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)

Acute myeloid leukaemia (AML) is a heterogeneous malignant disease in which disease progression at the level of CD34 positive cells has a major impact in drug resistance and relapse. The multi-drug resistance (MDR1) gene product, P-glycoprotein is expressed mainly in CD34 positive AML cells and Bcl-2 is expressed simultaneously with several putative drug resistance parameters in these cells. Bcl-2 over-expression is associated with CD34 positivity, poor response to chemotherapy and reduced overall survival in AML patients. Recently, all-trans retinoic acid (RA) has been reported to enhance cytarabine-induced apoptosis and downregulate Bcl-2 in several human myeloid leukaemia CD34 negative cells. The two CD34 positive human myeloid leukaemia cell lines: KG1 and KGla have the unique feature of expressing significant functional P-glycoprotein. Thus, the efficacy of RA in enhancing cytrabine- and fludarabine-induced apoptosis and overcoming the resistance was examined in both KG1 (CD34+CD7-) and KGla (CD34+CD7+) human myeloid leukaemia cells in the present study. Both cytarabine and fludarabine induced a dose dependent increase in the number of apoptotic cells in both CD34 positive cell types. Interestingly, the cytarabine-induced apoptosis was significantly more than fludarabine-induced apoptosis in both cell types. All-trans RA alone failed to induce apoptosis or inhibit proliferation of either of the two human CD34 positive leukaemia cell types. However, RA enhanced cytarabine- or fludarabine-induced apoptosis and inhibition of proliferation in KG1 CD34+CD7- but not in KGla CD34+CD7+ myeloid leukaemia cells. As single agents, RA, cytarabine and fludarabine reduced Bcl-2 expression in a dose dependent manner in both cell types. Using a quantitative ELISA assay, the Bcl-2 protein concentration was reduced by 86 or 100%, after 72 h of treatment with 10 microM cytarabine or fludarabine, respectively, in both CD34 positive leukaemia cell types. The addition of RA to cytarabine enhanced its induced reduction of Bcl-2 in KG1 CD34+CD7- but not in KGla CD34+CD7+ human myeloid leukaemia cells. Meanwhile, RA failed to augment fludarabine-induced reduction of Bcl-2 in both cell types. In conclusion, the present results suggest a potential role for the combination of RA and cytarabine in the treatment of refractory and/or relapsed AML patients with CD34+CD7- but not CD34+CD7+ blast cells.
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PMID:Effect of all-trans retinoic acid on chemotherapy induced apoptosis and down-regulation of Bcl-2 in human myeloid leukaemia CD34 positive cells. 1045 72

We analysed the relationship between all-trans retinoic acid (ATRA) resistance and P-glycoprotein (P-gp)-associated multidrug resistance (MDR) in acute promyelocytic leukaemia (APL). There was no difference in the intracellular ATRA accumulation between NB4 cells and an MDR1 cDNA-transduced NB4 subline and between ATRA-resistant NB4 cells (NB4/RA) and an MDR1 cDNA-transduced NB4/RA subline. PSC833, a MDR modifier, did not increase the intracellular accumulation of ATRA or affect the expression of CD11b, the nitroblue tetrazolium (NBT) reduction activity, the proportion of apoptotic cells or the morphology of these four ATRA-treated cell lines. Similar results were obtained in the analysis of APL cells from five patients relapsed after ATRA-induced complete remission.
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PMID:Role of P-glycoprotein in all-trans retinoic acid (ATRA) resistance in acute promyelocytic leukaemia cells: analysis of intracellular concentration of ATRA. 1065 29

Lovastatin, a competitive inhibitor of HMG-CoA reductase, reportedly inhibits proliferation and induces apoptosis of tumor cells with MDR-1 coded P-glycoprotein (Pgp) expression. In this study we investigated the sensitivity to lovastatin of eight myeloid leukemia cell lines: K562, NOMO-1, NB4 and its retinoic acid (RA) resistant subline NB4/RA, and their multidrug-resistant (MDR) sublines: K562/ADR, NOMO-1/ADR, NB4/MDR and NB4/RA/MDR. MTT and apoptosis assays revealed that K562/ADR, NOMO-1/ADR and NB4/RA/MDR were more sensitive to lovastatin than their parental cell lines, while NB4/MDR showed the same level of sensitivity as parental NB4 cells, which already were very sensitive to lovastatin. Significant elevation of transcript levels of HMG-CoA reductase was observed by semiquantitative RT-PCR analysis in more than three lovastatin-sensitive MDR sublines, but not in NB4/MDR compared with the parental cell lines. HMG-CoA reductase mRNA levels were up-regulated more than two-fold by the exposure to lovastatin in all of the parental non-Pgp-expressing cell lines. In NB4/MDR, HMG-CoA reductase mRNA level was elevated to a similar extent as in parental NB4, whereas in three other MDR sublines which showed preferential sensitivity to lovastatin, their HMG-CoA reductase mRNA levels were not significantly elevated after 24- and 48-h treatment with lovastatin. These results indicate a connection between drug resistance and regulation of the mevalonate pathway, and further strengthen the clinical possibility that drug resistant leukemias would be susceptible to treatment with lovastatin.
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PMID:Increased sensitivity of multidrug-resistant myeloid leukemia cell lines to lovastatin. 1094 41

