Cyclins are a group of proteins that act as activators to cyclin-dependent kinases and are required for normal cell cycle transitions. Cyclin A is involved in the transitions between G1 to S and G2 to M. Its deregulation has been linked to a number of neoplasms, including endometrial cancer. The prognostic significance of cyclin A expression seems to be cancer-specific, and current knowledge on its impact on survival of endometrial cancer is limited. This study aimed to investigate the effect of cyclin A expression on cancer-specific survival and its correlation with conventional prognostic factors in endometrioid adenocarcinoma. Biopsies obtained from 211 patients were immunohistochemically stained for cyclin A and differences in expression analyzed at the Oulu University Hospital. Patients were divided into two groups utilizing the ROC curve. Further survival analyses were carried out between these two groups. In this study, we show that cyclin A expression correlates with tumor grade and FIGO stage. We also show that cyclin A is an independent prognostic factor in endometrioid adenocarcinoma. Whether cyclin A plays a role in tumorigenesis or merely is a marker of increased proliferation requires further studies.

Cyclins are a group of cell cycle regulatory proteins. Cyclin B acts as an activator to cyclin-dependent kinase 1 (CDK1), a protein kinase essential for G2/M phase transition. Deregulation of cyclins has been linked to a number of malignant neoplasms, but the impact on clinicopathological parameters seems to be cancer-specific. Overexpression of cyclin B has been shown to affect survival in some malignant tumors, including breast and esophageal cancer, but its impact on endometrial cancer has not been extensively studied. For this study, 211 endometrial endometrioid adenocarcinoma samples were obtained from patients surgically treated at the Oulu University Hospital. The samples were immunohistochemically stained and analyzed for cyclin B expression. The relationships between cyclin B expression and conventional prognostic factors were analyzed. A discrimination threshold for survival analyses was calculated by utilizing the receiver operator characteristic (ROC) method. Cyclin B expression correlated with grade and advanced stage. Survival analyses showed that cyclin B expression affects cancer-specific survival in univariate analysis. In multivariate analysis, the results were indicative that cyclin B may hold independent prognostic significance, but further studies are required to assess this.

Combining the expression level of different cyclins may be useful in determining the prognosis in endometrial cancer. Unfortunately, it remains unclear whether high p27 expression is a poor or a favorable prognostic factor. Further large-scale studies are required to assess the effects of cyclins and p27 in endometrial cancer.