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)

The multidrug-resistance gene, MDR1 is expressed in many normal tissues, but little is known about its expression in normal hematopoietic cells. Using the monoclonal antibody C219 and flow cytometric analysis, P-glycoprotein (P-gp) was found to be expressed in all peripheral blood (PB) subpopulations (CD4, CD8, CD14, CD19, CD56) except granulocytes. To specifically determine MDR1 gene expression, these PB subpopulations were isolated by fluorescence-activated cell sorting (FACS) and analyzed for MDR1 mRNA by polymerase chain reaction (PCR). All subsets were positive by PCR, but only minimal MDR1 mRNA was detected in monocytes and granulocytes. Significant efflux of Rhodamine-123 (Rh-123), a measure of P-gp function, was detected in CD4+, CD8+, CD14+, CD19+, and CD56+ cells but not in granulocytes. Next, PCR-analysis was performed on FACS-sorted bone marrow (BM) cells to assess MDR1 expression in different maturational stages. Precursors (CD34+), early and late myeloid cells (CD33+/CD34+, CD33+/CD34-) as well as lymphocytes of the B-cell lineage (CD19+/CD10+, CD19+/CD10-) expressed the MDR1 gene. BM monocytic cells (CD33++/CD34-) were negative, and a very weak signal was detected in erythroid cells (glycophorin A+). Significant Rh-123 efflux was found in CD34+, CD10+, CD33+, and CD33++ BM cells, but not in glycophorin A+ cells. We conclude that PB and BM lymphocytes, PB monocytes, BM progenitors, and immature myeloid cells, but not late BM monocytes, erythroid cells, and PB granulocytes, express MDR1 mRNA and a functional P-gp. These results have to be taken into account when MDR1 expression is determined in tumor samples containing normal blood cells.
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PMID:Subpopulations of normal peripheral blood and bone marrow cells express a functional multidrug resistant phenotype. 850 83

Anti-B4-blocked ricin (anti-B4-bR) is an immunotoxin directed against CD19-positive cells that is currently being tested in several B-cell leukemia/lymphoma clinical trials. To explore the possibility of using anti-B4-bR in combination with chemotherapy protocols, we investigated the in vitro and in vivo cytotoxic effects of combining it with doxorubicin or etoposide using the lymphoma cell line Namalwa and a P-glycoprotein-expressing cell line, Namalwa/mdr-1, obtained by retroviral infection of Namalwa cells with the mdr-1 gene. Namalwa/mdr-1 cells were slightly more sensitive to anti-B4-bR than Namalwa cells; IC37 values were approximately 4 pmol/L and 8 pmol/L, respectively. When anti-B4-bR was combined simultaneously with doxorubicin or etoposide, additive to supra-additive killing of Namalwa and Namalwa/mdr-1 cells was observed. In xenografts of Namalwa/mdr-1 cells in severe combined immunodeficiency (SCID) mice, doxorubicin and etoposide at their maximum tolerated doses (3 mg/kg x 3 or 15 mg/kg x 3) showed no therapeutic effect. However, treatment with 5 daily bolus injections of anti-B4-bR (50 micrograms/kg) followed by treatment with doxorubicin or etoposide significantly increased the life span of the mice by 129% and 115%, respectively. After treatment with anti-B4-bR, the Namalwa/mdr-1 population expressed lower levels of P-glycoprotein, and this decrease may account for the synergistic action of the drug combinations. These results suggest that anti-B4-bR could be used to good effect in combination with current treatment regimens and further hint at a promising role for this immunotoxin in treatment of disease at the minimal residual disease stage, where cells may be resistant to chemotherapy.
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PMID:Anti-B4-blocked ricin synergizes with doxorubicin and etoposide on multidrug-resistant and drug-sensitive tumors. 749 89

