MRP1 Gene Research Articles

Crocin suppresses multidrug resistance in MRP overexpressing ovarian cancer cell line.

BackgroundCrocin, one of the main constituents of saffron extract, has numerous biological effects such as anti-cancer effects. Multidrug resistance-associated proteins 1 and 2 (MRP1 and MRP2) are important elements in the failure of cancer chemotherapy. In this study we aimed to evaluate the effects of crocin on MRP1 and MRP2 expression and function in human ovarian cancer cell line A2780 and its cisplatin-resistant derivative A2780/RCIS cells.MethodsThe cytotoxicity of crocin was assessed by the MTT assay. The effects of crocin on the MRP1 and MRP2 mRNA expression and function were assessed by real-time RT-PCR and MTT assays, respectively.ResultsOur study indicated that crocin reduced cell proliferation in a dose-dependent manner in which the reduction in proliferation rate was more noticeable in the A2780 cell line compared to A2780/RCIS. Crocin reduced MRP1 and MRP2 gene expression at the mRNA level in A2780/RCIS cells. It increased doxorubicin cytotoxicity on the resistant A2780/RCIS cells in comparison with the drug-sensitive A2780 cells.ConclusionTotally, these results indicated that crocin could suppress drug resistance via down regulation of MRP transporters in the human ovarian cancer resistant cell line.

An event-specific method for the detection and quantification of ML01, a genetically modified Saccharomyces cerevisiae wine strain, using quantitative PCR

The availability of genetically modified (GM) yeasts for winemaking and, in particular, transgenic strains based on the integration of genetic constructs deriving from other organisms into the genome of Saccharomyces cerevisiae, has been a reality for several years. Despite this, their use is only authorized in a few countries and limited to two strains: ML01, able to convert malic acid into lactic acid during alcoholic fermentation, and ECMo01 suitable for reducing the risk of carbamate production. In this work we propose a quali-quantitative culture-independent method for the detection of GM yeast ML01 in commercial preparations of ADY (Active Dry Yeast) consisting of efficient extraction of DNA and qPCR (quantitative PCR) analysis based on event-specific assay targeting MLC (malolactic cassette), and a taxon-specific S. cerevisiae assay detecting the MRP2 gene. The ADY DNA extraction methodology has been shown to provide good purity DNA suitable for subsequent qPCR. The MLC and MRP2 qPCR assay showed characteristics of specificity, dynamic range, limit of quantification (LOQ) limit of detection (LOD), precision and trueness, which were fully compliant with international reference guidelines. The method has been shown to reliably detect 0.005% (mass/mass) of GM ML01 S. cerevisiae in commercial preparations of ADY.

MRP3 as a novel resistance factor for sorafenib in hepatocellular carcinoma.

The mechanism of resistance of hepatocellular carcinoma (HCC) to sorafenib is unknown and no useful predictive biomarker for sorafenib treatment has been reported. Accordingly, we established sorafenib-resistant HCC cells and investigated the underlying mechanism of resistance to sorafenib. Sorafenib-resistant cell lines were established from the HCC cell line PLC/PRF5 by cultivation under continuous exposure to increasing concentration of sorafenib. The IC50 values of the 2 resistant clones PLC/PRF5-R1 and PLC-PRF5-R2 were 9.2±0.47 μM (1.8-fold) and 25±5.1 μM (4.6-fold) respectively, which were significantly higher than that of parental PLC/PRF5 cells (5.4±0.17 μM) (p < 0.01 respectively), as determined by MTT assay. Western blot analysis of signal transduction-related proteins showed no significant differences in expression of AKT/pAKT, mTOR/pmTOR, or ERK/pERK between the 2 resistant clones versus parent cells, suggesting no activation of an alternative signal transduction pathway. Likewise, when expression of membrane transporter proteins was determined, there were no significant differences in expression levels of BSEP, MDR1, MRP2, BCRP, MRP4 and OCT1 between resistant clones and parent cells. However, the expression levels of MRP3 in the 2 resistant clones were significantly higher than that of parent cells. When MRP3 gene was knocked down by siRNA in PLC-PRF5-R2 cells, the sensitivity of the cells to sorafenib was restored. In the analysis of gene mutation, there was no mutation in the activation segment of Raf1 kinase in the resistant clones. Our data clearly demonstrate that the efflux transporter MRP3 plays an important role in resistance to sorafenib in HCC cells.

