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:3.6.3.44 (P-glycoprotein)
13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this report the effects of single doses of ionizing radiation on the mRNA expression of several proteins involved in multiple drug resistance were analyzed. Murine NIH 3T3 cells treated with single doses of 5, 10 and 20 Gy during the time interval from 1.5 to 72 h after irradiation were compared with their corresponding controls at the same points of time. The glutathione S-transferase-pi (GST pi) level was elevated in cells treated with 10 or 20 Gy from 24 to 72 h after irradiation compared with the control. Topoisomerase II alpha and thymidylate synthase were decreased in irradiated cells 24-72 h after exposure. These down-regulations were associated with cellular proliferation, determined by mRNA expression of the proliferation marker histone 3. Irradiated cells exhibited no alteration in the P-glycoprotein or glutathione peroxidase mRNA content. The finding that GST pi mRNA was overexpressed after irradiation was validated by investigations on a human lung carcinoma cell line (LXF 289) on the mRNA and protein level. Thus, our results indicate that irradiation alters the expression of proteins involved in multidrug resistance and may, therefore, play a role in clinical drug response.
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PMID:Effects of single doses of irradiation on the expression of resistance-related proteins in murine NIH 3T3 and human lung carcinoma cells. 755 53

Microvessel density was investigated by immunostaining endothelial cells for factor VIII antigen in 84 non-small cell lung carcinomas and compared with the expression of several resistance-related proteins. Glutathione S-transferase-pi, thymidylate synthase, metallothionein and, with limitations, P-glycoprotein were overexpressed in tumors with poor vascularization.
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PMID:Up-regulation of resistance-related proteins in human lung tumors with poor vascularization. 755 65

The aim of the study was to prove whether or not an association exists between the heat shock protein 70 (hsp70) and drug resistance. Tumor samples of 90 patients with previously untreated non-small lung carcinomas were investigated immunohistochemically for expression of resistance related proteins. Additionally, resistance to doxorubicin was determined using a short term test. No association between resistance related proteins. Additionally, resistance to doxorubicin was determined using a short term test. No association between resistance to doxorubicin and hsp70 was found. Of 63 resistant tumors, 33 showed low and 30 high hsp70 expression. Of the 26 sensitive tumors, 11 had low and 16 had high hsp70 expression. No relationship could be found between P-glycoprotein which is related to multidrug resistance and hsp70 expression or between hsp70 expression and expression of topoisomerase II, thymidylate synthase and metallothionein. On the other hand, a trend was noted for tumors with high glutathione S-transferase-pi expression to show high hsp70 expression. In addition, there was a significant relationship between hsp70 and catalase positivity. These data indicate that heat shock and stress promote intracellular oxidative damage and catalase is necessary for protection.
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PMID:Heat shock (hsp70) and resistance proteins in non-small cell lung carcinomas. 765 30

The expression of several resistance markers (P-glycoprotein, glutathione S-transferase-pi, thymidylate synthase, dihydrofolate reductase) was analyzed in matched primary tumors and lymph node metastases from 21 patients with lung cancer using immunohistochemistry. The analysis showed that expression of these resistance proteins is generally congruent in primary lung cancer and simultaneously resected lymph node metastases. This suggests that in general the resistance of a primary tumor predicts for the resistance of the metastases and vice versa.
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PMID:Detection of resistance proteins in matched primary lung tumors and lymph node metastases. 791 93

Malignant activation of oncogenes ras or trk is implicated in a number of solid tumors and leukemias. We determined the chemosensitivity profile of wild-type mouse NIH-3T3 fibroblasts, and that of NIH-3T3 lines transformed by the H-ras (S2-721) and trk (106-632) oncogenes, against 11 different drugs from various classes. Differences in sensitivity were related to drug accumulation and metabolism. Both ras- and trk-transformed cell lines were less sensitive to cisplatin (CDDP) and doxorubicin (DXR) than the wild type. NIH-3T3 transformants expressing H-ras were less sensitive than those expressing trk or the wild type to the indoloquinone EO9, methotrexate and arabino-furanosylcytosine. No clear difference in sensitivity was observed for vincristine, VP-16, or the new cytidine analog 2',2'-difluoro-deoxycytidine. In both ras- and trk-transformed cell lines sensitivity to 5FU was increased moderately, but sensitivity to 5'deoxy-5-fluorouridine (5'dFUR) was increased markedly. Only the trk-transformed line NIH-3T3 was more sensitive to 2'deoxy-5-fluorouridine. Expression of P-glycoprotein was not different between the 3 cell lines but DXR accumulation in both mutants was decreased, indicating a non-P-glycoprotein-associated difference in sensitivity. Conversion of 5'dFUR to 5FU (catalyzed by pyrimidine nucleoside phosphorylases) was 5-10 times higher in both mutants than in the wild type. The activity of the phosphoribosyl-transferase (direct conversion of 5FU to FUMP) was comparable, but the rate of conversion of 5FU to fluorouridine (FUR) was lower in the wild type, as well as that of 5FU to FUMP via FUR. In contrast, the activity of thymidylate synthase, the target enzyme for fluoropyrimidines, was higher in the wild-type cells. The concentrations of both purine and pyrimidine nucleotides were lower in cells expressing trk. In conclusion, transformation of cells with the H-ras or trk oncogenes can markedly influence sensitivity to several drugs and affect normal metabolism and that of several anti-cancer agents.
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PMID:Transformation of mouse fibroblasts with the oncogenes H-ras OR trk is associated with pronounced changes in drug sensitivity and metabolism. 850 20

