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。

Multidrug resistance 1 gene in inflammatory bowel disease: A meta-analysis

The MDR1 gene is an attractive candidate gene for the pathogenesis of inflammatory bowel disease （IBD） and perhaps response to therapy, with evidences at both functional and genetic levels. Its product, the P-glycoprotein （P-gp） functions as a transmembrane efflux pump thus influencing disposition and response of many drugs, some of whom （i.e. glucocorticoids） central to IBD therapy. In addition P-gp is highly expressed in many epithelial surfaces, included gastrointestinal tract （G-I） with a putative role in decreasing the absorption of endogenous or exogenous toxins, and perhaps host-bacteria interaction. Many genetic variations of MDR1 gene has been described and in some instances evidences for different P-gp expression as well drugs metabolism have been provided. However data are often conflicting due to genetic heterogeneity and different methodologies employed. Perhaps the greatest piece of evidence of the physiological importance of P-gp in the G-I tract has come from the description of the mdrl knock-out mice model, which develops a spontaneous colitis in a specific pathogen-free environment. Studies investigating MDR1 gene polymorphism and predisposition to IBD have also shown conflicting results, owing to the known difficulties in complex diseases, especially when the supposed genetic contribution is weak. In this study we have undertaken a metaanalysis of the available findings obtained with two SNPs polymorphism （C3435T and G2677T/A） in IBD; a significant association of 3435T allele and 3435TT genotype has been found with UC （OR = 1.17, P = 0.003 and OR = 1.36, P = 0.017, respectively）. In contrast no association with CD and the G2677T/A polymorphism could be demonstrated.

Prognostic Value of P-gp and p27 in Patients with Esophageal Squamous Cell Carcinoma

Objective： To evaluate the prognostic value of P-gp and p27 expression in patients with esophageal squamous cell carcinoma （ESC）. Methods： The expressions of P-gp and p27 were detected by immunohistochemistry in 104 cases of ESC, and the clinicopathological characteristics were analyzed as well. Results： The positive rate of P-gp expression in 104 cases of ESCs was 32.7%. The positive rate of P-gp expression in the group that survived over 3 years （17.5%） was significantly lower than that in the group died within 3 years （53.3%） （x^2=14.227, P〈0.001）. The positive rate of p27 expression in 104 cases of ESCs was 67.3%. The positive rate of p27 expression in the group that survived over 3 years （75.8%） was significantly higher than that in the group died within 3 years （56.5%） （x^2=4.361, P〈0.05）. The patients with poorer differentiation whole wall invasion, lymph node metastasis and more advanced TNM stage had a shorter survival than did those with better differentiation, more superficial invasion, no lymph node involvement and earlier TNM stage; and it was statistically significant （P〈0.05）. However, tumor size, macropathologic type, age and gender had no prognostic impact on ESC patients （P〉0.05）. Conclusion： P-gp and p27 expression levels had a clinical prognostic significance in ESC. It could provide a reference basis for selecting the chemotherapy projection. The tumor differentiation degree, depth of invasion, lymph node involvement and TNM stages all were correlated to ESC patients＇ survival.

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.

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.

P-glycoprotein mediated interactions between Chinese materia medica and pharmaceutical drugs

P-glycoprotein(P-gp)is an important transmembrane ATP-binding cassette(ABC)drug efflux transporter expressed in various human tissues such as the intestines,liver,kidneys,and bloodbrain barrier.It limits the intracellular concentration of xenobiotics by pumping them out of the cells,affecting drug pharmacokinetics and therapeutic effects.With its broad substrate specificity,it has the potential to remove a wide range of drugs from Chinese materia medica(CMM),including conventional medicines and active compounds.Increasing evidence has confirmed the superior therapeutic effectiveness of CMM in treating a wide range of diseases worldwide,as well as in conjunction with western drugs.As a result,herbal medicine-drug compounds have prompted widespread concern,with the majority of these interactions involving transporters such as P-gp.This review systematically summarizes the inhibition or induction of P-gp expression/function by active CMM compounds and the underlying regulatory mechanisms.It will aid in improving understanding of the synergistic or inhibiting effects associated with transporter P-gp as well as rational safety concerns for using CMM,particularly in combination with drugs.

