IFN-α upregulates CEBPB and promotes exhaustion of CD34⁺CML stem cells derived from CML-CP patients. (A) Effects of IFN-α on CEBPB and CEBPA mRNA expression in lin⁻ CD34⁺ cells obtained from 5 CML patients. CEBPB and CEBPA mRNA levels were normalized against the corresponding level of GAPDH mRNA. Purified cells were subjected to quantitative RT-PCR after IFN-α treatment of 0.5 or 3 hours in vitro. Data from 5 independent experiments are shown as scatter plot. Bold horizontal lines, mean values from 3 or 5 samples; vertical lines, SD of each group of data. *P < .02; **P < .01. (B) Number of total colonies derived from lin⁻ CD34⁺ BM cells from 5 CML patients. IFN-α was added at the indicated concentrations shown as red (control), blue (100 U/mL), or green (500 U/mL) bars. Experiments were all performed in triplicate; data are means ± SD. Differences between controls (IFN-α = 0 U/mL) and test samples were statistically analyzed. *P < .05; **P < .01. (C) Changes in colony types in response to IFN-α shown as pie charts: blue, myeloid colonies; red, erythroid colonies; and green, mixed colonies. Data are means of triplicates. Actual mean and SD values and statistical analysis of the percentage of each classification are shown in supplemental Table 7. (D) Flow cytometric analysis of the first-round colonies. Representative dot plots for UPN3 are shown. Dot plots indicate the percentage of CD66b⁺ cells in each sample. Data are means ± SD. *P < .05; **P < .01. n.s., not significant; UPN, unique patient number.