ABCG2 and breast cancer: Contrary to the above-described mechanisms, an increase in cellular ceramide (e.g., by addition of exogenous ceramide, by inhibition of the sphingomyelin synthase, by incubation with the RXR agonist bexarotene combined with the FXR antagonist guggulsterone) increased BCRP in EVs released by MDA-MB-231 breast cancer cells, concomitant with a decrease in cellular BCRP protein levels and, most likely, an increase in the accumulation of its substrates.