Human homologue for Caenorhabditis elegans CUL-4 protein overexpression is associated with malignant potential of epithelial ovarian tumours and poor outcome in carcinoma.
CUL-4 plays a critical role in DNA replication in Caenorhabditis elegans, and interacts with p53 and p21 proteins in cell cycle regulation and response to genomic instability. However, the role of CUL-4 in human carcinomas is widely unknown. To investigate the expression of CUL-4 protein and its association with p53 and p21, and to determine its prognostic relevance in invasive ovarian carcinoma. CUL-4, p53 and p21 protein expression was determined retrospectively by immunohistochemistry in 140 specimens of human epithelial ovarian tumours (98 invasive carcinomas and 42 tumours of low malignant potential; LMP). Overexpression of CUL-4 was observed in 41 (41.8%) of carcinoma samples and in 10 (23.8%) LMP tumours. CUL-4 was significantly more often overexpressed in invasive carcinomas compared with LMP tumours (p=0.042, χ(2) test, OR 2.302, 95% CI 1.018 to 5.203). In invasive carcinoma, CUL-4 overexpression was found to be a prognostic factor for overall (p=0.017, Cox regression, HR 2.387, 95% CI 1.17 to 4.869) and disease-free survival (p=0.005, Cox regression, HR 3.5, 95% CI 1.465 to 8.365), respectively. In subgroup analysis, CUL-4 was only of prognostic relevance in carcinomas without p53 expression. These data indicate for the first time that CUL-4 might play a relevant role in the development and progression of ovarian carcinoma, warranting further investigations. Degradation of wild-type p53 might be a key mechanism to explain why CUL-4 leads to more aggressive clinical behaviour. Not only CUL-4 itself, but also its associated proteins might represent targets for novel, selective therapeutic strategies.