MULTIPLE DRUG RESISTANCE PROTEINS OF PULMONARY SOMATIC CELLS AND THEIR SPECIFIC EXPRESSION IN FIBROUS CAVERNOUS TUBERCULOSIS

Cells of the host containing special proteins-transporters, so-called proteins of multiple drug resistance (MDR proteins) can contribute to the drug resistance formation. Goal of the study: to define specific expression of gene and distribution of main MDR proteins (MDR1/Pgp, MRP1, lRP, BCRP) in the pulmonary cells in case of active tuberculosis. Materials and methods. Expression of MDR protein genes was evaluated by RT-PCR for mRNA isolated from the surgical specimen of fibrous cavernous tuberculosis patients. Localization of MDR proteins was performed by immunohistochemical staining and confocal laser microscopy. Main results. Intensity of MDR protein genes expression varies in different zones of tuberculous lesions: MDR1 and BCRP are characterized by the highest level and MRP1 gene is characterized by the minimum level. The level of lRP gene expression depends on the inflammation zone and it is maximum in perifocal zone where protein is detected in the cells of alveolar epithelium and macrophages. High expression of MDR protein genes in various parts of tuberculous lesions witnesses about the potential involvement of these proteins in the development of drug resistance to anti-tuberculosis drugs.

CHARACTERISTICS OF MULTIDRUG RESISTANCE IN HUMAN SKIN MELANOMA CELL LINES

MDR is the main obstacle to chemotherapy efficiency. MDR can grow in cancer cells even if only the one cytostatic agent will act. The aim of the nowadays work is to characterize MDR in metastatic human skin melanoma cell lines prepared in “N.N. Blokhin Russian Cancer Research Center”. pgpl70 expression was detected by immunofluorescence methods. mRNA of MDR gene was identified by Reverse Transcriptase- PCR( RT-PCR) method. Rhodamine 123 (Rhl23) emission has been evaluated by flow cyto- fluorimetiy, cytotoxic activity was estimated by MTT-tests. The cells sensitivity to Aianoza cytostatic effects has showed that mel Kor cells were sensitive to Aranoza acting, but mel Ibr and mel Mtp X were not. Mel Ibr cells had expressed pgpl70 from 35 to 50 per cent, it was detected by immunofluorescence reaction. Mel Kor and mel Mtp-X cells were not expressed P-glycoprotein. mRNA of genes responsible for multi-drug resistance - MDR1, BCRP, MRP1 and LRP (MVP) - were detected by PCR. mRNA of BCRP and MRP1 genes has low expression, barely visible stripes after 33 cycles in all cell lines samples. LRP (MVP) genes expression of mRNA, unfortunately, never managed to see. YB1 gene mRNA expression is well, it is typically for cancer cells. mRNA of gene was found in mel MtpX and mel Ibr subclones cell lines. Mel Kor cells didn't contain mRNA of MDR1 gene. The study of the Rhl23 emission from cells showed that mel Kor control cells had accumulated Rhl23 and didn't throw it out. Mel Ibr cell line accumulated Rhl23 and threw out the half part of it. Mel MtpX cell tine had accumulated the less part of Rhl23 and almost all were thrown out. Thus, the study shows that mel Kor cell tine that are sensitive to Aranoza doesn't express pgpl70, not contain mRNA of multi-chug resistance genes and does not throw Rhl23. Mel Ibr cells resistant to the Aranoza cytotoxic action express pgpl70 ,contain mRNA of MDR1 gene and throw out Rhl23. However, mel MtpX cell line resistant to Aranoza does not express pgpl70, but contains mRNA of MDR1 gene and actively throws out Rhl23.

Silencing pancreatic adenocarcinoma upregulated factor (PAUF) increases the sensitivity of pancreatic cancer cells to gemcitabine.

