Consistent detection of TLS/FUS-ERG chimeric transcripts in acute myeloid leukemia with t(16;21)(p11;q22) and identification of a novel transcript.

16;21 translocation is a recurrent primary abnormality in acute myeloid leukemia (AML). The genes involved in this translocation are ERG on chromosome 21 and TLS/FUS on chromosome 16. The rearrangement of the two chromosomes forms the TLS/FUS-ERG fusion gene and produces a consistent chimeric transcript on the der (21) chromosome. In this study, we analyzed the clinical characteristics of 19 patients with t(16;21)-AML, including 2 patients who evolved from myelodysplastic syndrome, and detected the chimeric transcripts of the TLS/FUS-ERG fusion gene in the patients during various clinical stages by the reverse transcriptase-polymerase chain reaction (RT-PCR) technique. We found that the patients with t(16;21) are characterized by a relatively younger age (median age, 22 years old), involvement of various subtypes of French-American-British classification and a poor prognosis: 18 of the 19 patients died of the disease (median survival was 16 months). Four types of TLS/FUS-ERG chimeric transcripts including a novel type were noted in the RT-PCR analysis. The novel transcript contained an additional 138 nucleotides consisting of TLS/FUS exon 8 and ERG exons 7 and 8 and had an in-frame fusion. These chimeric transcripts were consistently detectable in the samples obtained not only at diagnosis and relapse but also in short and long complete remission, suggesting that t(16;21)-AML is resistant to conventional chemotherapy. Thus, we recommend that t(16;21) should be monitored by RT-PCR even in clinical remission and the patients should be treated by other more powerful modality like stem-cell transplantation in the first remission.