Acute promyelocytic leukemia (APL) is a unique disease that responds to differentiation-inducing effects of all-trans-retinoic acid (ATRA). ATRA induces complete clinical remissions (CRs) in most patients and now constitutes a standard therapy in patients with APL. However, CRs induced by ATRA are usually brief, and resistance to the therapy rapidly develops, leading to relapses in almost every patient; thus limiting the use of ATRA as a single agent. On the basis of clinical and in vitro studies, the following mechanisms have been proposed to explain ATRA resistance: 1) induction of accelerated metabolism of ATRA, 2) increased expression of cellular retinoic acid-binding proteins (CRABPs), 3) constitutive degradation of PML-RAR alpha, 4) point mutations in the ligand-binding domain of RAR alpha of PML-RAR alpha, 5) P-glycoprotein expression, 6) transcriptional repression by histone deacetylase activity, 7) isoforms of PML-RAR alpha, 8) persistent telomerase activity, and 9) expression of type II transglutaminase. In this review, we discuss the evidence provided in support of each mechanism, the mechanism's possible impact on the outcome of APL, and the newer approaches that are being employed to overcome ATRA resistance.
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PMID:ATRA(ouble) in the treatment of acute promyelocytic leukemia. 1150 68

Treatment of ovarian carcinomas with the antimitotic antitumor drug paclitaxel is highly efficacious. However, development of drug resistance presents a major obstacle. The common cellular phenotypes associated with paclitaxel resistance are an increased expression of the drug transport protein P-glycoprotein (P-gp), an alteration in the levels of beta-tubulin isotypes, and/or changes in the drug binding affinity of the microtubules. We established two paclitaxel-resistant human ovarian carcinoma cell lines. The 2008/17/4 cells exhibited a "classic" multidrug-resistant phenotype (overexpression of P-gp associated with cross-resistance to natural product drugs), whereas the 2008/13/4 cells were an atypical multidrug-resistant subline (no overexpression of P-gp). In addition to being paclitaxel resistant (250-fold), the 2008/13/4 cells were also cross-resistant to etoposide (39-fold) and vincristine (460-fold). To identify the alterations in the gene expression profile associated with the development of atypical paclitaxel resistance, we used the Clontech Atlas Human Cancer cDNA Microarray (spotted with 588 genes). The expression of retinoic acid receptor (RAR)-gamma was significantly higher in the paclitaxel-resistant (2008/13/4 and 2008/17/4) cells than in the parental (2008) cells. Northern blotting analysis demonstrated that the expression of RAR-gamma was 7-fold higher in the 2008/13/4 and 2008/17/4 cells than in the 2008 cells, whereas the expression of RAR-alpha and RAR-beta was not observed in any cell line. Whereas the 2008, 2008/13/4, and 2008/17/4 cells were found to resist the antiproliferative effects of all-trans-retinoic acid, the paclitaxel-resistant cells were 6- to 7-fold cross-resistant to the antiproliferative effects of CD437 (a synthetic RAR-gamma-selective agonist; 6-[-(1-admantyl)-4-hydroxyphenyl]-2-naphthalenecarboxylic acid) compared with the sensitivity of the parental cells. To further understand the association of paclitaxel and CD437 resistance with the observed RAR-gamma overexpression, we transfected the 2008 cells with a full-length RAR-gamma cDNA construct. Two transfectants with increased expression of the RAR-gamma mRNA and protein were isolated and subjected to growth inhibition assays in the presence of various concentrations of paclitaxel, etoposide, vincristine, and CD437. The sensitivity of the 2008 transfected clones (displaying increased expression of RAR-gamma) to the cytotoxic effects of paclitaxel, etoposide, vincristine, and CD437 was similar to that observed in the parental 2008 cells. These results suggest that the overexpression of RAR-gamma (observed in the 2008/13/4 and 2008/17/4 cells) by itself is not capable of inducing paclitaxel and CD437 resistance (or resistance to etoposide and vincristine).
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PMID:Cross-resistance to the synthetic retinoid CD437 in a paclitaxel-resistant human ovarian carcinoma cell line is independent of the overexpression of retinoic acid receptor-gamma. 1192 43

