ABCG2 and cancer: We previously reported that troglitazone (TRG), an insulin sensitizer of the thiazolidinedione class used in the treatment of DM2 (metformin is an unrelated biguanide insulin sensitizer), reduced the protein levels of the ABC transporter class of drug efflux pumps elevated in multiple aggressive cancer cells (MDR-1 and BCRP in MCF7 DOXRes, and MDR-1 in K562 DOXRes cells) [15].