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 measurement of rhodamine 123 (Rho123) efflux in hematological malignancies, using flow-cytometry, provides an accurate assessment of multidrug resistance (MDR) of both P-glycoprotein and MRP. While their normal counterparts display high levels of PgP and Rho123 efflux, we investigated the MDR status of marked T/NK proliferations. When diagnosed according to natural killer (NK) markers (CD16, CD56, CD57) 8 of nine NK lymphoproliferative disorders (LPD) were markedly positive (3 NK non Hodgkin's lymphomas (NHL), 1 NK lymphoproliferative disease of large granular lymphocytes (LGL), and 5 T/NK LGL). These results are in accordance with the observed response to chemotherapy in the treated cases. Mature T LPD (prolymphocytic leukemia (PLL), and NHL) cells gave varying results, as did cells from Sezary syndromes. Marked Rho123 efflux was detected in the two cases of T-PLL suggesting the expression of MRP as previously described. Immature T-lymphomas or leukemias (6 cases) were all negative. These data should be considered in relation to NK proliferations which clearly display an MDR phenotype and therefore raise the question, of the relevance of this phenotype in normal cells, and secondly of the negativity of immature T-LPD. The latter could indicate that MDR inhibitors may be superfluous in the initial treatment of acute lymphoblastic leukemia (ALL). Finally the resistance to treatment of T-ALL or mature T cells LPD invokes the importance of exploring other mechanisms of drug resistance such as the lung resistance related protein (LRP).
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PMID:Multidrug resistance in aggressive lymphoproliferative disorders of T and natural-killer origin. 971 68

Extranodal natural killer (NK)/T-cell lymphoma, nasal type, and aggressive NK-cell leukemia are rare, and their standard therapy has not been established. They are Epstein-Barr virus-associated lymphoid malignancies, and tumor cells express P-glycoprotein leading to multidrug resistance of the disease. Patients with stage IV, relapsed or refractory diseases have a dismal prognosis, with survival measured in months only. To develop an efficacious chemotherapeutic regimen, we conducted a dose-escalation feasibility study of a new chemotherapeutic regimen, SMILE, comprising the steroid dexamethasone, methotrexate, ifosfamide, L-asparaginase, and etoposide. The components of SMILE are multidrug resistance-unrelated agents and etoposide. Etoposide shows both in vitro and in vivo efficacy for Epstein-Barr virus-associated lymphoproliferative disorders. Eligible patients had newly diagnosed stage IV, relapsed or refractory diseases after first-line chemotherapy, were 15-69 years of age, and had satisfactory performance scores (0-2). Four dose levels of methotrexate and etoposide were originally planned to be evaluated. At level 1, six patients with extranodal NK/T-cell lymphoma, nasal type, were enrolled. Their disease status was newly diagnosed stage IV (n = 3), first relapse (n = 2), and primary refractory (n = 1). All of the first three patients developed dose-limiting toxicities, and one of them died of sepsis with grade 4 neutropenia. A protocol revision stipulating early granulocyte colony-stimulating factor administration was made. Two out of three additional patients developed dose-limiting toxicities that were all manageable and transient. For the six enrolled patients, the overall response rate was 67% and the complete response rate was 50%. Although its safety and efficacy require further evaluation, we recommend a SMILE chemotherapy dose level of 1 for further clinical studies.
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PMID:Phase I study of dexamethasone, methotrexate, ifosfamide, L-asparaginase, and etoposide (SMILE) chemotherapy for advanced-stage, relapsed or refractory extranodal natural killer (NK)/T-cell lymphoma and leukemia. 1829 94

The natural killer (NK)-cell neoplasms are rare, representing less than 1% of non-Hodgkin lymphoma, except in Asia and Latin America, where they represent 3% to 6%. NK-cell neoplasms include immature acute leukemias; a blastic NK-cell lymphoma, which is obsolete because of its plasmacytoid dendritic-cell origin; and mature NK neoplasms, comprising extranodal NK/T-cell lymphoma (ENKL), nasal-type; aggressive NK-cell leukemia; and chronic NK-cell lymphoproliferative disorders, which are often reactive. Epstein-Barr virus is usually detected in tumor cells of ENKL and aggressive NK-cell leukemia. The latter two mature NK neoplasms are relatively chemoresistant because of the frequent expression of P-glycoprotein. Early radiation is advocated for localized nasal ENKL. Stem cell transplantation is recommended for advanced disease, owing to a poor prognosis. Novel agents, including chemotherapy, inhibitors of molecular pathways, and monoclonal antibodies, are under investigation.
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PMID:Natural killer-cell neoplasms. 2042 14

