ERα increases endometrial cancer cell resistance to cisplatin via upregulation of BAG3

Endometrial cancer is a leading cause of cancer-associated mortality in women and has a poor prognosis in advanced stages. Our previous study revealed that BCL-2-associated athanogene 3 (BAG3) may contribute to enhancing cell viability through downregulation of microRNA (miR)-29b in endometrial cancer cell lines. In addition, a relationship between estrogen receptor α (ERα) and BAG3 was recently reported in several cancer cell types. The present study investigated the relationship between ERα and BAG3 in endometrial cancer cell lines. The results demonstrated that exogenous ERα overexpression enhanced BAG3 expression in the EMTOKA endometrial cancer cell line, which does not endogenously express ERα, but had no effect on BAG3 expression levels in the Ishikawa cell line, which does endogenously express ERα. In addition, ERα overexpression suppressed miR-29b expression and enhanced the expression of Mcl-1, a mediator situated downstream of BAG3, in EMTOKA cells, but not Ishikawa cells. ERα overexpression also enhanced EMTOKA, but not Ishikawa, endometrial cancer cell viability in the presence of cisplatin. These findings suggested that ERα may contribute to enhancing endometrial cancer cell resistance to anticancer agents through BAG3 overexpression.