Woon Kim, and Bo Lu1 Department of Radiation Oncology, Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee Abstract Aurora kinase B is critical SRT1720 SRT-1720 to the process of mitosis, aiding in chromosome condensation by phosphorylating histone H3. We investigated the effects of AZD1152, an AURKB inhibitor, on radiosensitivity of androgen insensitive prostate cancer cells. The goal of this study was to test whether AZD1152 increases the susceptibility of hormone refractory prostate cancer cells to radiation induced DNA damage and to determine the conditions of AZD1152 treatment that maximize radiosensitization. PC3 and DU145 cells were treated with various AZD1152 doses for various durations to elucidate the conditions that yielded maximal increases in G2/M phase and polyploid cells.
To assess DNA damage, γ H2AX phosphorylation was quantified for cells grown under radiosensitizing conditions and subjected to either no radiation or 5 Gy radiation. Radiosensitivity was determined Triciribine by clonogenic assays. Cell cycle effects in both cell lines were maximized by treatment with 60 nM AZD1152 for 48 h. AZD1152 treated cells exhibited significantly increased DNA damage 30 min postirradiation , with additional DNA damage 6 h postirradiation . Radiosensitivity was increased in both cell lines, with dose enhancement ratios of 1.53 for PC3 cells and 1.71 for DU145 cells . This study identifies the optimal AZD1152 treatment conditions to maximize the radiosensitization of PC3 and DU145 cells. These results suggest a major role for DNA damage and impairment of DNA repair mechanisms in AZD1152 induced radiosensitization of prostate cancer cells.
INTRODUCTION Prostate cancer is the most commonly diagnosed non cutaneous malignancy in men in the U.S., with an estimated 186,320 new cases in 2008 . Surgical resection, radiation therapy and hormone therapy are the main treatment modalities for prostate cancer. Although there are several promising treatment strategies, prostate cancer continues to be a major cause of cancer death in males in the U.S. The most challenging cases of prostate cancer include those that are insensitive to androgen blockade and those that have become hormone refractory after initial hormone and radiotherapy treatment. Aurora Kinase B has recently emerged as a promising therapeutic target for several malignancies.
Aurora kinases are a class of serine/threonine kinases necessary for cell cycle progression. AURKB is a component of the chromosomal passenger complex, functioning in chromosome orientation and in regulation of spindle attachment . © 2011 by Radiation Research Society. 1Address for correspondence: Department of Radiation Oncology, Vanderbilt University, 1301 22nd Avenue South, B 902 TVC, Nashville, TN, bo.luvanderbilt. NIH Public Access Author Manuscript Radiat Res. Author manuscript, available in PMC 2012 April 1. Published in final edited form as: Radiat Res. 2011 April , 175: 444 451. doi:10.1667/RR2317.1. NIH PA Author Manuscript NIH PA Author Manuscript NIH PA Author Manuscript AURKB phosphorylates histone H3 at the serine 10 position, allowing for chromosome condensation, thus facilitating cytokinesis .
In normal cell lines, expression of AURKB naturally peaks at the G2/M cell cycle phase transition, thus facilitating cell cycle progression at this juncture . AURKB overexpression is associated with increased genomic instability, and upregulation of the protein has been detected in a number of solid tumors, including prostate cancer . Additionally, its expression has been associated with poorer prognoses in ovarian, brain and hepatocellular carcinomas . Inhibition of AURKB activity has been shown to result in shrinkage of tumor xenografts via induction of apoptosis and radiosensitization . Because of the association of AURKB upregulation with tumorigenesis, inhibition of this kinase may prove to be a promising treatment strategy for a variety of cancers. AZD1152, along with other inhibitors o