B De Moerloose

A new recurrent inversion, inv(7)(p15q34), leads to transcriptional activation of HOXA10 and HOXA11 in a subset of T-cell acute lymphoblastic leukemias

Chromosomal translocations with breakpoints in T-cell receptor (TCR) genes are recurrent in T-cell malignancies. These translocations involve the TCRαδ gene (14q11), the TCRβ gene (7q34) and to a lesser extent the TCRγ gene at chromosomal band 7p14 and juxtapose T-cell oncogenes next to TCR regulatory sequences leading to deregulated expression of those oncogenes. Here, we describe a new recurrent chromosomal inversion of chromosome 7, inv(7)(p15q34), in a subset of patients with T-cell acute lymphoblastic leukemia characterized by CD2 negative and CD4 positive, CD8 negative blasts. This rearrangement juxtaposes the distal part of the HOXA gene cluster on 7p15 to the TCRβ locus on 7q34. Real time quantitative PCR analysis for all HOXA genes revealed high levels of HOXA10 and HOXA11 expression in all inv(7) positive cases. This is the first report of a recurrent chromosome rearrangement targeting the HOXA gene cluster in T-cell malignancies resulting in deregulated HOXA gene expression (particularly HOXA10 and HOXA11) and is in keeping with a previous report suggesting HOXA deregulation in MLL-rearranged T- and B cell lymphoblastic leukemia as the key factor in leukaemic transformation. Finally, our observation also supports the previous suggested role of HOXA10 and HOXA11 in normal thymocyte development.

P-glycoprotein is an independent prognostic factor predicting relapse in childhood acute lymphoblastic leukaemia : results of a 6-year prospective study

P‐glycoprotein (P‐gp), a cellular drug‐efflux pump, is thought to be one of the major causes of multidrug resistance (MDR) in malignancies. Since therapeutic strategies are being developed to circumvent drug resistance by inhibiting P‐gp function, large prospective studies evaluating the clinical relevance of P‐gp in childhood acute lymphoblastic leukaemia (ALL) are warranted. P‐gp expression was evaluated over a period of 6 years in 102 consecutive patients with de novo childhood ALL and in 35 children with relapse of ALL. Bone marrow and blood smears were studied immunocytochemically with two monoclonal antibodies at initial diagnosis and at relapse. P‐gp expression was found in 14 (14%) patients at initial diagnosis. After induction treatment, complete remission was achieved in 100/102 patients (98%), of whom 19 relapsed. Cumulative event‐free survival was significantly higher in the P‐gp‐negative group compared with the P‐gp‐positive population (Logrank P = 0.02). Multivariate analysis showed the results to be independent of age, WBC count and karyotype, and concomitantly underlined the importance of MDR1 phenotype detection in childhood ALL. P‐gp expression was more frequently found at relapse (34%) than at primary diagnosis (P = 0.01). In the relapsed patient group, P‐gp‐positive patients had a 2‐fold greater risk for adverse clinical outcome than the P‐gp‐negative relapsed patients. P‐gp expression was not induced by exposure to previous chemotherapy since the majority of P‐gp‐negative patients remained negative at relapse. P‐glycoprotein expression in newly diagnosed childhood ALL is an independent adverse prognostic parameter with a predictive value for relapse.

MicroRNA-193b-3p acts as a tumor suppressor by targeting the MYB oncogene in T-cell acute lymphoblastic leukemia

The MYB oncogene is a leucine zipper transcription factor essential for normal and malignant hematopoiesis. In T-cell acute lymphoblastic leukemia (T-ALL), elevated MYB levels can arise directly through T-cell receptor-mediated MYB translocations, genomic MYB duplications or enhanced TAL1 complex binding at the MYB locus or indirectly through the TAL1/miR-223/FBXW7 regulatory axis. In this study, we used an unbiased MYB 3′untranslated region–microRNA (miRNA) library screen and identified 33 putative MYB-targeting miRNAs. Subsequently, transcriptome data from two independent T-ALL cohorts and different subsets of normal T-cells were used to select miRNAs with relevance in the context of normal and malignant T-cell transformation. Hereby, miR-193b-3p was identified as a novel bona fide tumor-suppressor miRNA that targets MYB during malignant T-cell transformation thereby offering an entry point for efficient MYB targeting-oriented therapies for human T-ALL.

