Real-world efficacy of daclatasvir and asunaprevir with respect to resistance-associated substitutions

AIM To investigate daclatasvir(DCV) and asunaprevir(ASV) efficacy in hepatitis C(HCV) patients, with respect to resistance-associated substitutions(RASs).METHODS A total of 392 HCV-infected patients from multiple centers were included in this study. We evaluated their clinical courses and sustained virologic responses(SVR) according to pretreatment factors(gender, age, history of interferon-based regimens, platelet counts, level of viremia, pretreatment NA5A:L31, and Y93 substitutions). We also analyzed the pretreatment and post-treatment major RASs of NS3:D168, NS5A:L31 and Y93 substitutions using a direct-sequencing method in 17 patients who were unable to achieve SVR at 12 wk after treatment completion(SVR12).RESULTS The overall SVR12 rate was 88.3%. Thirty-one patients discontinued treatment before 24 wk because of adverse events, 23 of whom achieved SVR12. There were no significant differences in SVR12 rates with respect to gender, age, history of interferon-based regimens, and platelet counts. The SVR12 rate in patients with viral loads of ≥ 6.0 log IU/m L was significantly lower than those with viral loads of < 6.0 log IU/m L(P < 0.001). The SVR12 rate in patients with Y93 substitution-positive was significantly lower than those with Y93 substitution-negative(P < 0.001). The L31 substitution-positive group showed a lower SVR12 rate than the L31 substitution-negative group, but the difference was not statistically significant. Seventeen patients who did not achieve SVR12 and had available pretreatment and post-treatment sera had additional RASs in NS3:D168, NS5:L31, and Y93 substitution at treatment failure.CONCLUSION Combination of DCV and ASV is associated with a high SVR rate. Baseline RASs should be thoroughly assessed to avoid additional RASs after treatment failure.

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 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 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.

In silico pharmacophore models to predict endogenous substrates for human multidrug resistance-associated proteins

Multidrug resistance-associated proteins （MRPs） can effiux structurally diverse drugs, drug conjugates, drug metabolites, as well as other small molecules out of the cells, and this is the main cause of producing multidrug resistance （MDR） of some anticaneer drugs. Therefore, it is crucial to uncover the molecular features of MRPs substrates in developing anti-MDR cancer therapy. In the present study, common feature pharmacophore models were developed by employing CATALYST Pharmacophore Modeling and Analysis tools using substrates of MRPs, including MRP1, -2, -3, -4, -5, -6, -8 and MRPs family, respectively. The models were validated using independent decoy sets generated in DUD-E, and the ones with best A UC （area under the curve） scores were chosen to predict endogenous substrates by screening the Human Metabolome Database （HMDB）. A number of molecules obtained by pharmacophore screening have been validated in the literatures. By comparing physical properties （ALOGP, Molecular_PolarSurfaceArea, Molecular_Volume, Molecular_Weight, Num H Acceptors, Num H Donors） and scaffold features of the screened candidates with the known substrates, we found that： 1） The two sets have consistent ALOGP, Molecule_Volume and Molecule_Weight distribution trend; 2） Substrates of MRP1 have a better lipophilicity than the other subtypes, which is consistent with the two hydrophobic centers on the MRP1 pharmacophore; 3） In the aspect of the scaffold structures, they have the identical or similar backbone fragments.

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.

Analysis of the effect of HCV resistance-associated substitutions on the short-term efficacy of DAA after single administration in three phase Ib clinical trials