Liposome-mediated Functional Expression of Multiple Drug Resistance Gene in Human Bone Marrow CD34^+ Cells

Summary: The expression and functional activity of multiple drug resistance (MDR1) gene in human normal bone marrow CD34+ cells was observed. Human normal bone marrow CD34+ cells were enriched with magnetic cell sorting (MACS) system, and then liposome-mediated MDR1 gene was transferred into bone marrow CD34+ cells. Fluorescence-activated cell sorter was used to evaluate the expression and functional activity of P-glycoprotein (P-gp) encoded by MDR1 gene. It was found that the purity of bone marrow CD34+ cells was approximately (91±4.56) % and recovery rate was (72.3±2.36) % by MACS. The expression of P-gp in the transfected CD34+cells was obviously higher than that in non-transfected CD34+ cells. The amount of P-gp in non-transfected CD34+ cells was (11.2±2.2) %, but increased to (23.6±2.34) % 48 h after gene transfection (P<0.0l). The amount of P-gp was gradually decreased to the basic level one week later. The accumulation and extrusion assays showed that the overexpression of P-gp could efflux Rh-123 out of cells and there was low fluorescence within the transfected cells. The functional activity of P-gp could be inhibited by 10 μg/ml verapamil. It was suggested that the transient and highly effective expression and functional activity of P-gp could be obtained by liposome-mediated MRD1 transferring into human normal bone marrow CD34+ cells.

Enhanced anticancer effect of doxorubicin by TPGS-coated liposomes with Bcl-2 siRNA-corona for dual suppression of drug resistance

Multiple drug resistance(MDR)is a tough problem in developing hepatocellular carcinoma(HCC)therapy.Here,we developed TPGS-coated cationic liposomes with Bcl-2 siRNA corona to load doxorubicin(Dox)i.e.,Bcl-2 siRNA/Dox-TPGS-LPs,to enhance anticancer effect of Dox in HCC-MDR.TPGS i.e.,d-α-tocopheryl polyethylene glycol 1000 succinate,inhibited Pglycoprotein(P-gp)efflux pump and Bcl-2 siRNA suppressed anti-apoptotic Bcl-2 protein.The Bcl-2 siRNA loaded in the liposomal corona was observed under transmission electron microscopy.The stability and hemolysis evaluation demonstrated Bcl-2 siRNA/Dox-TPGSLPs had good biocompatibility and siRNA-corona could protect the liposomal core to avoid the attachment of fetal bovine serum.In drug-resistant cells,TPGS effectively prolonged intracellular Dox retention time and siRNA-corona did improve the internalization of Dox from liposomes.In vitro and in vivo anticancer effect of this dual-functional nanostructure was examined in HCC-MDR Bel7402/5-FU tumor model.MTT assay confirmed the IC50 value of Dox was 20–50 fold higher in Bel7402/5-FU MDR cells than that in sensitive Bel7402 cells.Bcl-2 siRNA corona successfully entered the cytosol of Bel7402/5-FU MDR cells to downregulate Bcl-2 protein levels in vitro and in vivo.Bcl-2 siRNA/Dox-TPGS-LPs showed superior to TPGS-(or siRNA-)linked Dox liposomes in cell apoptosis and cytotoxicity assay in Bel7402/5-FU MDR cells,and 7-fold greater effect than free Dox in tumor growth inhibition of Bel7402/5-FU xenograft nude mice.In conclusion,TPGS-coated cationic liposomes with Bcl-2 siRNA corona had the capacity to inhibit MDR dual-pathways and subsequently improved the anti-tumor activity of the chemotherapeutic agent co-delivered to a level that cannot be achieved by inhibiting a MDR single way.

Advance in Pre-Clinical Pharmacokinetics of Paeoniflorin, a Major Monoterpene Glucoside from the Root of <i>Paeonia lactiflora</i>

Paeoniflorin (PF) is one of the main bioactive components of total glucosides of paeony (TGP) extracted from the root of Paeonia lactiflora Pall. TGP exhibit various biological activities such as improvement in memory, hepatoprotection, antimutagenic properties and platelet aggregation inhibition. The aim of this paper is to review the pharmacokinetics (PK) of PF as a pure compound and in single or multiple herb(s) of traditional Chinese medicine (TCM) prescriptions. The distribution of PF or PF in TCM fitted one or two compartmental model after oral administration or intravenous injection, respectively. However, PF has a low bioavailability (BA) in rabbit (7.24%) and rat (3.24%) after oral administration. The PK profiles and BA of PF were remarkably improved when co-administered with sinomenine or glycyrrhizin acid. The PK profiles and BA of PF in Radix Paeonia Rubra (RP-R) and Jing-zhi guan-xin were improved, but in co-administration of RP-R with Radix Angelicae Sinensis, the BA was significantly reduced. PK profiles and BA of PF in Shan yao gan-cao tang or Danggui-Shaoyao-San was either remarkably improved or not. However, neither the PK profiles nor the BA of PF in Radix paeonia alba, Huangqin-tang Si ni san or Tang-Min-Ling-Wan was improved. Metabolism in the liver did not play any role in the low oral BA of PF. The low BA was thus attributed to poor permeation due to low lipophilicity, P-glycoprotein mediated efflux, intestinal bacteria and hydrolytic degradation in the intestine by the intestinal brush border lactase phlorizin hydrolase (LPH) and certain esterases. These findings show the in vivo course of PF and provide information on the maximum biological actions of PF that may help traditional Chinese herbal medicinal practitioners.