In contrast to its clearly defined role as a multidrug efflux pump in neoplastic cells, the physiologic function of P-glycoprotein (P-gly) in normal cells is unclear. Recent reports identifying P-gly in normal blood and bone marrow suggest that hematopoietic development or function may be dependent on P-gly. To understand the normal function of P-gly in the blood, its level of expression and function must first be quantitated relative to a known standard. In this study, P-gly, MDR1 gene expression, and P-gly function were quantitated in normal leukocytes. P-gly and MDR1 expression were analyzed in individual leukocyte lineages (T-helper, T-suppressor, monocyte, granulocyte, B-lymphocyte, NK cell) from normal volunteers. P-gly on the cell surface was detected by fluorescent double-labeling for lineage (CD4, CD8, CD14, CD15, CD19, CD56, respectively) and P-gly (MRK16) with analysis by flow cytometry and in some cases immunoblot analysis. MDR1 mRNA analysis on purified lineages was performed using quantitative reverse transcription-polymerase chain reaction. P-gly function was determined for each lineage using dual-labeling for lineage and P-gly substrate (rhodamine 123). The P-gly expressing human myeloma cell line, 8226/Dox6, was used as a reference of comparison for levels of P-gly, MDR1 mRNA, and function. CD56+ cells expressed the highest levels of MDR1 mRNA followed by CD8+ > CD4+ approximately equal to CD15+ > CD19+ > CD14+, with percentage values relative to Dox6 of 49%, 17%, 8%, 8%, 4%, and 2%, respectively. The assays for P-gly immunofluorescence and function correlated well with mRNA analysis except for CD15+ cells (granulocytes), which showed a moderate MDR1 mRNA level with a lack of both function and surface P-gly staining. Granulocyte membranes did show P-gly on immunoblot analysis when probed with either C219 or JSB1. We conclude that (1) P-gly and the MDR1 mRNA are expressed in normal leukocytes, (2) this P-gly expression is lineage specific with relatively high levels among CD56+ cells, and (3) the expression of P-gly in granulocytes is not associated with transport of the P-gly substrate, rhodamine 123, out of the cell.
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PMID:P-glycoprotein expression and function in circulating blood cells from normal volunteers. 751 98

Clinical and cytologic characteristics were correlated to immunologic markers in 154 patients with newly diagnosed acute myeloid leukemia (AML). The panel of monoclonal antibodies (MoAbs) was selected to identify differentiation-associated antigens of both the myeloid and the lymphoid lineages (CD13, CD33, CD14, CD15, CD7, CD34, CD10, HLA-DR, CD19, CD2, CD5, TdT). The expression of multidrug resistance P-glycoprotein (P-170) was also evaluated in 117 patients. Differences in antigenic expression was observed among the various French-American-British (FAB) subgroups. HLA-DR was poorly expressed on the blasts of acute promyelocytic leukemia (M3), and was always found in FAB M5. CD34 was detectable in all M0 cases and only in one M3 (p < 0.001). Lymphoid-associated antigens were positive in 74 cases (48.1%). In particular, CD7 was found in 49 patients (31.8%), and TdT in 30 (21.3%), 15 samples displaying coexpression of these two antigens. The incidence of CD7+ cases was particularly elevated in M0 and M5 AML (p = 0.005). It significantly correlated with the expression of CD34, HLA-DR, P-170 (p < 0.001, p = 0.018 and p = 0.034 respectively), and with a leukocyte count > 50 x 10(9)/l (p = 0.038). Sixty-nine (59%) samples demonstrated P-170 positivity. Again, this phenotype was particularly expressed in the poorly differentiated forms (M5, M0 and M1) and showed significant correlation with the immaturity markers CD34, CD7 and HLA-DR (p = 0.013, p = 0.022 and p = 0.001, respectively). Expression of individual antigens correlated with prognosis. Refractoriness to first line therapy was associated with CD7 expression (p = 0.002) and P-170 (p = 0.001). The CD7 marker was also significantly associated with a very low overall survival (p < 0.001) and continuous complete remission (p < 0.001). CD14 expression also significantly predicted lower survival rates (p = 0.033). The combination (CD7+ CD14+) identified a subset of patients with a particularly adverse outcome. The prognostic value of CD7 expression, alone or in combination with other markers, was confirmed in multivariate analysis.
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PMID:Prognostic value of cell marker analysis in de novo acute myeloid leukemia. 790 93

