TEL-AML1 Fusion Transcript in Relapsed Childhood Acute Lymphoblastic Leukemia

The Landscape of Secondary Genetic Rearrangements in Pediatric Patients with B-Cell Acute Lymphoblastic Leukemia with t(12;21)

The most frequent chromosomal rearrangement in childhood B-cell acute lymphoblastic leukemia (B-ALL) is translocation t(12;21)(p13;q22). It results in the fusion of the ETV6::RUNX1 gene, which is active in the regulation of multiple crucial cellular pathways. Recent studies hypothesize that many translocations are influenced by RAG-initiated deletions, as well as defects in the RAS and NRAS pathways. According to a "two-hit" model for the molecular pathogenesis of pediatric ETV6::RUNX1-positive B-ALL, the t(12;21) translocation requires leukemia-causing secondary mutations. Patients with ETV6::RUNX1 express up to 60 different aberrations, which highlights the heterogeneity of this B-ALL subtype and is reflected in differences in patient response to treatment and chances of relapse. Most studies of secondary genetic changes have concentrated on deletions of the normal, non-rearranged ETV6 allele. Other predominant structural changes included deletions of chromosomes 6q and 9p, loss of entire chromosomes X, 8, and 13, duplications of chromosome 4q, or trisomy of chromosomes 21 and 16, but the impact of these changes on overall survival remains unclarified. An equally genetically diverse group is the recently identified new B-ALL subtype ETV6::RUNX1-like ALL. In our review, we provide a comprehensive description of recurrent secondary mutations in pediatric B-ALL with t(12;21) to emphasize the value of investigating detailed molecular mechanisms in ETV6::RUNX1-positive B-ALL, both for our understanding of the etiology of the disease and for future clinical advances in patient treatment and management.

Other (Non-CNS/Testicular) Extramedullary Localizations of Childhood Relapsed Acute Lymphoblastic Leukemia and Lymphoblastic Lymphoma-A Report from the ALL-REZ Study Group

Children with other extramedullary relapse of acute lymphoblastic leukemia are currently poorly characterized. We aim to assess the prevalence and the clinical, therapeutic and prognostic features of extramedullary localizations other than central nervous system or testis in children with relapse of acute lymphoblastic leukemia (ALL) and lymphoblastic lymphoma (LBL) treated on a relapsed ALL protocol.

PATIENTS AND METHODS

Patients with relapse of ALL and LBL, treated according to the multicentric ALL-REZ BFM trials between 1983 and 2015, were analyzed for other extramedullary relapse (OEMR) of the disease regarding clinical features, treatment and outcome. Local treatment/irradiation has been recommended on an individual basis and performed only in a minority of patients.

RESULTS

A total of 132 out of 2323 (5.6%) patients with ALL relapse presented with an OEMR (combined bone marrow relapse n = 78; isolated extramedullary relapse n = 54). Compared to the non-OEMR group, patients with OEMR had a higher rate of T-immunophenotype (p < 0.001), a higher rate of LBL (p < 0.001) and a significantly different distribution of time to relapse, i.e., more very early and late relapses compared to the non-OEMR group (p = 0.01). Ten-year probabilities of event-free survival (pEFS) and overall survival (pOS) in non-OEMR vs. OEMR were 0.38 ± 0.01 and 0.32 ± 0.04 (p = 0.0204) vs. 0.45 ± 0.01 and 0.37 ± 0.04 (p = 0.0112), respectively. OEMRs have been classified into five subgroups according to the main affected compartment: lymphatic organs (n = 32, 10y-pEFS 0.50 ± 0.09), mediastinum (n = 35, 10y-pEFS 0.11 ± 0.05), bone (n = 12, 0.17 ± 0.11), skin and glands (n = 21, 0.32 ± 0.11) and other localizations (n = 32, 0.41 ± 0.09). Patients with OEMR and T-lineage ALL/LBL showed a significantly worse 10y-pEFS (0.15 ± 0.04) than those with B-Precursor-ALL (0.49 ± 0.06, p < 0.001). Stratified into standard risk (SR) and high risk (HR) groups, pEFS and pOS of OEMR subgroups were in the expected range whereas the mediastinal subgroup had a significantly worse outcome. Subsequent relapses involved more frequently the bone marrow (58.4%) than isolated extramedullary compartments (41.7%). In multivariate Cox regression, OEMR confers an independent prognostic factor for inferior pEFS and pOS.

CONCLUSION

OEMR is adversely related to prognosis. However, the established risk classification can be applied for all subgroups except mediastinal relapses requiring treatment intensification. Generally, isolated OEMR of T-cell-origin needs an intensified treatment including allogeneic stem cell transplantation (HSCT) as a curative approach independent from time to relapse. Local therapy such as surgery and irradiation may be of benefit in selected cases. The indication needs to be clarified in further investigations.