Pancreatic adenocarcinoma upregulated factor (PAUF) is a new oncogene that activates signaling pathways that play a critical role in resistance to gemcitabine. We thus speculated that PAUF also plays a role in resistance to gemcitabine of pancreatic cancer cells. We established BxPC-3 cell lines with stable PAUF knockdown (BxPC-3_shPAUF) and controls (BxPC-3_shCtrl) and evaluated sensitivity to gemcitabine in vitro by MTT and flow cytometry. We established a xenograft model of human pancreatic cancer to examine PAUF function in gemcitabine resistance in vivo. Gene chip microarrays were performed to identify differentially expressed genes in BxPC-3_shPAUF and BxPC-3_shCtrl cells. Silencing PAUF increased the sensitivity of BxPC-3 cells to gemcitabine in vitro and in vivo. PAUF-knockdown BxPC-3 cell lines treated with gemcitabine showed increased proliferation inhibition and apoptosis compared with controls. Gemcitabine exhibited a more pronounced effect on reduction of BxPC-3_shPAUF tumors than BxPC-3_shCtrl tumors. Terminal deoxynucleotidyl transferase dUTP Nick-End Labeling (TUNEL) assays confirmed a significantly higher apoptotic rate of BXPC-3_shPAUF tumors compared with BXPC-3_shCtrl tumors. Gene array showed that PAUF function in gemcitabine sensitivity might involve MRP2, MRP3, MDR1, PIK3R1, and NFkB2 genes. PAUF could be considered as a key molecular target for sensitizing pancreatic cancer cells to gemcitabine.

Effect of Expression of Multidrug Resistance Genes on Efficacy the Treatment of Multiple Myeloma By Proteasome Inhibitor

Background: Increased expression of efflux protein, such as P-glycoprotein, multidrug resistance protein, lung resistance protein, breast cancer resistance protein are a major reason for resistance to existing or previously effective therapy multiple myeloma (MM). Effect of the expression of genes of multidrug resistance (MDR) - MDR1, MRP1, LRP, and BCRP on the efficacy of therapy with proteasome inhibitor is currently not well understood.Aim: Determination of mRNA expression of genes responsible for the development of drug resistance, such as MDR1, MRP1, LRP, BCRP in bone marrow aspirates in patients with newly diagnosed and refractory / relapsed MM before start bortezomib-containing chemotherapy programs.Materials and methods: We studied bone marrow aspirates of 29 patients (12 men and 17 women) aged 48 to 77 years (median 60 years) with stage 3 MM by classification Durie-Salmon. 14 of studied patients made a group of newly diagnosed MM. 15 patients made a clinically refractory / relapsed group MM. The bone marrow in this group of patients was studied after treatment with alkylating agents at the time of registration of resistance to the given therapy. In the future, all patients were treated by bortezomib - containing chemtheapy regimens. mRNA expression studied genes was determined by semi-quantitative polymerase chain reaction reverse transcription.Results: In both groups of patients had comparable expression of all studied MDR`s genes. In the group of newly diagnose patients the MDR 1 mRNA expression was detected in 93% (13/14) of the samples, the mRNA of the gene MRP 1 was detected in 79% (11/14). The BCRP mRNA expression was detected in 100% of the investigated samples. The expression of mRNA of the gene LRP was identified in 71% of the studied cases (10/14). In the group of patients after treatment with alkylating agents the expression of mRNA of MDR1 was detected in 87% (13/15) of samples, MRP 1 was detected in 93% (14/15), BCRP was in 100% of cases, and the LRP mRNA was detected in 13/15 (87%) of the samples.Treatment efficacy was assessed by Iinternational Unified Response Criteria for multiple myeloma after the 6 cycles of treatment. Evaluation of treatment efficacy in patients previously non-treated with chemotherapy as well as in the group of clinical resistance patients showed comparable results by the number of objective response rate (57% and 60% respectively).Conclusions: The expression of MDR genes does not determine the resistance of tumor cells to bortezomib. The proteasome inhibitor bortezomib can overcome the MDR gene activity, attaching it to alkylating drugs increases the sensitivity to them of resistant tumor cells. DisclosuresGolenkov:Novartis: Consultancy.

