Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A mouse-human chimeric monoclonal antibody (mAb), MH162, against P-glycoprotein was previously found to be more effective than an all-mouse mAb (MRK16) in lysis of multidrug-resistant (MDR) tumor cells by blood mononuclear cells. The present study was performed to identify the effector cells responsible for the chimeric mAb-dependent cell-mediated cytotoxicity (ADCC) against MDR cells. The ADCC reaction was assessed by a 6-h 51Cr release assay. Highly purified lymphocytes (greater than 99%), monocytes (greater than 99%) and neutrophils (greater than 96%) were obtained from peripheral blood of the same healthy donors. A comparison of these three effector cell populations showed no difference between MH162 and its all-murine counterpart MRK16 in MDR cell lysis by monocytes or neutrophils. But MH162 was more effective than MRK16 in lymphocyte-mediated lysis of the MDR cells. The lymphocytes responsible for this ADCC had CD16+ Fc receptors. Pretreatment of monocytes with colony-stimulating factors (IL-3, GM-CSF and M-CSF) caused significant increase in their MH162-mediated lysis of MDR cells. Another anti-P-glycoprotein chimeric mAb (MH171) was also more effective than its murine counterpart MRK17 in lymphocyte-mediated lysis of MDR cells. These findings suggest that mouse-human chimeric mAbs may be useful therapeutically for in vivo destruction of MDR cancer cells by the ADCC reaction.
 ...
PMID:Effector cell analysis of human multidrug-resistant cell killing by mouse-human chimeric antibody against P-glycoprotein. 135 55

Modulation of the expression of P-glycoprotein, a plasma membrane protein associated with multidrug resistance, was examined in drug-sensitive and drug-resistant tumor cells treated with leukoregulin, a M(r) 50,000 cytokine from human lymphocytes that rapidly permeabilizes the plasma membrane of many tumor cells facilitating the uptake of doxorubicin and other tumor-inhibitory antibiotics. P-glycoprotein expression was measured flow cytometrically by the binding of C219 or MRK16 monoclonal antibody to multidrug-sensitive human K562 erythroleukemia and 8226/S myeloma cells, compared to multidrug-resistant 8226/DOX40 myeloma cells. Cells were treated for up to 2 h with up to 80 units of leukoregulin/ml or one of a variety of unrelated cytokines including interleukin 1 alpha (IL-1 alpha), IL-1 beta, IL-2, IL-3, IL-4, IL-5, IL-6, colony-stimulating factor, macrophage colony-stimulating factor, granulocyte macrophage colony-stimulating factor, tumor necrosis factor alpha, gamma-interferon, alpha-interferon, epidermal growth factor, platelet-derived growth factor AA, platelet-derived growth factor BB, insulin-like growth factor I, insulin-like growth factor II, fibroblast growth factor, or transforming growth factor beta. Leukoregulin caused a concentration-dependent decrease in P-glycoprotein expression; however, P-glycoprotein expression was unaffected by the other cytokines (< 12% decrease in expression). Leukoregulin-induced membrane permeabilization, determined flow cytometrically by intracellular fluorescein efflux, and decreased P-glycoprotein expression occurred simultaneously within 15 min in drug-sensitive and -resistant cells. Enhanced doxorubicin uptake, measured flow cytometrically by doxorubicin influx, was also present within 15 min. Leukoregulin enhancement of doxorubicin uptake and increased membrane permeability varied directly with the decrease in P-glycoprotein expression. Leukoregulin in combination with doxorubicin enhanced the inhibition of cell proliferation in 8226/DOX40 multidrug-resistant cells over expressing P-glycoprotein. In contrast, combined treatment of HL-60/MX2 multidrug-resistant human promyelocytic leukemia cells that do not overexpress P-glycoprotein in association with their multidrug resistance resulted in no greater growth inhibition than observed with HL-60/MX2 cells treated with doxorubicin alone. This is the first demonstration that a naturally occurring macromolecule with anticancer activities can modulate the expression of P-glycoprotein concomitant with enhanced drug uptake and inhibition of cell proliferation.
 ...
PMID:Decreased P-glycoprotein expression in multidrug-sensitive and -resistant human myeloma cells induced by the cytokine leukoregulin. 135 22

