Although the action of estrogens has been traditionally explained by the binding to and transactivation of the
nuclear estrogen receptor (ER)α and ERβ, recently the G protein-coupled receptor GPR30/GPER has been involved in the
rapid estrogen signaling. We investigated the ability of two original molecules, which were named GPER-L1 and GPERL2,
to bind to and activate the GPER transduction pathway in cancer cells. Competition assays, docking simulations,
transfection experiments, real-time PCR, immunoblotting, gene silencing technology and growth assays were performed
to ascertain the selective action of GPER-L1 and GPER-L2 in activating the GPER-mediated signaling. Both compounds,
which did not show any ability to bind to and activate the classical ERs, were able to bind to GPER and to trigger the
rapid activation of the GPER/EGFR/ERK transduction pathway which led to the up-regulation of GPER-target genes.
Notably, GPER-L1 and GPER-L2 induced the proliferation of SkBr3 breast and Ishikawa endometrial cancer cells at nM
concentrations through GPER, hence providing further evidence on their capability to elicit relevant biological responses
mediated by GPER. The identification and characterization of these novel compounds as selective GPER agonists
represent a valuable tool to further dissect the pharmacology of this novel estrogen receptor and to better differentiate the
specific functions elicited by each estrogen receptor subtype in cancer cells.