Improving and Maintaining Responses in Pediatric B-Cell Acute Lymphoblastic Leukemia Chimeric Antigen Receptor-T Cell Therapy

ABSTRACT

Chimeric antigen receptor T therapy has heralded a new era in the treatment of acute lymphoblastic leukemia (ALL) and other hematologic malignancies. In this autologous immunotherapy, patient-derived T cells are genetically engineered and then infused back to kill the leukemia cells. The observed response rates in ALL are a testament to the success of this therapy. However, there have been instances where the patients either did not respond or relapsed after initial response. Emergence of resistance due to antigen loss and T-cell exhaustion has been observed. This poses a challenge in making this therapy successful for every ALL patient and warrants deeper understanding of emergence of resistance and potential approaches to overcome them. Here we discuss current perspectives and advances in this area.

The European Medicines Agency Review of Kymriah (Tisagenlecleucel) for the Treatment of Acute Lymphoblastic Leukemia and Diffuse Large B-Cell Lymphoma

Chimeric antigen receptor (CAR)-engineered T-cell therapy is becoming one of the most promising approaches in the treatment of cancer. On June 28, 2018, the Committee for Advanced Therapies (CAT) and the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Kymriah for pediatric and young adult patients up to 25 years of age with B-cell acute lymphoblastic leukemia (ALL) that is refractory, in relapse after transplant, or in second or later relapse and for adult patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL) after two or more lines of systemic therapy. Kymriah became one of the first European Union-approved CAR T therapies. The active substance of Kymriah is tisagenlecleucel, an autologous, immunocellular cancer therapy that involves reprogramming the patient's own T cells to identify and eliminate CD19-expressing cells. This is achieved by addition of a transgene encoding a CAR. The benefit of Kymriah was its ability to achieve remission with a significant duration in patients with ALL and an objective response with a significant duration in patients with DLBCL. The most common hematological toxicity was cytopenia in both patients with ALL and those with DLBCL. Nonhematological side effects in patients with ALL were cytokine release syndrome (CRS), infections, secondary hypogammaglobulinemia due to B-cell aplasia, pyrexia, and decreased appetite. The most common nonhematological side effects in patients with DLBCL were CRS, infections, pyrexia, diarrhea, nausea, hypotension, and fatigue. Kymriah also received an orphan designation on April 29, 2014, following a positive recommendation by the Committee for Orphan Medicinal Products (COMP). Maintenance of the orphan designation was recommended at the time of marketing authorization as the COMP considered the product was of significant benefit for patients with both conditions. IMPLICATIONS FOR PRACTICE: Chimeric antigen receptor (CAR)-engineered T-cell therapy is becoming the most promising approach in cancer treatment, involving reprogramming the patient's own T cells with a CAR-encoding transgene to identify and eliminate cancer-specific surface antigen-expressing cells. On June 28, 2018, Kymriah became one of the first EMA approved CAR T therapies. CAR T technology seems highly promising for diseases with single genetic/protein alterations; however, for more complex diseases there will be challenges to target clonal variability within the tumor type or clonal evolution during disease progression. Products with a lesser toxicity profile or more risk-minimization tools are also anticipated.

Pathogenesis of ETV6/RUNX1-positive childhood acute lymphoblastic leukemia and mechanisms underlying its relapse

ETV6/RUNX1 (E/R) is the most common fusion gene in childhood acute lymphoblastic leukemia (ALL). Multiple lines of evidence imply a “two-hit” model for the molecular pathogenesis of E/R-positive ALL, whereby E/R rearrangement is followed by a series of secondary mutations that trigger overt leukemia. The cellular framework in which E/R arises and the maintenance of a pre-leukemic condition by E/R are fundamental to the mechanism that underlies leukemogenesis. Accordingly, a variety of studies have focused on the relationship between the clones giving rise to the primary and recurrent E/R-positive ALL. We review here the most recent insights into the pathogenic mechanisms underlying E/R-positive ALL, as well as the molecular abnormalities prevailing at relapse.

Mechanism of ETV6-RUNX1 Leukemia

The t(12;21)(p13;q22) translocation is the most frequently occurring single genetic abnormality in pediatric leukemia. This translocation results in the fusion of the ETV6 and RUNX1 genes. Since its discovery in the 1990s, the function of the ETV6-RUNX1 fusion gene has attracted intense interest. In this chapter, we will summarize current knowledge on the clinical significance of ETV6-RUNX1, the experimental models used to unravel its function in leukemogenesis, the identification of co-operating mutations and the mechanisms responsible for their acquisition, the function of the encoded transcription factor and finally, the future therapeutic approaches available to mitigate the associated disease.