As crucial factors in hepatitis C virus(HCV)management,resistance-associated substitutions(RASs)are associated with the treatment outcome of some direct-acting antiviral(DAA)-based regimens.In this study,we mainly analyzed the impact of baseline Y93 H or Y93 Y/H on the short-term efficacy after single administration of NS5 A inhibitors in three phaseⅠb clinical trials(yimitasvir phosphate,KW-136 and fopitasvir),and analyzed the prevalence of baseline RASs and treatment-emergent RASs.A total of 94 treatment-naive HCV genotype(GT)-1 b(n=63)and GT-2 a(n=31)Chinese patients were enrolled in three phase lb clinical trials.We investigated RASs in 77 patients with next generation or Sanger sequencing.In the 7-day trial of yimitasvir phosphate,the mean maximum HCV RNA decrease of patients with baseline Y93 H or Y93 Y/H was lower than that of patients without the mutation in the 30 mg and 200 mg cohorts(0.83 vs.2.45 log10 IU/mL and 1.92 vs.2.63 log10 IU/mL).In the3-day trial of KW-136,the mean maximum HCV RNA decrease in patients with baseline Y93 H or Y93 Y/H was lower than that of patients without the mutation in the 30,60 and 120 mg cohorts(1.58 vs.2.89 log10 IU/mL,3.16 vs.4.09 log10 IU/mL and3.00 vs.5.04 log10 IU/mL,respectively).In the 3-day trial of fopitasvir,only 30 mg group had baseline Y93 H or Y93 Y/H,and the average maximum HCV RNA decrease of patients with baseline Y93 H or Y93 Y/H was lower than that of patients without the mutation(1.45 vs.3.59 log10 IU/mL).In the three trials,baseline RASs were observed in 54 patients(70.1%;54/77).The most prevalent baseline RASs were Y93 H and Y93 Y/H(18.2%;14/77),followed by L3 IM(16.9%;13/77).The most common RASs after single administration of DAA were Y93 H and Y93 Y/H.Our data could provide reference for future clinical treatment and clinical trial.

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,

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.

Exploring the hepatitis C virus genome using single molecule realtime sequencing

Single molecular real-time(SMRT)sequencing,also called third-generation sequencing,is a novel sequencing technique capable of generating extremely long contiguous sequence reads.While conventional short-read sequencing cannot evaluate the linkage of nucleotide substitutions distant from one another,SMRT sequencing can directly demonstrate linkage of nucleotide changes over a span of more than 20 kbp,and thus can be applied to directly examine the haplotypes of viruses or bacteria whose genome structures are changing in real time.In addition,an error correction method(circular consensus sequencing)has been established and repeated sequencing of a single-molecule DNA template can result in extremely high accuracy.The advantages of long read sequencing enable accurate determination of the haplotypes of individual viral clones.SMRT sequencing has been applied in various studies of viral genomes including determination of the full-length contiguous genome sequence of hepatitis C virus(HCV),targeted deep sequencing of the HCV NS5A gene,and assessment of heterogeneity among viral populations.Recently,the emergence of multi-drug resistant HCV viruses has become a significant clinical issue and has been also demonstrated using SMRT sequencing.In this review,we introduce the novel third-generation PacBio RSII/Sequel systems,compare them with conventional next-generation sequencers,and summarize previous studies in which SMRT sequencing technology has been applied for HCV genome analysis.We also refer to another long-read sequencing platform,nanopore sequencing technology,and discuss the advantages,limitations and future perspectives in using these thirdgeneration sequencers for HCV genome analysis.

Evaluation of the Mrp2-mediated flavonoid-drug interaction potential of quercetin in rats and in vitro models

