Two consecutive immunophenotypic switches in a child with MLL-rearranged acute lymphoblastic leukemia.

An 18-month-old girl was diagnosed with prepre-B ALL/t(4;11) leukemia, which during thetreatment and after matched bone marrow transplantation(BMT), underwent two consecutiveswitches from lymphoid to myeloid lineage andvice versa. The high expression of HOXA9 andFLT3 genes remaining genotypically stable in aleukemia throughout phenotypic switches, suggeststhat this leukemia may have originated as acommon B/myeloid progenitors

Diagnosis and genetic subtypes of leucemia combining gene expression and flow cytometry.

Acute leukemia, defined as a genetic disease, is the most common cancer in children representing about one half of all cancers among persons younger than 15 years. Acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) each represents a heterogeneous complex of disorders, with genetic abnormalities presenting in more than 80% of ALLs and more than 90% of AMLs. The diagnostic gold standard and classification of leukaemia involves various methods including morphology, cytochemistry, cytogenetics and molecular genetics, immunophenotyping, and molecular biology. These diagnostic methods are a prerequisite for individual treatment strategies and for the evaluation of treatment response especially considering that many distinct types of acute leukemia are known to carry predictable prognoses and warrant specific therapy. The quantification of gene expression is essential in determination of tailored therapeutic decisions. Microarray technology offers the possibility of quantifying thousands of genes in a single analysis, thus potentially becoming an essential tool for molecular classification to be used in routine leukaemia diagnostics. MLL+ leukaemia is a perfect example as to the exact correspondence between gene expression and protein expression evaluated by flow cytometry. Applying computational analysis to flow cytometry results, it is possible to distinguish the MLL+ acute leukemia from MLL- acute leukemia using as the top ranked antigen some top ranked genes described in the Microarray evaluation. Key markers discriminating different leukemia phenotypes can be identified by univariate hypothesis testing from a data set of immunophenotypic markers described by two variables, one reflecting the intensity of expression (MESF) and the other the pattern of distribution (CV). A current multi center study called Microarray Innovations in Leukemia (MILE Study) uses higher density gene chips providing nearly complete coverage of the human genome. The study which has analyzed thus far 1837 retrospective cases shows that each important leukemia subtype has a specific genetic fingerprint, meaning that different combinations of genes whose expression is linked to each subtype can be identified allowing for patient tailored therapy. Moreover, the study has achieved 97% diagnostic accuracy on samples from tested patients. Statistical analysis has shown a high concordance level between standard diagnostic procedures and those of the microarray technology--globally around 95.6%. Additionally it is possible to correctly classify some subgroups incorrectly identified using gold standard methods. Thus, from a technical viewpoint, gene expression profiling in tandem with flow cytometry should be a viable alternative to standard diagnostic approaches. Whether gene expression profiling will become a practical diagnostic alternative remains to be seen

Hepatocyte growth factor receptor c-MET is associated with FAS when activated enhances drug-induced apoptosis in pediatric B-acute lymphoblastic leukemia with TEL-AML1 translocation.

Expression of c-MET, the HGF (hepatocyte growth factor) tyrosine kinase receptor, was investigated in pediatric B-acute lymphoblastic leukemia (ALL) patients. c-MET was found to be expressed in normal B cells and in B-ALL patients with the t(12;21) TEL-AML1 translocation, but it is not expressed in the most part of B-ALL without the t(12;21). We also found that c-MET, related to proliferation and protection from apoptosis, is associated with the pro-apoptotic protein FAS in TEL-AML1 B-ALL cells and in normal B lymphocytes. The possible role of this protein complex in drug-induced apoptosis was thus investigated in REH TEL-AML1 B-ALL cell line. REH cells prestimulated with HGF and treated with doxorubicin had shown a higher apoptotic rate than non-HGF-prestimulated ones (p = 0.03). REH cells stimulated with IL-3 and treated with doxorubicin did not undergo apoptosis more than nonstimulated cells, demonstrating that increased proliferation in itself is not directly related to the higher apoptotic sensitivity observed with HGF stimulation. These results indicate that c-MET activation enhances specifically FAS-mediated apoptosis in TEL-AML1 ALL cells and, considering that the c-MET/FAS complex is present only in normal B lymphocytes and in TEL-AML1 leukemias, this implies that it may have an important contribution in cellular homeostasis and in high sensitivity of TEL-AML1 ALL to chemotherapeutic regimens

Two consecutive immunophenotypic switches in a child with MLL-rearranged acute lymphoblastic leucemia.

An 18-month-old girl was diagnosed with pre-pre-B ALL/t(4;11) leukemia, which during the treatment and after matched bone marrow transplantation (BMT), underwent two consecutive switches from lymphoid to myeloid lineage and vice versa. The high expression of HOXA9 and FLT3 genes remaining genotypically stable in a leukemia throughout phenotypic switches, suggests that this leukemia may have originated as a common B/myeloid progenitor