Chk1 and Chk2 are differentially involved in homologous recombination repair and cell cycle arrest in response to DNA double-strand breaks induced by camptothecins.

Abstract

Camptothecins (CPT) activate S or G(2)-M arrest and the homologous recombination (HR) repair pathway in tumor cells. In this process, both checkpoint kinases 1 and 2 (Chk1 and Chk2, respectively) are activated, but their differential roles, especially in the coordination of checkpoint and repair control, and potential clinic relevance remain to be fully elucidated. In this study, the repairable double-strand breaks were induced in human colon cancer HCT116 cells by 1-h exposure to 25 or 100 nmol/L CPT and its novel derivative chimmitecan. The cellular disposal of double-strand breaks was reflected as the progressive dispersal of gamma-H2AX foci, reduction of "comet" tails, dynamic activation of RAD51-mediated HR repair, and reversible G(2)-M arrest. In this model, the differential kinetics of Chk1 and Chk2 activation was characterized by the progressively increased phosphorylation of Chk2 until 72 h, the degradation of Chk1, and the disappearance of phosphorylated Chk1 48 h after drug removal. Using RNA interference, we further showed that Chk2 was essential to G(2)-M arrest, whereas Chk1 was mainly required for HR repair in CPT-treated HCT116 cells. Moreover, Chk2, rather than Chk1, predominated over the control of cell survival in this model. The differential roles of Chk1 and Chk2 in regulating HR repair and G(2)-M phase arrest were also confirmed in HT-29 colon cancer cells. Together, these findings systematically dissect the differential roles of Chk1 and Chk2 in a favorable model pursuing CPT-driven DNA damage responses, providing critical evidence to further explore checkpoint modulation, especially Chk2 inhibition as a therapeutic strategy in combination with CPT.

• Authors: Min Huang, Ze-Hong Miao, Hong Zhu, Yu-Jun Cai, Wei Lu, Jian Ding
• Journal: Molecular cancer therapeutics (Mol Cancer Ther) Vol. 7 Issue 6 Pg. 1440-9 (Jun 2008) ISSN: 1535-7163 [Print] United States
• PMID: 18566216 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• chimmitecan
• Protein Kinases
• Checkpoint Kinase 2
• CHEK1 protein, human
• CHEK2 protein, human
• Checkpoint Kinase 1
• Protein Serine-Threonine Kinases
• RAD51 protein, human
• Rad51 Recombinase
• Camptothecin

Topics

• Apoptosis (drug effects)
• Camptothecin (analogs & derivatives, pharmacology)
• Cell Cycle (drug effects)
• Cell Survival (drug effects)
• Checkpoint Kinase 1
• Checkpoint Kinase 2
• DNA Breaks, Double-Stranded (drug effects)
• DNA Repair (drug effects)
• Enzyme Activation (drug effects)
• G2 Phase (drug effects)
• HCT116 Cells
• HT29 Cells
• Humans
• Kinetics
• Mitosis (drug effects)
• Protein Kinases (metabolism)
• Protein Serine-Threonine Kinases (metabolism)
• Rad51 Recombinase (metabolism)
• Recombination, Genetic (drug effects)