with an anthracycline drug （epirubicin hydrochloride; anthracycline group）, and the remaining 21 were treated with a non-anthracycline drug （mitoxantrone hydrochloride in 11 patients and carboplatin in 10 patients; non-anthracycline group）. The relationship between the chemotherapeutic efficacy and the results of immunostaining were compared between the two groups. RESULTS： Before the start of the treatment, PGPpositive rate was 90.2% （strongly-positive, 36.6%） and p53 protein-positive rate was 34.1% （strongly-positive, 19.5%）. In the anthracycline group, the response rate was 40.0%. The number of patients showing poor response to the treatment was significantly larger in the patients with strongly positive PGP expression （P= 0.005）, and their prognoses were poor （P= 0.001）. in the nonanthracycline group, the response rate was 42.9%,and there was no significant relationship between the chemotherapeutic drug efficacy and the PGP or p53 protein expression. When only the data from the 11 patients treated with anthraquinone drug, mitoxantrone, were analyzed, however, the number of patients who showed poor response to treatment was significantly higher among the p53-positive patients （P= 0.012）, irrespective of the survival outcome. CONCLUSION： The chemotherapeutic efficacy with an anthracycline drug for advanced HCC can be predicted by immunohistochemical analysis of PGP expression. Similarly, immunostaining to evaluate p53 protein may be useful to predict the response in patients treated with an anthraquinone drug.

Identification of the Interaction between P-Glycoprotein and Anxa2 in Multidrug-resistant Human Breast Cancer Cells

Objective To explore the interaction of Anxa2 with P-Glycoprotein （P-gp） in the migration and invasion of the multidrug-resistant （MDR） human breast cancer cell line MCF-7/ADR. Methods A pair of short hairpin RNA （shRNA） targeting P-gp was transfected into MCF-7/ADR cells, and monoclonal cell strains were screened. The expression of P-gp was detected by Western blot. Transwell chambers were used to observe the cell migration capacity and invasion ability. The interaction between P-gp and Anxa2 was examined by immunoprecipitation and immunofluorescence confocal microscopy analyses. Results P-gp expression was significantly knocked down, and there were notable decreasing trends in the migration and invasion capability of MDR breast cancer cells （P〈0.05）. There was a close interaction between Anxa2 and P-gp. Conclusions MCF-7/ADR is an MDR human breast cancer cell line with high migration and invasion abilities. The knockdown of P-gp notably impaired the migration and invasion abilities of the tumor cells. The interaction of Anxa2 with P-pg may play an important role in time enhanced invasiveness of MDR human breast cancer cells.

Relationship between P-glycoprotein and CD44 expression in esophageal carcinoma

Objective： To investigate the relationship between P-glycoprotein （P-gp） and adhesion molecule CD44 expression as well as their clinical significance in esophageal carcinoma. Methods： To examine the expressed level of P-gp and CD44 by flow cytometry （FCM） in the operated samples of 70 cases with esophageal carcinoma and their normal mucosa of esophageal incision, and to evaluate their relationship with clinicopathological factors. Results： Among the 70 cases with esophageal carcinoma, the expression of P-gp in the 27 cases （38.6%） was negative （positive cells 〈25%）; 11 cases （15.7%） were 25%-40% expression of P-gp positive cells; 14 cases （20%） were 41%-60% expression of P-gp positive cells; 18 cases （25.7%） were the high expression （positive cells 〉60%） of P-gp. Of the cases with the tumor sizes being more than 4 cm, the expression of CD44 showed a significant difference （P〈0.05） in 25 cases with P-gp positive, compared with 19 cases with P-gp negative. Of the cases with high-mild differentiated esophageal carcinoma, the expression of CD44 showed a significant difference （P〈0.05） in 22 cases with P-gp positive, compared with 17 cases with P-gp negative. Of the cases with clinical Ⅲ-Ⅳ stage, the expression of CD44 showed a significant difference （P〈0.05） in 26 cases with P-gp positive, compared with 10 cases with P-gp negative. Of the cases with lymph node metastasis, the CD44 expression showed a significant difference （P=0.050） in 27 cases with P-gp positive, compared with 11 cases with P-gp negative. Of the cases of the patients＇ age being more than 56 years, the expression of CD44 showed a significant difference （P〈0.01） in 27 cases with P-gp positive, compared with 12 cases with P-gp negative. When the P-gp and CD44 expression were positive, the clinical Ⅱ stage and Ⅲ-Ⅳ stage in esophageal carcinoma was showed a significant difference （P〈0.05）. Conclusion： When the CD44 and P-gp both have the positive high expression, it will be significantly associated with the esophageal carcinoma progression and metastasis, so both were a positive expression in esophageal carcinoma, it might suggest a poor and unfavorable prognosis result.