This study was aimed at evaluating the influence of 5637-conditioned medium (5637-CM) and human recombinant cytokines on both expression and function of P-glycoprotein (P-gp) in TF-1, a GM-CSF/IL-3-dependent acute myeloid leukemia cell line which constitutively expresses functional P-gp. P-gp expression was measured by flow cytometry using MRK16 monoclonal antibody. P-gp function was measured by rhodamine 123 (Rh 123) efflux kinetics. When TF-1 cells were cultured with 5637-CM (50% v/v), both P-gp expression and P-gp efflux capacity were increased in a time-dependent manner with a 4-fold increase in P-gp expression level at day 6 whereas TF-1 cell differentiation status remained unchanged as assessed by morphological studies, phenotypical and cytochemistry analysis. Recombinant cytokines including GM-CSF, G-CSF, IL-1 beta, IL-6, stem cell factor, LIF, erythropoietin, and IL-3 had no effect on P-gp expression whereas TNF alpha induced dose- and time-dependent P-gp and mdr-1 gene overexpression. However, TNF alpha-induced P-gp overexpression had no influence on P-gp efflux capacity. Furthermore, when TF-1 cells were exposed to IL-3 for periods longer than 1 month, we found that P-gp efflux capacity was increased as compared to cells cultured with GM-CSF whereas P-gp expression was unchanged. Both TNF alpha and IL-3 did not induce TF-1 differentiation. Collectively, these results suggest that cytokines may influence both expression and function of P-gp in TF-1 cells without interfering with their differentiation status. In contrast to cytokines, phorbol esters enhanced expression and efflux capacity of P-gp in parallel with TF-1 cell monocytic differentiation. Finally, our study suggests that paracrine and/or autocrine secretion of cytokines may interfere with P-gp activity in some acute myeloid leukemia cells.
 ...
PMID:Effect of 5637-conditioned medium and recombinant cytokines on P-glycoprotein expression in a human GM-CSF-dependent leukemic myeloid cell line. 756 16

P-glycoprotein (P-gp) expression in mononuclear bone marrow cells was analyzed in 119 patients, including 60 with chronic myelogenous leukemia (CML), 48 with myelodysplastic syndromes (MDS), and 11 with acute myelogenous leukemia (AML). For P-gp measurement an immunocytological method using monoclonal antibodies C219, 4E3, and MRK 16 and the reverse transcription-polymerase chain reaction technique were applied. According to our results obtained in healthy volunteers using the immunocytological method, the limit for P-gp overexpression was set at > or = 10% P-gp-positive mononuclear bone marrow cells and at > or = 30% P-gp-positive mononuclear peripheral blood cells. All 42 CML patients in chronic phase had normal P-gp expression. P-gp overexpression was demonstrated in four of six patients in accelerated myelogenous blast cell phase and in four of 12 CML-BC patients. Of eight CML patients in blast crisis (BC) with normal P-gp expression, partial remission was achieved in three and minor response in five after prednisone/vindesine therapy. All four of the 12 CML-BC patients with P-gp overexpression did not respond to this therapy. Normal P-gp expression was seen in 41 (85.4%) of 48 untreated MDS patients. While P-gp overexpression did not develop during therapy in any of the myelodysplastic syndrome patients treated with low-dose ara-C alone, four of eight treated with low-dose ara-C plus GM-CSF and four of 11 treated with low-dose ara-C and IL-3 developed P-gp overexpression after therapy. Furthermore, 11 AML patients at primary diagnosis, including five AML patients with P-gp overexpression, who were treated with idarubicin, vepesid, and cytarabine V (ara-C) showed a complete remission. Additionally, one daunorubicin-cytarabine-pretreated refractory AML patient was treated with the oral form of the P-gp modulator drug dexniguldipine and achieved complete remission for a duration of 7 months. Our results suggest that in CML patients in BC, P-gp expression influences outcome after therapy. Further more, studies in a larger series of patients are necessary to prove the efficacy and toxicity of idarubicin/vepesid and cytardbine--or dexniguldipine-containing--therapy in relation to P-gp expression of AML patients.
 ...
PMID:Clinical importance of P-glycoprotein-related resistance in leukemia and myelodysplastic syndromes--first experience with their reversal. 791 49

