Abstract 3641: The predictive and prognostic roles of DNA damage response genes in epithelial ovarian cancer

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Background: Despite platinum-based chemotherapy, 5-year survival of advanced stage ovarian cancer patients is only 15-30%. Exposure to platinum-based chemotherapeutics induces double strand DNA breaks (DSBs) and subsequently leads to activation of the DNA damage response (DDR). Therefore inhibition of components of the DDR may lead to better response to therapy. Aim of this study was to investigate in a large series of ovarian cancer patients the predictive and prognostic role of the activation status of four DDR-proteins- ATM, a key controller in the DDR, and three ATM substrates, including Chk2, 53BP1 and γ-H2AX, of which the latter is a direct readout for DNA damage. Methods: Expression of phospho-ATM, Chk2, phospho-Chk2, 53BP1, phospho-53BP1 and γ-H2AX was immunohistochemically assessed in 309 patients with chemo-naive ovarian cancer. Expression levels were related to clinicopathological characteristics and survival. Response to platinum-based chemotherapy was analyzed by defining two populations with either an optimal therapy response or a very poor therapy response. Both groups consisted of patients with advanced stage ovarian cancer, >2 cm residual disease after primary surgery and were all treated with platinum-based chemotherapy. The responder group had a well-defined PFS of more than 18 months while the non-responder group had a PFS of less than 6 months. Results: In the two well-defined groups with the largest contrast regarding response to treatment, positive γ-H2AX expression (OR=0.193; p=0.036) and positive Chk2 expression (OR=0.149; p=0.011) were related to a good response to platinum-based chemotherapy. In advanced stage patients, phospho-53BP1 expression was independently related to a worse disease-specific survival (HR=1.905; p= 0.044). Conclusion: High DDR protein expression in advanced stage ovarian cancers suggests a high degree of genomic instability, while the negative prognostic impact of phospho-53BP1 may be due to enhanced repair capacity of chemotherapy-induced DSBs on the long term. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3641. doi:1538-7445.AM2012-3641