ESR1 and hepatocellular carcinoma: GPER1 acts as a tumor promoter in thyroid cancer (Manfroi et al., 2020), hepatocellular carcinoma (Chaturantabut et al., 2019), and renal cell adenocarcinoma (Feldman et al., 2016), whereas GPER1 can inhibit the proliferation of lung cancer (Narayanankutty, 2019), prostate cancer (Salata et al., 2019), and estrogen receptor-negative breast cancer cells (Wei et al., 2014).