GPER1 and cancer: The GPER-specific agonist G1, which is wildly employed in the study of numerous cancer types (12, 13, 18–25, 27–31, 34–37), shows extremely high affinity for GPER, but not for classical ERs (14, 38, 39) and 25 other important G-protein coupled receptors (GPCRs) (40, 41), and G1 also had no activity in GPER-knockout mice (42).