Cell fractionation and immunocytochemistry revealed GPR30 to be localized at the plasma membrane in both the SKBR3 (GPR30+, ERα−, ERβ−) and MDA-MB-231 (GPR30−, ERα−, ERβ+; GPR30 overexpression) breast cancer cell lines (77). Here, ESR1 is linked to breast carcinoma.