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)

We investigated the capabilities of flow cytometry in the analysis of a multidrug resistant (MDR) human ovarian cancer cell line 2780AD and its drug sensitive parental A2780. A functional assay using daunorubicin (DNR) as a fluorescent probe was combined with an immunofluorescence assay of P-glycoprotein (P-gp) using the monoclonal antibody MRK-16. Functionally MDR could be demonstrated by the lower DNR-content of MDR cells compared to DNR-content of drug sensitive cells. When incubation was performed with DNR in the presence of verapamil, DNR-content increased in the MDR cells. However the content of the A2780 cells was never attained. Differences in DNR-content were not related to differences in DNA-content. In experimental cell lines immunofluorescence data were inversely related with those of DNR-content: MDR cells had high levels of P-gp expression and low levels of DNR-content (and vice versa in drug sensitive cells). Both assays can be easily combined in a multiparametric flow cytometric procedure to evaluate both parameters simultaneously in the same cells. Analysis of clinical samples demonstrates the existence of aberrant subpopulations which would not be detected by using a single parameter assay.
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PMID:Flow cytometric double labeling technique for screening of multidrug resistance. 168 85

This communication describes the cellular and ultrastructural localization in the central nervous system of P-glycoprotein (P-GP) recognized by a murine monoclonal antibody, MRK 16. At the ultrastructural level P-GP was strictly confined to the luminal surface of the endothelial cells which comprise the capillary vessels of the brain and the spinal cord. No P-GP was found in the endothelial cells of other organs. Our findings may be useful as a means to define the blood-brain barrier, and they imply that the blood-brain barrier is anatomically characterized by the presence of intercellular tight junctions between continuous nonfenestrated endothelial cells.
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PMID:Specialized localization of P-glycoprotein recognized by MRK 16 monoclonal antibody in endothelial cells of the brain and the spinal cord. 197 5

This paper describes the cellular and tissue distribution of P-glycoprotein (P-GP) (mdr1 gene product), the role of P-GP in vivo and immunodiagnosis of multi-drug-resistant cancers. We mainly used MRK 16 monoclonal antibody (MAb) reactive with P-GP. P-GP was found to be expressed very strongly in the adrenal cortex of adults and strongly in the renal tubules of the kidney, capillary blood vessels of the brain, and also in placenta. Interestingly, P-GP was not distributed in fetal and neonatal adrenals, and thus may be closely related to adrenal maturation. A high level of P-GP expression was also seen in all cases of functional hormone-producing adrenal tumor, one case of insulinoma, two cases of untreated colonic cancer, one case each of untreated lung cancer, gastric cancer and breast cancer, six cases of renal cell carcinoma and 17 cases of bladder cancer. Using flow cytometry and immunocytochemistry, we investigated the reactivity of MRK 16 MAb with peripheral human mononuclear cells (mainly blastic cells and lymphocytes) from 31 patients with leukemia or malignant lymphoma. Reactivity with MRK 16 MAb was observed in five cases. Some cases reflected the prior administration of adriamycin, vincristine and VP-16, which are known to induce P-GP expression. P-GP-MRK 16-protein A-Sepharose complex derived from human adrenal possessed marked ATPase activity. These data suggest that P-GP may play a physiological role in the human adrenal. Finally, diagnostic criteria of multi-drug-resistant cancers are presented.
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PMID:Expression and functions of P-glycoprotein (mdr1 gene product) in normal and malignant tissues. 197 61

