GPER1 and breast cancer: However, G1 showed a specific effect on GPER stimulation indicating in both knockdown of GPER in cancer cell lines which improved cell proliferation and in vivo experiments on tumor xenograft mice models of estrogen receptor (-) BC cells [23], HCT116 CRC [12] and ASG or SNU-216 gastric cancer [44] where tumor size is reduced by G1.