IKZF1 deletion is an independent prognostic marker in childhood B-cell precursor acute lymphoblastic leukemia, and distinguishes patients benefiting from pulses during maintenance therapy: results of the EORTC Children's Leukemia Group study 58951

The added value of IKZF1 gene deletion (IKZF1del) as a stratifying criterion in B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is still debated. We performed a comprehensive analysis of the impact of IKZF1del in a large cohort of children (n=1223) with BCR-ABL1-negative BCP-ALL treated in the EORTC-CLG trial 58951. Patients with IKZF1del had a lower 8-year event-free survival (EFS, 67.7% versus 86.5%; hazard ratio (HR)=2.41; 95% confidence interval (CI)=1.75–3.32; P<0.001). Importantly, despite association with high-risk features such as high minimal residual disease, IKZF1del remained significantly predictive in multivariate analyses. Analysis by genetic subtype showed that IKZF1del increased risk only in the high hyperdiploid ALLs (HR=2.57; 95% CI=1.19–5.55; P=0.013) and in ‘B-other‘ ALLs, that is, lacking classifying genetic lesions (HR=2.22; 95% CI=1.45–3.39; P<0.001), the latter having then a dramatically low 8-year EFS (56.4; 95% CI=44.6-66.7). Among IKZF1del-positive patients randomized for vincristine-steroid pulses during maintenance, those receiving pulses had a significantly higher 8-year EFS (93.3; 95% CI=61.3–99.0 versus 42.1; 95% CI=20.4–62.5). Thus, IKZF1del retains independent prognostic significance in the context of current risk-adapted protocols, and is associated with a dismal outcome in ‘B-other‘ ALL. Addition of vincristine-steroid pulses during maintenance may specifically benefit to IKZF1del patients in preventing relapses.

Surveillance of cytomegalovirus (CMV) DNAemia in pediatric allogeneic stem cell transplantation: incidence and outcome of CMV infection and disease

Abstract: Cytomegalovirus (CMV) remains a serious problem after hematopoietic stem cell transplantation (HSCT). To investigate the incidence of CMV infection and outcome we retrospectively analyzed 70 consecutive pediatric allogeneic HSCTs monitored by CMV polymerase chain reaction (PCR), with at least 1‐year follow‐up or until death. All patients at risk for CMV infection (CMV‐seropositive patients and CMV‐seronegative recipients transplanted from CMV‐seropositive donors) received hyperimmune anti‐CMV globulins whereas in the group of HSCT patients with both donor and recipient CMV negativity, polyvalent immunoglobulins were given, both at a dose of 400 mg/kg. All patients received acyclovir at prophylactic doses for at least 6 months. Patients were monitored twice a week by CMV PCR. Patients with 2 positive results for CMV DNAemia received ganciclovir for 14 days and continued until 2 consecutive negative results were obtained. The incidence of CMV DNAemia was 12.8% (9/70) in the whole group, with significant higher risk for patients with CMV‐seropositive recipient status, 8 out of 22 (36%), vs. patients with seronegative status, 1 out of 48 (2%) (P=0.0002). Three out of 9 patients with DNAemia developed CMV disease despite adequate preemptive treatment. The transplant‐related mortality was higher in the CMV‐seropositive recipient group (P=0.05). Age, use of hyperimmune anti‐CMV globulins at a high dose, and the low incidence of graft‐versus‐host disease might be contributing factors to this low incidence.

