ESR1 and ovarian carcinoma: The use of ERα-positive BG-1 ovarian carcinoma cells showed that both 17β-estradiol and G1 (the GPER-1 agonist) induced c-fos expression and up-regulated cyclins D1, E and A. Both GPER1 and ERα were required for c-fos stimulation and ERK activation in response to either G1 or 17β-estradiol.