Expression of the proto-oncoprotein breast cancer nuclear receptor auxiliary factor (Brx) is altered in eutopic endometrium of women with endometriosis

Objective: To evaluate the expression of estrogen receptor alpha (ERα), estrogen receptor beta (ERβ), and breast cancer nuclear receptor auxiliary factor (Brx) in eutopic endometrium of normal women and women with endometriosis. Design: Prospective observational study. Setting: Tertiary care and research center. Patient(s): Twenty-nine women with endometriosis and 35 healthy ovulatory volunteers of similar ages. Intervention(s): Endometrial biopsy. Main Outcome Measure(s): Expression of immunohistochemical staining intensity and localization of ERα, ERβ, and Brx proteins in eutopic endometrium during the menstrual cycle. Result(s): Expression of ERα and ERβ was highest in the proliferative phase and was similar in both groups. Brx expression differed between healthy volunteers and those with endometriosis. During the proliferative phase, immunostaining intensity of Brx was greater in both the glandular and the stromal compartments of biopsies from patients with endometriosis compared to healthy volunteers; nuclear stromal Brx staining was more common in patients with endometriosis. Conclusion(s): The spatiotemporal expression of Brx was altered in eutopic endometrium of women with endometriosis. These findings suggest a fundamental alteration in the endometrium of women who have endometriosis. The role of Brx in ectopic implantation of endometrium deserves further study.