BCR-ABL induces oncogene-induced senescence (OIS) in CML mouse model. (A-B) Quantitative assessment of SPiDER-β-galactosidase activity in BM obtained from CML mice (A)  and mice that were transplanted with GFP-transduced KLS⁺ cells (B). BCR-ABL⁺ or BCR-ABL⁻ cells were purified from total BM cells obtained from LIC recipients 3 weeks following the BM transplantation (n = 5). GFP⁺ or GFP⁻ cells were purified from the total BM cells 18 days after the BM transplantation with GFP-transduced KLS⁺ cells (n = 4). SPiDER-β-galactosidase activity was determined in each purified cell fraction, and normalized to the averaged value of BCR-ABL⁻ cells or GFP⁻ cells. (C) Immunohistochemical analysis of p16 and p21 expression in BM. BMs were obtained from LIC recipients 3 weeks after the transplantation or from age-matched untreated mice, and immunostained with either anti-p16 or anti-p21 antibodies. Representative results from 5 mice are shown on the left (original magnification, ×100; scale bar, 50 μm). Positive areas were quantified in 5 individual animals as described in "Materials and methods" (right). (D) Expression levels of senescence-related genes in BM. Total RNA was extracted from BMs obtained from the LIC recipients 3 weeks after the transplantation or from age-matched untreated mice, and subjected to qRT-PCR (n = 5). The expression level was calculated relative to Gapdh gene and was subsequently normalized to the averaged value of the control. Data are presented as the mean ± standard deviation (SD). Statistical significance was evaluated using the 2-sided Student t test. *P < .05; **P < .01. N.S., not significant.