Defective DNA Strand Break Repair after DNA Damage in Prostate Cancer Cells

Abstract

Together with cell cycle checkpoint control, DNA repair plays a pivotal role in protecting the genome from endogenous and exogenous DNA damage. Although increased genetic instability has been associated with prostate cancer progression, the relative role of DNA double-strand break repair in malignant versus normal prostate epithelial cells is not known. In this study, we determined the RNA and protein expression of a series of DNA double-strand break repair genes in both normal (PrEC-epithelial and PrSC-stromal) and malignant (LNCaP, DU-145, and PC-3) prostate cultures. Expression of genes downstream of ATM after ionizing radiation-induced DNA damage reflected the p53 status of the cell lines. In the malignant prostate cell lines, mRNA and protein levels of the Rad51, Xrcc3, Rad52, and Rad54 genes involved in homologous recombination were elevated ϳ2-to 5-fold in comparison to normal PrEC cells. The XRCC1, DNA polymerase-␤ and -␦ proteins were also elevated. There were no consistent differences in gene expression relating to the nonhomologous end-joining pathway. Despite increased expression of DNA repair genes, malignant prostate cancer cells had defective repair of DNA breaks, alkali-labile sites, and oxidative base damage. Furthermore, after ionizing radiation and mitomycin C treatment, chromosomal aberration assays confirmed that malignant prostate cells had defective DNA repair. This discordance between expression and function of DNA repair genes in malignant prostate cancer cells supports the hypothesis that prostate tumor progression may reflect aberrant DNA repair. Our findings support the development of novel treatment strategies designed to reinstate normal DNA repair in prostate cancer cells.

Cytotoxic Effects of Escin on Human Castration-resistant Prostate Cancer Cells Through the Induction of Apoptosis and G2/M Cell Cycle Arrest

“…p21 Cip1/Waf1 has been shown to regulate cell cycle progression in both G1 and G2 phases through p53-dependent or p53-independent pathways (Niculescu, Chen et al 1998). Consistent with the findings of previous research (Patlolla, Raju et al 2006), neither DU-145 nor PC-3 cell lines expressed functional p53 (Fan, Kumaravel et al 2004) in the present study , suggesting that p53 may not play an essential role in escin-induced apoptosis or conventional chemotherapeutic agents is mediated by p53 (Brown and Wouters 1999), the p53-independent activation of p21 WAF1/CIP1 triggered by escin treatment can represent an alternative therapeutic approach for prostate cancer patients who fail to respond to conventional agents targeting p53 . inactive.…”

Human papillomavirus type 16 E7 oncoprotein causes a delay in repair of DNA damage

“…For example, it has been suggested to contribute to drug resistance in prostate cancer [37]. p16 INK4A , a protein overexpressed in HPV+ cancers due to the effects of E7 has recently been shown to impair the recruitment of Rad51 to sights of DNA damage [38].…”

RNF168 and USP10 regulate topoisomerase IIα function via opposing effects on its ubiquitylation

“…Neutral comet assay was performed as previously described61. Single-cell suspensions of MEFs were collected after treatment with 20 μM etoposide for 30 min.…”