Cyclin E-associated kinase activity predicts response to platinum-based chemotherapy

Purpose: The role of cyclin E as a predictive marker of response to chemotherapy remains unknown. We have previously shown that deregulation of cyclin E in an ovarian tumor cell line model enhances cyclin E - associated kinase activity and sensitizes tumor cells to cisplatinum. We hypothesized that cyclin E deregulation would predict for responsiveness to platinum-based regimens in ovarian cancer patients. Experimental Design: Patients who met the following criteria were retrospectively identified from the institutional tumor bank records: (a) high-grade ovarian epithelial malignancy, (b) stage III/stage IV disease, (c) optimally debulked, (d) completed platinum-based therapy. Tumor samples were analyzed for cyclin E, p21, and p27 by Western blot analysis and assessed for cyclin E - associated kinase activity. Results: Seventy-five patients, who met the study criteria, were identified. Cyclin E protein levels did not correlate with cyclin E - cdk2 kinase activity (Spearman's rho, 0.07; P = 0.58). Cyclin E - associated kinase activity was the only significant predictive marker for response to platinum-based therapy, with higher response rates seen in patients with higher levels of activity (P = 0.045). Cyclin E protein levels did not predict for platinum sensitivity (P = 0.20). In contrast, cyclin E protein levels, but not cyclin E - associated kinase activity, was a significant predictor for freedom from recurrence (P = 0.01 and P = 0.25, respectively). Conclusions: Cyclin E overexpression and cyclin E - associated kinase activity have distinct roles in predicting for response to chemotherapy and outcome in ovarian cancer patients. These results suggest a compartmentalization of cyclin E functions in the oncogenic process.