(A) SP and MP fractions were isolated from RPMI 8226 cells by a cell sorter, and the expression of ABCG2, ABCB1, CD138 and HM1.24 was analyzed by flow cytometry. RPMI 8226 and KMS-11 cells were mixed with PBMCs from 3 healthy donors at the E/T ratio of 5, and treated with Len (3 µM) or YB-AHM (0.1 µg/mL) alone or both in combination for 24 hours. Then, flow cytometric SP analysis was performed. SP fractions were determined by Hoechst 33342 dye staining with verapamil, and gated as indicated. (B) Representative flow cytometric results are shown. The percentages of SP fractions within whole living cells are shown. (C) % change of SP fractions after the indicated treatments using PBMCs from 3 normal donors are shown. Data presented are mean ±SD (*, p<0.05; **, p<0.01).