title: Effect of MDR modulators verapamil and promethazine on gene expression levels of MDR1 and MRP1 in doxorubicin-resistant MCF-7 cells.
abstract: OBJECTIVE
  One of the major problems of cancer chemotherapy is the development of multidrug resistance (MDR) phenotype. Among the numerous mechanisms of MDR, a prominent one is the increased expression of membrane transporter proteins, the action of which leads to decreased intracellular drug concentration and cytotoxicity of drugs. Among them, P-gp and MRP1, encoded by MDR1 and MRP1 genes, respectively, have been associated with MDR phenotype. Chemical modulators can be used to reverse MDR. These chemicals can either modulate MDR due to their substrate analogy (such as calcium channel blocker verapamil) or interact with phospholipid membranes (such as antihistaminic drug promethazine). This study focuses on the effect of verapamil and promethazine on the expression levels of MDR1 and MRP1 genes and the drug transport activity in doxorubicin-resistant MCF-7 breast carcinoma cell line.
  
  
  METHODS
  Doxorubicin-resistant MCF-7 (MCF-7/Dox) cells were incubated with either verapamil or promethazine, and total RNA was isolated. Real-time PCR (qPCR) was carried out by using specific primers for MDR1, MRP1, and β-actin genes. Intracellular doxorubicin accumulation was also examined by confocal laser scanning microscopy in treated cells.
  
  
  RESULTS
  Results demonstrated a significant decrease in both MDR1 and MRP1 expression levels after promethazine applications. It has also been shown that treatment of the cells with verapamil results in significant decrease in MDR1 mRNA levels. Confocal laser scanning microscopy images demonstrated that the intracellular accumulation of doxorubicin was increased after verapamil treatment in MCF-7/Dox cells.
  
  
  CONCLUSIONS
  The present study gives an idea about the efficiency of verapamil and promethazine on MDR reversal both in gene expression and in transport activity levels.
authors.affiliation: Department of Biological Sciences, Middle East Technical University, 06531 Ankara, Turkey.
authors.forename: Yaprak
authors.initials: Y
authors.lastname: Dönmez
authors.forename: Laila
authors.initials: L
authors.lastname: Akhmetova
authors.forename: Özlem Darcansoy
authors.initials: ÖD
authors.lastname: İşeri
authors.forename: Meltem Demirel
authors.initials: MD
authors.lastname: Kars
authors.forename: Ufuk
authors.initials: U
authors.lastname: Gündüz
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D001692:Biological Transport; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D018613:Microscopy, Confocal; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000187:drug effects* / Q000235:genetics; D016133:Polymerase Chain Reaction; D011398:Promethazine / Q000494:pharmacology*; D012313:RNA / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology*
chemical_list: D000903:Antibiotics, Antineoplastic; D004317:Doxorubicin; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D011398:Promethazine; D012313:RNA; D014700:Verapamil; C421109:multidrug resistance-associated protein 1