Cytogenetic instability in childhood acute lymphoblastic leukemia survivors

Contemporary anticancer therapies have largely improved the outcome for children with cancer, especially for Acute Lymphoblastic Leukemia (ALL). Actually, between 78% and 85% of patients achieve complete remission and are alive after 5 years of therapy completion. However, as cure rates increase, new concerns about the late effects of genotoxic treatment emerge, being the risk of developing secondary neoplasias, the most serious life-threatening rising problem. In the present paper, we describe and review the cytogenetic findings in peripheral lymphocytes from ALL survivors, and discuss aspects associated to the occurrence of increased chromosome rearrangements in this growing cohort.

Interphase FISH on TEL/AML1 positive acute lymphoblastic leukemia relapses--analysis of clinical relevance of additional TEL and AML1 copy number changes

OBJECTIVES

TEL/AML1 (ETV6/RUNX1) fusion resulting from the translocation t(12;21)(p13;q22) constitutes the most common chimeric fusion gene in initial childhood B-cell precursor (BCP) acute lymphoblastic leukemia (ALL) (19-27%) and has been associated with good prognosis. Three secondary aberrations in TEL/AML1 positive ALL have been suspected to negatively influence outcome: deletion of the second TEL allele (T), gain of the second AML1 allele (A) and duplication of the derivative chromosome 21 (der(21), TA). Many studies have explored such aberrations in initial disease, while only few reports have investigated them in relapses.

METHODS

In this study, bone marrow samples from 38 children with relapsed TEL/AML1 RT-PCR positive and negative BCP-ALL were analyzed for these mutations by interphase fluorescence in situ hybridization and results were compared with published data.

RESULTS

In children with TEL/AML1 positive ALL relapse, additional (a) TEL loss, (b) combined AML1 and der(21) gain, (c) combined TEL loss and AML1 gain as well as (d) the occurrence of a subpopulation with the signal pattern 1T/3A/1TA appear to be related to higher peripheral blast counts (PBCs) at relapse diagnosis (a and d) or a tendency towards the occurrence of a subsequent relapse (b and c) (P-values <0.05).

CONCLUSIONS

Our data together with published results on TEL/AML1 positive ALL suggest that frequencies of additional TEL and AML1 mutations are, with the exception of loss of untranslocated TEL, higher in first relapses than in initial disease. They also show that it is important to consider combined mutations in the analysis of this leukemia entity.

Non-classical karyotypic features in relapsed childhood B-cell precursor acute lymphoblastic leukemia

Karyotype analysis of acute lymphoblastic leukemia (ALL) at diagnosis has provided valuable prognostic markers for treatment stratification. However, reports of cytogenetic studies of relapsed ALL samples are limited. We compared the karyotypes from 436 nonselected B-cell precursor ALL patients at initial diagnosis and of 76 patients at first relapse. We noticed a relative increase of karyotypes that did not fall into the classic ALL cytogenetic subgroups (high hyperdiploidy, t(12;21), t(9;22), 11q23, t(1;19), <45 chromosomes) in a group of 29 patients at relapse (38%) compared to 130 patients at presentation (30%). Non-classical cytogenetic aberrations in these 29 patients were mostly found on chromosomes 1, 2, 7, 9, 13, 14, and 17. We also describe six rare reciprocal translocations, three of which involved 14q32. The most frequent abnormalities were found in 9p (12/29 cases) and were associated with a marked decrease in the duration of the second remission, but not of the probability of 10-year event-free survival after relapse treatment. From 29 patients with non-classical cytogenetic aberrations, only 8 (28%) had been stratified to a high risk-arm on the first treatment protocol, suggesting that this subgroup might benefit from the identification of new prognostic markers in future studies.

Polymorphism of Biotransformation Genes and Risk of Relapse in Childhood Acute Leukemia

Leukemia is a hematological malignancy that involves bone marrow. Polymorphism of biotransformation genes plays an important role in primary childhood leukemia and affects the incidence and character of acute leukemia relapse. A biochip designed to assess some polymorphisms of biotransformation genes was used to determine the frequency of the polymorphic variants ofCYP1A1, CYP2D6, GSTT1, GSTM1, MTHFR, MTRR, NQO1, CYP2C9, CYP2C19andNAT2in 332 children with acute lymphoblastic leukemia (ALL) and 71 children with acute myeloblastic leukemia (AML). TheCYP1A1 *1/*2A, GSTT1non null andGSTM1non null genotypes were more frequent in patients with primary leukemia than in relapse. Analysis of theNAT2genotype frequency revealed a characteristic genotype for each type of leukemia, which prevailed in patients with relapse: the genotype341C/-, 481T/-, 590G/G, 857G/Gprevailed in ALL patients with relapse, and the genotype341T/T, 481C/C, 590A/- in AML patients with relapse when compared with patients having primary ALL or AML, respectively. Thus, the polymorphisms ofCYP1A1, GSTT1, GSTM1andNAT2genes can be considered as markers for risk of relapse in childhood acute leukemia and can be used for the prognosis and individualization of standard therapy.

