ABCG1 and neoplasm: LXR agonists bind to nuclear receptors, increase the expression of cholesterol efflux transporters ABCA1 and ABCG1, and trigger the degradation of LDLR through upregulation of IDOL E3 ligase.[13, 14, 16, 17, 18] These mechanisms all work in concert to lower intracellular cholesterol levels, deprive the tumor cells of cholesterol and trigger tumor cell death in GBM.