Seeking to optimize the immunocytochemical assay of P-glycoprotein, a 170-kilodalton (P-170) molecule associated with multidrug resistance, we experimented with a variety of antibodies (JSB-1, C219, and MRK-16), fixation conditions, and titers using both human myeloma cell lines and clinical myeloma specimens. Under optimized conditions, using all three antibodies and the cell lines as standards and controls, the ICC method proved sensitive, specific, reliable, rapid, and within the realm of everyday hospital laboratory expertise. The 3 anti-P-glycoprotein antibodies revealed different reactivities with P-170. Both C219 and JSB1 were optimized by fixation in cold acetone. With MRK-16 optimal results were obtained on unfixed or formalin fixed specimens. Under optimal fixation and titering conditions, low level (DOX 4) detection was possible. Given that the three antibodies differ in reactivity and recognize different P-170 epitopes, it follows that using the antibodies in a small panel is a useful strategy in increasing the likelihood of detecting true P-glycoprotein expression by the immunocytochemical method. In dilution experiments, the immunocytochemical method was as sensitive as RNase protection assay and more sensitive than Western blot detection. Immunocytochemistry coupled to computer-assisted single-cell densitometry, showed a strong correlation (R = 0.98) between cellular P-170 density and in vitro resistance to doxorubicin. Multidrug-resistant specific probes for RNA expression and Western blot assays confirmed the specificity of P-170 expression in both cell lines and clinical samples. Thus, a small panel of antibodies, under optimized immunocytochemical conditions, appears to have potential as a rapid, sensitive, clinically useful assay for multidrug resistance in myeloma.
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PMID:Optimization of immunocytochemical P-glycoprotein assessment in multidrug-resistant plasma cell myeloma using three antibodies. 197 62

We examined the effectiveness of a previously characterized plasma cell-reactive monoclonal antibody (MoAb), MM4, in eliminating multi-drug resistant (MDR1) multiple myeloma (MM) clonogenic colony-forming cells (CCCs). MDR1 sublines with 6-fold (RPMI8226/DOX6) and 40-fold (RPMI 8226/DOX40) resistance to doxorubicin (DOX) were selected from the chemosensitive MM parent line RPMI 8226/S. Both sublines remained reactive with plasma cell MoAbs MM4 and PCA-1, as measured by flow cytometric immunophenotype analysis. MM4 and rabbit complement (C') were cytotoxic to MDR DOX6 (74 +/- 8.5%) and DOX40 (75 +/- 11.3%) cells as well as to chemosensitive 8226/S (80 +/- 5.6%) cells. Treatment with MM4 + C' depleted up to 3 logs of chemosensitive and MDR myeloma CCCs (8226/S: 99.26 +/- 0.52%; DOX6 99.91 +/- 0.08%' DOX40 99.15 +/- 0.55%). In addition, this approach abrogated the selfrenewing capacity of chemoresistant and MDR1 myeloma cell lines, according to doubling time analyses. By comparison, the P-glycoprotein-reactive MoAb MRK-16 and C' was effective in deleting MDR1 CCCs (DOX10: 95.71 +/- 2.51%; DOX40: 99.61 +/- 0.43%) but affected chemosensitive myeloma CCCs only slightly (5.93 +/- 14.52%). When DOX40 cells were mixed with normal bone marrow (BM) in a ratio of 10:90 (MM:BM), treatment with MM4 plus C' deleted MM CCCs (98.80 +/- 0.71%) without affecting the majority of normal BM progenitors. The combination of MM4 and MRK-16 did not enhance MDR myeloma CCC depletion. These observations suggest that MM4 + C' may be useful for depleting MDR as well as chemosensitive myeloma clonogenic cells from human bone marrow.
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PMID:Elimination of chemoresistant myeloma clonogenic cells from human bone marrow by monoclonal antibody and complement. 230 79

Two monoclonal antibodies of F (ab')2 form, MRK 16 and MRK 20 that recognize P-glycoprotein and P85 kD protein respectively, were useful to detect multidrug resistant cells in human lymphoma, leukemia and gastrointestinal cancer cell lines. They were classified into 4 groups: Group I (4 cell lines) was insensitive to vinca alkaloids, anthracyclines, etoposide (VP-16) and actinomycin-D (ACT-D), and reactive to MRK 16 and MRL 20. Group II (2 cell lines) was insensitive to vincristine (VCR), but not reactive to both antibodies. Group III (3 cell lines) was insensitive to anthracyclines and VP-16, but sensitive to vinca alkaloids and ACT-D, and reactive to MRK 20 but not to MRK 16. Group IV (all other cell lines) was sensitive to these drugs, and not reactive to both antibodies. MRK 16 detects P-glycoprotein-associated multidrug resistance (MDR), while MRK 20 detects P 85kd-associated novel MDR. These monoclonal antibodies were useful for detection of MDR cells in clinical samples.
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PMID:[Detection of multidrug resistant cells in human malignant diseases by monoclonal antibodies and strategy to eradicate resistant malignant cells]. 256 3

