Abstract 3298: Elf3 as negative regulation for epithelial-mesenchymal transition in ovarian cancer

Abstract

Abstract Objective: To delineate the role of Elf3, an epithelially restricted member of the ETS transcription factor family, in regulating epithelial-mesenchymal transition in malignant serous ovarian epithelial cells. Methods: Based on microarray study, Elf3 was indentified as one of the significantly upregulated transcription factor encoded genes in the malignant serous ovarian epithelia compared with that in normal ovarian surface epithelium. To further evaluate differential Elf3 expression in serous epithelia, immunolocalization of Elf3 was performed and clinical significance of nuclear Elf3 expression was evaluated by Cox and Kaplan-Meier analyses on patients with HGSC. In order to delineate the function of Elf3, expression levels of Elf3 in various ovarian cancer cell lines and normal human ovarian surface epithelial cells (HOSE) were evaluated by western blot analysis. Low Elf3 expresser, OVCA429 and SKOV3 ovarian cancer cells were stably transfected with full-length Elf3 to evaluate its effect on cell growth. To investigate the role of Elf3 in epithelial-mesenchymal transition, expression level, and subcellularlocalization of various transition markers were evaluated by western blot analysis and confocal microscopy. Results: Immunohistochemistry showed that nuclear Elf3 expression was significantly higher in benign, borderline and low-grade serous epithelia compared to that in high-grade serous epithelia, and down-regulation of Elf3 in advanced stage high-grade serous ovarian cancer was significantly associated with poor overall survival, suggesting that Elf3 is a favorable prognostic marker of this disease. Western blot and confocal microscopy confirmed that nuclear Elf3 expressed in ovarian cancer cells in vitro but not in normal HOSE. Cell proliferation assay demonstrated a significant decrease in growth rate in OVCA429 and SKOV3 cells transfected with Elf3 compared with that of the vector control (46.3%, p<0.001). Bright field microscopy showed that Elf3 overexpressing SKOV3 cells demonstrated mesechymal-epithelial transition. Cells were less elongated and gained cobble stone-like morphology. Forced expressing Elf3 in SKOV3 cells also induced translocation of Snail from the nucleus to the cytoplasm and β -catenin from the nucleus to the cell membrane. In addition, western blot analysis detected increased expression of cell-cell adhesion protein E-cadherin, and decreased expression of mesechymal elements N-cadherin, Slug and Vimentin in SKOV3 cells transfected with Elf3 compared with that of the mock transfectant. Conclusions: Our data suggest that Elf3 is a negative regulator of epithelial-mesechymal transition and demonstrates growth inhibitory effect in malignant ovarian epithelial cell lines. These observed supports our pervious clinical findings that nuclear Elf3 expression is associated with improved patient survival. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3298.