TEL/AML1 Translocation, Dual Fusion LPH 012

The TEL1 (or ETV6 - Erythroblastosis Variant Gene 6 translocation, ETS) / AML1 (or RUNX1 - Runt-Related Transcription Factor 1) fusion is brought about by the cytogenetically invisible t(12;21) translocation.

The rearrangement is the most common in childhood B-ALL and has been detected using FISH in around 21% of cases,¹ compared to a pick-up rate of 0.05% by conventional cytogenetics. The translocation is associated with a favourable outcome though it has also been implicated with late relapse. TEL1 has also been shown to be deleted in some children with ALL where the deletion is cytogenetically invisible but where there is loss of heterozygosity (LOH) of chromosome 12p12-13. This deletion is often associated with a TEL1/AML1 translocation². Both the TEL1 and AML1 genes encode transcription factors, but TEL1 has been shown to be required specifically for proper transcription during haematopoiesis within the bone marrow. The translocation results in an almost intact AML1 protein fused with part of the TEL1 protein resulting from breakpoints beyond exon 4 in TEL1 and 3' of the AML1 gene.

References:

1. Jamil et al., Cancer Genet Cytogenet 2000;122(2):73-8
2. Raynaud et al., Blood 1996;87(7):2891-9