This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Devlin, H.-L. Articles by deVere White, R. W. PubMed PubMed Citation Articles by Devlin, H.-L. Articles by deVere White, R. W.

---

DNA Damage and Cellular Stress Responses

Impairment of the DNA Repair and Growth Arrest Pathways by p53R2 Silencing Enhances DNA Damage–Induced Apoptosis in a p53-Dependent Manner in Prostate Cancer Cells

¹ Department of Internal Medicine, ² Division of Basic Sciences, Cancer Center, and Departments of Biochemistry and Molecular Medicine, ³ Microbiology and Immunology, and ⁴ Urology, University of California, Davis, School of Medicine and Cancer Center, Sacramento, California

Requests for reprints: Ralph W. deVere White, Department of Urology, University of California, Davis, School of Medicine, 4860 Y Street, Suite 3500, Sacramento, CA 95817. Phone: 916-734-2824; Fax: 916-734-8094. E-mail: rwdeverewhite{at}ucdavis.edu

p53R2 is a p53-inducible ribonucleotide reductase that contributes to DNA repair by supplying deoxynucleotide triphosphate pools in response to DNA damage. In this study, we found that p53R2 was overexpressed in prostate tumor cell lines compared with immortalized prostatic epithelial cells and that the protein was induced upon DNA damage. We investigated the effects of p53R2 silencing on DNA damage in LNCaP cells (wild-type p53). Silencing p53R2 potentiated the apoptotic effects of ionizing radiation and doxorubicin treatment as shown by increased sub-G₁ content and decreased colony formation. This sensitizing effect was specific to DNA-damaging agents. Comet assay and -H2AX phosphorylation status showed that the decreased p53R2 levels inhibited DNA repair. Silencing p53R2 also reduced the levels of p21^WAF1/CIP1 at the posttranscriptional level, suggesting links between the p53-dependent DNA repair and cell cycle arrest pathways. Using LNCaP sublines stably expressing dominant-negative mutant p53, we found that the sensitizing effect of p53R2 silencing is mediated by p53-dependent apoptosis pathways. In the LNCaP sublines (R273H, R248W, and G245S) that have defects in inducing p53-dependent apoptosis, p53R2 silencing did not potentiate DNA damage–induced apoptosis, whereas p53R2 silencing was effective in a LNCaP subline (P151S) which retains the ability to induce p53-dependent apoptosis. This study shows that p53R2 is a potential therapeutic target that could be used to enhance the effectiveness of ionizing radiation or DNA-damaging chemotherapy in a subset of patients with prostate cancer. (Mol Cancer Res 2008;6(5):808–18)