GPER1 and cancer: Additionally, BPA treatment (1 μM) increased the proliferation of breast tumor-derived fibroblasts, in addition to SKBR3 breast cancer cells, and the conditioned medium from the BPA-treated fibroblasts enhanced the migration of SKBR3 cells in a GPER-dependent manner [26], suggesting that BPA may also affect the secretion of factors that promote cancer cell migration in fibroblasts.