Background
Cyclin E is an important regulator of cell-cycle progression. High levels of cyclin E protein in breast cancer have been reported in association with higher disease stage, poor histological differentiation of tumor, and lack of steroid receptors. Data concerning the prognostic relevance of cyclin E expression in breast cancer are conflicting. The aim of this retrospective study was to evaluate the prognostic relevance of cyclin E expression assessed by immunohistochemistry in patients with operable invasive ductal breast cancer.
Material and Method
The expression of cyclin E was analyzed by immunostaining in 174 women with breast cancer after radical mastectomy with a median follow-up period of 58 months. Tumor samples were judged to be negative (<2%) or positive (> or =2%) according to the percentage of cells showing the nuclear staining pattern. Ninety-nine (56.9%) tumor samples were regarded as cyclin E-positive.
Results
Positive staining for cyclin E determined poor prognosis compared with cyclin E-negative patients in all cases (five-year cancer-specific survival rate of 64.5 vs. 84.5%, p=0.005), in the node-positive group (50.9 vs. 82.1%, p=0.008), and in patients treated with adjuvant chemotherapy (71.0 vs. 96.6%, p=0.008). In a multivariate analysis, high expression of cyclin E was associated with a higher risk of death in the node-positive group (hazard ratio: 3.2, 95%CI: 1.3-8.2, p=0.015).
Conclusions
It was demonstrated that a high expression of cyclin E measured by immunohistochemistry was a significant factor of poor prognosis, especially in the node-positive group.

Keywords: Oncogene Proteins - metabolism, Proportional Hazards Models, Multivariate Analysis, Cyclin E - metabolism, Chemotherapy, Adjuvant, Breast Neoplasms - surgery