Objective. The estrogen-responsive ring finger protein (Efp) gene, one of estrogen receptor (ER) target genes, is considered to be essential for estrogen-dependent cell proliferation. To understand the estrogenic action on ovarian cancer, we studied the relationships between Efp and ERs expressions and the correlations of Efp expression with clinicopathological parameters in epithelial ovarian cancer. Methods. The protein expressions for Efp, ERα and ERβ were examined by immunoblotting in 12 ovarian cancer cell lines. Efp mRNA expressions were evaluated by quantitative RT-PCR in 12 ovarian cancer cell lines. A total of 100 surgical specimens diagnosed as epithelial ovarian cancer were examined immunohistochemically using antibodies for Efp, ERα and ERβ. Results. Efp protein was detected in 8 out of 12 cell lines. In Efp protein-positive cell lines, Efp mRNA was expressed higher than that in negative (P = 0.021). All of the Efp protein-positive cell lines simultaneously expressed either ERα or ERβ protein. By immunohistochemical staining, Efp immunoreactivity was detected in 63 out of 100 ovarian cancer specimens and positive signals were in the cytoplasm of carcinoma cells. There were significant correlations between Efp and ERα, ERβ immunoreactivity (Efp and ERα, P = 0.022; Efp and ERβ, P = 0.032). Efp expression was significantly higher in a subgroup with serous adenocarcinoma (P = 0.010) and with advanced disease (P = 0.026). No significant relationship was detected between Efp immunoreactivity and overall survival. Conclusion. The expression of Efp was detected in human epithelial ovarian cancer and high expression of Efp was correlated with advanced disease and serous adenocarcinoma, and ERs status.
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