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)

The immunological findings and clinical course of 33 patients with granular lymphocyte-proliferative disorders (GLPD) are presented. Based on the surface phenotypes of peripheral blood granular lymphocytes (GL), the GLPD were divided into two groups, namely CD3+ T cell-lineage GLPD (T-GLPD) and CD3- CD16+ NK cell-lineage GLPD (NK-GLPD). Twenty-one patients had T-GLPD, and 12 had NK-GLPD. One patient with T-GLPD and two patients with NK-GLPD had progressive clinical courses and died of the disease despite receiving combination chemotherapy. Among eleven patients analysed for the expression of multidrug resistance P-glycoprotein, six of eight patients with T-GLPD and all three patients with NK-GLPD clearly expressed P-glycoprotein. Since patients with immature NK-GLPD appear to undergo a progressive clinical course, we suggest that therapeutic trials using P-glycoprotein blockers in addition to chemotherapy might be beneficial for such patients.
Leuk Lymphoma 1994 Jun
PMID:Expression of multidrug resistance P-glycoprotein on peripheral blood mononuclear cells of patients with granular lymphocyte-proliferative disorders. 792 Feb 24

Cytochemical screening for a panel of enzymes revealed increased 5' nucleotidase (5'NT) expression in 3 of 3 P-glycoprotein 170 (Pgp170)-positive multidrug-resistant (MDR) variants of the murine EL4 T-lymphoma cell line (EL4/ADM, ER2 and ER13). Electron microscopic localization established the presence of the membrane-bound ecto-form of the enzyme. Nine other murine, human and Chinese hamster cell lines and their MDR variants were tested for ecto-5'NT. Of these, 4 MDR variants (human cell lines MCF7A6, MCF7A2, HeLaJ2C and the murine cell line L1210A) showed increased expression of ecto-5'NT, when compared with their parental cell lines. The findings with cells of human origin were confirmed by immunofluorescent localization with a specific monoclonal antibody (MAb) (27.2) against the human ecto-5'NT. All MDR cell lines with elevated ecto-5'NT expression were generated by doxorubicin treatment. These cells were more sensitive than their parental cell lines to AMP at concentrations of 1.5-3.0 mM, confirming that the expressed ecto-5'NT was biologically active. The parental and MDR cells did not differ, in general, in their sensitivity to adenosine. An inhibitor of ecto-5'NT, alpha,beta-methyleneadenosine 5'-diphosphate, completely reversed the resistance of the EL4/ADM cell line to doxorubicin. The possibility exists of a functional relationship between the ecto-5'NT molecule and the members of the ATP-binding cassette transporter superfamily, important components of MDR, in some cell types.
 ...
PMID:Ecto-5'-nucleotidase (CD73) in multidrug-resistant cell lines generated by doxorubicin. 792 9

The methoxymorpholino derivative of doxorubicin (MMDX; FCE 23672) has recently entered clinical trials because of its broad spectrum of preclinical antitumor activity and non-cross-resistance in multidrug-resistant (MDR) tumor models. MMDX is activated in the liver to a > 10 times more potent metabolite that cross-links DNA. To assess the potential of this drug in hematologic malignancies, we studied the myelotoxicity in vitro and antitumor effect of MMDX as well as its bioactivated form (MMDX+) in a panel of 14 different human leukemia and lymphoma cell lines. The tumor specificity of MMDX in CEM and K562 cells was similar to that of doxorubicin (DOX), and that of MMDX+ was slightly superior. All of the 14 cell lines were found to be more sensitive to MMDX and MMDX+ than were granulocyte-macrophage progenitors. On a molar basis, MMDX was approximately 3-100 times more active than DOX, and MMDX+ was 10-1,000 times more potent than DOX. The cytotoxic effect of MMDX and MMDX+ in two P-glycoprotein-positive MDR sublines was greatly improved in comparison with that of DOX. Whereas the response to DOX in the different leukemia and lymphoma cell lines was highly heterogeneous, the response to MMDX and MMDX+ was rather homogeneous. The novel anthracycline MMDX and its bioactivated form MMDX+ are highly active against this panel of human leukemia and lymphoma cell lines and demonstrate potentially greater selectivity for tumor cells in vitro as compared with normal bone marrow precursors.
 ...
PMID:Effects of the methoxymorpholino derivative of doxorubicin and its bioactivated form versus doxorubicin on human leukemia and lymphoma cell lines and normal bone marrow. 826 83

