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)

Multidrug resistance (MDR) is one of the major obstacles to successful cancer chemotherapy. MDR is a complex and multifactorial phenomenon. One important and common mechanism used by cancer cells as a defense against cytotoxic drugs is a 170-kD plasma membrane glycoprotein, P-glycoprotein (P-gp). P-gp confers resistance by actively pumping cytotoxic drugs out of cancer cells. Paradoxically, P-gp overexpression on tumor cells is frequently associated with enhanced susceptibility to lymphokine-activated killer cell activity. This enhanced susceptibility is not observed with P-gp- MDR cells, nor is susceptibility to natural killer cells increased. The physiologic, evolutionary and immunologic concepts with regard to the P-gp and the possible intervention of the function of the P-gp in cancer therapy are reviewed.
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PMID:P-glycoprotein-mediated multidrug resistance and cytotoxic effector cells. 135 93

We evaluated the susceptibility to natural killer (NK) or lymphokine activated killer (LAK) cell-mediated cytolysis of two pairs of drug sensitive/resistant tumor cell lines which were extensively characterized at phenotypic and genotypic level. In the DAUDI cell system, the acquired capability of tumor cell variants to grow in the presence of a relatively high concentration of vinblastine (VBL) is associated with a marked increase to NK and LAK susceptibility. In contrast in the K-562 cell system, no correlation between drug-resistance, P-glycoprotein expression and susceptibility to NK or LAK activity seems to occur.
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PMID:The over-expression of P-glycoprotein in K-562 and DAUDI cells, is associated with a high susceptibility to NK and LAK cells. 168 2

Considering the possibility to overcome drug resistance by other treatment strategies than chemotherapy we investigated the susceptibility of three independently selected multidrug-resistant sublines of the T-lymphoblastoid leukemic cell line CCRF-CEM to lymphokine-activated killer (LAK) cells. We found that two of the multidrug-resistant sublines were significantly less susceptible targets to LAK cells. A third one, however, was as susceptible as the parental CCRF-CEM cell line. Moreover, a multidrug-resistant subline that reverted to an almost drug-sensitive phenotype was observed to be also revertant for resistance against LAK cells. We found an inverse relationship between the expression of the mdr1 gene (P-glycoprotein) and the susceptibility to LAK cells. Verapamil, a calcium channel blocker, while increasing the drug sensitivity of a multidrug-resistant subline, did not induce a reversal of the suppression of LAK susceptibility. The possibility of enhanced resistance to LAK cells of multidrug-resistant cells should be taken into account when one is looking for therapy strategies to overcome multidrug resistance.
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PMID:Susceptibility of multidrug-resistant human leukemia cell lines to human interleukin 2-activated killer cells. 169 43

Relatively little is understood about the antigen recognition and target structures used by natural killer (NK) cells. The purpose of this study was to analyze the relationship of a multidrug-resistant cell line expressing the P-glycoprotein (GP170 surface glycoprotein) derived from the parent non-drug-resistant malignant tumor cell line for susceptibility to lysis by either NK or lymphokine-activated killer cells. Our results demonstrate no significant difference in NK activity against either the non-drug-resistant or drug-resistant malignant cell line; Interleukin-2 induces a significant increase in cytolytic activity toward the multidrug-resistant cell line. These data suggest that malignant cells refractory to treatment or occurring after successful treatment are susceptible to immunotherapeutic intervention.
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PMID:Potentiation of human natural killer cell activity by recombinant interleukin-2 towards multidrug-resistant human epidermoid carcinoma. 197 84

The using of multidrug-resistant (MDR) cell variants represents one of the major obstacles to an effective cancer therapy based on the administration of cytotoxic compounds. In the present article we describe experimental procedures able to eradicate, in vitro, by using specific immunological reagent, MDR tumor cells. In an allogeneic cell system, natural killer (NK) and lymphokine activated killer (LAK) cells result effective against MDR variants of the human T-lymphoblastoid CEM cell line. Surprisingly effector cells discriminate in their lytic capacity target cells possessing a MDR phenotype. A direct relationship between the degree of relative resistance shown by target cells and cytotoxic level exerted by peripheral lymphocytes stimulated and non by IL-2 was observed. The preincubation of MDR cell variants with a monoclonal antibody (MoAb57) specific for an extramembranal epitope of P-glycoprotein induced, in presence of effector cells, a strong antibody-dependent cell-mediated cytolysis (ADCC). This phenomenon was observed only in MDR variants over-expressing in concomitance with drug-resistance high level of P-glycoprotein. In identical experimental conditions, drug-sensitive parental cells does not show valuable ADCC.
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PMID:Susceptibility of multidrug-resistant human T-lymphoblastoid CEM cell line to cell-mediated cytolysis. 198 4

The development of resistance to anticancer drugs urges the search for different treatment modalities. Several investigators have reported the concomitant development of drug resistance and resistance to natural killer (NK), lymphokine-activated killer (LAK) or monocyte/macrophage cell lysis, while others described unchanged or even increased susceptibility. We investigated this subject in the rat colon carcinoma cell line, CC531-PAR, which is intrinsically multidrug-resistant (MDR), and in three sublines derived from this parental cell line: a cell line with an increased MDR phenotype (CC531-COL), a revertant line from CC531-COL (CC531-REV), which demonstrates enhanced sensitivity to anticancer drugs of the MDR phenotype, and an independently developed cisplatin-resistant line (CC531-CIS). In a 4-h 51Cr-release assay we found no difference in susceptibility to NK cell lysis. No significant differences in lysability by adherent LAK (aLAK) cells were observed in a 4-h assay. In a prolonged 20-h 51Cr-release assay an enhanced sensitivity to aLAK-cell-mediated lysis was observed in the revertant, P-glycoprotein-negative cell line and in the cisplatin-resistant cell line (CC531-CIS). None of the cell lines was completely resistant to lysis by aLAK cells. Therefore, a role for immunotherapy in the treatment of drug-resistant tumors remains a realistic option.
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PMID:Drug resistance in rat colon cancer cell lines is associated with minor changes in susceptibility to cytotoxic cells. 840 37