Screening of virulence-associated genes as a molecular typing method for characterization of Streptococcus suis isolates recovered from wild boars and pigs

Streptococcus suis is an important zoonotic pathogen associated with a wide range of diseases in pigs, but has also been isolated from wild animals such as rabbits and wild boars. In the current study, 126 S. suis isolates recovered from pigs (n = 85) and wild boars (n = 41) were tested by polymerase chain reaction (PCR) for the presence of nine virulence-associated genes. S. suis isolates from wild boars were differentiated by the lower detection rates of the epf, sly, mrp, sao and dltA genes (0%, 2.4%, 2.4%, 4.8% and 21.9%, respectively) compared with the isolates from pigs (56.5%, 75.3%, 56.5%, 88.2.0% and 88.2%, respectively). The differences in the content of these virulence-associated genes were statistically significant (P < 0.05). There was a correlation between the variants saoM and saoL and serotypes 2 and 9, respectively (P < 0.05). Isolates were classified into 31 virulence-associated gene profiles (VPs). Ten VPs were detected among wild boar isolates and 22 VPs among pig isolates, with only two VPs common to wild boars and pigs. The predominant VPs among isolates from wild boars (VP1, VP7) were different from those observed in pig isolates (VP16 and VP26). VP16 was detected exclusively in clinical pig isolates of serotype 9 and VP26 was detected in 71.4% of the serotype 2 clinical pig isolates. Further multilocus sequence typing (MLST) analysis showed a significant correlation association between certain VPs and STs (VP16 and VP17 with ST123 and ST125 and VP26 with ST1). In conclusion, the current study showed that combination of virulence-associated gene profiling and MLST analysis may provide more information of the relatedness of the S. suis strains from different animal species that could be useful for epidemiological purposes.

Modulation of the xenobiotic transformation system and inflammatory response by ochratoxin A exposure using a co-culture system of Caco-2 and HepG2 cells

Cytotoxicity of ochratoxin A (OTA) was evaluated using the MTS assay, and membrane integrity was measured using transepithelial electrical resistance (TEER). A transwell system was used to investigate the effect of OTA on the expression of the CYP450 (1A1, 2A6, 2B6, 3A4 and 3A5), NAT2, COX-2, LOX-5, and MRP2 genes in Caco-2 and HepG2 cells. TEER decreased by a mean of 63.2% after 24 h in Caco-2 differentiated cells without inducing cell detachment; revealing damage to the intestinal epithelial cell tight junction proteins and an increase in cell permeability. Gene expression analysis showed that modulation of gene expression by OTA was higher in Caco-2 cells than in HepG2 cells, and generally, the duration of exposure to OTA had a more significant effect than the OTA dose. A general OTA down-regulation effect was observed in Caco-2 cells, in contrast with the down- and up-regulation observed in HepG2 cells. In Caco-2 cells, CYP1A1 was the gene with the highest regulation, followed by CYP3A4 and CYP3A5. Conversely, in HepG2 cells, CYP2B6 was highly regulated at 3 and 12 h compared to the other cytochromes; CYP1A1 was slightly modulated during the first 12 h, but an overexpression was observed at 24 h.Our data support the involvement of the COX-2 and 5-LOX genes in liver metabolism of OTA. On the basis of the gene expression analysis, the results suggest a possible impairment in OTA secretion at the intestinal and hepatic level due to MRP2 repression. In addition, we provide evidence of the effect of OTA on NAT2 gene expression, which had not been reported before.

Virulence genotyping and population analysis of Streptococcus suis serotype 2 isolates from China

Streptococcus suis is one of the most important swine pathogens worldwide. In this study, a total of 22 virulence-related genes in 101 strains of S. suis serotype 2 (SS2) were detected by PCR, namely, mrp, epf, sly, fbps, rgg, ofs, srtA, pgdA, gapdh, iga, endoD, ciaRH, salKR, manN, purD, rgg, DppIV, neuB, dltA, SMU_61-like, SpyM3_0908 (Permease) and the SspA gene. The distribution of virulence-related genes among isolates was visualized using BioNumerics software to study similarities among the isolates. Two clusters of SS2 were apparent on the phylogenetic tree, namely, Clusters A and B. Both mouse and zebrafish infection models revealed that strains in Cluster B were more virulent than those in Cluster A. Statistical comparison between the two clusters was performed, and structure analysis demonstrated that epf, sly, rgg, endoD, SMU_61-like and SpyM3_0908 were possible predictive markers for SS2 virulence. The transcription levels of highly prevalent genes in both clusters were detected by qRT-PCR in representative strains. For Cluster A isolates, the transcription levels of neuB, dltA, fbps and pgdA were significantly lower, but the transcription level of iga was significantly higher than that in Cluster B isolates. Although encoded in the genomes of the selected Cluster A isolates, DppIV and mrp genes were not expressed. These results revealed the genetic differences between virulent and low-virulence SS2 isolates from China and provide a better understanding of the SS2 pathogenic mechanism.