Long-term outcome of initially homogenously treated and relapsed childhood acute lymphoblastic leukaemia in Austria--a population-based report of the Austrian Berlin-Frankfurt-Münster (BFM) Study Group

Relapsed acute lymphoblastic leukaemia (ALL) is the most common cause for a fatal outcome in paediatric oncology. Although initial ALL cure rates have improved up to 80%, the prognosis of recurrent ALL remains dismal with event-free-survival (EFS) rates about 35%. In order to analyse a population-based cohort with uniform treatment of initial disease, we examined the outcome of children suffering from relapsed ALL in Austria for the past 20 years and the validity of the currently used prognostic factors (e.g. time to and site of relapse, immunophenotype). Furthermore, we compared survival rates after chemotherapy alone with those after allogeneic stem cell transplantation (SCT). All 896 patients who suffered from ALL in Austria between 1981 and 1999 were registered in a prospectively designed database and treated according to trials ALL-Berlin-Frankfurt-Münster (BFM)-Austria (A) 81, ALL-A 84 and ALL-BFM-A 86, 90 and 95. Of these, 203 (23%) suffered from recurrent disease. One-hundred-and-seventy-two patients (85%) achieved second complete remission. The probability of 10-year EFS for the total group was 34 +/- 3%. Clinical prognostic markers that independently influenced survival were time to relapse, site of relapse and the immunophenotype. Additionally, a Cox regression model demonstrated that allogeneic SCT after first relapse was associated with a superior EFS compared with chemo/radiotherapy only (hazard ratio = 0.254; P = 0.0017).

Cytogenetic and molecular analysis of MLL rearrangements in acute lymphoblastic leukaemia survivors

The successful treatment of paediatric malignancies by multimodal therapy has improved outcomes for children with cancer, especially those with acute lymphoblastic leukaemia (ALL). Second malignant neoplasms, however, represent a serious complication after treatment. Depending on dosage, 2-12% of patients treated with topoisomerase II inhibitors and/or alkylating agents develop treatment-related acute myeloid leukaemia characterized by translocations at 11q23. Our goal was to study MLL rearrangements in peripheral lymphocytes using cytogenetic and molecular methods in order to evaluate the late effects of cancer therapy in patients previously treated for childhood ALL. Chromosomal rearrangements at 11q23 were analysed in cytogenetic preparations from 49 long-term ALL survivors and 49 control individuals. Patients were subdivided depending on the inclusion or omission of topoisomerase II inhibitors (VP-16 and/or VM-26) in their treatment protocol. The statistical analysis showed significant (P = 0.007) differences between the frequency of translocations observed for the groups of patients and controls. These differences were also significant (P = 0.006) when the groups of patients (independent of the inclusion of topoisomerase II inhibitors) and controls were compared (P = 0.006). The frequencies of extra signals, however, did not differ between groups of patients and controls. Several MLL translocations were detected and identified by inverse polymerase chain reaction, followed by cloning and sequencing. Thirty-five patients (81%) presented putative translocations; among those, 91% corresponded with t(4;11) (q21;q23), while the other 9% corresponded with t(11;X), t(8;11)(q23;q23) and t(11;16). Our results indicate an increase in MLL aberrations in childhood ALL survivors years after completion of therapy. The higher frequency in this cohort might be associated with therapy using anti-tumoural drugs, independent of the inclusion of topoisomerase II inhibitors. Even though the biological significance of these rearrangements needs further investigation, they demonstrate a degree of genome instability, indicating the relevance of cytogenetic and molecular studies during the follow-up of patients in complete clinical remission.

Persistence of TEL-AML1 fusion gene as minimal residual disease has no additive prognostic value in CD 10 positive B-acute lymphoblastic leukemia: a FISH study

Objectives

We have analyzed t(12;21)(p13:q22) in an attempt to evaluate the frequency and prognostic significance of TEL-AML1 fusion gene in patients with childhood CD 10 positive B-ALL by fluorescence in situ hybridization (FISH). Also, we have monitored the prognostic value of this gene as a minimal residual disease (MRD).

