We examined the expression of Ikaros isoforms in 11 leukemic cell lines and adult acute lymphoblastic leukemia cells from 36 patients with B-precursor acute lymphoblastic leukemia (pre-B ALL) and nine with T-precursor acute lymphoblastic leukemia (pre-T ALL), using reverse transcriptase-polymerase chain reaction (RT-PCR) analysis.
The 'promiscuous' E2A gene, at 19p13.3, is fused with two different molecular partners, PBX1 and HLF, following two chromosome translocations recurrent in childhood pre-B ALL.
Thus rearrangement of the E2A gene is not restricted to cases with pre-B ALL but may also occur in acute leukemias with other immunological phenotypes.
The E2A gene is involved by the t(1;19)(q23;p13) in acute pre-B-cell leukemias and the LYL1 gene is structurally altered by a t(7;19)(q34;p13) in T-cell ALL.
Using a specific E2A gene probe spanning the DNA binding and dimerization domain obtained by PCR methodology, we were able to detect the rearrangement of the E2A gene in four cases (three patients and one cell line) of pre-B acute lymphoblastic leukemia with t(1;19) translocation.
Interestingly, we found that human FMN2 is overexpressed in approximately 95% of pre-B acute lymphoblastic leukemia with the highest expression levels in patients with a TEL/AML1 rearrangement.
The TEL-AML1 transgenic zebrafish models human pre-B ALL, identifies the molecular pathways associated with leukemia development, and serves as the foundation for subsequent genetic screens to identify modifiers and leukemia therapeutic targets.
The authors describe a 7-year-old boy with TEL/AML1-positive pre-B acute lymphoblastic leukemia, with hemizygous 9p21 deletion at presentation and no p16(INK4A) protein expression.
The IgH, TCR and TEL-AML1 markers can be used as targets by real-time PCR under the same cycling profile, allowing quantitation of MRD in more 95% of patients with pre-B ALL.
We propose, in some cases, that the TEL-AML1 translocation occurs in a stem or B progenitor cell, and that recurrent TEL-AML1-positive pre-B ALL represents a de novo-transformed population that retains the same diagnostic initiating event.