Reversion of Multidrug-Resistance by Proteasome Inhibitor Bortezomib in K562/DNR Cell Line

Objective：To observe the reversion of multi-drug resistance by proteasome inhibitor bortezomib in K562/DNR cell line and to analyze the possible mechanism of reversion of multidrug-resistance.Methods：MTT method was used to determine the drug resistance of K562/DNR cells and the cellular toxicity of bortezomib.K562/DNR cells were cultured for 12 hours,24 hours and 36 hours with 100 μg/ml DNR only or plus 4 μg/L bortezomib.The expressions of NF-κB,IκB and P-gp of K562/DNR were detected with Western blot method,the activity of NF-κB was tested by ELISA method and the apoptosis rate was observed in each group respectively.Results：The IC50 of DNR on cells of K562/S and K562/DNR groups were 1.16 μg/ml and 50.43 μg/mL,respectively.The drug-resistant fold was 43.47.The IC10 of PS-341 on Cell strain K562/DNR was 4 μg/L.Therefore,4 μg/L was selected as the concentration for PS-341 to reverse drug-resistance in this study.DNR induced down-regulation of IκB expression,up-regulation of NF-κB and P-gp expression.After treatment with PS-341,a proteasome inhibitor,the IκB degradation was inhibited,IκB expression increased,NF-κB and P-gp expression decreased in a time dependent manner.Compared to DNR group,the NF-κB p65 activity of DNR＋PS-341 group was decreased.Compared to corresponding DNR group,DNR induced apoptosis rate increases after addition of PS-341 in a time dependent manner.Conclusion：Proteasome inhibitor bortezomib can convert the leukemia cell drug resistance.The mechanism may be that bortezomib decreases the degradation of IκB and the expression of NF-κB and P-gp,therefore induces the apoptosis of multi-drug resistant cells.

Detoxification of toxic herbs in TCM prescription based on modulation of efflux transporters

Traditional Chinese medicines(TCMs)have been used to prevent and treat various diseases for thousands of years.Promoting efficacy and reducing toxicity by the compatibility theory of TCMs has attracted increasing attention,especially for the toxicity of herbs.Studies have pointed out the interactions between the active compounds of herbs and transporters in the detoxification process of toxic compounds.Here,we summarize data on five toxic herbs commonly used in TCMs and their related efflux transporters to reduce toxicity to offer a scientific rationale for the compatibility principle of TCMs and provide guidance for the rational clinical use of TCMs.

Effects of Jianpi Jiedu Recipe (健脾解毒方)on Reversion of P-Glycoprotein-Mediated Multidrug Resistance through COX-2 Pathway in Colorectal Cancer

Objective： To evaluate the underlying mechanism of Jianpi Jiedu Recipe （健脾解毒方, JJR） in the reversion of multidrug resistance concerning colorectal cancer in vitro and in vivo. Methods： Mice were treated orally with JJR at a daily 4.25 g/（kg.day） or injected with vinblastine （VCR） 2.5 mg/（kg day） for 3 weeks after having been inoculated with HCT8N cells; tumor tissues were assayed by hematoxylin and eosin staining. Firstly, the effects of JJR on the expression of cyclooxygenase-2 （COX-2） were tested by real-time polymerase chain reaction （PCR） technique and COX-2 gene silenced by siRNA. Secondly, the variation of intracellular concentration of oxaliplatin （L-OHP） was evaluated by the inductively coupled plasma mass spectroscopy （ICP- MS） in HCT8N and its COX-2 siRNA cells; the concentration of J JR combined with chemotherapeutic drugs and the reverse effect of multidrug resistance （MDR） in HCT8N cells was evaluated by the MTT assay. Thirdly, real-time quantitative PCR and Western blot analysis were used to detect the multidrug resistance gene 1 （MDR1） mRNA and P-gp expression. Results： JJR had an inhibitory effect on the growth of tumors in vivo, and it, in combination with chemotherapeutic drugs, could reverse the drug-resistance of HCT8N cells and increase the sensitivity of HCT8N cells to VCR, DDP, 5-Fu, and THP. ICP-MS results showed that JJR could increase the concentration of drugs in HCT8/V cells （P〈0.01）. Furthermore, it was shown that JJR could reverse drug resistance of colorectal cancer cells by decreasing MDR1 expression and P-gp level via downregulation of COX-2, which has been represented as one of the major mechanisms that contributes to the MDR phenotype （P〈0.01）. Conclusion： JJR reversed multidrug resistance and enhanced the sensitivity to chemotherapy, which could be attributed to the down-regulation of COX-2 in MDRl/P-gp-mediated MDR colorectal cancer after chemotherapy.