Multidrug resistance (MDR) is a phenomenon in malignancy whereby tumor cells generate mechanisms to resist cytotoxic treatments. Several such mechanisms have been identified. However, to date the most significant research on MDR has involved the adenosine triphosphate binding cassette (ABC) transporter proteins, including P-glycoprotein (P-gp) and multidrug resistance associated protein (MRP). These proteins have natural functions involving substrate transport in normal cells but are detrimental to treatment when expressed in the membrane of tumor cells. It remains unclear whether ABC mediated MDR functions primarily through protein up-regulation or via a relevant signaling mechanism, or is simply due to selective pressure on an already resistant tumor cell subpopulation. Here we present an overview of MDR in the chronic lymphoproliferative disorders (CLPDs), in particular that attributed to the ABC transporter protein family.
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PMID:Multidrug resistance in the chronic lymphoproliferative disorders. 2084 98

Peripheral blood lymphocytes from 60 patients with drug-resistant chronic lymphoproliferative disorders (LPD) were examined for expression of P-glycoprotein (P-gp) by direct immunofluorescence (IF) test using monoclonal antibody (MoAb) C219. Four of the 15 patients with prolymphocytic leukaemia (PLL), and both patients with Adult T cell leukaemialymphoma (ATLL) expressed P-gp. However, none of the 3 hairy cell leukaemia (HCL) patients expressed P-gp. Two of the 14 patients with anthracycline resistant chronic lymphocytic leukaemia (CLL) expressed P-gp but none of the 26 CLL patients resistant only to chlorambucil expressed it. The percentage of cells expressing P-gp varied considerably between different groups as well as different individuals (20-100%). Activation of peripheral blood lymphocytes from non-resistant CLL patients with phorbol myristic acetate (PMA) did not induce P-gp expression. It appears that multidrug resistance in ATLL is most likely mediated by over-expression of P-gp and this may also be an important mechanism in multidrug resistance in some PLL and CLL patients.
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PMID:P-Glycoprotein Expression in Drug-Resistant Chronic Lymphoproliferative Disorder. 2746 50

Epstein-Barr virus (EBV)-associated T- and natural killer (NK)-cell malignancies, such as extranodal NK-/T-cell lymphoma (ENKTL), exhibit high chemoresistance and, accordingly, such patients have a poor prognosis. The rare nature of such cancers and nonmalignant T/NK lymphoproliferative disorders, such as chronic active EBV (CAEBV), has limited our understanding of the pathogenesis of these diseases. Here, we characterize a panel of ENKTL- and CAEBV-derived cell lines that had been established from human tumors to be used as preclinical models of these diseases. These cell lines were interleukin-2 dependent and found to carry EBV in a latency II gene-expression pattern. All cell lines demonstrated resistance to cell death induction by DNA damage-inducing agents, the current standard of care for patients with these malignancies. This resistance was not correlated with the function of the multidrug efflux pump, P-glycoprotein. However, apoptotic cell death could be consistently induced following treatment with A-1331852, a BH3-mimetic drug that specifically inhibits the prosurvival protein BCL-XL. A-1331852-induced apoptosis was most efficacious when prosurvival MCL-1 was additionally targeted, either by BH3-mimetics or genetic deletion. Xenograft models established from the ENKTL cell line SNK6 provided evidence that A-1331852 treatment could be therapeutically beneficial in vivo. The data here suggest that therapeutic targeting of BCL-XL would be effective for patients with EBV-driven T/NK proliferative diseases, however, MCL-1 could be a potential resistance factor.
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PMID:BCL-XL inhibition by BH3-mimetic drugs induces apoptosis in models of Epstein-Barr virus-associated T/NK-cell lymphoma. 3301 68