GPER1 and endometrial cancer: GPER mediates the proliferative effects of estrogen and tamoxifen in endometrial cancer cells through EGF-R transactivation leading to the activation of ERKs and PI3K pathways (Vivacqua et al., 2006a; Prossnitz et al., 2008b; He et al., 2009, 2012; Du et al., 2012a; Lappano et al., 2012; Wei et al., 2012).