Resistance to chemotherapy represents a major cause for cancer treatment failure. Several biological mechanisms implicated in chemoresistance have been described, including multidrug resistance (MDR1/P-glycoprotein [P-gp] or p170), resistance-related proteins (p95 and p110), multidrug resistance-associated protein (p190), proteins implicated in cell detoxification such as glutathione S-transferase and genes affecting DNA structure (topoisomerases). MDR1 has been the most studied in hematological malignancies, particularly in lymphoma and multiple myeloma (MM), diseases generally considered as overexpressing such mechanisms in relapse. Overexpression of chemoresistance is generally an induced phenomenon caused or amplified by the drugs, as demonstrated by the development of drug-resistant cell lines in vitro. It may be defined as a profile of chemoresistance depending on the drug used for induction. This may have a potential implication for monitoring chemoresistance to modulate or to prevent its amplification. Several questions are always open to discussion, including the method of detection, the true prognostic impact of chemoresistance, the dynamic expression of such mechanisms, depending on the cell status, the host response and the mechanism of induction. In MM, the over-expression of MDR1/P-gp is usually less than 10% at diagnosis, leading to 59-80% at relapse, depending on the clinical status. The percentage of positivity depends on the cumulative dose of vincristine and/or doxorubicin. GST pi is (over)expressed in 10-70% of patients at diagnosis, and in 30% at relapse, but in small series, as well as for topoisomerases I and II which are concerned in 53% and 6%, respectively, at diagnosis.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Chemoresistance and multiple myeloma: from biological to clinical aspects. 852 May 14

Multidrug resistance gene (mdr1) RNA levels were determined in 55, and P-glycoprotein expression in 37 samples of peripheral leukemic cells from 17 patients with acute myeloblastic leukemia (AML) and 7 patients with acute lymphocytic leukemia (ALL). Between sample collections, patients were treated with various chemotherapy regimens. Mdr1 RNA levels were quantified by a RNA-RNA solution hybridization assay. P-glycoprotein was determined by Western blot analysis. Samples from 14 patients (9 AML, 5 ALL) had undetectable mdr1 RNA levels at initial analysis. Only two of these had detectable levels after chemotherapy. Ten patients (8 AML, 2 ALL) had detectable mdr1 RNA levels at initial analysis (median 1.0 transcript per cell, range 0.2-1.4). Increase of mdr1 RNA levels after chemotherapy were observed in cells from 3 patients, one patient had a lower level after chemotherapy and the 6 remaining patients had essentially unchanged mdr1 RNA levels in their leukemic cells. Samples from 13 patients were sequentially analysed for P-glycoprotein expression. In one patient, no P-glycoprotein was detectable at initial analysis but was weakly positive after chemotherapy. In the remaining 12 patients, P-glycoprotein levels stayed stable during disease progression. In conclusion, combination chemotherapy seems only rarely to be associated with an increase of mdr1 gene expression in residual leukemic cells. The addition of resistance modifiers to chemotherapy in order to overcome P-glycoprotein mediated resistance might therefore be more effective in chemotherapy naive patients since it is possible that during later disease progression additional mechanisms of resistance may be more operative.
Leuk Lymphoma 1995 Aug
PMID:Multidrug resistance (Mdr1) gene expression in peripheral blasts from patients with acute leukemia only rarely increases during disease progression after combination chemotherapy. 852 50

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.
Leuk Lymphoma 1995 Aug
PMID:Expression of multidrug resistant gene (mdr-1/P-glycoprotein) in a megakaryoblastic cell line, CMK, and its enhancement during megakaryocytic differentiation. 852 62

Over-expression of the MDR-1 gene, which codes for P-glycoprotein, is thought to be an important mechanism in the drug resistance exhibited by many tumours. A number of chemotherapeutic agents which induce MDR-1 expression are also components of combination chemotherapies that are used in the treatment of high grade non-Hodgkin's lymphomas (NHL). We have therefore examined expression of MDR-1 in a series of NHL by Northern blot analysis as well as investigated the localization of P-glycoprotein by immunohistochemistry. The series included 11 hyperplastic reactive nodes and tonsils, 17 low grade NHL and 15 high grade NHL. The levels of MDR-1 mRNA were quantified by scanning densitometry and comparison with levels of glucose-6-phosphate dehydrogenase (G6PD). The MDR-1 mRNA was observed in both non-malignant and NHL tissues. Immunohistochemical staining revealed that expression of MDR-1 mRNA in reactive nodes was related to the presence of P-glycoprotein in lymphocytes, however, P-glycoprotein was apparent in both the reactive lymphocytes and tumour cells in the NHL samples. Elevated mRNA levels (2-3 fold increase) were observed in some low grade and high grade NHL relative to those observed in reactive lymphoid tissue. There appeared to be little correlation, however, between expression of the MDR-1 gene and either treatment intensity or response to therapy. The drug resistance that is often encountered in NHL patients is therefore likely to involve mechanisms other than over-expression of P-glycoprotein.
Leuk Lymphoma 1995 Jul
PMID:MDR-1 expression in non-Hodgkin's lymphomas is unrelated to treatment intensity or response to therapy. 853 96

