Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of Klebsiella pneumoniae endotoxin on the biliary excretion and renal handling of rhodamine-123 were investigated in rats at different times after intraperitoneal injection (1 mg/kg of body weight). The typical substrates for P glycoprotein, i.e., cyclosporine, colchicine, and erythromycin, inhibited the biliary clearance of rhodamine-123, whereas a substrate for organic cation transporter, cimetidine, did not inhibit clearance, suggesting that rhodamine-123 is transported mainly by P glycoprotein. The biliary, renal, and tubular secretory clearances of rhodamine-123 and the glomerular filtration rate significantly decreased 6 h after injection of endotoxin but returned to control levels by 24 h. These results suggest that endotoxin-induced decreases in P-glycoprotein-mediated biliary excretion and renal handling of rhodamine-123 were probably due to impairment of P-glycoprotein-mediated transport ability. Pretreatment with pentoxifylline (50 mg/kg) significantly inhibited endotoxin-induced increases in tumor necrosis factor alpha (TNF-alpha) levels in plasma, which ameliorated the endotoxin-induced reduction of the biliary excretion of rhodamine-123. It is likely that endotoxin-induced impairment of the transport of rhodamine-123 is caused, in part, by overproduction of TNF-alpha. The effect of endotoxin on the expression of P-glycoprotein mRNA in liver and kidneys of rats was investigated by using a reverse transcriptase PCR. The expression of Mdr1a mRNA in both liver and kidney decreased 6 h after endotoxin injection and returned to control levels after 24 h, whereas the expression of Mdr1b mRNA in liver increased at both times and that in kidney decreased at 24 h. These findings suggest that K. pneumoniae endotoxin dramatically decreases P-glycoprotein-mediated biliary and renal excretion of rhodamine-123 probably by decreasing the expression of Mdr1a, which is likely due to increased plasma TNF-alpha levels.
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PMID:Effect of endotoxin on P-glycoprotein-mediated biliary and renal excretion of rhodamine-123 in rats. 1170 25

Using a cDNA microarray 12 differentially expressed genes were identified in a multidrug resistant (MDR) cell line K562/A02. The differential expression of sorcin, which was one of the 12 genes, has been confirmed by Northern blot. To determine the clinical role of sorcin, we have measured its expression in leukemic blast cells of 65 acute myeloid leukemia (AML) patients by reverse transcriptase polymerase chain reaction (RT-PCR). Sorcin overexpression in AML patients was associated with poor clinical outcomes, the complete remission (CR) rate in sorcin- cases was significantly higher than that of sorcin+ cases (P<0.001). Furthermore, sorcin expression in AML patients was positively correlated with mdr1 expression (r=0.841, P<0.001). Combination of sorcin and mdr1 was related to clinical outcome too, cases with sorcin-/mdr1- had best response to induction chemotherapy. Our results indicated that sorcin might be one of the factors that contributes to drug resistance of AML patients.
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PMID:Expression of sorcin predicts poor outcome in acute myeloid leukemia. 1252 18

The objective of this study was to determine the role of transport proteins in daunorubicin (Dnr) accumulation and efflux in leukemia cells from 36 patients with acute myeloid leukemia (AML). Mononuclear cells were isolated and incubated with 1 microM Dnr with/without addition of 3 microM cyclosporin A (CyA) or metabolic inhibitors (MI). Cellular Dnr concentration in leukemia blast cells was measured with flow cytometry. After washing and reincubation of the cells in drug-free medium, Dnr efflux was followed with/without addition of CyA or MI. Levels of mRNA expression for mdr1, multidrug resistance associated protein (mrp) and lung resistance protein (lrp) were determined with reverse transcriptase-polymerase chain reaction (RT-PCR). MI enhanced cellular Dnr accumulation to a higher extent than CyA whereas CyA reduced Dnr efflux more efficiently than MI (P<0.001). There was a significant difference in Dnr accumulation between samples with low and high mdr1 mRNA levels but only in the presence of MI or CyA. Our results imply that other factors than P-glycoprotein (Pgp) are of major importance for in vitro Dnr accumulation in AML blasts and that the role of Pgp as a drug efflux pump is not conclusive.
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PMID:Different effects of metabolic inhibitors and cyclosporin A on daunorubicin transport in leukemia cells from patients with AML. 1252 24

