Chemosensitivity of TEL-AML1 fusion transcript positive acute lymphoblastic leukemia cells

The TEL-AML1 fusion which results from a cryptic t(12;21) translocation is the most frequently occurring genetic abnormality in childhood acute lympho blastic leukemia (ALL) and has been associated with an excellent treatment outcome. In the present study, we examined the FAS/BCL-2 expression profile s and chemosensitivity of primary leukemic cells from children with newly d iagnosed t(12;21)TEL-AML1 fusion transcript-positive versus t(12;21)TEL-AML 1 fusion transcript-negative standard risk ALL. TEL-AML1(+) ALL cells expre ssed higher levels of the pro-apoptotic protein Fas and lower levels of the anti-apoptotic protein Bcl2 than TEL-AML1(-) ALL cells, as determined by c onfocal laser scanning microscopy. TEL-AML1(+) ALL cells were more sensitiv e to the apoptosis-inducing effects of serum deprivation, dexamethasone and vincristine than TEL-AML1(-) ALL cells. This study provides novel mechanis tic insights regarding the chemosensitivity of TEL-AML1(+) ALL cells and pr ovides a cogent explanation for the excellent leukemia-free survival outcom e of children with TEL-AML1(+) ALL treated on contemporary chemotherapy pro grams.