Abstract 4057: Functional domain of Annexin A4: which domain is indispensable for chemoresistance to platinum drugs.

Background: Platinum drugs are often used for the postoperative adjuvant therapy or treatment in advanced and recurrent ovarian cancer. We have previously reported that ovarian clear cell carcinoma (CCC) has increased expression of Annexin A4 (Anx A4) in comparison with other subtype of ovarian cancer. Enhanced expression of Anx A4 has been shown to induce chemoresistance via extracellular efflux of carboplatin. Purpose: To identify the domain of Anx A4 relevant to chemoresistance. Materials and methods: Anx A4 possesses the NH2-terminal domain and four annexin repeat domains with one Ca2+-binding site in each domain. Deleting annexin repeat domains one by one from C-terminal site, we generated four deletion mutants of Anx A4 named R1, 2, 3, and 4 (arabic figure shows the number of annexin repeat domains). Stable cell lines overexpressing each deletion mutants were established in NUGC3 cells. Chemosensitivity to platinum drugs was evaluated using the MTT assay. Results. Compared with mock transfected cells, all the four deletion mutants induced chemoresistance to both cisplatin and carboplatin. Conclusions. The deletion derivative covering only one annexin repeat domain can induce chemoresistance to platinum drugs. Further study is underway to determine the specific site for chemoresistance of Anx A4. Citation Format: Akiko Morimoto, Takayuki Enomoto, Shinya Matsuzaki, Kousuke Hiramatsu, Yutaka Ueda, Kiyoshi Yoshino, Masami Fujita, Takuhei Yokoyama, Satoshi Serada, Tetsuji Naka, Tadashi Kimura. Functional domain of Annexin A4: which domain is indispensable for chemoresistance to platinum drugs. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4057. doi:10.1158/1538-7445.AM2013-4057