GPER1 and breast cancer: Moreover, a growing body of evidence has revealed that E2 stimulation increases intracellular cAMP, thereby enhancing PKA activity in breast cancer cells25, 26; and that G-protein-coupled oestrogen receptor (E2-GPR30), which is potentially involved in breast carcinogenesis27, 28, 29, 30, 31, initiates a rapid response through adenylyl cyclase activation and cAMP accumulation, which further leads to PKA activation25.