Cell cycle-related kinase supports ovarian carcinoma cell proliferation via regulation of cyclin D1 and is a predictor of outcome in patients with ovarian carcinoma.

Our previous study has suggested that the cell cycle-related kinase (CCRK) is a putative candidate oncogene in glioblastoma tumorigenesis. The potential oncogenic role of CCRK and its clinical/prognostic significance, however, in ovarian carcinoma are unclear. In this study, CCRK expression was examined by immunohistochemistry in a series of ovarian carcinoma tissues. Overexpression of CCRK was detected in 53% of the ovarian carcinomas, and it was positively correlated with an ascending histological grade and/or advanced clinical stage of the disease (p < 0.05). In addition, overexpression of CCRK in ovarian carcinoma was determined to be a strong and an independent predictor of short overall survival (p < 0.05). In ovarian carcinoma cells, CCRK knockdown by RNAi led to a G1 phase cell cycle arrest, while CCRK overexpression by stable transfection of CCRK-containing plasmid pcDNA-CCRK promoted cell proliferation in vitro and tumor growth in vivo. In addition, CCRK knockdown was found to reduce cyclin D1 expression. Consistently, CCRK overexpression increased cyclin D1 expression, and furthermore, a significant correlation between expression of CCRK and cyclin D1 in ovarian carcinomas was observed (p < 0.001). These findings suggest a potential important role of CCRK in the control of cell proliferation via regulation of cyclin D1 expression, and the overexpression of CCRK, as detected by immunohistochemistry, is an independent molecular marker for shortened survival time of patients with ovarian carcinoma.