CD25⁺F⁻LSK cells retain higher LIC capacity than CD25⁻F⁻LSK cells. (A) Survival curves of secondary recipients injected with BCR-ABL⁺CD25⁺F⁺LSK (n = 4), CD25⁺F⁻LSK (n = 13), and CD25⁻F⁻LSK cells (n = 17). (B) Expansion capacity of CD25⁺F⁻LSK or CD25⁻F⁻LSK cells ex vivo. Left, Cell numbers of indicated fractions; right, representative profiles (means ± SD, n = 4). (C) Experimental design. BCR-ABL⁺CD25⁺LSK or BCR-ABL⁺CD25⁻LSK cells were transplanted into lethally irradiated recipient mice. (D) Survival curves of the CD25⁺LSK (n = 8) and CD25⁻LSK (n = 16) groups after transplantation. (E-G) Spleen weight (E), spleen cell number (F), and percentage of BCR-ABL⁺ cells in spleens (G) of the CD25⁺LSK (n = 4) and CD25⁻LSK groups (n = 11) created in panel C were examined 11 days after transplantation (means ± SD). (H) Limiting-dilution analysis of the leukemia-initiating ability of the CML LIC population. Seven mice in each group (CD25⁺LSK or CD25⁻LSK) received transplants with each dosage of cells (70, 700, or 7000). **P < .01.