Two novel multidrug resistance associated protein (MRP/ABCC) from the Mediterranean mussel (Mytilus galloprovincialis): characterization and expression patterns in detoxifying tissues

Multidrug resistance associated proteins (MRP) belong to the ABCC branch of the ABC transporters. The MRP together with P-gp (P-glycoprotein; MDR1; ABCB1) and BCRP (breast cancer resistance protein; ABCG2) confer multixenobiotic resistance (MXR) in marine vertebrates. In aquatic invertebrates, little is known about the presence and role of these ABC transporters. The ABC transporters play an important role in the absorption, distribution, and excretion of drugs, xenobiotics, and endogenous compounds and are predominantly expressed in excretory organs. In the present study, we identified and characterized two MRP/ABCC transporters (mrp1 and mrp2) from the Mediterranean mussel (Mytilus galloprovincialis Lamarck, 1819). The two cDNAs finally obtained were 4648 bp for mrp1 and 5065 bp for mrp2 with open reading frames of 1500 and 1524 residues, respectively. Analysis of the amino acid sequences revealed the structural organization of ABC transporters with the typical and highly conserved motifs. The expression levels of these genes revealed that the highest expression of mrp1 and mrp2 genes was found in the digestive gland followed by gills, and the lowest expression of the three tissues was detected in the mantle. The expression of these genes was also studied in mussels naturally contaminated with okadaic acid (from a bloom of Dinophysis acuminata Claparède and Lachmann, 1859). The overexpression of mrp2 in the digestive gland suggests that this gene is involved in the process of detoxification of okadaic acid in M. galloprovincilais. These expression patterns agree with the suggested role of these genes in the protection against endogenous or exogenous compounds in aquatic organisms.

Hypoxia-inducible factor-1α induces multidrug resistance protein in colon cancer.

Multidrug resistance is the major cause of chemotherapy failure in many solid tumors, including colon cancer. Hypoxic environment is a feature for all solid tumors and is important for the development of tumor resistance to chemotherapy. Hypoxia-inducible factor (HIF)-1α is the key transcription factor that mediates cellular response to hypoxia. HIF-1α has been shown to play an important role in tumor resistance; however, the mechanism is still not fully understood. Here, we found that HIF-1α and the drug resistance-associated gene multidrug resistance associated protein 1 (MRP1) were induced by treatment of colon cancer cells with the hypoxia-mimetic agent cobalt chloride. Inhibition of HIF-1α by RNA interference and dominant-negative protein can significantly reduce the induction of MRP1 by hypoxia. Bioinformatics analysis showed that a hypoxia response element is located at −378 to −373 bp upstream of the transcription start site of MRP1 gene. Luciferase reporter assay combined with mutation analysis confirmed that this element is essential for hypoxia-mediated activation of MRP gene. Furthermore, RNA interference revealed that HIF-1α is necessary for this hypoxia-driven activation of MRP1 promoter. Importantly, chromatin immunoprecipitation analysis demonstrated that HIF-1α could directly bind to this HRE site in vivo. Together, these data suggest that MRP1 is a downstream target gene of HIF-1α, which provides a potential novel mechanism for HIF-1α-mediated drug resistance in colon cancer and maybe other solid tumors as well.

