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 clinical effects of cyclosporin were evaluated during cytotoxic treatment in a 61 year old man with acute myeloid leukaemia. He had required a renal transplant 18 months before presenting with acute myeloid leukaemia (FAB subtype M4). He had received cyclosporin 3.5-4.0 mg/kg daily to maintain a plasma cyclosporin concentration of 75-150 ng/ml. Cyclosporin was continued during induction chemotherapy with daunorubicin, cytarabine, and 6-thioguanine (DAT). He had fever and oropharyngeal candidiasis that was unresponsive to anti-bacterial drugs but responsive to systemic amphotericin. Bone marrow examination 14 days after chemotherapy showed complete haematological remission. Subsequently he tolerated consolidation treatment with DAT with no serious complications. Unfortunately he developed fatal septicaemia following a second consolidation with mitozantrone and cytarabine. Inhibition of P-glycoprotein activity by cyclosporin may not significantly increase the toxicity of aggressive chemotherapeutic regimens, and as benefit may be achieved by this approach further clinical evaluation is justified.
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PMID:Treatment of acute myeloid leukaemia in a renal allograft recipient: implications of cyclosporin immunosuppressive treatment. 189 Feb 6

We looked for bcl-2 protein expression by immunocytochemistry on bone marrow slides from 51 cases of myelodysplastic syndrome (MDS), of whom 25 received some form of chemotherapy. Forty-six of them had at least 20% bcl-2 positive blasts and the median percentage of positive blasts was 80%, whereas myeloid cells beyond blasts were always negative. No correlation was found between bcl-2 expression and the FAB type of MDS, CD34 expression and P-glycoprotein expression. A strong correlation between weak bcl-2 expression and the presence of a p53 mutation detected by SSCP analysis and direct sequencing was found. Response to chemotherapy (intensive chemotherapy or low-dose Ara-C) and survival were not significantly influenced by the intensity of bcl-2 expression in blasts, although there was a trend for better response to chemotherapy and longer survival in patients with strong bcl-2 expression. This trend was no longer found, however, if patients with a p53 mutation were excluded. Our findings show that blasts from a majority of MDS cases have bcl-2 expression and that strong bcl-2 expression is not associated with a poor prognosis. The correlation between weak bcl-2 expression and p53 mutation suggests a possible downregulation of bcl-2 gene expression by mutated p53, the mechanism of which remains to be established.
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PMID:bcl-2 expression in myelodysplastic syndromes and its correlation with hematological features, p53 mutations and prognosis. 772 10

The purpose of our investigations was to measure P-glycoprotein (P-170) activity in blast cells of 35 adults with acute myeloid leukemia (AML), and 24 children and adults with acute lymphoblastic leukemia (ALL) at time of diagnosis. Studies were based on a flow cytometric assay that detects efflux of the fluorescent dye rhodamine 123 (Rh123), which is transported from the cell by the P-170 pump. Dual-fluorescence staining with Rh123 and phycoerythrin-labeled monoclonal antibodies allowed selective measurement of Rh123 efflux in blast cells. Samples were scored positive when the fraction of blast cells showing Rh123 efflux exceeded 10% after a 120-min incubation. Activity of P-170 was observed in 19 (54%) of the 35 AML cases and was completely blocked in the presence of multidrug resistance inhibitors. Efflux activity was significantly higher in CD34-positive AML samples (p < 0.02). All AML patients with the FAB-subtype M5 (n = 5) lacked Rh123 pumping activity (p < 0.03). The complete remission rate in response to induction chemotherapy was significantly higher for Rh123-negative (11/13, 85%) than for Rh 123-positive AML patients (4/15, 27%) (p < 0.007). At a median follow-up of 9 months overall survival was significantly shorter for Rh123-positive than for Rh123-negative patients (p < 0.05). In contrast to AML, we could detect Rh123 efflux in only two (8%) out of 24 ALL cases. The immunological subtypes of these two positive cases was of B-ALL and pre-T-ALL. Bone marrow cryostat sections from 13 AML and five ALL patients were further analyzed for staining with monoclonal antibodies MM4.17 and JSB1. Ten of 13 AML and two of five ALL cases expressed the MDR protein. Our results indicate that there is a rather low frequency of P-170 pumping activity in ALL compared with AML. Further, functional activity of P-170 contributes to chemoresistance in de novo AML.
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PMID:Low frequency of activity of P-glycoprotein (P-170) in acute lymphoblastic leukemia compared to acute myeloid leukemia. 786 74

