title: DNA-PK, ATM and MDR proteins inhibitors in overcoming fludarabine resistance in CLL cells.
abstract: OBJECTIVE
  To perform the comparative study of the effects of DNA-dependent protein kinase (DNA-PK) inhibitors vanillin and NU7026, ataxia telangiectasia mutated kinase (ATM)/ ATM and Rad3 related (ATR) kinase inhibitor caffeine and multidrug resistance (MDR) protein modulator cyclosporine A (CsA) on fludarabine resistant and sensitive lymphocytes from chronic lymphocytic leukemia (CLL) patients.
  
  
  METHODS
  Cells sensitivity in vitro was determined with 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT). DNA-PKs and ATM expression in CLL cells was evaluated using Western blotting. Multidrug tansporter protein expression and function was assessed by flow cytometry. Pro- or anti-apoptotic genes (BAX, LICE BCL-2, BCL-XS FLICE, FAS, TRAIL) expression on mRNA level was evaluated.
  
  
  RESULTS
  Caffeine, vanillin, NU7026 and CsA increased fludarabine cytotoxicity against fludarabine-resistant CLL cells samples in comparison with sensitive cell samples. However, fludarabine-sensitive CLL samples were sensitized with inhibitors to a greater extent compared with resistant CLL samples. ATM expression increased in fludarabine-resistant CLL samples, but no apparent correlation between DNA-PKs level and fludarabine sensitivity in vitro or sensitization effect of DNA-PK inhibitors were observed. Fludarabine-resistant CLL lymphocytes showed tendency for depressed MDR efflux and decreased level of mRNA of pro-apoptotic gene BCL-XS.
  
  
  CONCLUSIONS
  Absence of any definite conformity between fludarabine-resistant cell susceptibility to combined action of fludarabine and inhibitors, and molecular pathways that might be involved in this process does not exclude drugs synergy in fludarabine-resistant cells that could be used for overcoming resistance to nucleoside analogs in CLL.
authors.affiliation: Republican Scientific and Practical Center for Hematology and Transfusiology, 160 Dolginovski Tract, Minsk 220053, Belarus. asvirnov@yandex.ru
authors.forename: A I
authors.initials: AI
authors.lastname: Svirnovski
authors.forename: T F
authors.initials: TF
authors.lastname: Serhiyenka
authors.forename: A M
authors.initials: AM
authors.lastname: Kustanovich
authors.forename: P V
authors.initials: PV
authors.lastname: Khlebko
authors.forename: V V
authors.initials: VV
authors.lastname: Fedosenko
authors.forename: I B
authors.initials: IB
authors.lastname: Taras
authors.forename: A V
authors.initials: AV
authors.lastname: Bakun
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000037:antagonists & inhibitors*; D000970:Antineoplastic Agents / Q000494:pharmacology; D064007:Ataxia Telangiectasia Mutated Proteins; D001547:Benzaldehydes / Q000494:pharmacology; D015153:Blotting, Western; D002110:Caffeine / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors*; D045744:Cell Line, Tumor; D002867:Chromones / Q000494:pharmacology; D016572:Cyclosporine / Q000494:pharmacology; D051747:DNA-Activated Protein Kinase / Q000037:antagonists & inhibitors*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D005434:Flow Cytometry; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000378:metabolism*; D009025:Morpholines / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors*; D014740:Vidarabine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: C479235:2-(morpholin-4-yl)benzo(h)chromen-4-one; D018435:ATP Binding Cassette Transporter, Subfamily B; D000970:Antineoplastic Agents; D001547:Benzaldehydes; D018797:Cell Cycle Proteins; D002867:Chromones; D004268:DNA-Binding Proteins; D009025:Morpholines; D047428:Protein Kinase Inhibitors; D025521:Tumor Suppressor Proteins; D002110:Caffeine; D016572:Cyclosporine; C100058:vanillin; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase; D017346:Protein Serine-Threonine Kinases; D014740:Vidarabine; C024352:fludarabine