PKA and actin play critical roles as downstream effectors in MRP4-mediated regulation of fibroblast migration

Multidrug resistance protein 4 (MRP4), a member of the ATP binding cassette transporter family, functions as a plasma membrane exporter of cyclic nucleotides. Recently, we demonstrated that fibroblasts lacking the Mrp4 gene migrate faster and contain higher cyclic-nucleotide levels. Here, we show that cAMP accumulation and protein kinase A (PKA) activity are higher and polarized in Mrp4−/− fibroblasts, versus Mrp4+/+ cells. MRP4-containing macromolecular complexes isolated from these fibroblasts contained several proteins, including actin, which play important roles in cell migration. We found that actin interacts with MRP4, predominantly at the plasma membrane, and an intact actin cytoskeleton is required to restrict MRP4 to specific microdomains of the plasma membrane. Our data further indicated that the enhanced accumulation of cAMP in Mrp4−/− fibroblasts facilitates cortical actin polymerization in a PKA-dependent manner at the leading edge, which in turn increases the overall rate of cell migration to accelerate the process of wound healing. Disruption of actin polymerization or inhibition of PKA activity abolished the effect of MRP4 on cell migration. Together, our findings suggest a novel cAMP-dependent mechanism for MRP4-mediated regulation of fibroblast migration whereby PKA and actin play critical roles as downstream effectors.

Establishment of stable MRP1 knockdown by lentivirus-delivered shRNA in the mouse testis Sertoli TM4 cell line

Sertoli cells around germ cells are considered a barrier that protects spermatogenesis from harmful influences. The transporter multidrug-resistance-associated protein 1 (MRP1) is a xenobiotic efflux pump that can export glutathione S-conjugated metabolites and xenobiotics from cells. In this study, the Mrp1 gene was stably knocked down in a mouse Sertoli cell line (TM4) using lentivirus vector-mediated RNA interference (RNAi) technology. Four shRNA interference sequences were chosen and designed to screen for the most effective shRNA in candidate cells. The results indicate that lentivirus vectors with high titres were generated and successfully transfected into TM4 cells with high efficiency. Puromycin was added to the culture medium to maintain constant selection during the establishment of the stable cell lines. The expression levels of Mrp1 mRNA and MRP1 protein in stably transfected TM4 cells were significantly lower than those in the control group. Importantly, the transport activity of MRP1 to Calcein and 5-carboxyseminaptharhodafluor (SNARF-1) were significantly reduced because of MRP1 silencing. Moreover, the silencing of the Mrp1 gene in the transfected TM4 cell lines remained highly stable for more than 6 months. These results suggest that the lentivirus-based RNAi stably knocks down the expression of the Mrp1 gene in the established TM4 cell line. This transfected TM4 cell line will provide a new and powerful tool to study the underlying mechanism of MRP1-mediated drug resistance and detoxication in the reproductive system.

Reversal effect study of vitamin D on leukemia multidrug resistance cells

Objective To investigate the reversal effect of vitamin D on drug resistance leukemia cell lines Jurcat vitamin D/ADR, K562/ADR and its mechanism. Methods Non-toxic concentration of vitamin D was chosen by methyl thiazolyl tetrazolium, and on line concentration experiment; the contents of vitamin D for soft erythromycin in the cell and the cell surface of P-glycoprotein(P-gp) expression level were detected by using flow cytometry instrument and vitamin D for intracellular mdr1 mRNA and mrp1 mRNA expression was detected by Real-time polymerase chain reaction; vitamin D for the change of intra cellular glutathione glycosides peptide(GSH) content was detected by adoping biochemistry method. Results Resistance reversal in experiments showed that vitamin D could decrease soft erythromycin in the accumulation of drug resistant cells, with a dose-dependent relationship; vitamin D treatment Jurcat/ADR, K562/ADR cells after 48 h, chemotherapy drugs could increase the cell concentration, and reduce P-gp and the expression of mdr1 and mrp1 gene; vitamin D treatment Jurcat/ADR, K562/ADR after 48 h could decrease the intracellular GSH content in K562, K562/ADR, Jurcat and Jurcat/ADR. Conclusions Vitamin D has the drug resis-tance reversal agents to Jurcat/ADR, K562/ADR, which might be relevant to the inhibition of cell surface of P-gp proteins function and expression and reduction of the mdr1 and mrp1 expressions of resistance genes and reduction of intracellular GSH content.Vitamin D by influencing the above mechanism, which increases the drug concentration in cells, can effectively kill the tumor cells. Key words: Vitamin D; Leukemia multidrug resistance cells; Multidrug resistance; Reversal

Effect of MRP2 and MRP3 Polymorphisms on Anastrozole Glucuronidation and MRP2 and MRP3 Gene Expression in Normal Liver Samples.

