Molecular detection of TEL-AML1 transcripts as a diagnostic tool and for monitoring of minimal residual disease in B-lineage childhood acute lymphoblastic leukemia

The chromosomal translocation t(12;21) (p12;q22) which results in the TEL-A ML1 fusion gene is the most frequent genetic rearrangement in childhood B-l ineage acute lymphoblastic leukemia (ALL). The rearrangement in this locus, however, is only rarely observed by routine karyotypic analysis. We establ ished a nested-reverse transcriptase-polymerase chain reaction (nested-RT-P CR) technique for the detection of the TEL-AML1 transcript, and used this t o investigate the incidence of the rearrangement, and to characterize the d isease present in TEL-AML1-positive B-lineage ALL patients, The TEL-AML1 fu sion transcript was detected in nine of fourteen patients, These patients w ere relatively homogeneous in that they were young and had low presenting l eukocyte counts, both features of which are associated with a favorable pro gnosis. Furthermore, we could detect the TEL-AML1 transcript in the periphe ral blood of t(12;21)-positive patients and we used this to assess minimal residual disease (MRD) in patients during chemotherapy, The data demonstrat e that nested-RT-PCR is a suitable tool for diagnosing t(12;21)-positive AL L, that these patients constitute a clinically distinct subgroup of ALL pat ients, and that the method could also be used to monitor MRD in these patie nts.