The clinical relevance of minor paroxysmal nocturnal hemoglobinuria clones in refractory cytopenia of childhood: a prospective study by EWOG-MDS

The clinical relevance of minor paroxysmal nocturnal hemoglobinuria clones in refractory cytopenia of childhood: a prospective study by EWOG-MDS

Applicability of a reproducible flow cytometry scoring system in the diagnosis of refractory cytopenia of childhood

Applicability of a reproducible flow cytometry scoring system in the diagnosis of refractory cytopenia of childhood

DISCREPANT FLOW CYTOMETRIC EXPRESSION AND FUNCTION OF P-GLYCOPROTEIN IN NEUROBLASTIC TUMORS

BACKGROUND Patients suffering from neuroblastic tumors are currently being classified into prognostic subsets based on different clinical and biologic features. In this study, a triple-color flow cytometric assay and a functional test were applied to neuroblastoma cell lines and patients with a neuroblastic tumor, and the value of P-glycoprotein expression and function as potential prognostic characteristics, was determined. METHODS Twenty-two single-cell suspensions prepared from tumors, and neuroblasts from four bone marrow samples were analyzed by triple-color flow cytometry. Neuroblasts were identified by NB84-positivity and absence of CD45. P-glycoprotein expression was evaluated using 4E3 and MRK16 antibodies. Eighteen samples were tested with a functional assay, based on accumulation and retention of rhodamine-123 with and without the inhibitor verapamil. Six neuroblastoma cell lines were also evaluated. RESULTS P-glycoprotein expression was seen in 18 of 26 patient samples and in three of six cell lines. The highest expression levels were found in low stage neuroblastoma and well-differentiated tumors; whereas the highest activities were found in stage 4 neuroblastoma and the lowest in ganglioneuroblastoma and ganglioneuroma patients. In 10 of 17 samples, concordant results were found between the flow cytometric immunological test and immunocytochemistry. CONCLUSIONS The described flow cytometric technique is a new, alternative approach to detect P-glycoprotein expression and function in neural crest tumors. Based on the expression level and the activity value, patients can be segregated into different phenotypic groups. In particular, those patients with high P-glycoprotein activity might benefit from treatment regimens containing reversal agents.

T-cell receptor Vβ skewing frequently occurs in refractory cytopenia of childhood and is associated with an expansion of effector cytotoxic T cells: a prospective study by EWOG-MDS

Immunosuppressive therapy (IST), consisting of antithymocyte globulin and cyclosporine A, is effective in refractory cytopenia of childhood (RCC), suggesting that, similar to low-grade myelodysplastic syndromes in adult patients, T lymphocytes are involved in suppressing hematopoiesis in a subset of RCC patients. However, the potential role of a T-cell-mediated pathophysiology in RCC remains poorly explored. In a cohort of 92 RCC patients, we prospectively assessed the frequency of T-cell receptor (TCR) β-chain variable (Vβ) domain skewing in bone marrow and peripheral blood by heteroduplex PCR, and analyzed T-cell subsets in peripheral blood by flow cytometry. TCRVβ skewing was present in 40% of RCC patients. TCRVβ skewing did not correlate with bone marrow cellularity, karyotype, transfusion history, HLA-DR15 or the presence of a PNH clone. In 28 patients treated with IST, TCRVβ skewing was not clearly related with treatment response. However, TCRVβ skewing did correlate with a disturbed CD4+/CD8+ T-cell ratio, a reduction in naive CD8+ T cells, an expansion of effector CD8+ T cells and an increase in activated CD8+ T cells (defined as HLA-DR+, CD57+ or CD56+). These data suggest that T lymphocytes contribute to RCC pathogenesis in a proportion of patients, and provide a rationale for treatment with IST in selected patients with RCC.

Repetitive analyses of P-glycoprotein in chronic myeloid leukaemia

Abstract P-glycoprotein, a pump located in the plasma cell membrane, extrudes several clinically important drugs from the cell, and hence causes multidrug resistance. Reversing clinical drug resistance is possible by using agents that inhibit the activity of P-glycoprotein. We describe the results of sequential flow cytometric determinations of P-glycoprotein expression and activity in two patients suffering from acute lymphoblastic transformation of chronic myeloid leukaemia. Neither P-glycoprotein expression, nor its activity could be detected in the initial sample of the first patient. In the second patient, no P-glycoprotein expression was found at diagnosis. However, after chemotherapy containing P-glycoprotein substrates, a significant expression was found in both patients and the functional flow cytometric test was positive. In order to achieve an accurate selection of patients that might benefit from the clinical use of Pgp inhibitors, repeated analyses are indicated in each patient suffering from acute leukaemia, during the course of the illness.