Multidrug resistance is a severe clinical problem in the chemotherapy of malignant disease. Acute megakaryoblastic leukemia (AMKL) is a rare form of childhood leukemia, and is often resistant to many anti-cancer chemotherapeutic drugs. Here we report the expression of the mdr-1/P-glycoprotein in a cell line, CMK, established from a patient with AMKL. Expression of mdr-1 mRNA in CMK11-5 cells, a well differentiated subline, was higher than in CMK6 cells, a poorly differentiated subline. The level of P-glycoprotein was also higher in CMK11-5 cells. The cytokines interferon-gamma (IFN-gamma), GM-CSF and IL-3, which were shown to induce megakaryocytic differentiation of CMK cells, enhanced the expression of the mdr-1 mRNA and levels of P-glycoprotein. These results imply that differentiated megakaryocytic cells may have higher levels of the P-glycoprotein expression, suggesting a possible normal physiological function of P-glycoprotein in mature megakaryocytes.
 ...
PMID:Expression of multidrug resistant gene (mdr-1/P-glycoprotein) in a megakaryoblastic cell line, CMK, and its enhancement during megakaryocytic differentiation. 852 62

Eighty six of 430 acute myeloblastic leukemia (AML) patients (20.0%) and forty of 173 acute lymphoblastic leukemia (ALL) patients (23.1%) had CD7 on their leukemia cells. CD7(+) AML occurred at a younger age than CD7(-) AML, and is more frequent in males. Hepatomegaly and central nervous system involvement were also more frequent in CD7(+) AML than in CD7(-) AML. The age of onset of CD7(+) ALL is also younger than that of CD7(-) ALL. Phenotypically, CD(+) AML expressed CD34, HLA-DR, and TdT more frequently than CD7(-) AML while CD7(+) ALL expressed CD13/33 more often than CD7(-) ALL cells responded most significantly to interleukin 3 (IL-3), whereas most CD7(-) AML cells responded more significantly to granulocyte macrophage-colony stimulating factor (GM-CSF) and/or granulocyte (G)-CSF than to IL-3. CD7(+)sCD3(-)CD4(-)CD8(-) ALL expressed G-CSF receptor and c-kit mRNA more frequently, which is not usual in other types of ALL. P-glycoprotein (P-gp)/multi-drug resistance gene (MDR1), thought to be expressed in hematopoietic stem cells, is expressed in CD7(+) AML and CD7(+)sCD3(-) CD4(-)CD8(-) ALL significantly more often than in CD7(-) acute leukemias and the CR rate and overall survival of CD7(+)AML was worse than CD7(-) AML. These data, collectively, suggest the close association of CD7(+) AML and CD7(+)sCD3(-)CD4(-)CD8(-) ALL, not only the common expression of CD7 itself but also because their phenotypical immaturity, cytokine receptor expression, P-gp/MDR1 expression and clinical manifestations including the frequent occurrence in males and the poor prognosis. We propose that CD7(+) acute leukemia is an hematopoietic stem cell leukemia which may be separate entity.
 ...
PMID:Biological characteristics of CD7(+) acute leukemia. 872 5

Transfer of the multidrug resistance-1 (MDR1) gene into hematopoietic progenitor cells may reduce myelotoxicity of MDR1-related cytotoxic agents and therefore allow dose intensification. Mobilized peripheral blood progenitor cells (PBPC) can be obtained in ample quantity and are a suitable target cell population. CD34-selected PBPC samples (n = 6) were transduced with cell-free supernatant (SNT) of a cell line producing recombinant retrovirus containing the human MDR1 gene. Limiting-dilution long-term cultures were employed that allow continuous monitoring of stroma-adherent cobblestone areas (CA) and comparison of their frequency in a 5-log range over time. MDR1 provirus integration in CA-containing wells followed single-hit kinetics. According to Poisson statistics, proviral DNA was contained in 22% of unselected cobblestone area-forming cells (CAFC) at week 6, which represent primitive hematopoietic precursors. In comparison, 1.0 +/- 0.44% (mean +/- SEM) of week-6 CAFC were expressing P-glycoprotein at sufficient levels to convey vincristine resistance, suggesting low expression of the retroviral vector or splicing of the vector-drived mRNA in hematopoietic progenitor cells. Next we analyzed lineage-committed progenitors. The proviral DNA was detectable in 20-66% of colony-forming units granulocyte-macrophage (CFU-GM) while corresponding percentages (25-52%) of CD34+ PBPC were in the S/G2M phase of the cell cycle at the end of the transduction period. The proportion of vincristine-resistant CFU-GM was similar to the CAFC data and no significant differences were found between various MDR1-SNT transduction schedules whereas MDR1 co-cultivation, which served as a positive control, yielded significantly higher proportions of resistant colonies (5.3 +/- 1.4%, IL-3, 96 hr, p < or = 0.05). Assessment of rhodamine-123 (Rh-123) efflux in the myelo-monocytic progeny of MDR1-transduced cells mirrored the colony assay results in the SNT and co-cultivation groups. Less culture effort was required in the Rh-123 assay and functional characterization of the transferred P-glycoprotein was possible using cyclosporin A. Further development toward an effective MDR1 gene therapy should be facilitated by the CAFC assay, which allows estimation of the retroviral gene transfer frequency into primitive hematopoietic cells, and by the Rh-123 assay, which permits tractable side-by-side assessments of numerous MDR1 transduction protocols or different MDR1-SNT lots.
 ...
PMID:Frequency analysis of multidrug resistance-1 gene transfer into human primitive hematopoietic progenitor cells using the cobblestone area-forming cell assay and detection of vector-mediated P-glycoprotein expression by rhodamine-123. 879 46

