GPER1 and cancer: The G protein-coupled receptor 30 (GPR30), which mediates the nongenomic signaling of 17-beta-estradiol (E2), is widely expressed in cancer cell lines and primary malignant tumors of the breast, endometrium, prostate and lungs [16,17], and is strongly associated with the proliferation, invasion, metastasis, and drug resistance of various cancer cell lines [18-24].