ABCB1 and cancer: As compared with non-stem cancer cells, CSCs exhibit much more active work of the reserpine- or verapamil-sensitive ABCB1 and ABCG2 transporters, which enables the use of flow cytometry for identification and isolation of the CSC fractions as cells more effectively excluding Hoechst 33342 dye or Rhodamine 123 dye (the so-called “side population” of less stained cells or SP cells) [1,3,10].