Here the relationship between all-trans retinoic acid (ATRA)-resistance and P-glycoprotein (P-gp)-associated multidrug resistance (MDR) is discussed in acute promyelocytic leukemia (APL). First, the remission rates of ATRA therapy are similar in relapsed/refractory APL to the preceding chemotherapy given and in newly diagnosed APL. Second, MDR1 cDNA-transduced NB4 (NB4/MDR) cells accumulate less Rhodamine-123 (Rh123) than NB4 cells, but there is no difference in the intracellular ATRA concentration between them. PSC833 or MS209. MDR modifiers, increases the intracellular accumulation of Rh123 in NB4/MDR and APL cells expressing P-gp, but not of ATRA. Third, the expression of CD11b, the NBT reduction activity, the proportion of apoptotic cells and the morphology are not different between NB4/MDR and NB4 cells, and between APL cells expressing P-gp and not. APL cells express little P-gp, and mainly express CD33 but no CD34. Despite previous reports that ATRA-resistant APL cells express more P-gp than ATRA-sensitive ones, P-gp and ATRA-resistance seems to exist independently.
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PMID:All-trans retinoic acid (ATRA) differentiates acute promyelocytic leukemia cells independently of P-glycoprotein (P-gp) related multidrug resistance. 1169 4

P-glycoprotein (P-gp)/multi-drug resistance 1 (MDR1) gene is recognized to be, at least in part, responsible for the refractoriness to chemotherapy of leukemia. The transcriptional mechanism of MDR1 gene is largely unknown. However, recent reports have clarified that early growth response 1 gene (Egr1) positively regulates MDR1 transcription, while Wilms' tumor suppressor gene (WT1) does negative regulation of MDR1 gene expression in 12-O-tetradecanoylphorbol-13-acetate treated K562 cells. In addition, Egr1 and WT1 are structurally related transcription factors and bind to quite similar DNA sequences. Our study of mRNA expression profile of Egr1, WT1 and MDR1 in fresh AML samples demonstrated that there are disease-specific patterns. Egr1 mRNA was frequently and strongly expressed in monocytic leukemia cells, especially in AML M4 cells. WT1 mRNA was undetectable in t(8;21) AML cells. mRNA expression of MDR1 was frequent in AML M1 and t(8;21) AML cells, in which the expression level was highest in AML M1 and was low in monocytic leukemia (M4 and M5). Then, expression level of MDR1 was inversely correlated with Egr1. By liquid culture of leukemia cell lines and fresh AML cells with the addition of all-trans retinoic acid (ATRA), modulation of P-gp/MDR1 and Egr1 was observed and the pattern of modulation was divided into four groups: (1) blastic AML type, in which distinct expression of P-gp/MDR1 and CD34 was not influenced by ATRA; (2) t(8;21)AML type, in which P-gp/MDR1 expression was augmented by ATRA, while CD34 was kept high; (3) AML M3 type, in which P-gp/MDR1 expression was reduced with granulocytic differentiation by ATRA; (4) monocytic AML type, in which P-gp/MDR1 expression was augmented by ATRA, while CD34 expression decreased, and strong Egr1 expression was downregulated just prior to the augmentation of P-gp/MDR1 expression. WT1 expression was not influenced by the addition of ATRA in each group. Previous reports have suggested that P-gp/MDR1 plays an important role in resistance to chemotherapy, and is recognized as one of the stem cell marker. However, P-gp/MDR1 expression augmented by ATRA, which was observed in monocytic AML, was recognized as a functional molecule of mature monocyte/macrophage, because CD34 expression decreased and CD13 expression increased by ATRA. Finally, expression of P-gp/MDR1 in monocytic leukemia, which was functionally confirmed by Rh123 efflux study, was thought to be closely related to the characteristic modulation of Egr1 expression by ATRA.
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PMID:Augmented expression of P-gp/multi-drug resistance gene by all-trans retinoic acid in monocytic leukemic cells. 1173 1

