Synthetic lethality of Chk1 inhibition combined with p53 and/or p21 loss during a DNA damage response in normal and tumor cells

Oncogene. 2013 Jan 31;32(5):577-88. doi: 10.1038/onc.2012.84. Epub 2012 Mar 19.


Cell cycle checkpoints ensure genome integrity and are frequently compromised in human cancers. A therapeutic strategy being explored takes advantage of checkpoint defects in p53-deficient tumors in order to sensitize them to DNA-damaging agents by eliminating Chk1-mediated checkpoint responses. Using mouse models, we demonstrated that p21 is a key determinant of how cells respond to the combination of DNA damage and Chk1 inhibition (combination therapy) in normal cells as well as in tumors. Loss of p21 sensitized normal cells to the combination therapy much more than did p53 loss and the enhanced lethality was partially blocked by CDK inhibition. In addition, basal pools of p21 (p53 independent) provided p53 null cells with protection from the combination therapy. Our results uncover a novel p53-independent function for p21 in protecting cells from the lethal effects of DNA damage followed by Chk1 inhibition. As p21 levels are low in a significant fraction of colorectal tumors, they are predicted to be particularly sensitive to the combination therapy. Results reported in this study support this prediction.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Antineoplastic Agents, Phytogenic / pharmacology
  • Apoptosis
  • Camptothecin / analogs & derivatives*
  • Camptothecin / pharmacology
  • Cell Cycle Checkpoints
  • Cell Line, Tumor
  • Checkpoint Kinase 1
  • Cyclin-Dependent Kinase Inhibitor p21 / deficiency*
  • DNA Damage / drug effects*
  • Irinotecan
  • Mice
  • Mice, Knockout
  • Protein Kinase Inhibitors / pharmacology*
  • Protein Kinases / metabolism*
  • Tumor Suppressor Protein p53 / genetics*


  • Antineoplastic Agents, Phytogenic
  • Cyclin-Dependent Kinase Inhibitor p21
  • Protein Kinase Inhibitors
  • Tumor Suppressor Protein p53
  • Irinotecan
  • Protein Kinases
  • CHEK1 protein, human
  • Checkpoint Kinase 1
  • Chek1 protein, mouse
  • Camptothecin