Anastrozole is an aromatase inhibitor (AI) used as adjuvant therapy for breast cancer. Anastrozole is subject to direct glucuronidation catalyzed by UDP-glucuronosyltransferase1A4 (UGT1A4). Interindividual variability in anastrozole glucuronidation may be affected by UGT1A4 SNPs. Interplay between drug metabolizing genes such as UGT1A4 and transporter genes may also be affected by genetic variability. Thus, we hypothesize that genetic variability in MRPs could influence anastrozole glucuronidation. The correlation between UGT1A4 and MRP2 or MRP3 transporter gene expressions and the correlation between MRP2 or MRP3 mRNA and anastrozole glucuronidation were analyzed in normal human liver samples. MRP2 and MRP3 mRNA levels were significantly correlated with UGT1A4 mRNA, with anastrozole glucuronidation and with each other (p<0.05). The data also demonstrated that MRP2 SNPs are positively correlated with MRP2 mRNA expression, while there was no association between MRP3 SNPs from this study and MRP3 expression. Significant correlations (p<0.05) between certain MRP2 SNPs (3972C>T, 2366C>T and -24C>T) and anastrozole glucuronidation were observed. There were no observed correlations between MRP3 SNPs and anastrozole glucuronidation. MRP2 polymorphisms have been identified as playing a role in the disposition of other drugs, and the data presented here indicate for the first time that MRP2 SNPs could influence anastrozole metabolism and contribute to interindividual variation in treatment responses.

The overexpression of MRP4 is related to multidrug resistance in osteosarcoma cells.

Doxorubicin (Adriamycin, ADM) is an antimitotic drug used in the treatment of a wide range of malignant tumors, including acute leukemia, lymphoma, osteosarcoma, breast cancer, and lung cancer. Multidrug resistance-associated proteins (MRPs) are members of a superfamily of ATP-binding cassette (ABC) transporters, which can transport various molecules across extra- and intra-cellular membranes. The aim of this study was to investigate whether there was a correlation between MRP4 and primary ADM resistance in osteosarcoma cells. In this paper, we chose the human osteosarcoma cell line MG63, ADM resistant cell line MG63/DOX, and the patient's primary cell GSF-0686. We checked the ADM sensitivity and cytotoxicity of all the three cells by cell proliferation assay. The intracellular drug concentrations were measured by using LC-MS/MS. We also examined MRP4 gene expression by RT-PCR and Western Blot. We found that the intracellular ADM concentration of the parent osteosarcoma cell line MG63 was higher than the ADM resistant osteosarcoma MG63/DOX cell line or the GSF-0686 cell after ADM treatment (P < 0.05). In addition, MRP4 mRNA and protein levels in ADM resistant osteosarcoma cells were higher than in MG63 cell (P < 0.05). Taking together, this work suggests that overexpression of MRP4 may confer ADM resistance in osteosarcoma cells.

Reversal of multidrug resistance of HepG2 by RNAi-mediated gene silence of MDR1 and MRP1

Objective To investigate the in vitro effect of silencing of gene MDR1 and MRP1 by siRNA on multidrug resistance reversal in hepatocellular carcinoma.Methods Plasmid vector of shRNA for gene MDR1 and MRP1 were constructed to transfect the multidrug resistance of hepatocellular carcinoma cell lines.Cells were grouped into control (HepG2),single gene silent (HepG2/MDR-1-si,HepG2/MRP-1-si),and combined gene silent (HepG2/mm-si).Cell cycle and apoptosis were measured by flowcytometry,and the resistance of transfected cells were measured by MTT.Cell activity and cell proliferation can be detected by CCK-8,activity of caspase-3 by A450,MDR1/mRNA and MRP1/mRNA by real-time PCR.Results Cell lines of pSUPER-HepG2/MDR-1-si and pSUPER-HepG2/MRP-1-si were constructed successfully.MRP-1-mRNA of HepG2/mm-si was equal to that of HepG2/MRP-1-si,and MDR-1-mRNA of HepG2/mm-si equals to that of HepG2/MRP-1-si (P ＞ 0.05).Activity of caspase-3 in HepG2/mm-si was higher than that of HepG2/MRP-1-si (14 623.7 ± 338.9 vs.13 215.7 ± 90.6,P ＜ 0.05).Cell activity and cell proliferation in HepG2/mm-si were lower than that of other groups (P ＜ 0.05).The sensitivity of HepG2/MDR-1-si and HepG2/MRP-1-si was higher than that of HepG2/mm-si (1.39-fold vs.1.0-fold,1.58-fold vs.1.0-fold,P ＜ 0.05).Cell count of apoptosis in HepG2/MDR-1-si and HepG2/MRP-1-si was larger than that of HepG2/mm-si (P ＜ 0.01).Conclusion In vitro silence of MDR1 and MRP1 gene by RNA interference can reverse the multidrug resistance of HepG2 cell line. Key words: Hepatocellular carcinoma; Multidrug resistance; RNA interference; Gene silence