To date no hematopoietic progenitors of dendritic Langerhans' cells (DLC), which represent an highly efficient class of antigen presenting cells, have been identified or the cytokines they elaborate have been defined. Here we describe an acute leukemia patient whose blasts (90-96% in peripheral blood and bone marrow) had a phenotype consistent with putative progenitors of DLC. The patient was treated with ara-C and VP-16 but did not achieve remission. The blasts had lobulated nuclei, no cytoplasmic vacuolation or Auer rods and were weakly positive for acid phosphatase and non-specific esterase and negative for PAS, granzyme A, dipeptidyl aminopeptidase IV, ATPase/ADPase and lysozyme production. The blasts were positive for CD1a, CD4, CD16, CD35, HLADR, HLADQ, CD11b, CD11c, CD14, CD33, CD34, CD11a, CD71, CD19, CD25, IL-2R beta and negative for CD2, CD7, CD8, CD10, CD22, CD56, CD57, surface or cytoplasmic CD3, TCR delta and TCR beta, HTLV-1p19 and P-glycoprotein. On liquid culture with or without 5 x 10(-9) M 12-O-tetradecanoylphorbol-13-acetate (TPA) for 3 days, the blasts formed aggregates of proliferating and elongating cells on the wall of the flasks with a decline in CD34, numerous dendritic processes appeared on the cells and there was strong positivity for ATPase/ADPase, but no other changes in phenotype. No macrophages were observed, indicating derivation from separate DLCs. Cytogenetic analysis showed chromosomal abnormalities and electron microscopy showed Birbeck granules. Southern blotting of DNA showed rearrangement of one allele for both JH and TCR beta but no HTLV-1 related sequences. Culture supernatants from blasts cultured with or without TPA showed the production of large amounts of IL-8, IL-6, TNF-alpha, MIP-1 alpha, IL-10 and interferon gamma and modest amounts of IL-1 alpha, GM-CSF and stem cell factor. The presence not only of CD1a, HLADR, HLADQ and many other characteristics including Birbeck granules, but also differentiation along the lines of DLC with appearance of dendritic processes on the cells and expression of ATPase/ADPase activity, indicate that the leukemic blasts in our patient represented a leukemic counterpart of normal progenitors of DLC and the leukemia a new entity which could possibly be classified as AML-M8. Lastly, many pro-inflammatory cytokines produced by DLC could contribute to inflammation and IL-10 to immunosuppression.
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PMID:Phenotype, genotype and cytokine production in acute leukemia involving progenitors of dendritic Langerhans' cells. 791 55

The MDR1 gene is of prognostic significance in acute myeloid leukemia (AML). The relationship of this gene to surface markers largely remains unclear. Therefore, we have studied the association of MDR1 gene expression with the expression of specific surface markers in AML. MDR1 RNA expression of leukemic cells was determined by slot blot analysis. Expression of P-glycoprotein and surface markers (CD7, CD13, CD19, CD34, HLA-DR, TdT, blood group H) was assessed by immunocytochemistry. MDR1 RNA (n = 79) and P-glycoprotein (n = 52) expression were detected in 63% and 63% of the patients, respectively. CD7, CD13, CD19, CD34, HLA-DR, TdT and blood group H were positive in 17%, 84%, 0%, 51%, 82%, 11% and 11% of the patients. MDR1 RNA or P-glycoprotein expression were not associated with the expression of either CD7, CD13, CD19, CD34, TdT or blood group H. However, P-glycoprotein expression was more frequent in HLA-DR positive than in HLA-DR negative patients (47% versus 10%, p = 0,04). Consistent with the latter finding, patients with intermediate or high MDR1 RNA expression expressed HLA-DR more frequently than patients with negative or weak MDR1 RNA expression (96% versus 76%, p = 0,03). In conclusion, MDR1 gene expression of AML cells was independent of surface markers except HLA-DR.
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PMID:Relationship between MDR1 gene and surface markers in acute myeloid leukemia. 906 14

One important mechanism of drug resistance in acute leukemia is the overexpression of the multi-drug resistance (MDR1) gene that encodes a 170-kDa membrane protein called P-glycoprotein. To estimate the incidence and role of MDR1 gene expression in patients with acute leukemia, we investigated the expression of MDR1 by using the RT-PCR method in blast cells from 40 cases of de novo acute leukemia. We found a high frequency of MDR1 gene expression: 10 out of 20 with de novo acute myeloid leukemia (AML), 8 out of 17 with de novo acute lymphoblastic leukemia (ALL), and none of the 3 with de novo acute mixed leukemia, were MDR1 mRNA-positive. No correlation between cluster designation (CD) surface markers (CD19, CD7, CD13, CD33, CD34, CD14, HLA-DR) and MDR1 gene expression in AML was found. The complete remission rate was correlated with MDR1 gene expression. Among 40 evaluable patients examined, 17% (3 of 18) with MDR1 mRNA-positive reached complete remission versus 77% (17 of 22) with MDR1 mRNA-negative (p=0.044). These results suggest that MDR1 gene expression can be used as a prognostic factor and may be helpful in determining chemotherapeutic protocol for patients with acute leukemia.
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PMID:Multi-drug resistance (MDR1) gene expression in de novo acute leukemia cells: correlations with CD surface markers and treatment outcome. 988 70

