BCR-ABL–induced senescence contributes to the maintenance of CML LICs. (A) p53 gene expression in BM. Total RNA was extracted from the BMs obtained from DKO-derived LIC recipients 3 weeks after the transplantation or from age-matched untreated mice and subjected to qRT-PCR (n = 4). The expression level was calculated relative to Gapdh gene and normalized to the averaged value of control. (B) Quantitative assessment of SPiDER-β-galactosidase activity in CML BM. Total BM cells were obtained from the recipients of DKO mouse-derived LICs 3 weeks after the BM transplantation. BCR-ABL⁺ or BCR-ABL⁻ cells were purified from the total BM cells. SPiDER-β-galactosidase activity was determined in each purified cell fraction, and normalized to the averaged value of BCR-ABL⁻ cells (n = 4). (C) Survival of recipients transplanted with BCR-ABL–transduced WT or DKO LICs. WT mice received 500 LICs from WT or DKO mice, and their survival rates were then evaluated (n = 10). (D) Survival of secondary transplantation recipients. WT mice received 5 × 10⁴ lineage⁻c-kit⁺ cells (percentages of LICs in WT and DKO donor cells were 11.9% ± 3.8% and 13.7% ± 3.6%, respectively) obtained from the recipients of the primary transplantation 17 days after the transplantation, and their survival rates were then evaluated (n = 10). LIC numbers in the BM of recipients of the primary (E) and secondary (F) transplantation. LIC numbers in the BM of recipients were determined 20 and 30 days after the primary and secondary transplantation, respectively (n = 4). (G) GFP⁺KLS⁺ cell numbers in the BM of recipients 20 days after secondary BM transplantation of control GFP-transduced KL⁺ cells. (n = 4). Data are presented as the mean ± SD. Statistical significance was evaluated using the 2-sided Student t test (A-B,E-G). Comparison of survival data were performed using log-rank test (C-D). **P < .01.