Spontaneous abrogation of the G2 DNA damage checkpoint has clinical benefits but promotes leukemogenesis in Fanconi anemia patients
Raphael Ceccaldi, … , Gérard Socié, Jean Soulier
Raphael Ceccaldi, … , Gérard Socié, Jean Soulier
Published December 22, 2010
Citation Information: J Clin Invest. 2011;121(1):184-194. https://doi.org/10.1172/JCI43836.
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Research Article

Spontaneous abrogation of the G2 DNA damage checkpoint has clinical benefits but promotes leukemogenesis in Fanconi anemia patients

Abstract

DNA damage checkpoints in the cell cycle may be important barriers against cancer progression in human cells. Fanconi anemia (FA) is an inherited DNA instability disorder that is associated with bone marrow failure and a strong predisposition to cancer. Although FA cells experience constitutive chromosomal breaks, cell cycle arrest at the G2 DNA damage checkpoint, and an excess of cell death, some patients do become clinically stable, and the mechanisms underlying this, other than spontaneous reversion of the disease-causing mutation, are not well understood. Here we have defined a clonal phenotype, termed attenuation, in which FA patients acquire an abrogation of the G2 checkpoint arrest. Attenuated cells expressed lower levels of CHK1 (also known as CHEK1) and p53. The attenuation could be recapitulated by modulating the ATR/CHK1 pathway, and CHK1 inhibition protected FA cells from cell death. FA patients who expressed the attenuated phenotype had mild bone marrow deficiency and reached adulthood, but several of them eventually developed myelodysplasia or leukemia. Better understanding of attenuation might help predict a patient’s clinical course and guide choice of treatment. Our results also highlight the importance of evaluating the cellular DNA damage checkpoint and repair pathways in cancer therapies in general.

Authors

Raphael Ceccaldi, Delphine Briot, Jérôme Larghero, Nadia Vasquez, Catherine Dubois d’Enghien, Delphine Chamousset, Maria-Elena Noguera, Quinten Waisfisz, Olivier Hermine, Corinne Pondarre, Thierry Leblanc, Eliane Gluckman, Hans Joenje, Dominique Stoppa-Lyonnet, Gérard Socié, Jean Soulier

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Figure 4

Inhibition of CHK1 and ATR, but not CHK2, ATM, or BRCA1, mimics the attenuated phenotype in FA cells.

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Inhibition of CHK1 and ATR, but not CHK2, ATM, or BRCA1, mimics the atte...
(A) Cell cycle analysis of MMC-induced G2 arrest in HeLa cells transfected with combinations of siRNAs (si) against luciferase (control), FANCD2, and the checkpoint genes CHK1, CHK2, ATR, ATM, and BRCA1, as indicated. FANCD2-silenced HeLa cells displayed a strong MMC-induced G2 arrest and were used as FA-like cells for convenience in cotransfection experiments. The immunoblot shows the knockdown of different proteins for each siRNA. Arrows and asterisks indicate typical FA G2 arrest and its abrogation, respectively. All data were obtained in at least 3 independent experiments for each targeted gene with consistent results. (B) Abrogation of MMC-induced G2 arrest by the CHK1 inhibitor SB-218078 (CHK1i) but not by the CHK2 inhibitor C3742 (CHK2i) in FA and non-FA EBV cells. DMSO was used as control, and all data were obtained in 3 independent experiments with consistent results. The arrows indicate the MMC-induced G2 arrest, and the asterisk designates the G2 checkpoint abrogation. Horizontal bars in A and B indicate the G1 and G2 cell cycle phases (M1 and M2, respectively).