BMI1 expression and probabilities of overall survival. (A) BMI1 expression in CD34⁺ immunomagnetically selected hematopoietic progenitors from diagnosis in a cohort of 64 CP CML patients, showing different disease evolution patterns: patients who developed blast crisis (BC) within 3 years of diagnosis were defined as having “aggressive disease” (n = 17), whereas those who survived for longer than 7 years prior to the onset of BC were defined as having “indolent disease” (n = 23). Patients who survived between 3 and 7 years without developing BC were categorized as having “intermediate disease” (n = 24). There was a significant difference in BMI1 expression among the 3 groups (P = .01 when comparing all 3 groups), between patients with “intermediate” and “aggressive” disease (P = .01), and between “indolent” and “aggressive” disease (P = .01) but not between “indolent” versus “intermediate” disease (P = not significant [NS]). The median age at diagnosis of the selected patients was 45.7 years (range, 17.6-68.3 years). The male-female ratio was 1.8:1 (41 males, 23 females). The majority of patients were diagnosed in the preimatinib era. (B) Overall survival according to BMI1 expression as assessed by Q-RT/PCR in the whole cohort of the above 64 patients. The median gene expression level is used to segregate the patients into a “low BMI1” group (BMI1 expression < median) and a “high BMI1” group (BMI1 expression > median). (C) Cox multivariate analysis yielded a model with the combination of low BMI1 and high proteinase-3 (PR3) expression as predictive of significantly improved survival. The median gene expression levels were used to segregate the patients into a “low BMI1-high PR3” group (BMI1 expression < median and PR3 > median; n = 21) and a “high BMI1-low PR3” group (BMI1 expression > median and PR3 < median; n = 43). Values of genes represent the Q-RT/PCR expression as a ratio of the gene of interest to the GAPDH control gene.