Two studies by Plaza Menacho et al. [58] and Morandi et al. [7] have shown that GDNF stimulation of MCF7 breast cancer cells induces ER phosphorylation at residue S118, which has been associated with Tamoxifen resistance in vitro and relapse following Tamoxifen treatment in patient samples [67]. Here, ESR1 is linked to breast carcinoma.