Coexpression of <b><i>NUP98/TOP1</i></b> and <b><i>TOP1/NUP98</i></b> in de novo Acute Myeloid Leukemia with t(11;20)(p15;q12) and t(2;5)(q33;q31)

The t(11;20)(p15;q11∼12) translocation is a very rare but recurrent cytogenetic aberration that occurs in myelodysplastic syndrome/acute myeloid leukemia (MDS/AML). This translocation was shown to form a fusion gene between <i>NUP98</i> at 11p15 and <i>TOP1</i> at 20q12. Here, we describe a new case of de novo AML M2 with t(11;20) which was associated with another balanced translocation. An 81-year-old man was admitted to undergo salvage therapy for relapsed AML. G-banding and spectral karyotyping showed 46,XY,t(2;5)(q33;q31),t(11;20)(p15;q12)[20]. Expression of the <i>NUP98/TOP1</i> fusion transcript was confirmed: <i>NUP98</i> exon 13 was in-frame fused with <i>TOP1</i> exon 8. The reciprocal <i>TOP1/NUP98</i> fusion transcript was also detected: <i>TOP1</i> exon 7 was fused with <i>NUP98</i> exon 14. After achieving hematological complete remission, the karyotype converted to 46,XY,t(2;5)(q33;q31)[19]/46,sl,t(11;20)(p15;q12)[1]. FISH analysis demonstrated that the 5q31 breakpoint of t(2;5) was centromeric to <i>EGR1</i>. In all 10 cases described in the literature, the <i>NUP98</i> exon 13/<i>TOP1</i> exon 8 fusion transcript was expressed, indicating that it may be responsible for the pathogenesis of MDS/AML with t(11;20). On the other hand, the <i>TOP1/NUP98</i> transcript was coexpressed in 4 cases of de novo AML, but not in 3 cases of therapy-related MDS. Thus, this reciprocal fusion may be associated with progression to AML.