Quercetin is a biologically active flavonoid that has been used as a popular health supplement.It is reported that quercetin may cause flavonoid-drug interaction mediated by P-glycoprotein,the most predominant efflux transporter.In this study,we comprehensively evaluated the potential of the pharmacokinetic interaction of quercetin mediated by multidrug resistance-associated protein 2(MRP2),another major efflux transporter.MRP2-transfected MDCKII cells and LS174T cells were used to evaluate the potential inhibition and induction of MRP2 by quercetin in vitro.To evaluate the induction effect of quercetin on Mrp2 in vivo,Mrp2 mRNA expression in rat liver,kidney,and small intestinal tissues was determined after the oral administration of quercetin(50,100,or 250 mg/kg)for seven days.Mrp2-mediated interaction potential was also evaluated by the pharmacokinetic study of phenolsulfonphthalein in rats after single or multiple doses of quercetin.Additionally,the effect of quercetin on absorption of docetaxel,a P-glycoprotein and CYP3A4 substrate,was also evaluated.Quercetin inhibited the function of MRP2 at 10μM and induced the mRNA expression of MRP2 at 50μM in vitro.Additionally,at 100 mg/kg,quercetin markedly increased Mrp2 expression in the small intestine of rats.However,there was no significant change in phenolsulfonphthalein pharmacokinetics due to single-(50,100,or 250 mg/kg)or multiple-dose(50,100,or 250 mg/kg for seven days)quercetin co-administration.By contrast,a significant interaction caused by quercetin(100 mg/kg)was observed in the absorption of docetaxel.The results suggested that although quercetin modulates the function and expression of MRP2 in vitro,it may have a low potential of Mrp2-mediated interaction and present negligible safety concerns related to the interaction.

Efficacy of direct-acting antiviral treatment for chronic hepatitis C: A single hospital experience

AIM To evaluate the efficacy of direct-acting antivirals(DAAs) in Kanto Rosai Hospital. METHODS All patients with hepatitis C virus(HCV) who underwent DAA prescription were enrolled in this study. The present study was a single center retrospective analysis using patients infected with HCV genotype 1 or 2. Resistance analysis was performed by using direct sequencing and cycleave PCR in genotype 1 patients treated with interferon(IFN)-free DAA. The primary endpoint was sustained virologic response at 12 wk after therapy(SVR12).RESULTS A total of 117 patients participated in the study, including 135 with genotype 1 and 42 with genotype 2. Of the 135 patients with genotype 1, 16 received protease inhibitor + IFN + ribavirin and all achieved SVR. Of the 119 patients who received IFN-free DAA(in different combinations), 102 achieved SVR and 9 failed(7/9 were on daclatasvir/asunaprevir and 2/9 on ledipasvir/sofosbuvir). Efficacy analysis was done only for 43 patients who received daclatasvir/asunaprevir. From this analysis, Y93 resistance-associated substitutions were significantly correlated with SVR.CONCLUSION The SVR rate was 98% for genotype 1 and 100% for genotype 2. However, caution is needed for HCV NS5 A resistance-associated substitutions that are selected by HCV NS5 A inhibitors because cerebrovascular adverse events are induced by some DAA drugs.

EXPRESSION OF MDRII MRP AND LRP GENES IN GASTRIC CARCINOMA AND THEIR CLINICAL SIGNIFICANCE

Objective: To explore the expression of mdrl,multidrug resistance-associated protein (MRP) and lungresistance protein (LRP) genes in human gastric cancerand their clinical significance. Methods: The mdrlmRNA was assayed by RT-PCR, the MRP and LRPwere detected by flow cytometry. Results: The positiverate of mdrl mRNA was 44.4% (12/27), and the meanMRP and LRP expression were independent uponpatient histologic type, nodal involvement, and TNMstage. The mdrl mRNA expression in patients withserosa invasion was 30.0% (6120), much lower than thatwithout serosa invasion (85.7%). Conclusion: Themultidrug resistance cells are present in primary gastriccarcinomas prior to chemotherapy, and analysis of mdrlgene, MRP, LRP may have guiding significance in thetreatment of gastric carcinoma.

