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)

To determine the role the multiple drug-resistance (MDR 1) gene plays in chronic lymphocytic leukemia (CLL), we measured the expression of the MDR 1 gene in 30 patients with this disease. A rapid, highly sensitive, and nonradioactive technique based on the polymerase chain reaction (PCR) was used for that purpose. In this technique, called differential PCR, the target (MDR 1) and a reference gene (beta 2-microglobulin) are co-amplified by PCR from random hexamer-primed cDNA in the same reaction vessel. The level of target gene expression is reflected in the ratio between the intensities of the two resulting PCR product bands, as measured by high-performance liquid chromatography (HPLC). MDR 1 gene expression was detectable in 29/30 (97%) patients with CLL, with a median expression level of 0.36 U (human placenta = 1 U). There was no correlation between expression of the MDR 1 gene and clinical stage, time from diagnosis, absolute lymphocyte count, several lymphocyte surface markers, or prior treatment in the patients analyzed. Immunocytochemical studies of the same material using the monoclonal antibody C219 showed a very low or undetectable expression of the P-glycoprotein in the lymphocytes of all patients studied, whereas granulocytes were significantly more immunoreactive. We conclude that the level of expression of the MDR 1 gene in CLL is generally low, that the removal of granulocytes is important in studies of expression of MDR 1 mRNA in CLL, and that differential PCR provides a rapid and reliable method for quantifying the amount of a specific mRNA, even in very small samples of total RNA.
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PMID:PCR-determined expression of the MDR1 gene in chronic lymphocytic leukemia. 136 Aug 21

Measurement of P-glycoprotein and the gene that encodes it, mdr-1, is an important tool for assessing the impact of multidrug resistance in clinical cancer. We evaluated mdr-1 expression by a quantitative polymerase chain reaction (PCR) assay in 78 biopsy samples from 48 patients with refractory lymphoma enrolled on a trial of infusional chemotherapy (EPOCH) in which R-verapamil was added as an antagonist of P-glycoprotein in a subset of patients whose tumors were unresponsive to treatment. Expression of mdr-1 was detectable in all biopsies at the time of enrollment on study, and a fourfold or greater increase in mdr-1 expression was noted in 42% of patients at the time of treatment failure. Expression of mdr-1 was also detectable in biopsies from patients at the time of diagnosis of lymphoma. An endogenous control gene, beta 2-microglobulin, was quantitated for normalization of the mdr-1 values. The use of beta 2-microglobulin expression for normalization was validated in a subset of samples by comparing Northern blots detecting beta 2-microglobulin, beta actin, and GAPDH gene expression. Immunoblot analysis suggested that no major discrepancy was present between mRNA expression and protein level. Immunophenotyping of lymphomatous lymph nodes showed that infiltration of tumor cells ranged from 8% to 95% and of normal T cells from 1% to 83%. Expression of mdr-1 in normal T cells and monocytes was also shown to be low. The mdr-1 levels in patient samples were independent of T-cell contamination, suggesting that the presence of normal cells has at best a small impact on mdr-1 measurements. Expression of mdr-1 in lymphoma can be quantitated by PCR, and wide variations in expression can be observed. Increased expression in patients with refractory disease supports an important role for Pgp in drug resistance in lymphoma. These studies will aid in the design and interpretation of clinical trials in lymphoma.
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PMID:Expression of mdr-1 in refractory lymphoma: quantitation by polymerase chain reaction and validation of the assay. 763 59

Resistance to multiple chemotherapeutic agents is related to the production of P-glycoprotein, a transmembrane drug efflux pump that is encoded by the multidrug resistance gene (MDR1). To detect low-level or heterogenous expression of the MDR1 gene in acute leukemia, we have developed sensitive, specific and semi-quantitative protocols for measuring levels of MDR1 mRNA, based on the polymerase chain reaction. Using this assay, we screened blasts from 20 patients with untreated adult acute leukemia for evidence of MDR1 gene expression. The level of MDR1 mRNA was normalized to beta 2-microglobulin mRNA and was defined by reference to the highly resistant trimetrexate-selected leukemia cells MOLT-3/TMQ200 (1.80). MDR1 mRNA was observed in 14 out of 20 patients. Higher MDR1 mRNAs were observed in three patients with phenotypes of undifferentiated or minimally differentiated nonlymphocytic acute leukemia, as compared with other types of acute leukemia (0.98 vs. 0.25). In contrast, lower MDR1 mRNAs were found in five patients with acute promyelocytic leukemia, as compared with other types of acute leukemia (0.08 vs. 0.45). These findings suggest that MDR1 gene expression is correlated with the leucocyte differentiation stage of leukemia. MDR1 gene expression may, in part, explain the responsiveness to chemotherapy in these distinct subtypes of acute leukemia.
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PMID:MDR1 (multidrug resistance) gene expression in adult acute leukemia: correlations with blast phenotype. 847 61