This preject is to explore the reversal efficacy of calmodulin antagonist berbamine (BBM) on multidrug resistance (MDR) and its mechanism. Human erythroleukemic cell line K562 and its adriamycin-resistant counterpart K562/A02 were used in the study. The cells were co-cultured with ADR and BBM in different concentrations. MTT assay was used to analyze the effect of BBM on cell growth inhibition. According to the MTT assay, the 50% inhibitory concentration (IC(50)), the multiples of drug resistance and increased sensitivity of ADR were calculated. The concentration of intracellular ADR and expression level of P-gp were detected by flow cytometry (FCM). The expression level of mdr1 mRNA and survivin mRNA was detected by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) with beta-actin as internal reference. The results showed that IC(50) of ADR in K562 and K562/A02 cells was 1.16 +/- 0.09 micro mol/L and 37.47 +/- 1.76 micro mol/L, respectively. The resistant multiple of K562/A02 cells to ADR was 32.30 higher than that of K562 cells. BBM increased the chemo-sensitivity of ADR in K562/A02 cells with dose-dependent relationship, i.e. when 5, 10 and 20 micro mol/L BBM was added in the culture the chemo-sensitivity of ADR was increased to 2.01-, 9.68-, and 41.18-fold (P < 0.01), respectively. After treating K562/A02 cells by 5 or 10 micro mol/L BBM for 2 hours the accumulation of intracellular ADR was increased to 1.41- and 1.52-fold (P < 0.01), respectively. Treating by BBM for 72 hours decreased 4.12% (P < 0.05) and 27.09% (P < 0.01) of P-gp expression, respectively, meanwhile down-regulated expression of mdr1 mRNA and survivin mRNA was found. In conclusion, BBM could increase intracellular concentration of ADR in K562/A02 that down-regulated expression level of mdr1 mRNA and P-gp and survivin so that the sensitivity of K562/A02 to ADR was increased significantly.
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PMID:[Reversal effect of berbamine on multidrug resistance of K562/A02 cells and its mechanism]. 1470 44

It has been proposed that some host factors may affect the intracellular drug concentration leading to the inability of drug regimens to inhibit human immunodeficiency virus (HIV) replication in cells. Among them, two factors, whose description is the main aim of this review, have been considered during the last years with particular emphasis. They are: i) altered uptake and reduced activation of nucleoside reverse transcriptase inhibitors (NRTIs) in target cells, and ii) efflux of NRTIs and protease inhibitors (PIs) by cellular transporter molecules. In fact, several authors have shown that: changes in the activity of various purine and pyrimidine biosynthetic enzymes may occur in lymphocytes of HIV-infected patients; HIV-infected patients on prolonged treatment with nucleoside analogs, such as zidovudine, show significantly decreased activity of thymidine kinase compared to untreated HIV-infected persons; NRTI and PIs are substrates for the so-called multidrug membrane transporters. With regard to the latter issue, it is known that the ATP-binding cassette transporter proteins such as the P glycoprotein, and the newly discovered family of multidrug resistance-associated proteins (MRP 1-9) promote the active extracellular efflux of a wide variety of therapeutics and overexpression of some of them lowers intracellular concentration of PIs. In the very near future such mechanisms, called by most authors "cellular drug-resistance", might be taken into account, together with other immunological, virological and behavioral factors, to explain "drug failure" and/or the variability of response in HIV patients undergoing an antiretroviral treatment.
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PMID:Host factors and efficacy of antiretroviral treatment. 1564 66

