Development of a curative treatment within the AML-BFM studies.

The first multicenter treatment study for AML in childhood in Germany was performed from 1978 onwards. The therapy plan was designed similar to that for the acute lymphoblastic leukaemia (ALL). The drugs with the highest efficacy in AML, cytarabine cutting catara-bine and anthracyclines, were combined during induction and consolidation, followed by preventive cranial irradiation and maintenance therapy similar to that in ALL. The remission rate of the initial study was 80%, and the 5-year survival rate increased from less than 10% before 1970 to 40%. 5 subsequent trials have further increased the 5-year survival to now 70% and even 90% in the subgroup of core-binding factor leukaemias by using an intensified and optimised treatment schedule.The AML-BFM studies were the only prospective study sequence testing the benefit of cranial irradiation. Results from study -87 including the non-randomized patients showed an increased risk of CNS and/or bone marrow relapses in non-irradiated patients. Later on there was evidence that 12 Gy resulted in the same relapse rate as 18 Gy. The AML-BFM studies always used the experience from the previous study to optimize the next study. This approach was essential together with improved supportive treatment and experience of the medical staff for the step-wise and considerable increase of longterm survival within the 6 subsequent AML-BFM studies.

CD99 ligation upregulates HSP70 on acute lymphoblastic leukemia cells and concomitantly increases NK cytotoxicity.

CD99 is present in many human cell types, including high-level surface expression on pediatric B and T leukemias and Ewing tumors (ETs). On B lymphocytes and respective malignancies, its level decreases with the stage of maturation. Inter-individual variability of CD99 on B-cell precursor acute lymphoblastic leukemia (BCP-ALL) blasts was shown recently to be associated with distinct cytogenetic backgrounds. However, CD99 targets remain mainly unknown. Here, we show that administration of an anti-CD99 antibody to B- and T-leukemia cell lines induces heat shock protein 70 (HSP70), both on the cell surface and in the cytoplasm. Investigation of primary BCP-ALL cells rendered similar results. Intriguingly, CD99-induced modulation of HSP70 on ET cells had profiles different from that on leukemia cells. Since HSP70 expression on tumor cells is a prerequisite for natural killer (NK) cell-mediated tumor lysis, we hypothesized that CD99-induced HSP70 may allow targeting of some CD99-positive malignancies via NK-cell cytotoxicity. Our experiments with NK92 cell line demonstrated that leukemia cells with upregulated HSP70 can be successfully killed by effector cells. We consider our data as a new view of CD99 functions and as a basis for the development of a potential anti-tumor strategy based on heat-shock protein activation via CD99 triggering.

Silencing of ETV6/RUNX1 abrogates PI3K/AKT/mTOR signaling and impairs reconstitution of leukemia in xenografts.

The ETV6/RUNX1 (E/R) gene fusion is generated by the t(12;21) and found in approximately 25% of childhood B-cell precursor acute lymphoblastic leukemia. In contrast to the overwhelming evidence that E/R is critical for the initiation of leukemia, its relevance for the maintenance of overt disease is less clear. To investigate this issue, we suppressed the endogenous E/R fusion protein with lentivirally transduced short hairpin RNA in the leukemia cell lines REH and AT-2, and found a distinct reduction of proliferation and cell survival. In line with the observed concurrent inactivation of the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, pharmacological inhibition diminished the phosphorylation of AKT and ribosomal protein S6, and significantly increased the apoptosis rate in E/R-positive leukemias. Moreover, PI3K/mTOR inhibitors sensitized glucocorticoid-resistant REH cells to prednisolone, an observation of potential relevance for improving treatment of drug-resistant relapses. Of note, knockdown of the E/R fusion gene also severely impaired the repopulation capacity of REH cells in non-obese deficient/severe combined immunodeficient mice. Collectively, these data demonstrate that the E/R fusion protein activates the PI3K/AKT/mTOR pathway and is indispensible for disease maintenance. Importantly, these results provide a first rationale and justification for targeting the fusion gene and the PI3K/AKT/mTOR pathway therapeutically.