The ability of malignant cells to survive exposure to cytotoxic agents is a major obstacle to cure in patients with cancer. Multidrug resistance and the expression of P-glycoprotein are emerging as a cause of chemotherapy failure. Immunologic effector cells such as lymphokine-activated killer (LAK) cells or cytokine-induced killer (CIK) cells are capable of killing a broad range of tumor cell lines or freshly isolated tumor cells. As demonstrated here, LAK, and CIK cells possess a high level of cytotoxic activity against tumor cell lines both resistant and sensitive to chemotherapeutic agents such as doxorubicin or vinblastine. CIK cells possessed a higher level of cytotoxic activity than LAK cells as determined by 51Cr release and a tumor colony assay. Monoclonal antibodies against P-glycoprotein did not block the lysis of tumor cells resistant to chemotherapy by CIK cells. In contrast, antibodies to LFA-1 and ICAM-1 blocked CIK cell-mediated tumor cell lysis. These data demonstrate that immunological approaches to cancer therapy may be useful in overcoming disease caused by drug resistance.
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PMID:Sensitivity of multidrug-resistant tumor cell lines to immunologic effector cells. 861 99

Multidrug resistance (MDR), which is due, in part, to the overexpression of P-glycoprotein, confers resistance to a variety of natural product chemotherapeutic agents such as daunorubicin, vincristine, and colchicine. RV+ cells are a P-glycoprotein overexpressing variant of the HL60 myeloid leukemia cell line. In addition to classic MDR, RV+ cells displayed relative resistance to complement-mediated cytotoxicity with both immunoglobulin G and M antibodies against different cell surface antigens, but not to antibody-dependent cellular cytotoxicity and lymphokine-activated killing. Complement resistance was reversed both by treatment with verapamil and with specific monoclonal antibodies (mAbs) capable of binding to P-glycoprotein and blocking its function. To further confirm that the resistance of RV+ cells was not a consequence of the selection of the cells on vincristine, a second system involving P-glycoprotein infectants was also investigated. K562 cells infected with the MDR1 gene, which were never selected on chemotherapeutic drugs, also displayed relative resistance to complement-mediated cytotoxicity. This MDR1 infection-induced resistance was also reversed by mAbs that bind to P-glycoprotein. Therefore, the MDR phenotype as mediated by P-glycoprotein provides resistance to complement-mediated cytotoxicity. The increased intracellular pH and the decreased membrane potential due to the MDR phenotype may result in abnormal membrane attack complex function. This observation may have implications for the possible mechanisms of action of P-glycoprotein and for a possible physiologic role for P-glycoprotein in protection against complement-mediated autolysis.
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PMID:The multidrug resistance phenotype confers immunological resistance. 867 93

A transmembrane pump for organic anions was identified in resting murine T helper (Th) 2, but not Th1 lymphocyte cell clones, as revealed by extrusion of a fluorescent dye. Dye extrusion inhibition studies suggested that the pump may be the multidrug-resistance protein (MRP). The different expression of the pump in resting Th1 and Th2 cell clones correlated with their respective levels of MRP mRNA. The pump was inducible in Th1 cells by antigenic stimulation in vitro leading to equal expression in activated Th1 and Th2 cell clones. This suggested that dye extrusion might allow the detection of Th2 (resting or activated) or of activated Th1 cells ex vivo based on a functional parameter. To test this, mice were infected with Leishmania major parasites to activate L. major-specific T cells of either Th1 (C57BL/6 mice) or Th2 (BALB/c mice) phenotype: 2-3% of CD4+ lymph node T cells of both strains of mice extruded the dye, defining a cell subset that did not coincide with subsets defined by other activation markers. Fluorescence-activated cell-sorting revealed that the lymphokine response (Th1 or Th2, respectively) to L. major antigens was restricted to this dye-extruding subset.
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PMID:A multidrug-resistance protein (MRP)-like transmembrane pump is highly expressed by resting murine T helper (Th) 2, but not Th1 cells, and is induced to equal expression levels in Th1 and Th2 cells after antigenic stimulation in vivo. 944 6

Intrinsic or acquired resistance to anticancer drugs necessitated the search for different treatment modalities. The sensitivity of tumor cells to lysis by natural killer (NK) and lymphokine-activated killer (LAK) cells was studied in multidrug resistant (MDR) small cell lung carcinoma (SCLC) by 51Chromium (51Cr) release and conjugate formation assays. The following observations were made: P-glycoprotein positive (P-gp+) MDR SCLC cell line variants were lysed by human LAK cells to a greater extent than were their drug sensitive counterparts. In contrast, P-gp, multidrug resistance protein positive (MRP+) variants of the same line did not exhibit an increased susceptibility to LAK cells. Differential LAK susceptibility is not due to a generalized increase in target fragility to cellular immunity, because NK sensitivity was not increased. Moreover, the P-gp+ MDR SCLC cells showed a higher frequency of binding to LAK cells than did the drug-sensitive parental line. These observations may lead to new insights on combining chemotherapy with immunotherapy.
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PMID:Lymphokine-activated killer cell susceptibility and multidrug resistance in small cell lung carcinoma. 989 92


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