White blood cells from a total of 19 patients diagnosed as having acute lymphoblastic (ALL) or acute myeloid (AML) leukaemia were analysed (36 samples) for amplification and expression of the mdr1 and mdr3 genes. Nine of the patients had samples analysed at presentation and at subsequent stages of the disease (24 samples, including 4 at second relapse). Patients received standard MRC UK Trial remission-induction treatment protocols appropriate to disease and age. No amplification of either the mdr1 or mdr3 gene was found in any of the samples, and neither were mdr3 transcripts detected by dot-blot analysis using gene-specific probes. Transcripts of the mdr1 gene were found in only 2 ALL samples (of 10). However, mdr1 transcripts were detected in all AML patients and there was a significant increase in the transcript levels in these patients who went on to first and second relapse, compared with levels measured at presentation (P < 0.001). The results support the hypothesis that P-glycoprotein-mediated drug resistance may be a significant factor in tumour cell resistance to chemotherapy at relapse following initial induction-remission therapy for acute myeloid leukemia.
Leuk Lymphoma 1995 Sep
PMID:Analysis of MDR1 and MDR3 multidrug resistance gene expression and amplification in consecutive samples in patients with acute leukaemias. 857 59

Multidrug resistance is a major clinical problem in chemotherapy of malignant disease. Acute megakaryoblastic leukemia (AMKL) is a rare form of childhood leukemia, and is often more resistant to many anticancer chemotherapeutic drugs compared to other types of childhood leukemia. There have been reports of the increased expression in hematologic malignancy of multidrug resistant (mdr-1) gene, which encodes for a transmembrane glycoprotein P-glycoprotein that acts as an efflux pump for structurally unrelated chemotherapeutic drugs. We investigated the malignant cells of 15 newly diagnosed childhood AMKL patients by immunocytochemical analysis and found P-glycoprotein expression in all samples from these patients. RNA prepared from five patients at the time of presentation confirmed the expression of mdr-1 specific message in all cases by Northern blot analysis. These results imply that malignant cells from all childhood AMKL might express the mdr-1/P-glycoprotein.
Leuk Lymphoma 1995 Nov
PMID:Expression of MDR-1/P-glycoprotein in childhood acute megakaryoblastic leukemia cells. 859 Aug 43

The cytotoxicity of mitotic spindle poisons, vinca alkaloids and the anthracycline, adriamycin, against cisplatin-sensitive and -resistant rat lymphoma and human ovarian carcinoma cell lines was investigated. Interestingly, it was found that all cell lines were more sensitive to the mitotic spindle poisons, vincristine and vinblastine. Adriamycin was the least effective and taxol had intermediate activity. The Walker rat lymphoma cell line resistant to cisplatin (WR) exhibited the multiple drug resistance phenotype since it showed collateral resistance to all drugs (ranging from twofold to taxol, colcemid and colchicine and sixfold to the vinca alkaloids). Verapamil potentiated the cytotoxic activity of adriamycin and vincristine in a striking fashion with the Walker cells. P-glycoprotein was found to be present in the plasma membranes of the Walker cells with approximately a 2.5-fold increase in the WR as compared to the sensitive (WS) cells. Glutathione levels were elevated in all of the cisplatin-resistant cell lines when compared to the cisplatin-sensitive parental cell lines. A profound effect of buthionine sulfoximine pretreatment on adriamycin cytotoxicity was observed. Glutathione S-transferase (pi) was present in all the human cell lines but the WS cells had markedly lower levels (almost negligible) when compared to the WR cells. These observations imply that cisplatin-resistant cells may be more sensitive to mitotic spindle poisons and vinca alkaloids, irrespective of the mechanism of platinum resistance, and that the cytotoxicity of vinca alkaloids could be further modulated by verapamil, irrespective of the presence or absence of P-glycoprotein.
 ...
PMID:Cross-resistance and collateral sensitivity to natural product drugs in cisplatin-sensitive and -resistant rat lymphoma and human ovarian carcinoma cells. 859 69


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>