FOXO3a associates with endogenous ER-α and ER-β. (a, b) Forkhead box class O (FOXO)3a interacts with endogenous ER-α. Panel a: total lysates of MCF-7 cells with 17β-estradiol (E2) were subjected to immunoprecipitation (IP) with an anti-FOXO3a (positive control) or negative control IgGs (lanes 2 and 3) or anti-estrogen receptor (ER)-α (lane 4), followed by immunoblotting (IB) with an anti-FOXO3a antibody. Panel b: the same lysates of MCF-7 cells with E2 were subjected to reciprocal IP with an anti-FOXO3a antibody (lane 1) or a negative control IgG (lanes 2 and 3) or an anti-ER-α (positive control) followed by IB with an anti-ER-α. (c, d) FOXO3a interacts with endogenous ER-β. Panel c: total lysates of MCF-7 with E2 were subjected to IP/IB (IP: control IgG or anti-FOXO3a [positive control] or anti-ER-β (lane 4); IB: anti-FOXO3a). Panel d: total lysates of MCF-7 with E2 were subjected to a reciprocal IP/IB (IP: control IgG or anti-ER-β [positive control] or anti-FOXO3a [lane 4]; IB: anti-ER-β).