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 K562/VCR cell line, exhibiting acquired multidrug resistance (MDR) with increased expression of a cell surface glycoprotein (P-glycoprotein), was isolated from human erythroleukemia K562 cells. Various compounds that induced erythroid differentiation of K562 cells were tested for their effects on growth and differentiation of these K562/VCR cells. Sodium butyrate, hemin, 1-beta-D-arabinofuranosylcytosine, and erythroid differentiation factor (EDF) induced erythroid differentiation of K562/VCR cells as well as K562 cells. The MDR of K562/VCR cells was partly overcome by treatment with EDF but not with the other inducers. Expression of P-glycoprotein by K562/VCR cells was measured by radioimmunoassay using MRK16 monoclonal antibody. Results showed that EDF caused down-regulation of P-glycoprotein in K562/VCR cells, whereas the other inducers did not cause its down-regulation. Thus, in addition to inducing erythroid differentiation, EDF enhanced the sensitivity of K562/VCR cells to multidrugs and suppressed expression of P-glycoprotein. These results suggest that differentiation inducers may be useful in chemotherapy of leukemic MDR cells.
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PMID:Inhibition by erythroid differentiation factor (activin A) of P-glycoprotein expression in multidrug-resistant human K562 erythroleukemia cells. 167 36

The cellular pharmacology of doxorubicin resistance (DOXR) has most commonly been associated with decreased drug uptake, enhanced drug efflux, cross-resistance to multiple anticancer agents, and the overproduction of a Mr 170,000 cell surface glycoprotein (termed P-glycoprotein). In this study, the pharmacological and genetic characteristics of two newly derived human DOXR sublines were examined. These DOXR sublines were established following continuously increasing DOX exposure until a 222-fold resistant fibrosarcoma subline (HT1080/DR4) and a 285-fold resistant colon adenocarcinoma subline (LoVo/DR5) were developed. However, three major lines of evidence suggest that despite the similar selection strategy, the mechanism of DOXR differs significantly between these two cell lines. First, Western blotting using the C219 antibody specific to P-glycoprotein revealed the overexpression of the Mr 170,000 cell surface glycoprotein in LoVo DOXR cells but not in HT1080 DOXR cells. Second, LoVo DOXR cells are cross-resistant to vincristine, actinomycin D, colchicine, etoposide, and gramicidin D, but not to 1-beta-D-arabinofuranosylcytosine. In contrast, HT1080 DOXR cells display cross-resistance to vincristine, actinomycin D, vinblastine, and etoposide; however, they are not cross-resistant to gramicidin D, and show an increased (approximately 18-fold) cross-resistance to 1-beta-D-arabinofuranosylcytosine. Third, intracellular DOX accumulation (as measured by [14C]DOX at 1-h and high-performance liquid chromatography analysis) was decreased approximately 2.7-fold in LoVo DOXR cells and approximately 2.0-fold in HT1080/DR4 cells. However, while net accumulation studies in the presence of 5 micrograms/ml verapamil reversed DOXR to parental values in LoVo colon adenocarcinoma cells, it only minimally decreased DOX resistance (12.6%) in HT1080/DR4 cells. Efflux patterns of [14C]DOX were similar for the DOXR sublines with an approximately 50% decrease in DOX retention after 1 h when compared to their respective parental cell lines. Our results suggest that DOXR in LoVo/DR5 cells may result from overexpression of P-glycoprotein. In contrast, DOXR in HT1080/DR4 appears to be non-P-glycoprotein mediated and may be related to an alternative mechanism capable of altering drug efflux or differential drug binding.
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PMID:Pharmacological and biological evidence for differing mechanisms of doxorubicin resistance in two human tumor cell lines. 289 69

