Differential prognostic impact of the cyclins E and B in premenopausal and postmenopausal women with lymph node-negative breast cancer

Cyclin E in normal and neoplastic cell cycles

Cyclin E-Cdk2 has long been considered an essential and master regulator of progression through G1 phase of the cell cycle. Although recent mouse models have prompted a rethinking of cyclin E function in mammals, it remains clear that cyclin E impacts upon many processes central to cell division. Normal cells maintain strict control of cyclin E activity, and this is commonly disrupted in cancer cells. Moreover, cyclin E deregulation is thought to play a fundamental role in tumorigenesis. In this review, we discuss the regulation and functions of cyclin E in normal and neoplastic mammalian cells.

Bringing Molecular Prognosis and Prediction to the Clinic

In the past 30 years, important advances have been made in the knowledge of breast cancer biology and in the treatment of the disease. However, the translation of these advances into clinical practice has been slow. With the advent of molecular-based medicine, it is hoped that the bridge between the bench and the bedside will continue to be shortened. Because breast cancer is a heterogeneous disease with wide-ranging subsets of patients who have different prognoses and who respond differently to treatments, the identification of patients who need treatment and the definition of the best therapy for an individual have become the priorities in breast cancer care. This article will review the crucial role of prognostic and predictive factors in achieving these goals. A critical review of classical and newer individual molecular markers, such as hormone receptors, HER2, urokinase-type plasminogen activator and plasminogen activator inhibitor 1, cyclin E, topoisomerase II, and p53, was performed, and the preliminary results obtained using the new gene expression profiling technology are described along with their potential clinical implications.

Cyclin E Expression in Operable Breast Cancer Quantified Using Real-Time RT–PCR: A Comparative Study with Immunostaining

OBJECTIVE

The main purpose of this retrospective study was to compare cyclin E expression levels in operable breast cancer patients determined using real-time RT-PCR and immunostaining. The prognostic relevance of cyclin E was also investigated.

METHODS

Specimens of invasive ductal breast cancer tissues obtained from 124 women during radical mastectomy were analyzed.

RESULTS

Of the tumor samples, 40.3 and 59.7% showed high expression of cyclin E in RT-PCR and immunostaining, respectively. The overall agreement probability was 0.032 according to Scott's pi statistic. With a median follow-up of 55.5 months, cyclin E expression assessed using immunostaining was an independent negative prognostic factor in the node positive group (hazard ratio 3.1; 95% CI 1.0-9.2; P = 0.045). Cyclin E expression correlated with absence of steroid receptors and younger age. RT-PCR results did not predict survival in any group of patients.

CONCLUSIONS

Disagreement between real-time RT-PCR and immunostaining was demonstrated. Immunostaining seems to be the more reliable method for assessing cyclin E in breast cancer cells.

CDK2 and cyclin E knockout mice: lessons from breast cancer

The recent discovery that murine embryos can develop normally in spite of ablation of either CDK2 or cyclin E challenges the previously held dogma that cyclin E-CDK2 activity is strictly required for the cell-division cycle. However, genetic, cellular, biochemical and clinical evidence correlate aberrant cyclin E expression with tumorigenesis and poor patient prognosis, particularly in breast cancer. Thus cyclin E is a crucial regulator of estrogen-mediated growth signaling in breast tissue and, in spite of the apparent dispensability of cyclin E-CDK2 in development, the relationship between cyclin E and the development of breast cancer is convincing.