Chk1, but not Chk2, is involved in the cellular response to DNA damaging agents: differential activity in cells expressing or not p53

Cell Cycle. 2004 Sep;3(9):1177-81. Epub 2004 Sep 13.


Mammalian Chk1 and Chk2 protein kinases are two important components of the G(2) DNA damage checkpoint. They are activated by upstream kinases (ataxia telangectasia mutated gene and ATM and Rad 3 related gene) and interfere with the activity of the cdc2/cyclinB1 complex, necessary for the G(2)-M transition, through the inactivation of the cdc25 phosphatases (cdc25A and cdc25C). To understand the role of Chk1 and Chk2 in the cellular response to different anticancer agents, we knocked down the expression of each protein or simultaneously of both proteins by using the small interfering RNA technique in the HCT-116 colon carcinoma cell line and in its isogenic systems in which p53 and p21 have been inactivated by targeted homologous recombination. We here show that inhibition of Chk1 but not of Chk2 in p21(-/-) and p53(-/-) cells caused a greater abrogation of G(2) block induced by ionizing radiation and cis-diamine-dichloroplatinum treatments and a greater sensitization to the same treatments than in the parental cell line with p53 and p21 wild type proteins. These data further emphasise the role of Chk1 as a molecular target to inhibit in tumors with a defect in the G(1) checkpoint with the aim of increasing the selectivity and specificity of anticancer drug treatments.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology*
  • Checkpoint Kinase 1
  • Checkpoint Kinase 2
  • Cisplatin / pharmacology
  • Cyclin-Dependent Kinase Inhibitor p21 / genetics
  • Cyclin-Dependent Kinase Inhibitor p21 / metabolism
  • DNA Damage / drug effects*
  • DNA Damage / physiology
  • Down-Regulation / physiology
  • Drug Resistance, Neoplasm / drug effects
  • Drug Resistance, Neoplasm / physiology
  • G1 Phase / drug effects
  • G1 Phase / physiology
  • G2 Phase / drug effects
  • G2 Phase / physiology
  • Genes, cdc / drug effects*
  • Genes, cdc / physiology
  • HCT116 Cells
  • Humans
  • Neoplasms / drug therapy*
  • Neoplasms / genetics
  • Neoplasms / metabolism
  • Protein Kinases / drug effects*
  • Protein Kinases / metabolism
  • Protein-Serine-Threonine Kinases / drug effects
  • Protein-Serine-Threonine Kinases / metabolism
  • RNA Interference / physiology
  • RNA, Small Interfering / pharmacology
  • Radiation, Ionizing
  • Tumor Suppressor Protein p53 / genetics
  • Tumor Suppressor Protein p53 / metabolism
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism*


  • Antineoplastic Agents
  • Cyclin-Dependent Kinase Inhibitor p21
  • RNA, Small Interfering
  • Tumor Suppressor Protein p53
  • Tumor Suppressor Proteins
  • Protein Kinases
  • Checkpoint Kinase 2
  • CHEK1 protein, human
  • CHEK2 protein, human
  • Checkpoint Kinase 1
  • Protein-Serine-Threonine Kinases
  • Cisplatin