After chemotherapy, tumor cells with multidrug resistance (MDR) often emerge. MDR is attributable to the expression of membrane transport proteins that inhibit the cellular influx and increase the efflux of many chemotherapeutic drugs. One such protein is P-glycoprotein (P-gp), which functions as an ATP-dependent active transporter. Recently, an anti-P-gp monoclonal antibody (MAb) that inhibits P-gp has been described. Previous studies from our laboratory using the anti-CD19 B-cell lymphoma-reactive MAb, HD37, have suggested that HD37 may also influence MDR. To test this directly, we used Namalwa/MDR1 cells to study the effect of HD37 on the efflux of rhodamine 123 from these cells. We found that HD37 and three other anti-CD19 MAbs inhibited the efflux of rhodamine 123 from Namalwa/MDR1 cells with approximately 50% of the efficiency of the well-known chemosensitizer, verapamil. In contrast, MAbs against seven other molecules expressed on these cells were ineffective. The inhibitory activity of HD37 did not require an Fc portion; F(ab')2 fragments were effective, but Fab' fragments were not, suggesting that higher avidity binding and/or cross-linking of CD19 are necessary. We could find no evidence that HD37 recognizes a cross-reactive epitope on P-gp, modulates P-gp from the cell surface, or enhances the ATPase activity of membranes from treated cells.
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PMID:Anti-CD19 antibodies inhibit the function of the P-gp pump in multidrug-resistant B lymphoma cells. 1063 21

The goal of this study was to develop a small, stable liposomal carrier for antisense oligodeoxynucleotides (asODN) that would have high trapping efficiencies and long circulation times in vivo. Traditional cationic liposomes aggregate to large complexes and, when injected intravenously, rapidly accumulate in the liver and lung. We produced charge-neutralized liposome-asODN particles by optimizing the charge interaction between a cationic lipid and negatively charged asODN, followed by a procedure in which a layer of neutral lipids coated the exterior of the cationic lipid-asODN particle. The coated cationic liposomes had an average diameter of 188 nm and entrapped 85-95% of the asODN. The biodistribution and pharmacokinetics of an 18-mer 125I-labeled phosphorothioate ODN formulated by this method were determined after tail vein injection in mice. The majority of the asODN was cleared from blood, with a half-life of >10 hours compared with <1 hour for free asODN. When coupled with an anti-CD19 targeted antibody, this formulation was also effective at delivering an MDR1 asODN to a multidrug-resistant human B-lymphoma cell line in vitro, decreasing the activity of P-glycoprotein. No inhibition was found for nontargeted formulations or for free asODN. A number of therapeutic opportunities exist for the use of small, stable, long-circulating, and targetable liposomal carriers such as this, with high trapping efficiencies for asODN.
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PMID:A novel, long-circulating, and functional liposomal formulation of antisense oligodeoxynucleotides targeted against MDR1. 1076 53

We evaluated the presence of P-glycoprotein (P-gp)-170, multidrug resistance protein (MRP), lung resistance protein (LRP)-56 and Bcl-2 in CD19-positive cells from 100 cases of chronic lymphocytic leukaemia (CLL). P-gp-170 was found in 73% of the CLL cases with no significant difference regarding stage or previous treatment. LRP-56 protein was homogeneously distributed with no differences for stage or treatment. MRP protein was detected at a low level of expression in 49.4% of CLL patients with no differences for stage or treatment. Bcl-2 protein was expressed at a high level in all CLL patients and higher levels were found in the advanced stage. This leads us to conclude that P-gp, MRP, LRP-56 and Bcl-2 are frequently expressed in CLL. P-gp, MRP and LRP are not correlated to stage or previous treatment. Bcl-2 is higher in advanced-stage patients. The clinical and biological significance of these zMDR mechanisms in CLL remains to be fully explained.
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PMID:Multidrug resistance mechanisms in chronic lymphocytic leukaemia. 1188 80


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