Patients with multiple myeloma (MM) commonly become refractory to chemotherapy despite a favorable response to induction treatment. We examined the effectiveness of a previously characterized plasma cell-reactive monoclonal antibody, MM4, in eliminating MM clonogenic colony-forming cells (CCC) with a multidrug-resistant (MDR) phenotype. Experiments were performed using MM cell lines that exhibit 6 (RPMI 8226/DOX6)- and 40 (RPMI 8226/DOX40)-fold resistance to doxorubicin (DOX). Both lines were selected from the chemosensitive MM line RPMI 8226/S and were cross-resistant to mitoxantrone, acronycine, etoposide, and vincristine. Surface marker analysis conducted in this study showed that DOX6 and DOX40 overexpressed the MDR1 gene product p170. Both MDR lines remained reactive to the plasma cell-reactive monoclonal antibodies MM4 and PCA-1 and expressed the relevant cytoplasmic immunoglobulin light chain. Treatment with MM4 and rabbit complement (C') was equally cytotoxic to RPMI 8226/S [80 +/- 5.6% (SD)], DOX6 [74 +/- 8.5], and DOX40 cells [75 +/- 11.3%], based on short-term chromium release studies. Furthermore, MM4 + C' deleted up to 3 logs of CCC colonies from chemosensitive and MDR lines (RPMI 8226/S, 99.87 +/- 0.11%; DOX6, 99.91 +/- 0.08%; DOX40, 99.55 +/- 0.44%). By comparison, the P-glycoprotein-reactive monoclonal antibody MRK-16 and C' inhibited tumor colony formation of MDR cells (8226/DOX6, 95.71 +/- 2.51%; 8226/DOX40, 99.61 +/- 0.43%) but affected that of chemosensitive cells only slightly (8.9 +/- 17.8%). In an attempt to optimize the depletion of myeloma CCC, MM4 was used together with MRK-16. This approach resulted in uniform depletion of myeloma clonogenic colony-forming cells from the chemosensitive (98.32 +/- 1.53%, n = 4) and MDR lines (8226/DOX6, 98.83 +/- 0.08%, n = 4; 8226/DOX40 99.29 +/- 0.62, n = 7) but did not result in enhanced CCC depletion. When DOX40 cells were mixed with normal bone marrow (BM) in the ratio of 90:10 (BM:MM), either MM4 or MRK-16 and C' depleted MM colonies (98.8 +/- 0.71% and 98.10 +/- 1.0%, respectively) without affecting the majority of BM progenitor cells. These observations suggest that either MM4 or MRK-16 is useful for depleting MDR myeloma clonogenic colony-forming cells.
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PMID:Elimination of chemoresistant multiple myeloma clonogenic colony-forming cells by combined treatment with a plasma cell-reactive monoclonal antibody and a P-glycoprotein-reactive monoclonal antibody. 256 59

Using flow cytometry and immunocytochemistry, we investigated the reactivities of two different murine monoclonal antibodies (MAbs), MRK 16 and MRK 20, specific to adriamycin-resistant K562 cells (K562/ADM) with peripheral human mononuclear cells (MNC) (mainly blastic cells and lymphocytes) from 31 patients with leukaemia or malignant lymphoma. Reactivity with MRK 16 MAb was observed in five cases and reactivity with MRK 20 MAb in 18 cases. The cases were divided into three groups according to their reactivity patterns: group I, only the proportion of MRK 16-positive cells was increased; group II, only the proportion of MRK 20-positive cells was increased; group III, both MRK 16-and MRK 20-positive cells were increased. Some cases reflected the prior administration of adriamycin, vincristine, vinblastine and VP-16, which are known to induce P-glycoprotein expression. Expression of Mr 85,000 protein was observed more frequently than that of P-glycoprotein in leukaemia and malignant lymphoma, and this was not associated with either the total dose or period of administration of anticancer drugs. The expression of Mr 85,000 protein recognised by MRK 20 was further confirmed by Western blot analysis.
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PMID:High-level expression of MRK 16 and MRK 20 murine monoclonal antibody-define proteins (170,000-180,000 P-glycoprotein and 85,000 protein) in leukaemias and malignant lymphomas. 257 70

