Abstract:      Background and purpose: The expression of ERβ in triple negative breast cancer(TNBC) might be associated with good prognosis in TNBC patients. ERβ and ERα have considerable homology. FOXA1 plays an important role in ERα expression and function. The aim of this study was to analyze the expression of FOXA1 and ERβ in TNBC and the relationship between them and the clinicopathologic characteristics and prognosis. Methods: The breast cancer samples in Peking Union Medical College Hospital were collected from Nov. in 2011 to Dec. in 2013, and TNBC were screened out based on the expression of ERα, PR and HER-2. Thirty ERβ-negative samples and 30 ERβ- positive samples were selected randomly according to the ERβ expression. We used immunohistochemical method to detect the expression of FOXA1. Finally, 48 TNBC samples were obtained to analyze the results. Results: The total positive rate of FOXA1 was 35.4% (17/48). In the ERβ-positive group, the positive rate of FOXA1 was 35.7% (10/28), and in the ERβ-negative group, the positive rate of FOXA1 was 35% (7/20). The expression of FOXA1 in these 2 groups had no significant difference (P=0.83), which indicated that there was no relation between ERβ and FOXA1. The FOXA1 positive group and FOXA1 negative group also showed no significant difference in age, tumor size, and lymphatic metastasis number in axilla, tumor grade, tumor stage, NPI and DFS. However, Ki-67 showed negative correlation with FOXA1 expression (P<0.01). Conclusion: FOXA1 expression had no relationship with ERβ expression in TNBC. Ki-67 showed negative correlation with FOXA1 expression, which might hint that the proliferation of tumor cell was lower in FOXA1 positive TNBC.

Key words: Triple negative breast cancer, FOXA1, Estrogen receptor β, Ki-67