We have used a T-cell receptor transgenic mouse model to study the role of antigen in the changes that occur as T cells age. We find that the characteristic shift in the CD4 population to a predominance of memory phenotype T cells which accompanies aging in non-transgenic mice does not occur, suggesting that this shift is a result of antigenic stimulation. Thus at least one component of aging must be antigen dependent. When responses of naive CD4 T cells from aged and young mice are directly compared in vitro, the former are relatively deficient in their ability to produce IL-2 and IL-3, they express altered levels of P-glycoprotein and they proliferate less well in the absence of exogenous cytokines. When the ability of both naive populations to generate effectors is compared, the number of effectors generated from aged naive cells is much reduced and the effectors generated express lower levels of IL-2R alpha and produce reduced levels of cytokines. Importantly, addition of IL-2 restores proliferation of aged naive T cells, restores efficient effector generation and results in effectors seemingly indistinguishable from those derived from young CD4 cells. Similar phenotypic and functional changes seen with aging are also found in T-cell populations from IL-2 and IL-2R alpha knockout mice. Thus the loss of optimal IL-2 production may participate in the aging process and may represent the main antigen-independent defect in the CD4 T-cell population.
 ...
PMID:From naive to effector--alterations with aging. 947 61

Mobilized peripheral blood progenitor cells (PBPC) are a potential target for the retrovirus-mediated transfer of cytostatic drug-resistance genes. We analyzed nonobese diabetic/severe combined immunodeficient (NOD/SCID) mouse-repopulating CD34+ PBPC from patients with cancer after retroviral transduction in various cytokine combinations with the hybrid vector SF-MDR, which is based on the Friend mink cell focus-forming/murine embryonic stem-cell virus and carries the human multidrug resistance 1 (MDR1) gene. Five to 13 weeks after transplantation of CD34+ PBPC into NOD/SCID mice (n = 84), a cell dose-dependent multilineage engraftment of human leukocytes up to an average of 33% was observed. The SF-MDR provirus was detected in the bone marrow (BM) and in its granulocyte fractions in 96% and 72%, respectively, of chimeric NOD/SCID mice. SF-MDR provirus integration assessed by quantitative real-time polymerase chain reaction (PCR) was optimal in the presence of Flt-3 ligand/thrombopoietin/stem-cell factor, resulting in a 6-fold (24% +/- 5% [mean +/- SE]) higher average proportion of gene-marked human cells in NOD/SCID mice than that achieved with IL-3 alone (P <.01). A population of clearly rhodamine-123(dull) human myeloid progeny cells could be isolated from BM samples from chimeric NOD/SCID mice. On the basis of PCR and rhodamine-123 efflux data, up to 18% +/- 4% of transduced cells were calculated to express the transgene. Our data suggest that the NOD/SCID model provides a valid assay for estimating the gene-transfer efficiency to repopulating human PBPC that may be achievable in clinical autologous transplantation. P-glycoprotein expression sufficient to prevent marrow aplasia in vivo may be obtained with this SF-MDR vector and an optimized transduction protocol. (Blood. 2000;95:1237-1248)
 ...
PMID:Quantitative assessment of retroviral transfer of the human multidrug resistance 1 gene to human mobilized peripheral blood progenitor cells engrafted in nonobese diabetic/severe combined immunodeficient mice. 1066 96