The effectiveness of ex vivo chemotherapy with drugs, such as vincristine, etoposide, and Adriamycin (doxorubicin, Adria Labs, Columbus, OH) for elimination of residual tumor cells from human bone marrow grafts could be undermined by the presence of multidrug-resistant tumor cells in the bone marrow. Therefore, to supplement chemoseparation, we investigated whether MRK-16, a monoclonal antibody (MoAb) to the surface moiety of multidrug resistance-associated P-glycoprotein antigen, can eliminate drug-resistant tumor cells in the presence of rabbit complement (RC). Two doxorubicin (DOX)-resistant human myeloma tumor cell line, 8226/DOX40 (resistant to 4 x 10(-7) mol/L DOX) and 8226/DOX6 (6 x 10(-8) mol/L DOX) with high and low amounts of cell surface P-glycoprotein, respectively, and the drug-sensitive parent cell line 8226/S were used as tumor models in this study. Using the limiting dilution assay, we have shown that three cycles of treatment with 25 micrograms/mL of MRK-16 MoAb and a 1:4 final dilution of RC eliminated 2.90 +/- 0.10 logs of 8226/DOX40 cells and 1.94 +/- 0.18 logs of 8226/DOX6 cells. One and two cycles of treatment were less effective, eliminating 0.47 +/- 0.40 and 1.94 +/- 0.36 logs of 8226/DOX40 and 0.12 +/- 0.20 and 1.63 +/- 0.58 logs of 8226/DOX6 cells, respectively. The 8226/S cell growth was unaffected by one to three cycles of treatment. The cell kill was not impaired when the antibody plus complement treatment was carried out on a mixture of 8226/DOX40 or 8226/DOX6 cells with a ninefold excess of irradiated bone marrow mononuclear cells (MNCs). The three cycles of treatment with antibody plus complement did not adversely affect granulocyte-macrophage colony-forming unit (GM-CFU) survival in hematologically normal marrows (92.5% to 104% survival) or in myeloma patient marrows (85% to 100%). These results show that it is possible to eliminate drug-resistant myeloma tumor cell lines from the admixed human bone marrow by treatment with MRK-16 MoAb plus RC. This method could prove to be effective for elimination of other drug-resistant tumor cell lines including those of leukemia and solid tumors, and will be further useful for supplementing chemopurging, and immunopurging of bone marrow with other antitumor cell antibodies.
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PMID:Elimination of drug-resistant myeloma tumor cell lines by monoclonal anti-P-glycoprotein antibody and rabbit complement. 257 83

A monoclonal antibody, MRK 16, specific to a human myelogenous leukemia cell line, K-562, and resistant to Adriamycin, was used to determine the localization of the antigen molecules (P-glycoprotein) recognized by the monoclonal antibody. P-glycoprotein was found to be expressed very strongly in the adrenal cortex and medulla of adults and strongly in the renal tubules of the kidney and the placenta. Interestingly, P-glycoprotein was not distributed in fetal and neonatal adrenals, and thus may be closely related to adrenal maturation. A high level of P-glycoprotein expression was also seen in one case each of untreated lung cancer (one of ten) and breast cancer (one of nine). Immunoelectron microscopically, the P-glycoprotein was distributed evenly on the membranes of K-562/ADM and 2780 cells. These results imply that the presence of the glycoprotein may be useful as a marker for in vitro studies of multidrug resistance in various malignancies and as an indicator of therapeutic efficacy of ex vivo eradication of multidrug-resistant cancer cells, although other mechanisms of drug resistance may exist, and there is a possibility that this MRK 16 monoclonal antibody may not recognize all P-glycoprotein.
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PMID:Tissue distribution of P-glycoprotein encoded by a multidrug-resistant gene as revealed by a monoclonal antibody, MRK 16. 289 94


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