Suppression of G Protein-coupled Estrogen Receptor 1 (GPER1) Enhances the Anti-invasive Efficacy of Selective ER beta Agonists

Background/Aim: G protein-coupled estrogen receptor 1 (GPER1) is often over-expressed in triple negative breast cancer (TNBC). GPER1 is responsible for many of the non-genomic, membrane-initiated effects of estrogens. Therefore, we have analyzed the effects of GPER1 knockdown using specific siRNA. Materials and Methods: Transient GPER1 silencing was conducted using RNA interference and confirmed by RT-PCR and western blot. Viability of human breast cancer cell lines MDA-MB 231 and HCC 1806 was tested using AlamarBlue assay. Cell invasion was analyzed by assessment of cell migration rate through an artificial basement membrane in a modified Boyden chamber. Results: Viability of both cell lines was slightly decreased after suppression of GPER1 expression. Knockdown of GPER1 resulted in a significantly reduced invasion of the TNBC cells. The anti-invasive effect of selective ER beta agonists was significantly stronger after knockdown of GPER1 expression. In addition, the efficacy of tamoxifen treatment was significantly increased after suppression of GPER1 expression. Conclusion: Suppression of GPER1 reduced the metastatic behavior of TNBC cells, improved the anti-invasive efficacy of selective ER beta agonists and sensitized cells to 4OH-tamoxifen.