New real-time-PCR method to identify single point mutations in hepatitis C virus

AIM To develop a fast, low-cost diagnostic strategy to identify single point mutations in highly variable genomes such as hepatitis C virus(HCV).METHODS In patients with HCV infection, resistance-associated amino acid substitutions within the viral quasispecies prior to therapy can confer decreased susceptibility to direct-acting antiviral agents and lead to treatment failure and virological relapse. One such naturally occurring mutation is the Q80 K substitution in the HCV-NS3 protease gene, which confers resistance to PI inhibitors, particularly simeprevir. Low-cost, highly sensitive techniques enabling routine detection of these single point mutations would be useful to identify patients at a risk of treatment failure. Light Cycler methods, based on real-time PCR with sequencespecific probe hybridization, have been implemented in most diagnostic laboratories. However, this technique cannot identify single point mutations in highly variable genetic environments, such as the HCV genome. To circumvent this problem, we developed a new method to homogenize all nucleotides present in a region except the point mutation of interest. RESULTS Using nucleotide-specific probes Q, K, and R substitutions at position 80 were clearly identified at a sensitivity of 10%(mutations present at a frequency of at least 10% were detected). The technique was successfully applied to identify the Q80 K substitution in 240 HCV G1 serum samples, with performance comparable to that of direct Sanger sequencing, the current standard procedure for this purpose. The new method was then validated in a Catalonian population of 202 HCV G1-infected individuals. Q80 K was detected in 14.6% of G1 a patients and 0% of G1 b in our setting. CONCLUSION A fast, low-cost diagnostic strategy based on real-time PCR and fluorescence resonance energy transfer probe melting curve analysis has been successfully developed to identify single point mutations in highly variable genomes such as hepatitis C virus. This technique can be adapted to detect any single point mutation in highly variable genomes.

Different gap junction-propagated effects on cisplatin transfer result in opposite responses to cisplatinin normal cells versus tumor cells

OBJECTIVE Previous work has shown that gap junction intercel ular communication(GJIC)enhances cisplatin(Pt)toxicity in testicular tumor cells but decreases it in non-tumor testicular cells.In this study,these different GJIC-propagated effects were demonstrated in tumor versus non-tumor cells from other organ tissues(liver and lung).METHODS We use several different mani pulations(no cell contact,pharmacological inhibition,and si RNA suppression)to down-regulate GJIC function.The in vivo results using xenograft tumor models were consistent with those from the above-mentioned cells.To better understand the mechanism(s)involved,we studied the effects of GJIC on Pt accumulation in tumor and non-tumor cells from the liver and lung.RESULTS The intracel ular Pt and DNA-Pt adduct contents clearly increased in non-tumor cells but decreasedin tumor cells when GJIC was downregulated.Further analysis indicated that the opposite effectsof GJIC on Pt accumulation in normal versus tumor cells from the liver were due to its different effects on copper transporter1 and multidrug resistance-associated protein2,membrane transporters attributed to intracellular Pt transfer.CONCLUSION GJIC protects normal organs from cisplatin toxicity while enhancing it in tumor cells via its different effects on intracellular Pt transfer.

Retreatment of patients with treatment failure of directacting antivirals: Focus on hepatitis C virus genotype 1b

The recent development of direct-acting antiviral agents(DAAs) against hepatitis C virus(HCV) infection could lead to higher sustained virological response(SVR) rates, with shorter treatment durations and fewer adverse events compared with regimens that include interferon. However, a relatively small proportion of patients cannot achieve SVR in the first treatment, including DAAs with or without peginterferon and/or ribavirin. Although retreatment with a combination of DAAs should be conducted for these patients, it is more difficult to achieve SVR when retreating these patients because of resistance-associated substitutions(RASs) or treatment-emergent substitutions. In Japan, HCV genotype 1 b(GT1 b) is founded in 70% of HCVinfected individuals. In this minireview, we summarize the retreatment regimens and their SVR rates for HCV GT1 b. It is important to avoid drugs that target the regions targeted by initial drugs, but next-generation combinations of DAAs, such as sofosbuvir/velpatasvir/voxilaprevir for 12 wk or glecaprevir/pibrentasvir for 12 wk, are proposed to be potential solution for the HCV GT1 b-infected patients with treatment failure, mainly on a basis of targeting distinctive regions. Clinicians should follow the new information and resources for DAAs and select the proper combination of DAAs for the retreatment of HCV GT1 b-infected patients with treatment failure.