Methods

All bone marrow samples of eighty patients diagnosed as CD 10 positive B-ALL in South Egypt Cancer Institute were evaluated by fluorescence in situ hybridization (FISH) for t(12;21) in newly diagnosed cases and after morphological complete remission as a minimal residual disease (MRD). We determined the prognostic significance of TEL-AML1 fusion represented by disease course and survival.

Results

TEL-AML1 fusion gene was positive in (37.5%) in newly diagnosed patients. There was a significant correlation between TEL-AML1 fusion gene both at diagnosis (r = 0.5, P = 0.003) and as a MRD (r = 0.4, P = 0.01) with favorable course. Kaplan-Meier curve for the presence of TEL-AML1 fusion at the diagnosis was associated with a better probability of overall survival (OS); mean survival time was 47 ± 1 month, in contrast to 28 ± 5 month in its absence (P = 0.006). Also, the persistence at TEL-AML1 fusion as a MRD was not significantly associated with a better probability of OS; the mean survival time was 42 ± 2 months in the presence of MRD and it was 40 ± 1 months in its absence. So, persistence of TEL-AML1 fusion as a MRD had no additive prognostic value over its measurement at diagnosis in terms of predicting the probability of OS.

Conclusion

For most patients, the presence of TEL-AML1 fusion gene at diagnosis suggests a favorable prognosis. The present study suggests that persistence of TEL-AML1 fusion as MRD has no additive prognostic value.

RUNX1 aberrations in ETV6/RUNX1-positive and ETV6/RUNX1-negative patients: its hemato-pathological and prognostic significance in a large cohort (619 cases) of ALL

A large-cohort study (619) of acute lymphoblastic leukemia (ALL) revealed an ETV6/RUNX1 (previously known as TEL/AML1) incidence of 18% in pediatric B-cell precussor ALL, indicating no geographical heterogeinity. Association of CD34-negative phenotype, peak incidence in the 3- to 7-year age group, and a comparatively low frequency of ETV6 homologue loss in ETV6/RUNX1-positive cases were distinct findings in this series. Additional genetic changes, such as ETV6 loss, extra RUNX1, ETV6/RUNX1 duplication, and MLL aberrations in the ETV6/RUNX1-positive group, supported the hypothesis of the ETV6/RUNX1 leukemogenic model that these secondary changes are necessary for leukemogenesis rather than progression of disease. This study disclosed RUNX1 alterations in the ETV6/RUNX1-negative group of BCP-ALL that encourages the investigation of RUNX1 at a large scale with longer follow-up, which will focus on the prognostic importance and the underlying biology of disease.

TEL/AML1 fusion gene in childhood acute lymphoblastic leukemia in southern Taiwan

Chromosomal abnormalities are found in 80-90% of childhood cases of acute lymphoblastic leukemia (ALL). Leukemia-specific chromosome aberrations not only have prognostic value, but also provide important clues for further investigation into leukogenesis, leukemic cell transformation, and proliferation. This study used reverse transcriptase-polymerase chain reaction techniques to detect transcripts of the leukemia-specific chromosome fusion gene, TEL/AML1, and to monitor the expression levels of the TEL-AML1 fusion transcript in ALL patients at sequential intervals during their treatment course. Twenty-five ALL patients were enrolled, including 20 who were newly diagnosed and five in relapse. The incidence of the TEL/AML1 fusion gene in this study was 32%. The clinical features of our eight TEL/AML1-positive ALL cases were similar to those in other studies. Blotting analysis of the levels of the TEL-AML1 fusion transcript was used to detect minimal residual disease. Reduced levels of TEL/AML1 expression were found in four of the six patients whose bone marrow or peripheral blood samples were obtained after treatment. Further investigation with a larger sample size is warranted.

High nerve growth factor receptor (p75NTR) expression is a favourable prognostic factor in paediatric B cell precursor-acute lymphoblastic leukaemia

Nerve growth factor (NGF) plays a pivotal role in cellular survival/death decisions with the low affinity receptor p75NTR predominately transmitting anti-proliferative signals. In spite of its established role in B-cell function and identification as a prognostically favourable marker in a number of malignancies, little is known about the expression pattern and prognostic significance of p75NTR in B cell precursor-acute lymphoblastic leukaemia (BCP-ALL). p75NTR expression was prospectively studied on primary ALL-blasts in a cohort of paediatric patients with common ALL (n = 86) and preB-ALL (n = 34) treated within the Co-operative study group for childhood acute lymphoblastic leukaemia (CoALL) protocol, CoALL06-97. Flow cytometric analysis showed that almost half of the patients expressed no or negligible amounts of p75NTR (<10%). The median expression in patients expressing p75NTR beyond that threshold was 49% (range 11-100%). In patients classified as low-risk at diagnosis, p75NTR expression was significantly higher than in high-risk patients (P = 0.001). Of note, p75NTR expression was lower in the 21 patients who subsequently developed relapse compared with those remaining in remission (P = 0.038). Accordingly, relapse-free survival was significantly better in patients expressing high surface p75NTR (P = 0.041). Thus, in this prospective analysis, high p75NTR expression was a strong prognostic marker that identified a group of paediatric ALL patients with favourable outcome.

