ABCG2 and breast cancer: A study by Kong et al. demonstrated that treating MDA-MB-231 BC cells with a combination of guggulsterone (GS), an antagonist of farnesoid X receptor (FXR), and bexarotene (BXT), an agonist of retinoid X receptor (RXR), reduced BCRP expression in cells by increasing the secretion of exosomes containing BCRP by elevating ceramide, which induces exosome secretion.