ESR1 and breast cancer: We and others have previously shown that 7-dehydrocholesterol and vitamin K3 inhibit melanoma cell proliferation and induce apoptosis via AKT /MAPK signaling pathways [61–63], while Nelson et al. found that the cholesterol metabolite 27HC promoted tumor growth and metastasis in mouse models of breast cancer by serving as a partial agonist for the estrogen receptor and liver X receptor [27].