Prevalence of ETV6-RUNX1 fusion gene in children with acute lymphoblastic leukemia in China

A series of 92 Chinese children newly diagnosed with acute lymphoblastic leukemia (ALL) were examined for the ETV6-RUNX1 (previously TEL-AML1) fusion gene by using a nested reverse transcriptase-polymerase chain reaction. ETV6-RUNX1 fusion transcripts were detected in 21 of 92 patients (22.8%): 16 with common ALL, 4 with precursor B-cell ALL, and 1 with T-ALL. The prevalence of ETV6-RUNX1 positivity was 24.7% (20/81) in childhood B-lineage ALL. The prevalence of ETV6-RUNX1 in Chinese pediatric ALL patients proved to be similar to that found in other countries.

Characteristics of patients with TEL-AML1-positive acute lymphoblastic leukemia with single or multiple fusions

BACKGROUND

The TEL-AML1 fusion in precursor-B ALL is generated by a cryptic 12;21 translocation that is detectable by fluorescence in situ hybridization (FISH). It is generally considered a favorable prognostic indicator. Some TEL-AML1+ ALL patients present at diagnosis with extra copies of the fusion, enumerated by FISH. The aim of the study was to determine whether additional copies of TEL-AML1 have clinical significance.

PROCEDURE

Charts of all TEL-AML1+ ALL patients at the UM and Children's Hospitals and Clinics of Minnesota between 1996 and 2004 were reviewed.

RESULTS

Eight patients (7 males/1 female, mean age 46 months) with two or more TEL-AML1 fusion signals and 24 with single TEL-AML1 fusion signals (18 males/6 females, mean age 52 months) were identified. There was no statistically significant difference in age or gender between the two groups. Patients with double TEL-AML1+ had a higher frequency of myeloid markers CD13 (P = 0.04) or CD33 (P = 0.003) than single TEL-AML1+ patients. Single TEL-AML1+ patients had higher WBC (P = 0.04) than double TEL-AML1+ patients. A trend toward slower therapy response was seen in double TEL-AML1+ patients versus single, (1 of 7 [14%] <5% marrow blasts on Day 7 vs. 13 of 23 [56%], P = 0.09). Double TEL-AML1+ patients had a higher relapse rate (P = 0.09) than single TEL-AML1+ patients.

CONCLUSIONS

Utilizing FISH to distinguish subgroups of TEL-AML1 fusion patients may have important prognostic implications. The presence of an extra fusion may portend poorer prognosis. A larger and longer-term follow-up study will be required to verify the possible clinical significance of the presence of multiple TEL-AML1 fusions.

Ethnic differences in the frequency of subtypes of childhood acute lymphoblastic leukemia: results of the Malaysia-Singapore Leukemia Study Group

Childhood acute lymphoblastic leukemia (ALL) is clinically heterogeneous with prognostically and biologically distinct subtypes. Although racial differences in frequency of different types of childhood ALL have been reported, many are confounded by selected or limited population samples. The Malaysia-Singapore (MA-SPORE) Leukemia Study Group provided a unique platform for the study of the frequency of major subgroups of childhood ALL in a large cohort of unselected multiethnic Asian children. Screening for the prognostically important chromosome abnormalities (TEL-AML1, BCR-ABL, E2A-PBX1, and MLL) using multiplex reverse-transcription polymerase chain reaction was performed on 299 consecutive patients with ALL at 3 study centers (236 de novo, 63 at relapse), with the ethnic composition predominantly Chinese (51.8%) and Malay (34.8%). Reverse-transcription polymerase chain reaction was successful in 278 (93%) of cases screened. The commonest fusion transcript was TEL-AML1 (19.1%) followed by BCR-ABL (7.8%), MLL rearrangements (4.2%), and E2A-PBX1 (3.1%). Chinese have a significantly lower frequency of TEL-AML1 (13.3% in de novo patients) compared with Malays (22.2%) and Indians (21.7%) (P=0.04). Malays have a lower frequency of T-ALL (6.2%) compared with the Chinese and Indians (9.8%). Both Malays (7.4%) and Chinese (5.0%) have significantly higher frequency of BCR-ABL compared with the Indian population (P<0.05) despite a similar median age at presentation. Our study suggests that there are indeed significant and important racial differences in the frequency of subtypes of childhood ALL. Comprehensive subgrouping of childhood ALL may reveal interesting population frequency differences of the various subtypes, their risk factors and hopefully, its etiology.