Consequences of Mrp2 deficiency for diclofenac toxicity in the rat intestine ex vivo

The non-steroidal anti-inflammatory drug diclofenac (DCF) has a high prevalence of intestinal side effects in humans and rats. It has been reported that Mrp2 transporter deficient rats (Mrp2−) are more resistant to DCF induced intestinal toxicity. This was explained in vivo by impaired Mrp2-dependent biliary transport of DCF-acylglucuronide (DAG), leading to decreased intestinal exposure to DAG and DCF. However, it is not known to what extent adaptive changes in the Mrp2− intestine itself influence its sensitivity to DCF toxicity without the influence of liver metabolites. To investigate this, DCF toxicity and disposition were studied ex vivo by precision-cut intestinal slices and Ussing chamber using intestines from wild type (WT) and Mrp2− rats. The results show that adaptive changes due to Mrp2 deficiency concerning Mrp2, Mrp3 and BCRP gene expression, GSH content and DAG formation were different between liver and intestine. Furthermore, Mrp2− intestine was intrinsically more resistant to DCF toxicity than its WT counterpart ex vivo. This can at least partly be explained by a reduced DCF uptake by the Mrp2− intestine, but is not related to the other adaptive changes in the intestine. The extrapolation of this data to humans with MRP2 deficiency is uncertain due to species differences in activity and regulation of transporters.

MDR-1 and MRP2 Gene Polymorphisms in Mexican Epileptic Pediatric Patients with Complex Partial Seizures.

Although the Pgp efflux transport protein is overexpressed in resected tissue of patients with epilepsy, the presence of polymorphisms in MDR1/ABCB1 and MRP2/ABCC2 in patients with antiepileptic-drugs resistant epilepsy (ADR) is controversial. The aim of this study was to perform an exploratory study to identify nucleotide changes and search new and reported mutations in patients with ADR and patients with good response (CTR) to antiepileptic drugs (AEDs) in a rigorously selected population. We analyzed 22 samples In Material and Methods, from drug-resistant patients with epilepsy and 7 samples from patients with good response to AEDs. Genomic DNA was obtained from leukocytes. Eleven exons in both genes were genotyped. The concentration of drugs in saliva and plasma was determined. The concentration of valproic acid in saliva was lower in ADR than in CRT. In ABCB1, five reported SNPs and five unreported nucleotide changes were identified; rs2229109 (GA) and rs2032582 (AT and AG) were found only in the ADR. Of six SNPs associated with the ABCC2 that were found in the study population, rs3740066 (TT) and 66744T > A (TG) were found only in the ADR. The strongest risk factor in the ABCB1 gene was identified as the TA genotype of rs2032582, whereas for the ABCC2 gene the strongest risk factor was the T allele of rs3740066. The screening of SNPs in ACBC1 and ABCC2 indicates that the Mexican patients with epilepsy in this study display frequently reported ABCC1 polymorphisms; however, in the study subjects with a higher risk factor for drug resistance, new nucleotide changes were found in the ABCC2 gene. Thus, the population of Mexican patients with AED-resistant epilepsy (ADR) used in this study exhibits genetic variability with respect to those reported in other study populations; however, it is necessary to explore this polymorphism in a larger population of patients with ADR.