Favorable outcome in infants with AML after intensive first- and second-line treatment: an AML-BFM study group report.

Infants <1 year of age have a high prevalence of prognostically unfavorable leukemias and a presumed susceptibility to treatment-related toxicities. A total of 125 infants with acute myeloid leukemia (AML) were treated in studies AML-BFM-98 (n = 59) and -2004 (n = 66). Treatment regimens of both studies were comparable, consisting of intensive induction followed by four courses (mainly high-dose cytarabine and anthracyclines). Allogeneic-hematopoietic stem-cell-transplantation (allo-HSCT) in 1st remission was optional for high-risk (HR) patients. Most infants (120/125=96%) were HR patients according to morphological, cytogenetic/molecular genetic and response criteria. Five-year overall survival was 66 ± 4%, and improved from 61 ± 6% in study-98 to 75 ± 6% in study-2004 (P(logrank) 0.14) and event-free survival rates were 44 ± 6% and 51 ± 6% (P(logrank) 0.66), respectively. Results in HR infants were similar to those of older HR children (1-<2- or 2-<10-year olds, P(logrank) 0.90 for survival). Survival rates of HSCT in 1st remission, initial partial response and after relapse were high (13/14, 2/8 and 20/30 patients, respectively). The latter contributes to excellent 5-year survival after relapse (50±8%). Despite more severe infections and pulmonary toxicities in infants, treatment-related death rate was identical to that of older children (3%). Our data indicate that intensive frontline and relapse AML treatment is feasible in infants, toxicities are manageable, and outcome is favorable.

Induction death and treatment-related mortality in first remission of children with acute lymphoblastic leukemia: a population-based analysis of the Austrian Berlin-Frankfurt-Münster study group.

In the management of the childhood acute lymphoblastic leukemia (ALL), 5% of failures are due to induction death and treatment-related deaths in first complete remission. We retrospectively analyzed the incidence, pattern and causes of death and its risk factors for 896 children with ALL enrolled into five Austrian (A) Berlin-Frankfurt-Münster (BFM) trials between 1981 and 1999. The estimated 10-year cumulative incidence of death significantly decreased from 6+/-1% (n=16/268) in trials ALL-BFM-A 81 and ALL-A 84 to 2+/-1% (n=15/628) in trials ALL-BFM-A 86, 90 and 95 (P=0.006). A significant reduction of death was evident during induction therapy (2.2% in trials ALL-BFM-A 81 and ALL-A 84 and 0.2% in trials ALL-BFM-A 86, 90 and 95, P=0.001). Of 31 patients, 21 (68%) patients died from infectious and 10 (32%) from noninfectious complications. Treatment in trial ALL-BFM-A 81, infant age and female gender were independent predictors of an enhanced risk for death. Conclusively, we found a progressive reduction of death rates that may be explained by the increasing experience in specialized hemato-oncologic centers and improved supportive and intensive care. We also identified a distinct subset of patients who are especially prone to death and may need a special focus when receiving intense chemotherapy.

Drug-induced immunophenotypic modulation in childhood ALL: implications for minimal residual disease detection.

Assessment of minimal residual disease (MRD) by flow cytometry is considered to be based on the reproducibility of the leukemic immunophenotype detected at diagnosis. However, we previously noticed modulation of surface antigen expression in acute lymphoblastic leukemia (ALL) during the early treatment. Hence, we investigated this in 30 children with B-cell precursor ALL consecutively enrolled in the AIEOP-BFM ALL 2000 protocol. Quantitative expression of seven antigens useful in MRD monitoring was studied at diagnosis and compared to that measured at different time points of remission induction therapy. Downmodulation in the expression of CD10 and CD34 occurred at follow-up. By contrast, upmodulation of CD19, CD20, CD45RA, and CD11a was observed, while the expression of CD58 remained stable. Despite this, we could unambiguously discriminate leukemic cells from normal residual B cells. This holds true when bone marrow (BM) samples from similarly treated T-ALL patients, but not from healthy donors, were used as reference. Our results indicate that immunophenotypic modulation occurs in ALL during the early phases of BFM-type protocols. However, the accuracy of MRD detection by flow cytometry seems not negatively affected if adequate analysis protocols are employed. Investigators should take this phenomenon into account in order to avoid pitfalls in flow cytometric MRD studies.

