Objective This study investigated the feasibility of screening residual normal ovarian tissues based on the expression of Bmi-1 and EZH2 in tissues adjacent to orthotopic ovarian carcinomas in nude mice. Methods The human epithelial ovarian cancer cell line OVCAR3 was grown in subcutaneous tissues and the tumor tissues were orthotopically implanted. The expression levels of Bmi-1 and EZH2 were detected by immunohistochemical staining and RT-PCR in cancer tissues, proximal and remote tissues with respect to the cancer tissues, and normal ovarian tissues of nude mice.Results Thirty-five ovarian tissue samples with normal biopsy results were obtained from 40 cases of human epithelial ovarian cancer in the nude mice in which the tumor tissues were orthotopically implanted. Bmi-1 and EZH2 expression levels were lower in proximal paraneoplastic tissue samples than in cancer tissue samples(P < 0.05) and higher than in remote paraneoplastic tissue samples(P < 0.01). No significant difference was found in the expression levels of Bmi-1 and EZH2 using immunohistochemistry among residual normal ovarian tissues obtained from orthotopically implanted models that differed in severity. The expression of Bmi-1 and EZH2 was negative in 20 normal ovarian tissue samples.Conclusion The expression levels of Bmi-1 and EZH2 were reduced with increasing distance from the cancer tissues. Negative expression of these tumor-associated genes can be used as a standard for the screening of normal ovarian tissues adjacent to tumor tissues. Normal ovarian tissues can be obtained from the tissues adjacent to tumors. Objective This study investigated the feasibility of screening residual normal ovarian tissues based on the expression of Bmi-1 and EZH2 in tissues adjacent to orthotopic ovarian carcinomas in nude mice. Methods The human epithelial ovarian cancer cell line OVCAR3 was grown in subcutaneous tissues and the tumor The tissues were orthotopically implanted. The expression levels of Bmi-1 and EZH2 were detected by immunohistochemical staining and RT-PCR in cancer tissues, proximal and remote tissues with respect to the cancer tissues, and normal ovarian tissues of nude mice. Results Thirty-five ovarian tissue samples with normal biopsy results were obtained from 40 cases of human epithelial ovarian cancer in the nude mice in which the tumor tissues were orthotopically implanted. Bmi-1 and EZH2 expression levels were lower in proximal paraneoplastic tissue samples than in cancer tissue samples ( P <0.05) and higher than in remote paraneoplastic tissue samples (P <0.01). No significant difference w as found in the expression levels of Bmi-1 and EZH2 using immunohistochemistry among residual normal ovarian tissues obtained from orthotopically implanted models that differed in severity. The expression of Bmi-1 and EZH2 was negative in 20 normal ovarian tissue samples. Confluence The expression levels of Bmi-1 and EZH2 were reduced with increasing distance from the cancer tissues. Negative expression of these tumor-associated genes can be used as a standard for the screening of normal ovarian tissues adjacent to tumor tissues. tissues adjacent to tumors.