Most patients with prostate cancer respond to androgen ablation therapy, but the tumor eventually progresses to an androgen-independent stage with multiple anti-cancer drug resistance. Novel therapeutic strategies for hormone independent prostate cancer need to be developed. The genes for Id-1, MIF and GSTpi were up-regulated in drug resistant cells of hormone independent prostate cancer cells using cDNA microarray gene expression analysis. In this study we aimed to investigate whether constitutive overexpression of these candidate genes in cells can affect cellular resistance to chemotherapeutic agents. The mRNA expression was determined by reverse transcriptase-polymerase chain reaction, and the Id-1, MIF and GSTpi protein contents in these cell lines were measured by Western blotting. Susceptibility of the cells to chemotherapeutic agents including doxorubicin, paclitaxel and cyclophosphamide was determined by microculture tetrazolium bromide assay. The analysis of apoptosis was assessed by annexin V assay. The cytotoxity assay results demonstrated that cells overexpressing the Id-1 gene increased in their resistance to doxorubicin, paclitaxel and cyclophosphamide. MIF expression can drive cells to increase in their resistance to paclitaxel, and GSTpi expression confers drug resistance to doxorubicin and cyclophosphamide. The induction of mdr1 gene expression was noted in up-regulation of MIF and GSTpi. Our findings suggest that overproduction of the Id-1, MIF and GSTpi proteins and coinduction of mdr-1 play an important role in the development of acquired drug resistance to various drugs of prostate cancer cells.
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PMID:The association of Id-1, MIF and GSTpi with acquired drug resistance in hormone independent prostate cancer cells. 1580 68

Ovarian cancer is currently the most lethal gynecologic malignancy in Europe and the US. Platin analogues and paclitaxel demonstrate high remission rates, but unfortunately the efficacy of cytostatic agents is limited by the development of multidrug resistance (mdr). Clinical paclitaxel resistance is often associated with mdr1 overexpression. In a recent study, we introduced a highly specific quantitative real-time reverse transcriptase polymerase chain reaction for the quantification of mdr1 transcripts. In the present study, we demonstrate that primary tumor cells from patients with recurrent ovarian cancer overexpress mdr1. To evaluate mdr1 expression, we collected tumor cells from 77 ovarian cancer patients (13 chemotherapy-naive ovarian cancer, 64 recurrent ovarian cancer). Cancer cells were aspirated from 49 solid specimens (63%) and 28 ascitic fluids (37%). Subsequently, cancer cells were exposed in 221 short-term cultures either to blank medium (control) or to a single anticancer drug, cisplatin, doxorubicin or paclitaxel. The drug concentrations applied referred to clinical relevant doses. mdr1 mRNA expression was significantly higher in specimens from recurrent ovarian cancer incubated in paclitaxel than in specimens from chemotherapy-naive ovarian cancer. No significant differences were detectable between the mean value of mdr1 mRNA expression in tumor specimens from recurrent ovarian cancer incubated in cisplatin or doxorubicin. Differences within the untreated patients group were also not statistically significant. The result of this study confirms clinical observations, as well as in-vitro studies based on tumor cell lines, that paclitaxel resistance is correlated with mdr1 overexpression.
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PMID:Anticancer drugs induce mdr1 gene expression in recurrent ovarian cancer. 1700 Nov 77

