title: Further characterisation of the cellular activity of the DNA-PK inhibitor, NU7441, reveals potential cross-talk with homologous recombination.
abstract: OBJECTIVE
  Inhibition of DNA repair is emerging as a new therapeutic strategy for cancer treatment. One promising target is DNA-PK, a pivotal kinase in double-strand break repair. The purpose of this study was to further characterise the activity of the DNA-PK inhibitor NU7441, giving some new insights into the biology of DNA-PK.
  
  
  METHODS
  We used NU7441, a potent DNA-PK inhibitor, to evaluate potential pharmacodynamic markers of DNA-PK inhibition, inhibition of DNA repair and chemo- and radio-potentiation in isogenic human cancer cells proficient (M059-Fus1) and deficient (M059 J) in DNA-PK.
  
  
  RESULTS
  NU7441 strongly inhibited DNA-PK in cell lines (IC(50) = 0.3 μM) but only weakly inhibited PI3 K (IC(50) = 7 μM). The only available anti-phospho-DNA-PK antibody also recognised some phosphoprotein targets of ATM. NU7441 caused doxorubicin- and IR-induced DNA DSBs (measured by γ-H2AX foci) to persist and also slightly decreased homologous recombination activity, as assessed by Rad51 foci. Chemo- and radio-potentiation were induced by NU7441 in M059-Fus-1, but not in DNA-PK-deficient M059 J cells. DNA-PK was highly expressed in a chronic lymphocytic leukaemia sample but undetectable in resting normal human lymphocytes, although it could be induced by PHA-P treatment. In K652 cells, DNA-PK expression was not related to cell cycle phase.
  
  
  CONCLUSIONS
  These data confirm NU7441 not only as a potent chemo- and radio-sensitiser clinical candidate but also as a powerful tool to study the biology of DNA-PK.
authors.affiliation: Northern Institute for Cancer Research, School of Medical Sciences, Newcastle University, Paul O' Gorman Building, Framlington Place, NE2 4HH Newcastle upon Tyne, UK.
authors.forename: Michele
authors.initials: M
authors.lastname: Tavecchio
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Munck
authors.forename: Celine
authors.initials: C
authors.lastname: Cano
authors.forename: David R
authors.initials: DR
authors.lastname: Newell
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Curtin
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002867:Chromones / Q000008:administration & dosage / Q000494:pharmacology*; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000473:pathology; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair / Q000187:drug effects*; D051747:DNA-Activated Protein Kinase / Q000037:antagonists & inhibitors*; D004317:Doxorubicin / Q000494:pharmacology; D005909:Glioblastoma / Q000188:drug therapy / Q000473:pathology; D006801:Humans; D020128:Inhibitory Concentration 50; D020014:K562 Cells; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009025:Morpholines / Q000008:administration & dosage / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays
chemical_list: C499693:8-dibenzothiophen-4-yl-2-morpholin-4-yl-chromen-4-one; D002867:Chromones; D009025:Morpholines; D004317:Doxorubicin; D051747:DNA-Activated Protein Kinase