Promising Perspectives of the Antiproliferative GPER Inverse Agonist ER alpha 17p in Breast Cancer

The estrogen receptor alpha (ER alpha) corresponds to a large platform in charge of the recruitment of a panel of molecules, including steroids and related heterocyclic derivatives, oligonucleotides, peptides and proteins. Its 295-311 region is particularly targeted by post-translational modifications, suggesting that it could be crucial for the control of transcription. In addition to anionic phospholipids, the ER alpha 295-311 fragment interacts with Ca2+-calmodulin, the heat shock protein 70 (Hsp70), ER alpha and possibly importins. More recently, we have demonstrated that it is prone to interacting with the G-protein-coupled estrogen receptor (GPER). In light of these observations, the pharmacological profile of the corresponding peptide, namely ER alpha 17p, has been explored in breast cancer cells. Remarkably, it exerts apoptosis through GPER and induces a significant decrease (more than 50%) of the size of triple-negative breast tumor xenografts in mice. Herein, we highlight not only the promising therapeutic perspectives in the use of the first peptidic GPER modulator ER alpha 17p, but also the opportunity to modulate GPER for clinical purposes.