In the present study, we demonstrate the strong correlation of GPER to angiocrine gene expression in breast tumours from several large cohorts totalling 4972 patients and evaluate the role of GPER in the regulation of VEGF expression and angiogenesis in GPER-positive but ER-negative primary CAFs obtained from breast tumour patients and SKBR3 breast cancer cells. Here, ESR1 is linked to breast cancer.