Incidence and relevance of secondary chromosome abnormalities in childhood TEL/AML1+ acute lymphoblastic leukemia: an interphase FISH analysis.

The aim of the present study was to determine the frequency and clinical relevance of the most common secondary karyotype abnormalities in TEL/AML1+ B-cell precursor acute lymphoblastic leukemia (ALL) as assessed with fluorescence in situ hybridization (FISH) analyses. Screening of 372 patients who were enrolled in two consecutive Austrian childhood ALL multicenter trials identified 94 (25%) TEL/AML1+ cases. TEL deletions, trisomy 21 and an additional der(21)t(12;21) were detected in 52 (55%), 13 (14%) and 14 (15%) TEL/AML1+ patients, respectively. The 12p aberrations (P=0.001) and near tetraploidy (P=0.045) were more common in TEL/AML1+ patients, whereas the incidence of diploidy, pseudodiploidy, hypodiploidy, low hyperdiploidy, near triploidy, del(6q), chromosome 9 and 11q23 abnormalities was similar among TEL/AML1+ and TEL/AML1- patients. None of the TEL/AML1+ patients had a high hyperdiploid karyotype. Univariate analysis indicated that among TEL/AML1+ patients those with a deletion of the nontranslocated TEL allele had a worse prognosis than those without this abnormality (P=0.034). We concluded that the type and incidence of the most common secondary aberrations in TEL/AML1+ ALL can be conveniently identified with little additional effort during interphase screening with appropriate TEL and AML1 FISH probes. We also provided preliminary evidence that the deletion of the nontranslocated TEL allele may adversely influence the clinical course of TEL/AML1+ ALL.

CD99 expression in T-lineage ALL: implications for flow cytometric detection of minimal residual disease.

Expression of CD99 is higher on immature than on mature T cells. We postulated that this marker could be used to assess minimal residual disease (MRD) in T-lineage acute lymphoblastic leukemia (T-ALL). In diagnostic bone marrow (BM) samples from 27 children with T-ALL, expression of CD99 on leukemic lymphoblasts by flow cytometry was in median 7.7 times higher than on normal T lymphocytes from within the same sample. In 85% of cases, leukemic MFI values were higher than the mean MFI+2 s.d. of normal populations. We applied CD99 to study MRD in 39 follow-up samples from 15 consecutive T-ALL patients, and compared the results with those obtained with the well-established MRD-marker terminal deoxynucleotidyl transferase (TdT). Either antibody was combined in four-color flow cytometry with CD7, surfaceCD3, and cytoplasmicCD3. We found that CD99 was a valid complement to TdT in quantifying T-ALL MRD. Given a considerable interpatient variability, CD99 could be favorably used in nine patients, and TdT in other five patients. Both approaches showed a similar very low nonspecific background throughout 12 weeks from diagnosis (in median 0.002% of nucleated BM cells in patients with non-T ALL). We conclude that CD99 is a highly informative tool for MRD detection in T-ALL, bearing the advantage of surface expression in contrast to TdT.

PAX5/ETV6 fusion defines cytogenetic entity dic(9;12)(p13;p13).

Recurrent chromosomal abnormalities present in malignant cells often define subentities with unique biological and clinical features. The molecular identification of genes involved in genetic alterations has led to the characterization of fusion genes with neoplastic properties. However, for many nonrandom translocations including the dic(9;12)(p11-13;p11-12), the molecular equivalent has not as yet been identified. The dicentric translocation dic(9;12) is a recurrent chromosome abnormality that accounts for close to 1% of childhood acute lymphoblastic leukemia (ALL). This specific alteration occurs almost exclusively in B-progenitor ALL, and unlike many other nonrandom translocations, is associated with an excellent prognosis. In this work, we provide strong evidence that the PAX5/ETV6 fusion transcript defines the clinical and biological entity that is associated with the presence of a dic(9;12) chromosome. As the PAX5 and ETV6 genes are localized at 9p13 and 12p13, respectively, the cytogenetic description of the dic(9;12)-PAX5/ETV6 rearrangement should be refined to dic(9;12)(p13;p13).