An important role for beta-catenin pathways in colorectal carcinogenesis was first suggested by the protein's association with adenomatous polyposis coli (APC) protein, and by evidence of dysregulation of beta-catenin protein expression at all stages of the adenoma-carcinoma sequence. Recent studies have, however, shown that yet more components of colorectal carcinogenesis are linked to beta-catenin pathways. Pro-oncogenic factors that also release beta-catenin from the adherens complex and/or encourage translocation to the nucleus include ras, epidermal growth factor (EGF), c-erbB-2, PKC-betaII, MUC1, and PPAR-gamma, whereas anti-oncogenic factors that also inhibit nuclear beta-catenin signaling include transforming growth factor (TGF)-beta, retinoic acid, and vitamin D. Association of nuclear beta-catenin with the T cell factor (TCF)/lymphoid enhancer factor (LEF) family of transcription factors promotes the expression of several compounds that have important roles in the development and progression of colorectal carcinoma, namely: c-myc, cyclin D1, gastrin, cyclooxygenase (COX)-2, matrix metalloproteinase (MMP)-7, urokinase-type plasminogen activator receptor (aPAR), CD44 proteins, and P-glycoprotein. Finally, genetic aberrations of several components of the beta-catenin pathways, eg, Frizzled (Frz), AXIN, and TCF-4, may potentially contribute to colorectal carcinogenesis. In discussing the above interactions, this review demonstrates that beta-catenin represents a key molecule in the development of colorectal carcinoma.
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PMID:Beta-catenin--a linchpin in colorectal carcinogenesis? 1183 57

In the present work, we studied the effects of fenretinide (N-(4-hydroxyphenyl)retinamide (HPR)), a hydroxyphenyl derivative of all-trans-retinoic acid, on sphingolipid metabolism and expression in human ovarian carcinoma A2780 cells. A2780 cells, which are sensitive to a pharmacologically achievable HPR concentration, become 10-fold more resistant after exposure to increasing HPR concentrations. Our results showed that HPR was able to induce a dose- and time-dependent increase in cellular ceramide levels in sensitive but not in resistant cells. This form of resistance in A2780 cells was not accompanied by the overexpression of multidrug resistance-specific proteins MDR1 P-glycoprotein and multidrug resistance-associated protein, whose mRNA levels did not differ in sensitive and resistant A2780 cells. HPR-resistant cells were characterized by an overall altered sphingolipid metabolism. The overall content in glycosphingolipids was similar in both cell types, but the expression of specific glycosphingolipids was different. Specifically, our findings indicated that glucosylceramide levels were similar in sensitive and resistant cells, but resistant cells were characterized by a 6-fold lower expression of lactosylceramide levels and by a 6-fold higher expression of ganglioside levels than sensitive cells. The main gangliosides from resistant A2780 cells were identified as GM3 and GM2. The possible metabolic mechanisms leading to this difference were investigated. Interestingly, the mRNA levels of glucosylceramide and lactosylceramide synthases were similar in sensitive and resistant cells, whereas GM3 synthase mRNA level and GM3 synthase activity were remarkably higher in resistant cells.
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PMID:Altered sphingolipid metabolism in N-(4-hydroxyphenyl)-retinamide-resistant A2780 human ovarian carcinoma cells. 1248 34

Retinoids are vitamin A (retinol) derivatives essential for normal embryo development and epithelial differentiation. These compounds are also involved in chemoprevention and differentiation therapy of some cancers, with particularly impressive results in the management of acute promyelocytic leukemia (APL). Although highly effective in APL therapy, resistance to retinoic acid (RA) develops rapidly. The causes of this resistance are not completely understood and the following factors have been involved: increased metabolism, increased expression of RA binding proteins, P-glycoprotein expression, and mutations in the ligand binding domain of RARalpha. RA exerts its molecular actions mainly through RAR and RXR nuclear receptors. In addition to the nuclear receptor based mechanism of RA action, covalent binding of RA to cell macromolecules has been reported. RA derives from retinol by oxidation through retinol and retinal dehydrogenases, and several cytochrome p450s (CYPs). RA is thereafter oxidized to several metabolites by a panel of CYPs that differs for the different RA isomers. Phase II metabolism, mainly glucuronidation, is also observed. The role RA metabolism plays in the expression of its biological actions is not completely understood: in several systems, metabolism decreases RA activity, whereas in other systems metabolism appears involved in its action. In addition, several RA metabolites have shown activity and cannot be classified as only catabolites. Therapy of cancer with retinoids is still in its infancy, but the use of new analogues with improved pharmacological properties, along with combination with other drugs, could undoubtedly improve the management of several cancers in the future.
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PMID:Retinoic acid metabolism and mechanism of action: a review. 1257 Jul 42


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