Independent lines of Chinese hamster ovary cells resistant to the antineoplastic drug, daunorubicin, were obtained by clonal isolation in increasing drug concentrations. A single daunorubicin-resistant phenotype typified by reduced cellular drug accumulation was observed. These mutants displayed a complex phenotype of resistance to a variety of unrelated drugs. Such properties are similar to those of membrane-altered colchicine-resistant lines (V. Ling and L.H. Thompson, J. Cell. Physiol., 83: 103-116, 1974). Analysis of the plasma membrane components of the daunorubicin-resistant clones by gel electrophoresis revealed a prominent cell surface glycoprotein with a molecular weight of about 170,000. This component was immunologically cross-reactive with the cell surface P-glycoprotein of about the same molecular weight, previously identified in colchicine-resistant cells. Thus, it appears that the mechanism of resistance characterized by P-glycoprotein expression could be the basis of many drug-resistant phenotypes.
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PMID:Daunorubicin-resistant Chinese hamster ovary cells expressing multidrug resistance and a cell-surface P-glycoprotein. 613 5

Multidrug resistance (MDR) genes, which are ATP-binding cassette family genes, encode the cell surface glycoprotein, P-glycoprotein, which functions as an energy-dependent drug efflux pump. Two relevant human genes, PGY1 and PGY3, are located on human chromosome 7, and three relevant mouse genes, mdr1a, mdr1b, and mdr2, are located on mouse chromosome 5. An LMD1 cell line was established after the transfer of a 580-kb yeast artificial chromosome (YAC) clone carrying the human MDR locus into mouse L cells; the cell line was shown to have stably integrated YAC DNA in an apparent intact form. Using LMD1 cells as the parental cell line, five vincristine-resistant sublines, designated LMD1-V50, LMD1-V100, LMD1-V200, LMD1-V500, and LMD1-V1000, were isolated by exposure to increasing concentrations of the drug. LMD1-V50, LMD1-V100, LMD1-V200, LMD1-V500, and LMD1-V1000 showed 3-, 7-, 13-, 45-, and 110-fold higher resistance to the cytotoxic effects of vincristine, respectively, than their parental counterpart, LMD1. Immunofluorescence, Western blot, and Northern blot analyses revealed that the human PGY1 gene or its product was overexpressed, accompanied by gene amplification. The human PGY3 gene was also overexpressed in the LMD1-V20, LMD1-V100, and LMD1-V1000 cell lines. Southern blot and fluorescence in situ hybridization (FISH) analyses demonstrated that although essentially the entire YAC DNA was integrated in mouse genome and amplified, the endogenous mouse mdr genes were not amplified in these drug-resistant cell lines. Similar results were obtained by the analyses of vincristine-resistant cell lines isolated from four independent subclones of LMD1 cells. Thus, in contrast to their mouse counterparts, the integrated human MDR genes retained susceptibility to both gene activation and amplification, during the selection of drug-resistant mouse cell lines. The possibility that transferred YACs may retain regulatory properties observed in the cells of origin, and may have a chromatin structure that favors augmented expression, is discussed.
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PMID:Functional expression of yeast artificial chromosome-human multidrug resistance genes in mouse cells. 859 12

CD56 antigen, a 200-220 kDa cell surface glycoprotein, identified as an isoform of the neural adhesion molecules (NCAM), has been found frequently expressed in several lympho-hematopoietic neoplasms including acute myeloid leukemias (AML). In fact, in these latter diseases it has been reported that the presence of CD56 antigen on the blasts of AML patients with t(8;21) (q22;q22), and in those with M3 subtype, identifies a subgroup of patients with a more unfavorable prognosis. On the basis of these findings, we evaluated in 152 newly diagnosed AML patients CD56 surface expression, and results were correlated with morphology, immunophenotype, cytogenetic pattern and clinical outcome. CD56 antigen was recorded in 37 out of 152 cases (24%) and particularly in those with M2 and M5 cytotypes. Moreover, CD56 expression was significantly associated with P-glycoprotein (PGP) hyperexpression (P = 0.007), unfavorable cytogenetic abnormalities (P = 0.008) and with a reduced probability of achieving complete remission (CR) (36% vs 68%) (P = 0.035) as well as with a shorter survival (6 vs 12 months) (P = 0.032). In conclusion, CD56 antigenic expression on AML cells represents an important adverse prognostic factor and therefore its presence should be regularly investigated for a better prognostic assessment of AML patients at diagnosis.
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PMID:CD56 antigenic expression in acute myeloid leukemia identifies patients with poor clinical prognosis. 1148 May 56