Antiepileptic drug-induced multidrug resistance P-glycoprotein overexpression in astrocytes cultured from rat brains

Background Intractable epilepsy may be due to multidrug resistance induced by conventional antiepileptic drugs. The phenomenon is sometimes associated with an overexpression of multidrug resistance gene 1 (MDR 1). The purpose of this study was to determine if the overexpression of MDR 1 could be induced in astrocytes from rat brains in vitro using antiepileptic drugs.Methods Astrocyte cell cultures from postnatal Wistar rats (within 24 hours of birth) were established. Different concentrations of the antiepileptic drugs phenytoin, phenobarbital, carbamazepine, and valproic acid were added to the cultures for 10, 20, or 30 days. The expression of P-glycoprotein (Pgp), the protein product of MDR 1, was investigated with immunocytochemistry. Results Less than 5% of normal, untreated astrocytes had detectable Pgp staining at any time point. Phenytoin, phenobarbital, carbamazepine, and valproic acid induced the overexpression of Pgp in astrocytes in a dose- and time-dependent manner. Significantly higher levels of Pgp staining were detected at therapeutic concentrations of certain antiepileptic drugs (20 μg/ml phenobarbital, 40 μg/ml phenobarbital, and 20 μg/ml phenytoin) on day 30. Upregulation of Pgp was detected when using higher concentrations of phenytoin, phenobarbital, and valproic acid on day 20 and when using higher concentrations of any of the four antiepileptic drugs on day 30. Conclusions Treatment with antiepileptic drugs may contribute to the overexpression in astrocytes of MDR 1 and its protein product, Pgp. The mechanism leading to MDR must be considered in patients undergoing long-term treatment with antiepileptic drugs.

ATP-responsive hollow nanocapsules for DOX/GOx delivery to enable tumor inhibition with suppressed P-glycoprotein

Multidrug resistance(MDR)restricts chemotherapy efficacy due to P-glycoprotein(P-gp)mediated drug efflux,whereas current approaches to suppressing P-gp expression suffer from intrinsic challenges,such as low transfection,high toxicity and poor specificity.Here,hollow ferric-tannic acid complex nanocapsules(HFe-TA),which can be effectively degraded by the reaction with adenosine triphosphate(ATP),are synthesized for the delivery of glucose oxidase(GOx)and doxorubicin(DOX)for tumor treatment.The findings indicate that the intracellular ATP is significantly decreased due to the combined effect of HFe-TA degradation and GOx-mediated glucose consumption.Along with this ATP down-regulation,P-gp expression of tumor cells is suppressed remarkably,which in turn promotes the intracellular accumulation and anticancer efficacy of DOX.In addition,the production of•OH by Fe ions released from HFe-TA is promoted by the by-products of the oxidation of glucose process by GOx.In consequence,HFe-TA nanocapsules loaded with DOX and GOx enable significant inhibition effect to tumors both in vitro and in vivo due to the synergistic effect of cascade reactions.This study has therefore provided an alternative therapeutic platform for effective tumor inhibition with the potential in overcoming intrinsic MDR.

肿瘤的多药耐药与p53

P糖蛋白（P-glycoprotein，P-GP，ABCBl）是肿瘤多药耐药中机制发现最早的。随着研究的不断深入，人们发现它的转录和表达与p53抑癌基因有一定的联系。一些研究表明野生型p53可以下调或者抑制P-GP启动子，而突变型p53可以激活或者上调P-GP启动子。

The 150 most important questions in cancer research and clinical oncology series: questions 94-101

Since the beginning of 2017,Cancer Communications(former title:Chinese Journal of Cancer)has published a series of important questions regarding cancer research and clinical oncology,to provide an enhanced stimulus for can-cer research,and to accelerate collaborations between institutions and investigators.In this edition,the following 8 valuable questions are presented.Question 94.The origin of tumors:time for a new paradigm?Question 95.How can we accelerate the identification of biomarkers for the early detection of pancreatic ductal adenocarcinoma?Question 96.Can we improve the treatment outcomes of metastatic pancreatic ductal adenocarcinoma through precision medicine guided by a combination of the genetic and proteomic information of the tumor?Question 97.What are the parameters that determine a competent immune system that gives a complete response to cancers after immune induction?Question 98.Is high local concentration of metformin essential for its anti-cancer activity?Question 99.How can we monitor the emergence of cancer cells anywhere in the body through plasma testing?Question 100.Can phytochemicals be more specific and efficient at targeting P-glycoproteins to overcome multi-drug resistance in cancer cells?Question 101.Is cell migration a selectable trait in the natural evolution of carcinoma?