The main line of defense now available against parasitic protozoa--which are responsible for major diseases of humans and domestic animals--is chemotherapy. This defense is being eroded by drug resistance and, with few new drugs in the pipeline, prevention and circumvention of resistance are medical and veterinary priorities. Although studies of resistance mechanisms in parasites have lagged behind similar studies in bacteria and cancer cells, the tools to tackle this problem are rapidly improving. Transformation with exogenous DNA is now possible with all major parasitic protozoa of humans. Hence, putative resistance genes can be tested in sensitive protozoa, allowing an unambiguous reconstruction of resistance mechanisms. Gene cloning, the polymerase chain reaction, and monoclonal antibodies against resistance-related proteins have made it possible to analyze potential resistance mechanisms in the few parasites that can be obtained from infected people. Hence, the prospect of applying new knowledge about resistance mechanisms to parasites in patients is good, even though today virtually all knowledge pertains to parasites selected for resistance in the laboratory. Resistance mechanisms highlighted in this review include: 1. Decrease of drug uptake because of the loss of a transporter required for uptake. This decrease contributes to resistance to arsenicals and diamidines in African trypanosomes. 2. The export of drugs from the parasite by P-glycoproteins and other traffic ATPases. This export could potentially be an important mechanism of resistance, as these proteins are richly represented in the few protozoa analyzed. There are indications that such transmembrane transporters can be involved in resistance to emetine in Entamoeba spp., to mefloquine in Plasmodium spp., and to antimonials in Leishmania spp. 3. The possible involvement of the P-glycoprotein encoded by the Plasmodium falciparum pfmdr1 gene in chloroquine resistance. We present the available data that lead to the conclusion that overproduction of the wild-type version of this protein results in chloroquine hypersensitivity rather than resistance. 4. The involvement of the PgpA P-glycoprotein of Leishmania spp. in low-level resistance to arsenite and antimonials. We raise the possibility that this protein transports glutathione conjugates of arsenite and antimonials rather than the compounds themselves. 5. Loss of drug activation as the main mechanism of metronidazole resistance in Trichomonas and Giardia spp. Recent evidence indicates that a decrease of the proximal cellular electron donor for metronidazole activation, ferredoxin, is the main cause of resistance in Trichomonas. 6. Resistance arising through alteration of drug targets. The amino acid substitutions in the dihydrofolate reductase-thymidylate synthase of Plasmodium spp. are good examples of this mechanism.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:New mechanisms of drug resistance in parasitic protozoa. 856 67

Doxorubicin- (OAW-dox, SK-OV-dox), taxol- (OAW-tax, SK-OV-tax) and cisplatin- (SK-OV-cis) resistant cells derived from the parental OAW-42 and SK-OV-3 cell lines were established. OAW-42 sublines showed high resistance, the SK-OV-3 sublines only low resistance. OAW-42 sublines showed a cross-resistance profile typical of multidrug resistance (MDR). The sublines of SK-OV-3 showed a cross-resistance profile different from the OAW-42 sublines. The mRNA expression of several resistance proteins and related factors was analyzed. An overexpression of P-glycoprotein 170 (P-170), glutathione-S-transferase-pi (GST-pi), thymidylate synthase (TS), glutathione peroxidase (GP) and c-jun was found in OAW-dox and OAW-tax cells. Additionally, OAW-tax cells expressed a higher mRNA level of protein kinase Cbeta2. DNA analysis revealed a 2-fold gene amplification of P-170, whereas the genes for GST-pi, TS and GP were not amplified. SK-OV-dox and SK-OV-tax cells showed a decreased level of histone 3 (H3) and TS mRNA. This shows that the sublines of OAW-42 developed resistance by co-expression of several resistance-related proteins and proto-oncogenes whereas the sublines of SK-OV-3 expressed resistance by decreased expression of the proliferation-dependent proteins H3 and TS.
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PMID:Messenger RNA expression of resistance proteins and related factors in human ovarian carcinoma cell lines resistant to doxorubicin, taxol and cisplatin. 907 15