Blast cells obtained from 104 children with untreated acute lymphoblastic leukaemia were analysed for the expression of P-glycoprotein (P-170) and glutathione S-transfer pi (GST-pi) using immunohistochemistry. Expression of P-170 was detected in 36 of 104 patients (35%) and increased GST-pi was seen in 52 patients (50%). Coexpression of both resistance proteins was observed in 22 leukaemias (21%), whereas no evidence of the resistance markers was found in 38 cases (37%). In patients with P-170-positive leukaemic cells, a significantly lower probability of remaining in first continuous complete remission (CCR) was observed when compared with patients with P-170-negative tumours (P < 0.05). However, only a trend for a more frequent expression of P-170 was found in the leukaemic cells of patients who experienced relapses (P = 0.099). Overexpression of GST-pi was correlated with a higher relapse rate (P = 0.001) and a lower probability of remaining in first CCR (P = 0.01). Expression of P-170 and GST-pi was independent of sex, FAB type, immunological subtype and initial blast cell count. The multivariate analysis indicated that only the expression of P-170 is an unfavourable prognostic factor for children with acute lymphoblastic leukaemia in addition to the prognostic clinical factors.
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PMID:P-glycoprotein and glutathione S-transferase pi in childhood acute lymphoblastic leukaemia. 798 Oct 66

P-glycoprotein (P-gp) is a crucial factor in the development of chemotherapy resistance in malignant disorders. Between 1989 and 1995, P-gp expression was studied in bone marrow blast cells of 322 (239 AML; 83 ALL) acute leukemia patients. 166 AML patients with the AML-6 protocol (EORTC), containing daunorubicin, vincristine and conventional-dose cytarabine (ara-C), and 63 AML patients treated with intermediate-does Ara-C plus amsacrine. Further 71 ALL patients were treated according to a German standard polychemotherapy protocol (BMFT04/1989). P-gp was determined by using monoclonal antibodies C219 and 4E3, and the cutoff point for P-gp overexpression was set at >/= 10%. A significant (P < 0.06) difference in P-gp overexpression was demonstrated between AML (21.6%) and ALL (10.2%) patients at primary diagnosis and between primary diagnosis and relapse/refractoriness in AML (21.6%; 51.0%) and ALL (10.2%; 27.2%) patients. According to FAB classification P-gp overexpression was detected in AML patients significantly (P < 0.05) more frequently in classes M4, M5a and M5b and less frequently in M3, as compared to other types. For AML patients with P-gp overexpression at primary diagnosis or early relapse/refractoriness, the predictive value for nonresponse to the AML-6 protocol was 91 and 95%, respectively, while late-relapsed AML patients with P-gp overexpression had a significantly (P < 0.05) lower predictive value of 73% for nonresponse. Additionally, in refractory and late-relapsed P-gp--overexpressing AML patients treated with intermediate-dose ara-C plus amsacrine the predictive values for nonresponse were 44 and 39%, respectively, significantly (P < 0.05) lower as compared to AML-6 protocol-treated refractory or late-relapsed AML patients. In P-gp-overexpressing treated ALL patients the predictive values of 50 and 55% for non-response were calculated at primary diagnosis and late relapse, respectively. We conclude that P-gp overexpression is a common phenomenon in AML patients at primary diagnosis or relapse, has an inverse influence on AML-6 treatment outcome and should be taken into consideration in the development of new therapy strategies.
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PMID:P-glycoprotein expression in patients with acute leukemia-clinical relevance. 865 97

Seventy-eight patients: 45 children, 33 adults and 27 normal healthy donors were enrolled in the study. Expression of P-glycoprotein (P-gp) was evaluated with three monoclonal antibodies (MAb's) directed to intra-(C219, JSB-1) and extra-cellular (MRK-16) epitopes of P-gp and immunocytochemical (IC) APAAP staining method. Twenty-seven healthy donors peripheral blood mononuclear cells (PBMC) were investigated by means of IC and FACScan analysis. Positive staining for P-gp was detected in 31% children's and 33% adults' leukemia samples. No reactivity of three MAb's was observed with peripheral blood mononuclear cells (PBMC) by means of IC. Flow cytometry analysis with C219 MAb revealed staining for P-gp present on sub-population of lymphocytes and monocytes. P-gp (+) as well as P-gp (-) cases were compared in respect to clinical outcome, FAB classification and blood group. Complete remission (CR) was achieved in 12/14 (85%) children's and 9/11 (81%) adults' P-gp (+) leukemia cases. Within the P-gp (-) leukemia cases CR was observed in 24/29 (82%) and 18/22 (81%), respectively. Partial remission, relapse, resistance and death were noticed in 14% children's and 18% adults' P-gp (+) samples. In P-gp (-) cases these parameters were observed in 17% and 18%, respectively. These results raise the question whether the expression of P-gp can be used as single prognostic marker to detect multidrug resistance (MDR phenomenon) in vivo?
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PMID:Is P-glycoprotein a sufficient marker for multidrug resistance in vivo? Immunohistochemical staining for P-glycoprotein in children and adult leukemia: correlation with clinical outcome. 875 Jun 36

