To determine whether a truncated BTG1 mRNA was expressed from the rearranged allele, RT-PCR using breakpoint-flanking primers was performed on three BCP-ALL cell lines with a BTG1 deletion (380, REH and SUP-B15 with deletions II, III and IV, respectively) and two cell lines that are BTG1 deletion negative (Nalm6 and RS4;11) (Figure 3). Here, BTG1 is linked to acute lymphoblastic leukemia.