Brief communication: stability and catalytic activity of novel circular DNAzymes

DNAzymes represent a new generation of catalytic nucleic acids for specific RNA targeting in order to inhibit protein translation from the specifically cleaved mRNA. The 10-23 DNAzyme was found to hydrolyze RNA in a sequence-specific manner both in vitro and in vivo. Although single-stranded DNAzymes may represent the most effective nucleic acid drug to date, they are nevertheless sensitive to nuclease degradation and require modifications for in vivo application. However, previously used stabilization of DNAzymes by site-specific phosphorothioate (PT) modifications reduces the catalytic activity, and the PTO displays toxic side effects when applied in vivo. Thus, improving the stability of DNAzymes without reducing their catalytic activity is essential if the potential of these compounds should be realized in vivo.

RESULTS

The Circozyme was tested targeting the mRNA of the most common genetic rearrangement in pediatric acute lymphoblastic leukemia TEL/AML1 (ETV6/RUNX1). The Circozyme exhibits a stability comparable to PTO-modified DNAzymes without reduction of catalytic activity and specificity and may represent a promising tool for DNAzyme in vivo applications.

CONCLUSION

The inclusion of the catalytic site and the specific mRNA binding sequence of the DNAzyme into a circular loop-stem-loop structure (Circozyme) of approximately 70 bases presented here represents a new effective possibility of DNAzyme stabilization.

Chemokine IL-8 and chemokine receptor CXCR3 and CXCR4 gene expression in childhood acute lymphoblastic leukemia at first relapse

In this study, we examined the gene expression of interleukin (IL)-8, CXCR3, and CXCR4 in leukemic cells from 100 children with relapsed B-cell progenitors (BCP) acute lymphoblastic leukemia (ALL), using quantitative real-time polymerase chain reaction (RT-PCR). IL-8, CXCR3, and CXCR4 were expressed in almost all bone marrow (BM) samples. The CXCR4 expression significantly correlated with known prognostic factors at relapse: time point and site of relapse. Patients who had a combined BM relapse (n=21) had lower IL-8 and CXCR4 expression than those who had an isolated BM relapse (n=79). The CXCR3 expression was higher in female patients (n=39) than in male patients (n=61). However, this did not reach prognostic relevance in relapsed ALL.

Detection of ETV6 and RUNX1 gene rearrangements using fluorescence in situ hybridization in Mexican patients with acute lymphoblastic leukemia: experience at a single institution

The t(12;21) produces the gene fusion ETV6/RUNX1 and is a frequent rearrangement in childhood ALL, associated with a good prognosis. In Mexico its prevalence has not been reported. This study evaluated a group of consecutive Mexican children with newly diagnosed ALL, to detect the fusion using fluorescence in situ hybridization (FISH). Seventy-one bone marrow samples were analyzed with FISH, using ETV6/RUNX1 DNA probes. Abnormalities of ETV6, RUNX1, or both were found in 31 of the 71 (44%) patients. Six showed ETV6/RUNX1 fusion and 17, with extra RUNX1 copies, presented an additional chromosome 21 or dup(21)(q22). Five patients had structural changes in ETV6, and three patients showed extra copies of ETV6 and RUNX1 from polysomy of chromosomes 12 and 21. Our results revealed a fusion in 8.5% of the 71 cases analyzed. This frequency is lower than that observed in other populations (9.5-32%). The structural rearrangements resulting in RUNX1 extra copies were found in 9.8% of patients, which is close to the range reported (1.5-9.7%) by other authors. Due to the prevalence of RUNX1 overrepresentation in our population and its unknown prognostic significance, further studies should be conducted in consecutive children with ALL, to correlate this abnormality with the patients' follow-up.

Genetic abnormalities associated with the t(12;21) and their impact in the outcome of 56 patients with B-precursor acute lymphoblastic leukemia

The ETV6/RUNX1 rearrangement is found in 20-30% of children with B-cell precursor acute lymphoblastic leukemia and is associated with a good outcome. To determine the cytogenetic and molecular abnormalities associated with the ETV6/RUNX1 rearrangement and the influence of this rearrangement in patients' evolution, we analyzed the molecular cytogenetic profiles of 56 children with this rearrangement and B-cell precursor acute lymphoblastic leukemia. Secondary changes detected with conventional cytogenetics and with fluorescence in situ hybridization were found in 71.4% of cases, the most frequent being the loss of the normal ETV6 allele, 12p aberrations, duplication of the fusion gene, and trisomy 21, as in replicating the results of previous studies. In this preliminary series, with a mean follow-up of 69.3 months, secondary abnormalities did not influence patients' outcome. It seems therefore that the prognostic value of the t(12;21) does not vary and that ETV6/RUNX1 rearrangement is an independent indicator of good prognosis.