Accurate measurement of P-glycoprotein (P-170) expression in clinical samples still remains a controversial issue. In this study tumor cell P-170 expression was assessed in 29 patients suffering from acute leukemia (17 acute myeloid leukemia (AML) and 12 acute lymphoblastic leukemia (ALL)) using three different techniques: flow cytometry measuring rhodamine 123 (Rh123) efflux (functional level), immunocytochemistry (protein level) and RT-PCR (mRNA level). Rh123 efflux was detectable in 10/29 (34%) of all cases, in 9/17 (53%) of AML and in 1/12 (8%) of ALL samples. In AML patients a significant association of CD34 expression and P-170 activity was observed (P < 0.02). All AML patients with the FAB subtype M5 were Rh123 negative (P < 0.007). Cytospin preparations were analyzed for staining with monoclonal antibodies JSB1 and MM4.17. Eight of 16 (50%) AML and 0/9 (0%) ALL cases expressed the multidrug resistance (MDR) protein assessed by JSB1. With MM4.17 87% of AML and 50% of ALL patients were scored positive. Agreement between both antibodies was found in only 13/23 (57%) samples. Extracted RNA from 12 patients was analyzed by RT-PCR to evaluate the expression of MDR1 and multidrug resistance-associated protein (MRP) mRNA. An increased level of MDR1 mRNA was detectable in 4/7 AML and 0/5 ALL cases. MRP expression was found in 3/7 AML and 0/5 ALL patients. Comparison of Rh123 assay and immunocytochemistry revealed a very good correlation when using MoAb JSB1 (P < 0.004) but not with MM4.17 (not significant (NS)). JSB1 also showed a much better association with the PCR results (P < 0.05) than MM4.17 (NS). Finally, we compared the results of the functional Rh123 assay and RT-PCR and observed a high correlation for Rh123/MDR1 (r = 0.819, P < 0.001) but low for Rh123/MRP (r = 0.562, NS). We conclude that measurement of Rh123 efflux and immunocytochemical staining of cytospin preparations with JSB1 allows the accurate monitoring of P-170 expression in acute leukemia. The simplicity of these two MDR assays suggests their use for routine MDR screening.
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PMID:Multidrug resistance in acute leukemia: a comparison of different diagnostic methods. 920 93

While assessing the prognostic implications of immunophenotyping in 382 patients enrolled in treatment protocols of the Eastern Cooperative Oncology Group (ECOG) for de novo adult acute myeloid leukaemia, we identified 95 patients with a unique antigen profile characterized by high expression of the leucocyte integrin CD11b (CD11b+ AML). High expression of CD11b was defined as > or = 32% positive blasts based on the retrospectively established prognostic cut-off point for this antigen. Although CD11b is normally expressed by mature monocytes, natural killer cells and granulocytes, leukaemic blasts in CD11b+ AML lacked other immunologic monocytic features (e.g. CD14 and CD122, the interleukin-2 receptor beta chain) and demonstrated a high degree of immaturity, as reflected by a high incidence of blasts expressing the stem cell factor receptor, CD117, and few blasts positive for the myeloid differentiation antigen CD15. Furthermore, by FAB criteria, only 41% of CD11b+ AML cases were classified as M4/M5. Patients with CD11b+ AML had a low response rate (54%) when compared with acute monocytic leukaemia (AMOL; 82%, P = 0.006) or AML overall (68%, P = 0.031), independent of age, cytogenetic abnormalities and P-glycoprotein expression. Because of its poor prognosis, recognition of CD11b+ AML is clinically warranted and, given its morphologic and cytogenetic ambiguity, must be based on the unique antigen profile.
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PMID:Acute myeloid leukaemia expressing the leucocyte integrin CD11b-a new leukaemic syndrome with poor prognosis: result of an ECOG database analysis. Eastern Cooperative Oncology Group. 948 12

