title: Gene dosage is not responsible for the upregulation of MRP1 gene expression in adult leukemia patients.
abstract: BACKGROUND
  Upregulation of multidrug resistance-associated protein (MRP1) gene has been detected in many in vitro systems and could be the basis of the drug resistance phenotype in vivo. Increase in gene dosage and overexpression are two major mechanisms for increasing MRP1 expression level. In many drug resistant cell lines, MRP1 gene amplification has been detected. However, it is not yet known whether gene amplification plays a role in inducing the multidrug resistance phenotype clinically.
  
  
  METHODS
  To establish whether MRP1 gene copy number is a common feature of the upregulation of MRP1 expression in cancer patients, we studied the MRP1 gene copy number in leukemia patients by fluorescent in situ hybridization (FISH) and real-time PCR. This involved determination of the MRP1 gene copy number and mRNA level in the peripheral blood of 52 adult leukemic patients and ten healthy volunteers. The leukemic CCRF-CEM cell line (drug sensitive) and its drug-resistant subline CCRF-E1000, which has MRP1 overexpression, were used as controls.
  
  
  RESULTS
  The MRP1 gene copy number in CCRF-CEM was normal but increased significantly in CCRF-E1000 cell line. However, in the presence or absence of MRP1 overexpression, increase in gene dosage was not detected in patients.
  
  
  CONCLUSIONS
  Our data suggest that the increase in MRP1 gene dosage observed in resistant cell lines is not responsible for the upregulation of MRP1 expression in leukemic patients.
authors.affiliation: Clinical Genetics Department, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran.
authors.forename: Masoud
authors.initials: M
authors.lastname: Golalipour
authors.forename: Frouzandeh
authors.initials: F
authors.lastname: Mahjoubi
authors.forename: Mohammad Hossein
authors.initials: MH
authors.lastname: Sanati
authors.forename: Kamran
authors.initials: K
authors.lastname: Alimoghaddam
authors.forename: Alimoghaddam
authors.initials: A
authors.lastname: Kamran
mesh_terms: D000293:Adolescent; D000328:Adult; D003582:Cytogenetics; D018432:Drug Resistance, Multiple; D005260:Female; D018628:Gene Dosage; D005786:Gene Expression Regulation; D018922:HL-60 Cells; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007938:Leukemia / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D015854:Up-Regulation
chemical_list: D027425:ATP-Binding Cassette, Sub-Family C Proteins; C421109:multidrug resistance-associated protein 1