ERα and ERβ co-expression: An indicator of aggressive tumors and hormonal sensitivity.

The estrogen receptors (ERs) ERα and ERβ are important factors in breast cancer progression. Nevertheless, the molecular interplay between ERα and ERβ and its clinical significance in breast cancer is controversial. The establishment of a clear association is required; therefore, the current study analyzed the expression patterns of ERα and ERβ in 32 breast tumor tissues using reverse transcription-quantitative polymerase chain reaction. Furthermore, human epidermal growth factor receptor 2 (HER2) and the Ki-67 status were detected by immunohistochemistry. The results revealed that the ERα and ERβ expression rates recorded were 68 and 65%, respectively. The ERα:ERβ ratio exhibited a decline along with disease progression. ERα and ERβ were found to be negatively correlated with HER2 status but positively correlated with Ki-67. Co-expression of ERα and ERβ was associated with breast cancer aggressiveness, including higher histological grade and positive nodal status, which commonly occur following the menopause. In addition, in cases where ERβ was coexpressed with ERα, HER2 expression was frequently found to be negative, whereas the Ki-67 index was upregulated. These data suggest that ERα and ERβ co-expression may be an indicator of tumor aggressiveness and the sensitivity of hormonal therapy via the downregulation of HER2.