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Children with acute lymphoblastic leukemia (ALL) with > or = 0.01% leukemic cells in the bone marrow after remission induction are at a greater risk of relapse. The most promising methods of detecting minimal residual disease (MRD) are flow cytometric identification of leukemia-associated immunophenotypes and polymerase chain reaction (PCR) amplification of antigen-receptor genes. However, neither assay can be applied to all patients. Moreover, both assays carry the risk of false-negative findings due to clonal evolution. The simultaneous use of both assays might resolve these problems, but the correlation between the methods is unknown. We studied serial dilutions of normal and leukemic cells by flow cytometry and PCR amplification of IgH genes and found the two methods highly sensitive (one leukemic cell among 10(4) or more normal cells), accurate (r2 was 0.999 for flow cytometry and 0.960 for PCR by regression analysis) and concordant (r2 = 0.962). We then examined 62 bone marrow samples collected from children with ALL in clinical remission. In 12 samples, both techniques detected MRD levels > or = 1 in 10(4). The percentages of leukemic cells measured by the two methods correlated well (r2 = 0.978). Of the remaining 50 samples, 48 had MRD levels < 1 in 10(4). In only two samples results were discordant: 2 in 10(4) and 5 in 10(4) leukemic cells by PCR but < 1 in 10(4) by flow cytometry. We conclude that immunologic and molecular techniques can be used in tandem for universal monitoring of MRD in childhood ALL. [ABSTRACT FROM AUTHOR]

Rhombotin-2 (RBTN-2) is a proto-oncogene only in the context of T lymphocytes. We postulated that the oncogenic effect of RBTN-2 in T cells is likely mediated by binding protein(s) with T cell-specific expression. By screening a T cell cDNA library, we identified a novel ets transcription factor that binds RBTN-2. This protein was named elf-2 because its DNA-binding domain is virtually identical to that of ets family member elf-1. Northern analyses showed similar levels of two elf-2 transcripts (3.5 kb and 3.8 kb) in all tissues except thymus. Thymocytes expressed four- to 10-fold greater amounts of the 3.5 kb transcript than other tissues. Sequence analyses of cDNA clones indicated that these transcripts encode proteins differing only at their amino termini, and likely represent alternatively spliced isoforms. These isoforms (elf-2a and elf-2b) contain identical RBTN-2 binding regions and DNA-binding domains. Elf-2b lacks a putative transactivation domain. The expression patterns suggest that RBTN-2 normally interacts equally with elf-2a and elf-2b. In contrast, when RBTN-2 is inappropriately expressed in T cells, RBTN-2 would interact predominantly with elf-2b; this interaction may lead to T cell proliferation. [ABSTRACT FROM AUTHOR]

We investigated the level of minimal residual disease (MRD) in 26 children with B-lineage acute lymphoblastic leukemia (ALL) after intensive induction therapy. A quantitative semi-nested polymerase chain reaction (PCR) detecting the clone-specific rearranged immunoglobulin heavy chain genes was developed to improve sensitivity and specificity of amplification. In all patients, one leukemic cell could be detected in a background of 10(5) normal blood mononuclear cells. All patients investigated were in complete remission at the end of induction therapy as evaluated by morphologic criteria. Nineteen patients (73%) had no detectable residual leukemic cells using the sensitive semi-nested PCR. Seven patients (27%) were PCR positive. Three had a low level (<2 x 10(-5) leukemic cells per bone marrow cell), while four patients had a high level (>2 x 10(5)) of detectable residual leukemic cells. All patients with low or undetectable levels of residual leukemia remained in complete remission at a median of 63 months from diagnosis (range 40-80 months), while all four patients with a high level of residual leukemia subsequently relapsed at a median of 21 months from diagnosis (range 13-37 months). The patient groups with undetectable or low, and high level of MRD did not differ significantly in other clinical or genetic features with prognostic significance. We conclude that the level of MRD at the end of the intensive induction therapy period is predictive of outcome in childhood B lineage ALL. If confirmed by large prospective studies, the level of MRD might be useful in stratifying patients into high and low risk categories. [ABSTRACT FROM AUTHOR]