This study was purposed to investigate the reversal effect of sodium selenite on multidrug resistance in adriamycin-resistant leukemic cell line K562/ADR and its mechanisms. The cytotoxicity and the reversal effect of sodium selenite on K562/ADR cells were assayed by MTT method; the apoptosis rate of K562 and K562/ADR cells were detected by flow cytometery, the mRNA expressions of mdr1 and bcl-2 were measured by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR). The results showed that 10 micromol/L sodium selenite significantly increased the cytotoxicity of adriamycin to K562/ADR cell and the reverse index (RI) was 2.31; the early apoptosis rate of K562 cells was elevated after treatment with 5 micromol/L Na(2)SeO(3) for 48 hours; and the medium-term and late apoptosis rate was elevated after treatment with both 5 and 10 micromol/L Na(2)SeO(3) for 48 and 72 hours. Both doses of 5 and 10 micromol/L Na(2)SeO(3) increased the early apoptosis rate of K562/ADR at 48 hours, and also increased the medium-term and late apoptosis rate after treating for 48 and 72 hours. The apoptosis rate was higher at dose of 10 micromol/L than that at 5 micromol/L, the apoptosis rate at 72 hours also was higher than that at 48 hours. The expressions of mdr1 mRNA and bcl-2 mRNA were decreased significantly by 10 micromol/L sodium selenite. It is concluded that sodium selenite can reverse the multidrug resistance in K562/ADR partially by down-regulating the expressions of mdr1 mRNA and bcl-2 mRNA, and increasing apoptosis rate of K562/ADR cells.
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PMID:[Reversal effect of sodium selenite on multidrug resistance in K562/ADR cell line and its mechanisms]. 1770 98

This study was purposed to investigate the reversal effect of glucosylceramide synthase (GCS) inhibitor D, L-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) hydrochloride, on multidrug resistance in K562/A02 cells and its mechanism. The IC(50) (the half maximal inhibitory concentration) of PDMP was measured by MTT method. Cell apoptosis and intracellular daunorubicin (DNR) concentration were detected by flow cytometry. The expression of GCS and mdr1 genes were assayed by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) and Western blot. The results showed that the IC(50) of DNR in K562 and K562/A02 cells were 0.23 +/- 0.02 and 7.15 +/- 0.24 microg/ml respectively. When the concentration of PDMP was equal to or less than 20 micromol/L ( < / = 20 micromol/L), the obviously inhibitory effect on proliferation of K562 and K562/A02 cells was not observed, but both 20 micromol/L and 10 micromol/L PDMP could enhance the sensitivity of K562/A02 cells to DNR (p < 0.01) and the reversal multiples were 2.59 and 1.69 respectively. After treating with 20 micromol/L and 10 micromol/L PDMP for 48 hours, the concentration of DNR in K562/A02 cells increased (p < 0.05) and the apoptotic rate also was elevated (p < 0.01). The expressions of GCS and mdr1 genes were down-regulated at mRNA and protein levels after treating K562/A02 cells with 20 micromol/L PDMP for 48 hours. It is concluded that PDMP can enhance the sensitivity of K562/A02 cells to DNR by increasing cell apoptosis rate and accumulation concentration of DNR in cells, which may be related to down-regulated expressions of GCS and mdr1 genes.
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PMID:[Effect of PDMP, a glucosylceramide synthase inhibitor, on reversion of daunorubicin resistance in human leukemia cell line K562/A02]. 2013 23

Oral lichen planus (OLP) is a stress induced inflammatory condition with malignant potency. The mdr1 (multidrug resistance) is a stress gene overexpressed in cancerous conditions and its translated form, the p-glycoprotein efflux transporter is usually overexpressed with chemotherapy, leading to chemoresistance. OLP, a lesion with carcinogenic potency, is broadly classified into the asymptomatic reticular form and the aggressive erosive form. The objective of the study was to verify the expression level of p-glycoprotein in antifungal-treated and untreated reticular OLP, in untreated erosive OLP and erosive OLP patients treated with corticosteroid. Semi-quantitative reverse transcriptase polymerase chain reaction (SQ-RTPCR) and ELISA were performed on biopsy tissue samples to evaluate the mdr1 mRNA and protein expression of p-glycoprotein, respectively. The present study shows for the first time that mdr1 mRNA as well as its translated form p-glycoprotein are overexpressed in OLP subjects compared to healthy individuals. This overexpression is significantly higher in erosive than in reticular OLP patients, further confirming that the erosive form has higher risk for multidrug resistance. A higher expression is also observed in corticosteroid-treated erosive cases than similar untreated ones. The gradation of expression is in conformity with severity of the disease.
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PMID:P-glycoprotein expression in oral lichen planus. 2926 59


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