Disease control by regulation of P-glycoprotein on lymphocytes in patients with rheumatoid arthritis

The main purpose of treatment of rheumatoid arthritis(RA) with disease modifying antirheumatic drugs(DMARDs) is to control activation of lymphocytes,although some patients do not respond adequately to such treatment. Among various mechanisms of multidrug resistance, P-glycoprotein(P-gp), a member of ATP-binding cassette transporters, causes drugresistance by efflux of intracellular drugs. Certain stimuli,such as tumor necrosis factor-α, activate lymphocytes and induce P-gp expression on lymphocytes, as evident in active RA. Studies from our laboratories showed spontaneous nuclear accumulation of human Y-boxbinding protein-1, a multidrug resistance 1 transcription factor, in unstimulated lymphocytes, and surface overexpression of P-gp on peripheral lymphocytes of RA patients with high disease activity. The significant correlation between P-gp expression level and RA disease activity is associated with active efflux of drugs from the lymphocyte cytoplasm and in drugresistance.However, the use of biological agents that reduce P-gp expression as well as P-gp antagonists(e.g., cyclosporine) can successfully reduce the efflux of corticosteroids from lymphocytes in vitro, suggesting that both types of drugs can be used to overcome drug-resistance and improve clinical outcome. We conclude that lymphocytes activated by various stimuli in RA patients with highly active disease acquire P-gpmediated multidrug resistance against corticosteroids and probably some DMARDs, which are substrates of P-gp. Inhibition/reduction of P-gp could overcome such drug resistance. Expression of P-gp on lymphocytes is a promising marker of drug resistance and a suitable therapeutic target to prevent drug resistance in patients with active RA.

Study on the Relationship between P-glycoprotein and CD44 Expression in Gastric Carcinoma

Objective： Investigation of the relationship between P-glycoprotein （P-gp） and adhesion molecule CD44 as well as their clinical significance in gastric carcinoma. Methods： To examine the expressed level of P-gp and CD44 in 98 cases with gastric carcinoma by flow eytometry and evaluate their relationships with elinieopathologieal factors. Results： Among the 98 gastric carcinomas, 40 cases （40.8%） were P-gp negative （positive cells 〈25%）; 14 cases （14.2%） were 25%-40% expression of P-gp positive cells; 17 cases （17.3%） were 41%-60% expression of P-gp positive cells; 27 cases （27.5%） were the high expression （positive cells 〉60%） of P-gp in all patients with gastric carcinoma. When the tumor sizes were more than 6 cm, the P-gp positive of CD44 showed a significant difference （P〈0.05） in 35 cases with P-gp positive, compared with it in 24 cases with P-gp negative. When the tumors were in low-moderate differentiated gastric carcinoma, the expression of CD44 showed a significant difference （P〈0.05） in 44 cases with P-gp positive, as compared with it in 30 cases with P-gp negative. When the patients were in clinical Ⅲ-Ⅳ stage, the expression of CD44 showed a significant difference （P〈0.05） in 42 cases with P-gp positive, as compared with it in 30 cases with P-gp negative. When the patients with lymph node metastasis, their CD44 expression showed a significant difference （P〈0.05） in 46 cases with P-gp positive, compared with it in 32 cases with P-gp negative. When the tumors P-gp expressed positive, their CD44 expression will be increase. Conclusion： When the CD44 and P-gp both have the positive high expression, it will be significantly associated with the gastric carcinoma progression and metastasis, so both were a positive expression in gastric carcinoma, it might suggest a poor and unfavorable prognosis result.