Association of Positive EBAG9 Immunoreactivity With Unfavorable Prognosis in Breast Cancer Patients Treated With Tamoxifen

作者：Ijichi Nobuhiro; Shigekawa Takashi; Ikeda Kazuhiro; Miyazaki Toshiaki; Horie Inoue Kuniko; Shimizu Chikako; Saji Shigehira; Aogi Kenjiro; Tsuda Hitoshi; Osaki Akihiko; Saeki Toshiaki; Inoue Satoshi^*

来源：Clinical Breast Cancer, 2013, 13(6): 465-470.

DOI：10.1016/j.clbc.2013.08.015

• EBAG9
• Endocrine therapy
• Immunohistochemistry
• Prognostic factor
• Tamoxifen resistance

Acquired tamoxifen resistance in breast cancer has not been fully understood. We examined immunohistochemical staining of estrogen receptor-binding fragment associated antigen 9 (EBAG9) in 100 breast cancer specimens excised from patients at surgery before tamoxifen treatment. Positive EBAG9 immunoreactivity (%26gt;50% of the total cells) was significantly associated with decreased disease-free survival. EBAG9 expression will be a prognostic factor in breast cancer patients treated with adjuvant tamoxifen therapy. %26lt;br%26gt;Introduction: Breast cancer is primarily a hormone-dependent tumor that is regulated by the status of the estrogen and progesterone receptors. We previously identified EBAG9 as an estrogen-responsive gene in MCF-7 human breast carcinoma cells. Upregulation of EBAG9 expression has been observed in several malignant tumors such as advanced breast cancers, indicating that EBAG9 might contribute to tumor progression. Patients and Methods: In the present study, we generated a monoclonal antibody against EBAG9, and then performed immunohistochemical analysis of EBAG9 expression in specimens obtained from breast cancer patients treated with tamoxifen as an adjuvant therapy. Results: EBAG9 immunoreactivity was detected in the cytoplasm of breast cancer cells and was significantly elevated in breast cancer samples from patients who relapsed during or after adjuvant tamoxifen treatment. Positive EBAG9 immunoreactivity was significantly correlated with poor patient prognosis. Conclusion: These results suggest that EBAG9 expression in tumor regions is associated with an unfavorable prognosis in breast cancer patients treated with tamoxifen.

• 出版日期2013-12