The expression and prognostic role of EBP1 and relationship with AR in HER2+ breast cancer.

Human epidermal growth factor receptor (HER)-2 positive (HER2) breast cancer (BC) has a poor survival rate and is more aggressive in nature. HER2-targeting agents could be beneficial for patients with HER2 BC. In addition, targeted therapy and chemotherapy have been successfully used. However, a few patients are resistant to treatment. ErbB3 binding protein 1 (EBP1) binds to HER3 and inhibits the proliferation and invasive potential of tumor cells. However, its role in HER2 BC has not been demonstrated. In this study, we aimed to analyze the relationship between androgen receptor (AR) and EBP1 expression in HER2 BC. A total of 282 cases (140 cases of HER2 invasive BC and 142 HER2-negative invasive BC) were included in this study. We performed immunohistochemistry (IHC) to analyze the expression of AR and EBP1; thereafter, we evaluated the relationship between these two biomarkers and estrogen receptor (ER), progesterone receptor (PR), HER2, p53, Ki67 expression, and other clinicopathological parameters. Of the HER2 cases, 67 (47.9%) showed high expression of EBP1 (EBP1) and 73 (52.1%) showed low/no expression of EBP1 (EBP1). EBP1 expression was correlated with AR expression, histological grade, and lymphatic metastasis (p < 0.001, < 0.001, and 0.013, respectively). Kaplan-Meier analysis revealed that AR and EBP1 group had poorer overall survival (OS) and disease-free survival (DFS) compared with other groups (AR and EBP1, AR and EBP1, and AR and EBP1). AR and EBP1 expression were independent prognostic factors for OS and DFS in HER2+ BC. This study showed the clinicopathological role of EBP1 and AR in HER2+ BC. Targeting EBP1 may be an effective treatment strategy for patients with AR HER2 BC.