TEL AML-1 DIMERIZES AND IS ASSOCIATED WITH A FAVORABLE OUTCOME IN CHILDHOOD ACUTE LYMPHOBLASTIC-LEUKEMIA/

Polymerase chain reaction-based screening of childhood acute lymphobla stic leukemia (ALL) samples showed that a TEL/AML1 fusion transcript w as detected in 27% of all cases, representing the most common known ge ne rearrangement in childhood cancer. The TEL/AML1 fusion results from a t(12;21)(p13:q22) chromosomal translocation, but was undetectable a t the routine cytogenetic level. TEL/AML1-positive patients had exclus ively B-lineage ALL, and most patients were between the ages of 2 and 9 years at diagnosis. Only 3/89 (3.4%) adult ALL patients were TEL/AML 1-positive. Most importantly, TEL/AML1-positive children had a signifi cantly lower rate of relapse compared with TEL/AML1-negative patients (0/22 v 16/54, P = .004). Co-immunoprecipitation experiments demonstra ted that TEL/AML-1 formed homodimers in vitro, and heterodimerized wit h the normal TEL protein when the two proteins were expressed together , The elucidation of the precise mechanism of transformation by TEL/AM L1 and the role of TEL/AML1 testing in the treatment of childhood ALL will require additional studies. (C) 1996 by The American Society of H ematology.