ESR1 and breast cancer: Indeed, in different breast cancer models, it was described that the 27-hydroxycholesterol (27-OHC), produced by the CYP27A1 enzyme, binds and interacts with both LXRβ and the estrogen-receptor (ER)-α and consequently promotes tumor progression, not only by direct effects on proliferating cancer cells but also by inducing high rates of HSC mobilization and differentiation of immunosuppressive granulocytes [193,194,195].