Abstract 1856: Functional analysis of annexin A4 and the implication in ovarian clear cell adenocarcinoma (OCCA) phenotypes

Abstract

Abstract Backgrounds: Ovarian carcinoma is the first leading cause of death in gynecologic malignancies. Unlike the histological majority, serous adenocarcinoma, ovarian clear cell adenocarcinoma (OCCA), the second most histology in Japan, is mostly resistant to the conventional chemotherapy. Patients with advanced OCCA have poorer prognosis than serous histology. By searching molecular characteristics for OCCA, we found and have reported annexin A4 as a protein much more expressed in OCCA than in other ovarian malignancies. Moreover, we found two types of annexin A4; the acidic and the basic forms in 2D-PAGE. The objective of this study is to elucidate the still unclear annexin A4 function in relation to the type-difference. Methods: Stable annexin A4 knock-down (KO) clones were established for OCCA cell lines, OVISE and OVTOKO by expression of shRNA targeting annexin A4 mRNA. Changes in several phenotypes in vitro, including cell growth, sensitivity for chemotherapeutics such as paclitaxel (PTX) and carboplatin (CBDCA), and migration/invasion activity were evaluated in these KO clones. Amounts of the two types of annexin A4 were estimated by 2D-PAGE followed by Western blot. In addition, OCCA clinical specimens were collected under the approval of the review board of our institute, and proteins extracted from frozen tumor tissues were subjected to the same 2D-PAGE analysis. Results: Cell growth and IC 50 for CBDCA were significantly decreased in annexin A4-KO-OVTOKO, while migration and invasion were suppressed in annexin A4-KO-OVISE. No other phenotypes were significantly altered by annexin A4-KO. The acidic annexin A4 was predominant in OVTOKO, and the basic in OVISE. As for the clinical tissues, the ratio of the two types of annexin A4 on 2D-PAGE showed diversities as patients. Implications: This is the first report to elucidate the annexin A4 function in OCCA cells by knocking down strategy. The result that annexin A4 may make cells more resistant to CBDCA is comparative to the previous report in which forced overexpression of annexin A4 in ovarian serous adenocarcinoma cells led to resistance to CBDCA. Because the phenotypic changes by annexin A4-KO found in OVTOKO and OVISE were not the same, one could speculate that the two different annexin A4 proteins have somewhat different functions at least in vitro; that is, the acidic form of annexin A4 might have a significant role in proliferation and CBDCA drug resistance, as the basic form might be related to migration / invasion ability. To elucidate the clinicopathological significance of annexin A4 in OCCA, analysis of the subtype difference will be meaningful. 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 1856. doi:1538-7445.AM2012-1856