In BCR–ABL+ cell lines, doses chosen (with the exception of busulfan) came close to the clinically relevant dose range; in primary CML progenitors we chose a dose range of 0.1–2.5 Gy γ-irradiation and 0.2–5.0 μM busulfan or treosulfan (Figure 5) which would be feasible to be used in vivo (Körbling et al, 1986; Jacobson et al, 2001; Scheulen et al, 2000). This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.