Construction of Multi-ribozyme Expression System and Its Characterization of Cleavage on the MDR1/MRP1 Double Target Substrate in vitro

To improve catalytic activity of ribozyme on its substrate, the multi-ribozyme expression system was designed and constructed from 20 cis-acting hammerhead ribozymes undergoing self-cleavage with 10 trans-acting hammerhead ribozymes inserted alternatively regularly and the plasmid of pGEM-MDR1/MRP1 used to transcribe the MDR1/MRPl（196/210） substrate containing double target sites was also constructed by DNA recombination. Endonuclease digestion analysis and DNA sequencing indicate all the recombinant plasmids were correct. The clea- vage activities were evaluated for the multi-ribozyme expression system on the MDR1/MRP1 substrate in the cell free system. The results demonstrate that the cis-acting hammerhead ribozymes in the multi-ribozyme expression system were able to cleave themselves and the 72 nt of 196Rz and the 71 nt of 210Rz trans-acting hammerhead ribozymes were liberated effectively, and the trans-acting hammerhead ribozymes released were able to act on the MDR1/MRP1 double target RNA substrate and cleave the target RNA at specific sites effectively. The multi- ribozyme expression system of the [Coat＇A196Rz/Coat＇B210Rz]5 is more significantly superior to that of the [Coat＇A 196Rz/Coat＇B210Rz] 1 in cleavage of RNA substrate. The fractions cleaved by [Coat＇A 196Rz/Coat＇B210Rz]5 on the MDR1/MRP1 substrate for 8 h at observed temperatures showed no marked difference. The studies of Mg^2＋ on cleavage efficiency indicate that cleavage reaction is dependent on Mg^2＋ ions concentration. The plot of lg（kobs） vs. lgc（Mg^2＋） displays a linear relationship between 2.5 mmol/L and 20 mmol/L Mg^2＋. It suggests that Mg^2＋ ions play a crucial role in multi-ribozyme cleavage on the substrate.

EFFECTS OF NEOADJUVANT CHEMOTHERAPY ON MDR1 AND MRP GENE EXPRESSION IN PRIMARY BREAST CANCER

Objective: To investigate the effects of neoadjuvant chemotherapy on the expression of drug resistance genes, multidrug resistance-1 (MDR1) and multidrug resistance-associated protein (MRP), in patients with primary breast cancer. Methods: MDR1 and MRP expression were detected by semi-quantitative RT-PCR in 20 patients with primary breast cancer, before and after chemotherapy. Results: Before chemotherapy, MDR1 and MRP expression can be detected in 15 cases (75%) and 18 cases (90%) respectively. After chemotherapy, expression of MDR1 is not significantly different from that before chemotherapy, but expression of MRP is significantly different from that before chemotherapy. Conclusion: Expression of drug resistance gene MRP, but not MDR1, is enhanced in patients with primary breast cancer submitted to neoadjuvant chemotherapy.

Study the relationship between the expression of MRP and the radiosensitivity of primary lesions of nasopharyngeal carcinoma

Objective: To study the relationship between the expression of multidrug resistance-associated protein (MRP) gene in nasopharyngeal carcinoma (NPC) and the radiosensitivity of primary lesions of NPC. Methods: Total 51 cases of NPC were analyzed retrospectively, who were treated by radiotherapy between January 1, 1999 and December 31, 2000 in our department, including the cases of pure radiotherapy and chemotherapy after radiotherapy. Using immunohistochemiscal S-P method, the expression of MRP in NPC was detected, and the relationship with the radiosensitivity of primary lesions of NPC was analyzed. Results: The rate of positive expression was 68.63% (35/51) in NPC, and there were significant difference between T stages (P<0.05), but no significant difference with radiosensitivity of primary lesions of NPC (P>0.05). Conclusion: There is a higher expression of MRP in NPC, but it has no relationship with radiosensitivity of primary lesions of NPC. So MRP can not be regarded as the predictive marker of radiosensitivity of primary lesions of NPC.