ESR1 and hepatocellular carcinoma: In this cell line a greater anti-proliferative effect of tamoxifen is observed in comparison with the other cell lines (MDA MB 231 and HCC 1937), reaching a 76.12% decrease in cell proliferation, this is because tamoxifen is an antiestrogenic drug that acts by binding with the estrogen receptor competing with estrogen and nullifying the biological effects of these molecules, the tamoxifen-estrogen receptor complex interacts with nuclear DNA and blocks the action of estrogen by inhibiting the production of growth factors, which negatively affects cell proliferation17.