Figure 2: ABCG2 was expressed in a minor population of SMMC-7721 cells. (a) The positive rate of ABCG2 in SMMC-7721 cells determined by flow cytometry was about 8.8% before cell sorting. P2 gate represents ABCG2 positive cells. Mouse IgG2b was used as isotype control. (b) Positive rate of ABCG2 in sorted ABCG2+/ABCG2− cells after 3 passages of culture. (c) Detection of ABCG2 protein level in freshly sorted cells by western blot. β-Actin was used as loading control. The optical density of specific bands was quantified and normalized to β-Actin. ** .