Human prostate epithelium lacks Wee1A-mediated DNA damage-induced checkpoint enforcement

doi:10.1073/pnas.0609299104

Human prostate epithelium lacks Wee1A-mediated DNA damage-induced checkpoint enforcement

*Molecular Cancer Biology Program, Biomedicum Helsinki and Haartman Institute, University of Helsinki, P.O. Box 63, FIN-00014, Helsinki, Finland;
^†Department of Pathology and Haartman Institute, University of Helsinki Hospital Laboratory Diagnostics, P.O. Box 21, FIN-00014, Helsinki, Finland;
^‡Karolinska Institutet, SE 17177, Stockholm, Sweden;
^§Department of Medical Oncology, Utrecht University Medical Center, 3584 CG, Utrecht, The Netherlands; and
^¶Department of Urology, Stanford University School of Medicine, Stanford, CA 94305

Edited by Richard B. Setlow, Brookhaven National Laboratory, Upton, NY, and approved March 8, 2007 (received for review October 20, 2006)

Abstract

Cellular DNA damage triggers the DNA damage response pathway and leads to enforcement of cell cycle checkpoints, which are essential for the maintenance of genomic integrity and are activated in early stages of tumorigenesis. A special feature of prostate cancer is its high incidence and multifocality. To address the functionality of DNA damage checkpoints in the prostate, we analyzed the responses of human primary prostate epithelial cells (HPECs) and freshly isolated human prostate tissues to γ-irradiation. We find that γ-irradiation activates the ataxia telangiectasia mutated-associated DNA damage response pathway in the HPECs but that the clearance of phosphorylated histone H2AX (γH2AX) foci is delayed. Surprisingly, γ-irradiated HPECs were unable to enforce cell cycle checkpoint arrest and had sustained cyclin-dependent kinase 2 (Cdk2)-associated kinase activity because of a lack of inhibitory Cdk phosphorylation by Wee1A tyrosine kinase. We further show that HPECs express low levels of Wee1A and that ectopic Wee1A efficiently rescues the checkpoints. We recapitulate the absence of checkpoint responses in epithelium of ex vivo irradiated human prostate tissue despite robust induction of γH2AX. The findings show that prostate epithelium has a surprising inability to control checkpoint arrest, the lack of which may predispose to accrual of DNA lesions.

Footnotes

^‖To whom correspondence should be addressed. E-mail: marikki.laiho{at}helsinki.fi
Author contributions: T.M.K.-a.H. and M.L. designed research; T.M.K.-a.H., S.J., M.M., and K.P. performed research; L.C.A., R.H.M., and D.M.P. contributed new reagents/analytic tools; T.M.K.-a.H., S.J., and M.L. analyzed data; and T.M.K.-a.H. and M.L. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0609299104/DC1.
Abbreviations:

ATM,

ataxia telangiectasia-mutated;

ATR,

ATM and Rad3-related;

Cdk,

cyclin-dependent kinase;

γH2AX,

phosphorylated histone H2AX;

HPEC,

human prostatic epithelial cell;

IR,

ionizing radiation.