Immunological detection of minimal residual disease in acute lymphoblastic leukemia.

Assessment of minimal residual disease (MRD) during the first months of therapy gives information on the timely response to treatment, and proves to be a powerful and independent indicator of treatment outcome in patients with acute lymphoblastic leukemia (ALL). Immunological evaluation by flow cytometry (FC) is one of the most attractive approaches to this. The present review summarizes the historical development of the technique over the last 20 years, showing that current methodology is based on the existence of leukemia-associated patterns of asynchrony in antigen expression with respect to normal differentiation or location of occurrence. Such asynchrony allows the sensitive detection of rare malignant cells by multiparametric FC, although completely leukemia-specific antigens for broad application do not exist. Clinical studies proved that the technology should now be applicable to almost all patients with ALL and that immunological MRD results correlate well with outcome. However, based on the available set of FC data, it is yet too early to draw firm conclusions for clinical application. Issues still to be addressed by comprehensive and non-selecting investigations on the basis of the most widely used treatment protocols are whether 1) quantitative data generated by PCR and FC are interchangeable, 2) differences between therapeutic regimens influence the significance of qualitative and quantitative aspects of MRD, and 3) absolute enumeration of MRD bears advantages over the common practice of relative quantification. Concluding remarks further relate to technical issues which may allow to simplify the approach in the future which should augment also its economic efficiency.

Detection of residual disease in pediatric B-cell precursor acute lymphoblastic leukemia by comparative phenotype mapping: method and significance.

The present review summarizes our efforts in developing a novel immunologic approach ("Comparative Phenotype Mapping") targeted at assessing minimal residual disease (MRD) in B-cell precursor (BCP) acute lymphoblastic leukemia (ALL) patients. The method relies on quantitatively aberrant, leukemia-associated antigen expression patterns which allow to discriminate leukemic from normal BCP using a limited panel of antibody combinations and multidimensional flow cytometry. In an analysis of 63 follow up bone marrow samples of patients with BCP-ALL we show that this approach enables to efficiently detect MRD. Further clinical observation revealed that the patients which were MRD-positive by flow cytometry (although in morphological remission) had a very high probability of early disease recurrence compared to the good chances of a relapse-free survival (RFS) in the MRD-negative cohort (RFS 0.0 vs. 0.76 at 3 years). Comparative Phenotype Mapping thus proves to be a reliable method for MRD detection in BCP-ALL. Concluding remarks relate to the optional applications of the method as well as to future perspectives. An ongoing large prospective study which we are now conducting on the basis of Comparative Phenotype Mapping will clarify the clinical significance of MRD detection in ALL patients by this method, and will determine its value compared to related as well as molecular-genetic techniques.

Reduced interferon-gamma expression in peripheral blood mononuclear cells of infants with severe respiratory syncytial virus disease.

We examined the in vivo cell-mediated immune response in infants with respiratory syncytial virus (RSV) infection in order to gain information about the pathogenesis of severe RSV disease in infancy. Semiquantitative reverse transcription-polymerase chain reaction and three-color flow cytometry were used to determine the levels of messenger RNA (mRNA) for interferon (IFN)-gamma in peripheral blood mononuclear cells, and the distribution of lymphocyte subsets in infants with acute RSV infection. The findings were correlated with the severity of the patients' illness and the production of RSV-specific IgE antibodies (RSV-IgE). Significantly lower IFN-gamma levels and T-lymphocyte counts in the acute phase of illness were observed in infants with severe RSV disease than in those with a milder clinical course of illness. The induction of RSV-IgE was not related to IFN-gamma levels in the acute phase of illness, but rather correlated with IFN-gamma expression during convalescence. The data indicate that reduced IFN-gamma expression may be an important factor in the pathogenesis of severe RSV disease in infancy.