The major vault lung resistance protein LRP is a cytoplasmic protein involved in drug resistance, especially in acute myeloid leukemia. We looked for LRP overexpression, using immunocytochemistry with LRP 56 monoclonal antibody, on marrow slides from 41 cases of myelodysplastic syndromes (MDS). LRP overexpression (LRP+) was defined by expression of LRP 56 in at least 20% of marrow blasts. LRP overexpression was seen in 19 (46%) cases. Concordant results between LRP overexpression and P-glycoprotein (PGP) expression were seen in 66% of the cases (p = 0.03), and discordant results (LRP+ and PGP-, or LRP- and PGP+) in 33% of the cases. No correlation was seen between LRP overexpression and FAB type, karyotype, CD34, p53 expression and bcl2 overexpression in blasts. Furthermore, in the 18 cases treated with anthracycline-AraC intensive chemotherapy and the 7 cases treated with low dose AraC, the response rate was not significantly different in LRP+ and LRP- patients. Survival was also similar in LRP+ and LRP- patients. In conclusion, LRP overexpression is probably more frequent in MDS than in de novo AML and, as in AML, is only partially correlated with PGP expression. In our experience, however, LRP was not a prognostic factor for response to chemotherapy and survival in MDS.
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PMID:Expression of lung resistance protein and correlation with other drug resistance proteins and outcome in myelodysplastic syndromes. 964 68

Resistance to chemotherapy-induced apoptosis and a multidrug-resistance (MDR) phenotype, mainly mediated by P-glycoprotein (P-gp), contribute to chemotherapy failure in hematologic malignancies. To study apoptosis-regulating factors in acute myeloid leukemia (AML), we investigated cell samples of adults with de novo AML by flow cytometry for constitutive expression levels of the apoptosis-related molecules CD95 (n = 135), Bcl-2 (n = 131), and Bax (n = 66), as well as spontaneous apoptosis in vitro (n = 104) and susceptibility to anti-CD95-induced apoptosis (CD95 sensitivity) (n = 93). We correlated these findings with P-gp function as detected by the rhodamine123-efflux test (n = 121), immunophenotype, FAB morphology, cytogenetics, and clinical data of the examined patients. Immature FAB M0/1 AML cells expressed significantly more Bcl-2 (P < 0.0002) and less CD95 (P < 0.0003) compared with AML cells of the more mature FAB M2-5 subtypes. No maturation-dependent difference in Bax expression was observed. FAB M2-5 AML cells were more susceptible to anti-CD95-induced apoptosis (P < 0.008) and showed a lower P-gp function (P < 0.002) than FAB M0/1 AML cells. Leukemic cells of AML patients who achieved a complete remission (CR) after induction chemotherapy expressed less Bcl-2 than non-responder (NR) (69 CR, 23 NR; P = 0.05). CR was associated with a higher extent of spontaneous apoptosis in vitro (58 CR, 17 NR; P=0.05) and a tendency towards a higher CD95 expression (73 CR, 23 NR; P = 0.08) compared to NR. CR also correlated with a low P-gp function (70 CR, 21 NR; P = 0.008) and a tendency towards CD34 negativity (73 CR, 23 NR; P = 0.08). No correlation between Bax expression and response to induction chemotherapy (49 CR, 12 NR) was observed. In stepwise logistic regression analyses, P-gp function and the extent of spontaneous apoptosis in vitro as well as CD95 sensitivity but not Bcl-2, CD95, Bax, and CD34 expression levels emerged as significant markers for response to induction chemotherapy. We conclude that the constitutive expression of CD95 and Bcl-2, as well as CD95 sensitivity and P-gp function but not constitutive Bax expression depend on the maturation stage of leukemic cells in adult de novo AML. P-gp function, the extent of spontaneous apoptosis in vitro and CD95 sensitivity are more predictive for response to induction chemotherapy in adult de novoAML than the constitutive expression levels of the apoptosis-related molecules CD95, Bcl-2 and Bax.
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PMID:Clinical significance of CD95, Bcl-2 and Bax expression and CD95 function in adult de novo acute myeloid leukemia in context of P-glycoprotein function, maturation stage, and cytogenetics. 1060 14


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