Resistance to some (lipophilic) antifolates has been associated with P-glycoprotein (P-gp)-mediated multidrug resistance (MDR). A possible relationship with non-P-gp MDR has not been established. We studied resistance to antifolates in SW-1573 human lung carcinoma cells, a P-gp overexpressing variant SW-1573/2R160 and a multidrug resistance protein (MRP) overexpressing variant SW-1573/2R120. In this study, thymidylate synthase (TS) inhibitors with different properties concerning the efficiency of membrane transport and the efficiency of polyglutamylation were tested for cross-resistance in SW-1573/2R120 and SW-1573/2R160 cells. Growth inhibition patterns in this cell line panel were measured by the Sulforhodamine B (SRB) assay. Resistance factors for TS inhibitors were: 2.4 and 0.4 for 5-fluorouracil (5FU), 18.8 and 8.8 for ZD1694, 17 and 0.7 for AG337, and 40 and 8.3 for BW1843U89 in SW-1573/2R160 and SW-1573/2R120, respectively. This study showed changes in the TS enzyme kinetics during the induction of doxorubicin resistance in both SW-1573 variants, resulting in 2-fold lower Km values for 2'-deoxyuridine-5'-monophosphate (dUMP) in both resistant variants compared to the parental cell line. TS activity, TS protein induction and TS mRNA expression all had 2-fold increased in the SW-1573/2R120 compared to the SW-1573/2R160. 3H-MTX influx was 2-fold lower in SW-1573/2R160 cells compared to SW-1573/2R120 and SW-1573 cells. In the SW-1573/2R160 cell line, an aberrant intracellular trafficking towards the target TS was observed, compared to SW-1573/2R120 and SW-1573 cells as measured by the TS in situ assay. The rate of TS inhibition by the TS inhibitors used in this study was similar in all cell lines. In conclusion, collateral sensitivity to 5FU and the lipophilic AG337 and cross-resistance to other antifolates were observed in non-P-gp MDR SW-1573/2R120 cells, as well as resistance to all antifolates in P-gp SW-1573/2R160 cells. The mechanism of resistance in SW-1573/2R160 cells possibly involves reduced influx and changes in intracellular trafficking routes. For the SW-1573/2R120 cell line, several changes related to the TS enzyme possibly play a role in the observed cross-resistance and collateral sensitivity pattern.
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PMID:Cross-resistance to antifolates in multidrug resistant cell lines with P-glycoprotein or multidrug resistance protein expression. 925 60

Data obtained from multiple sources indicate that no single mechanism can explain the drug resistance and the poor prognosis of patients with lung cancer. The resistance-related proteins P-glycoprotein, glutathione-dependent enzymes, topoisomerase II, metallothioneins, O-6-alkylguanine-DNA alkyltransferase, thymidylate synthase, dihydrofolate reductase and heat shock proteins have been found in lung carcinomas, but these alone cannot explain the drug-resistant phenotype. Cell cycle-related proteins, angiogenic factors, protooncogenes, and tumor suppressor genes also play a role in the phenotype that is resistant lung cancer. A key future challenge involves determining the relative quantitative contributions of each of these mechanisms to overall resistance.
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PMID:Resistance mechanisms and their regulation in lung cancer. 925 4

Resistance of tumor cells to chemotherapeutic drugs can not only be caused by treatment with antineoplastic agents but also by radiotherapy. The aim of this study was to analyze whether ionizing radiation can influence the mRNA expression of proteins which have been found to be involved in drug resistance of tumor cells. Human tumor cell lines (MCF-7, LXF and Sk-Mel) were treated with single doses of irradiation (5, 10 and 20 Gy). The expression of the resistance related proteins glutathione S-transferase-pi (GST-pi), topoisomerase II alpha (Topo II), thymidylate synthase (TS), O6-methylguanine-DNA-methyltransferase (MGMT), P-glycoprotein (Pgp), glutathione peroxidase (GPX) multidrug resistance-associated protein (MRP) and also of the heat-shock protein 70 (HSP 70) were determined at the mRNA level during the time interval from 1.5 to 72 h post-irradiation and compared with their corresponding controls. We also examined whether a relationship exists between these proteins and the proliferative activity (histone 3, Ki-67, statin) of the cells. We found that exposure of MCF-7, LXF and Sk-Mel cells to ionizing radiation increases the expression of the mRNA of GST-pi. Topo II, TS, HSP 70 and proliferation markers were also altered by exposure to ionizing radiation, but there was no common response of the three cell lines. No significant changes were observed in the expression of MGMT, Pgp, GPX and MRP after radiation treatment. Drug resistance tests revealed that irradiated MCF 7 cells were less sensitive to doxorubicin than non-irradiated control cells. Our results indicate that ionizing irradiation modifies the expression of some proteins involved in drug resistance and the response of MCF 7 cells to doxorubicin and may, therefore, play a role in clinical drug response.
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PMID:Messenger RNA expression of resistance factors in human tumor cell lines after single exposure to radiation. 941 87


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