Chk1 signaling pathways that mediated G(2)M checkpoint in relation to the cellular resistance to the novel topoisomerase I poison BNP1350

Biochem Biophys Res Commun. 2002 Jul 12;295(2):435-44. doi: 10.1016/s0006-291x(02)00683-6.


A novel karenitecin, BNP1350, is a topoisomerase I-targeting anticancer agent with significant antitumor activity in vitro and in vivo. A BNP1350-resistant human head and neck carcinoma A253 cell line, denoted A253/BNPR, was developed. The A253/BNPR cell line was approximately 9-fold resistant to BNP1350 and 4-fold cross-resistant to another topoisomerase I inhibitor SN-38, the active metabolite of irinotecan. After drug treatment with equimolar concentrations of BNP1350 (0.7 microM) for 2h, activation of the DNA double-strand break repair protein complexes was similar in the two cell lines, suggesting that DNA dsb repair is not attributable to resistance to BNP1350 in the A253/BNPR cells. Cell cycle analysis indicates that the A253 cell line accumulated primarily in S phase, but G(2) phase accumulation was observed in the A253/BNPR cell line at 48 h after drug removal. Elevated chk1 phosphorylation at Ser(345) following DNA damage induced by BNP1350 was accompanied by G(2) accumulation in the A253/BNPR cell line, while exposure to equimolar concentrations of BNP1350 (0.7 microM) induced S-phase arrest and no increased phosphorylation of chk1 at Ser(345) in the A253 cell line. Under the same conditions, increased chk1 activity was observed in the A253/BNPR cell line, but not in the A253 cell line. Moreover, stimulated binding of 14-3-3 proteins to chk1 was observed in BNP1350-treated A253/BNPR cells. To confirm relationship between chk1 expression/phosphorylation and drug resistance to topo I poisons, we examined the effects of chk1 or chk2 antisense oligonucleotides on the cellular growth inhibition. Chk1 antisense oligonucleotide can sensitize the A253/BNPR cells to killing by topo I inhibitor BNP1350, but no significant sensitization of BNP1350-induced growth inhibition was observed in the drug-sensitive cell line. Chk2 antisense oligonucleotide has only a small sensitization effect on BNP1350-induced growth inhibition in both cell lines. The data indicate that the chk1 signaling pathways that mediate cell cycle checkpoint are associated with cellular resistance to BNP1350 in the A253/BNPR cell line.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 14-3-3 Proteins
  • Camptothecin / analogs & derivatives*
  • Camptothecin / pharmacology*
  • Cell Division / drug effects
  • Checkpoint Kinase 1
  • DNA Damage
  • DNA Repair
  • Drug Resistance, Neoplasm*
  • Enzyme Inhibitors / pharmacology*
  • G2 Phase*
  • Humans
  • Mitosis*
  • Oligonucleotides, Antisense / metabolism
  • Phosphorylation
  • Protein Kinases / metabolism*
  • Signal Transduction*
  • Topoisomerase I Inhibitors*
  • Tumor Cells, Cultured
  • Tyrosine 3-Monooxygenase / metabolism


  • 14-3-3 Proteins
  • Enzyme Inhibitors
  • Oligonucleotides, Antisense
  • Topoisomerase I Inhibitors
  • cositecan
  • Tyrosine 3-Monooxygenase
  • Protein Kinases
  • CHEK1 protein, human
  • Checkpoint Kinase 1
  • Camptothecin