CD99 (MIC2) expression in paediatric B-lineage leukaemia/lymphoma reflects maturation-associated patterns of normal B-lymphopoiesis.

We have recently shown that CD99 (MIC2) is differentially expressed during normal early B-cell development in the bone marrow (BM). Since immature B-cell precursors (BCP) are assumed to correspond to some extent to acute lymphoblastic leukaemia (ALL) and non-Hodgkin's lymphoma (NHL) cells with respect to patterns of phenotypic differentiation, we wondered whether the particular maturation-associated expression patterns of CD99 in the normal BCP stages were conserved also in malignant cells. Therefore we compared malignant and physiological B cells from paediatric ALL/NHL and normal BM samples with respect to CD99 expression using selective gating and semi-quantitative flow cytometry. Common-ALLs (n = 45) were similar to their corresponding, very immature BCPs (stage 1) in expressing very high levels of CD99. Most pre-B ALLs (n = 16) were also CD99hi and thus differed from the patterns found in normal cytoplasmic mu-chain+ (cmu+) pre-B cells (stage 2, CD99lo). In particular, we found that those pre-B-ALL cases which were CD34+ also showed higher CD99 expression than the CD34- cases. This prompted us to investigate the levels of CD99 in those rare normal BCPs which also coexpress CD34 and cmu; these cells, which are transitory from stage 1 to stage 2, were found also CD99hi, thus precisely reflecting the patterns of CD34+ pre-B ALLs. The blasts of Burkitt-type B-cell ALL/NHL samples (n = 13) expressed considerably less CD99, similarly to the more differentiated BCP stages 2 (cmu+) and 3 (surface mu-chain+). In summary, we found that paediatric B-lineage malignancies display remarkable synchrony regarding the levels of CD99 expression compared to their putative normal counterparts.

Skin-associated lymphocytes in the peripheral blood of patients with atopic dermatitis: signs of subset expansion and stimulation.

BACKGROUND: Skin-associated T cells are defined by the cutaneous lymphocyte-associated antigen (CLA). In atopic dermatitis (AD), CLA+ T cells harbor allergen-reactive memory cells, spontaneously secrete TH2 cytokines, and display signs of increased in vivo activation, thus relating the subset to the central disease pathomechanisms. OBJECTIVES: It is not known whether the proportion of circulating CLA+ T cells might be expanded in AD. We were therefore prompted to compare the peripheral blood lymphocyte subpopulations of patients with AD with those of control subjects. METHODS: We used 3-color flow cytometry to investigate age-matched peripheral blood samples of pediatric and young adult patients with mild (n = 21) or severe (n = 15) AD, patients with allergic/atopic diseases not involving the skin (n = 9), and healthy control subjects (n = 14). RESULTS: We found no differences among the study groups with respect to the general proportions of T cells, CD4(+) T cells, CD8(+) T cells, B cells, NK cells, CD103(+) T cells, and CD25(+) T cells among total circulating lymphocytes. However, there were slightly more CD4(+) memory cells and clearly more HLA-DR+ T cells in patients with severe AD. Most remarkably, patients with severe AD had a significantly expanded proportion of CLA+ T cells (P =.024) and CLA+/CD4(+) T cells (P =.006) but similar proportions of CLA+/CD8(+) T cells compared with control subjects. Patients with severe AD also had distinctly more HLA-DR+/CLA+ T cells than control subjects (P =. 005). Similar alterations were seen in patients with mild AD, but these were not statistically significant. After correction for age, all differences were significant only in probands less than 10 years of age. CONCLUSIONS: Circulating skin-associated T cells (CLA+) show signs of subset expansion and enhanced activation in patients with AD. These alterations, compared with control values, affect CD4(+) memory T cells in particular and are prominent only in children less than 10 years of age.