Protein expression patterns of cell cycle regulators in operable breast cancer.

BACKGROUND-AIM: To evaluate the prognostic role of elaborate molecular clusters encompassing cyclin D1, cyclin E1, p21, p27 and p53 in the context of various breast cancer subtypes. METHODS: Cyclin E1, cyclin D1, p53, p21 and p27 were evaluated with immunohistochemistry in 1077 formalin-fixed paraffin-embedded tissues from breast cancer patients who had been treated within clinical trials. Jaccard distances were computed for the markers and the resulted matrix was used for conducting unsupervised hierarchical clustering, in order to identify distinct groups correlating with prognosis. RESULTS: Luminal B and triple-negative (TNBC) tumors presented with the highest and lowest levels of cyclin D1 expression, respectively. By contrast, TNBC frequently expressed Cyclin E1, whereas ER-positive tumors did not. Absence of Cyclin D1 predicted for worse OS, while absence of Cyclin E1 for poorer DFS. The expression patterns of all examined proteins yielded 3 distinct clusters; (1) Cyclin D1 and/or E1 positive with moderate p21 expression; (2) Cyclin D1 and/or E1, and p27 positive, p53 protein negative; and, (3) Cyclin D1 or E1 positive, p53 positive, p21 and p27 negative or moderately positive. The 5-year DFS rates for clusters 1, 2 and 3 were 70.0%, 79.1%, 67.4% and OS 88.4%, 90.4%, 78.9%, respectively. CONCLUSIONS: It seems that the expression of cell cycle regulators in the absence of p53 protein is associated with favorable prognosis in operable breast cancer.

The Prognostic Value of the Immunohistochemical Expression of Phosphorylated RB and p16 Proteins in Association with Cyclin D1 and the p53 Pathway in a Large Cohort of Patients with Breast Cancer Treated with Taxane-based Adjuvant Chemotherapy.

BACKGROUND: The retinoblastoma (RB) gene is a tumor-suppressor gene that plays a central role in regulating the cell cycle. Inactivation of this gene is involved in breast cancer. PATIENTS AND METHODS: A total of 827 patients with breast cancer treated with taxane-based adjuvant chemotherapy were included in the study. Protein expression of RB, phosphorylated RB (pRB), p16, cyclin D1 and p53 was evaluated by immunohistochemistry. RESULTS: Neither of the retinoblastoma markers (RB and pRB) reached statistical significance in terms of their association with disease-free or overall survival. Nevertheless, when clustering analysis was performed, patients with tumors featuring low levels of p16, cyclin D1 and p53 with concomitantly high levels of pRB had reduced risk for relapse (Wald's p=0.015). CONCLUSION: The p53-mediated sensitivity of breast cancer cells to chemotherapeutic agents appears to be driven mostly by pRB. Using agents that enhance RB phosphorylation might possibly increase the chemosensitivity of breast cancer cells.