Re-purposing clinical kinase inhibitors to enhance chemosensitivity by overriding checkpoints

Cell Cycle. 2014;13(14):2172-91. doi: 10.4161/cc.29214. Epub 2014 Jun 23.


Inhibitors of the DNA damage checkpoint kinase, Chk1, are highly effective as chemo- and radio-sensitizers in preclinical studies but are not well-tolerated by patients. We exploited the promiscuous nature of kinase inhibitors to screen 9 clinically relevant kinase inhibitors for their ability to sensitize pancreatic cancer cells to a sub-lethal concentration of gemcitabine. Bosutinib, dovitinib, and BEZ-235 were identified as sensitizers that abrogated the DNA damage checkpoint. We further characterized bosutinib, an FDA-approved Src/Abl inhibitor approved for chronic myelogenous leukemia. Unbeknownst to us, we used an isomer (Bos-I) that was unknowingly synthesized and sold to the research community as "authentic" bosutinib. In vitro and cell-based assays showed that both the authentic bosutinib and Bos-I inhibited DNA damage checkpoint kinases Chk1 and Wee1, with Bos-I showing greater potency. Imaging data showed that Bos-I forced cells to override gemcitabine-induced DNA damage checkpoint arrest and destabilized stalled replication forks. These inhibitors enhanced sensitivity to the DNA damaging agents' gemcitabine, cisplatin, and doxorubicin in pancreatic cancer cell lines. The in vivo efficacy of Bos-I was validated using cells derived directly from a pancreatic cancer patient's tumor. Notably, the xenograft studies showed that the combination of gemcitabine and Bos-I was significantly more effective in suppressing tumor growth than either agent alone. Finally, we show that the gatekeeper residue in Wee1 dictates its sensitivity to the 2 compounds. Our strategy to screen clinically relevant kinase inhibitors for off-target effects on cell cycle checkpoints is a promising approach to re-purpose drugs as chemosensitizers.

Keywords: Checkpoint override; DNA damage; Kinase inhibitors; Mitosis; drug repurposing.

Publication types

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

MeSH terms

  • Aniline Compounds / pharmacology
  • Animals
  • Antineoplastic Agents / pharmacology*
  • Cell Cycle Checkpoints / drug effects*
  • Cell Cycle Proteins / antagonists & inhibitors
  • Cell Cycle Proteins / metabolism
  • Cell Line, Tumor
  • Cell Proliferation / drug effects*
  • Checkpoint Kinase 1
  • Cisplatin / pharmacology
  • DNA Damage
  • DNA Replication
  • Deoxycytidine / analogs & derivatives
  • Deoxycytidine / pharmacology
  • Dose-Response Relationship, Drug
  • Doxorubicin / pharmacology
  • Drug Repositioning*
  • Drug Resistance, Neoplasm / drug effects*
  • Humans
  • Male
  • Mice, Inbred C57BL
  • Mice, SCID
  • Models, Molecular
  • Nitriles / pharmacology
  • Nuclear Proteins / antagonists & inhibitors
  • Nuclear Proteins / metabolism
  • Pancreatic Neoplasms / drug therapy*
  • Pancreatic Neoplasms / enzymology
  • Pancreatic Neoplasms / genetics
  • Pancreatic Neoplasms / pathology
  • Protein Kinase Inhibitors / chemistry
  • Protein Kinase Inhibitors / pharmacology*
  • Protein Kinases / chemistry
  • Protein Kinases / genetics
  • Protein Kinases / metabolism*
  • Protein-Tyrosine Kinases / antagonists & inhibitors
  • Protein-Tyrosine Kinases / metabolism
  • Quinolines / pharmacology
  • Signal Transduction / drug effects*
  • Time Factors
  • Xenograft Model Antitumor Assays


  • Aniline Compounds
  • Antineoplastic Agents
  • Cell Cycle Proteins
  • Nitriles
  • Nuclear Proteins
  • Protein Kinase Inhibitors
  • Quinolines
  • Deoxycytidine
  • bosutinib
  • Doxorubicin
  • gemcitabine
  • Protein Kinases
  • Protein-Tyrosine Kinases
  • WEE1 protein, human
  • CHEK1 protein, human
  • Checkpoint Kinase 1
  • Chek1 protein, mouse
  • Cisplatin