ABCG2 and cancer: ATP generated by the respiration of mitochondria in the proximity of the plasma membrane and transported from the mitochondrial matrix to the cytosol nearby plasma membrane produces a local rise of ATP level for the active transporter’s need (Linton and Higgings, 2007), thus explaining why mitochondrial and not glycolytic ATP preferentially fuels ABC transporter activity in chemoresistant cancer cells (Linton and Higgings, 2007).