Co-existence of multiple subclones in TEL-AML1 at diagnosis of acute lymphoblastic leukaemia in association with submicroscopic deletion of AML1

The TEL/AML1 (ETV6/RUNX1) fusion gene is the most common genetic rearrangement in paediatric acute lymphoblastic leukaemia (ALL). Although considered to be a low-risk leukaemia, it is associated with a relapse rate of 10-20%. The coexistence of different subclones at diagnosis, based on polymerase chain reaction (PCR) studies of IG/TCR gene rearrangement, with differential response to chemotherapy, was recently reported in this subtype of ALL. We wished to demonstrate such subclones at diagnosis by a recently developed technique of quantitative multiparametric fluorescence in situ hybridization (FISH). Bone marrow cells from 80 paediatric patients with ALL at diagnosis were analysed for the presence of the TEL/AML1 fusion gene by interphase FISH. Fourteen patients were positive for the translocation. Four of them had several subclones associated with various combinations of additional chromosomal abnormalities. The most striking was an atypical and unexpected hybridization pattern consistent with a submicroscopic deletion of the 5' region of the AML1 breakpoint. Other abnormalities included TEL deletion, trisomy and tetrasomy 21 as well as double TEL-AML1 fusion. The presence of numerous subclones in about 25% of patients with TEL/AML1+ ALL suggests extensive clonal evolution by the time of diagnosis.

ETV6/RUNX1 fusion at diagnosis and relapse: some prognostic indications

This study was undertaken in order to compare the interphase and metaphase cytogenetics of 28 patients with ETV6/RUNX1 positive acute lymphoblastic leukemia, at diagnosis and relapse. The median time to relapse was 26 months. The significant fusion positive population heterogeneity revealed at interphase by a commercial probe for ETV6/RUNX1 fusion has not been described before. Six diagnostic samples had a single abnormal population; others had up to five each, which differed in the numbers of RUNX1 signals, and in the retention or loss of the second ETV6 signal. In contrast, the number of fusion signals was more constant. At relapse, there were fewer populations; the largest or unique clone was sometimes a re-emergence of a minor, diagnostic one, with a retained copy of ETV6 and the most RUNX1 signals. Abnormal, fusion negative clones were identified in bone marrow samples at extra-medullary relapse. Variant three or four-way translocations, which involved chromosomes 12 and 21, were prominent among the complex rearrangements revealed by metaphase FISH. The frequency of their occurrence at diagnosis and reappearance at relapse, sometimes accompanied by minor clonal evolution, was another new observation. Other recurrent cytogenetic features included a second copy of the fusion signal in six cases, partial duplication of the long arm of the X chromosome in two cases, and trisomy 10 in three cases. In comparing our data with previously reported cases, a picture is beginning to emerge of certain diagnostic features, which may provide circumstantial evidence of an increased risk of relapse.

Equal frequency of TEL/AML1 rearrangements in children with acute lymphoblastic leukemia with and without Down syndrome

Constitutional trisomy 21 is the most prominent predisposing factor to childhood leukemia, whereas the t(12;21)(p13;q22) with its molecular genetic counterpart, the TEL/AML1 fusion gene, is the most common acquired chromosomal rearrangement in childhood B-cell precursor (BCP) acute lymphoblastic leukemia (ALL). Thus, it was somewhat surprising that according to the currently available literature the incidence of TEL/AML1+ BCP ALL is extremely low in patients with Down syndrome (DS). To further investigate this issue in a population-based fashion, the authors retrospectively assessed the number of DS patients with a TEL/AML1+ ALL in two consecutive Austrian ALL multicenter trials. Accordingly, they were able to analyze 8 of 10 individuals with DS and a BCP ALL, two of whom who suffered from a TEL/AML1+ leukemia. Based on this observation they concluded that individuals with BCP leukemia and a constitutional trisomy 21 may have similar likelihood to have a TEL/AML1 rearrangement as BCP ALL patients without this specific predisposing factor.

Cytokine/cytokine receptor gene expression in childhood acute lymphoblastic leukemia

BACKGROUND

Recent studies have shown that cytokines/cytokine receptors (C/CR) affect leukemic cell growth and survival. The goal of the current study was to investigate possible correlations between gene expression patterns of C/CR in leukemic cells, clinical features, and outcome in children with acute lymphoblastic leukemia (ALL) at first disease recurrence.

METHODS

Between January 1997 and December 2000, bone marrow (BM) samples were collected from 68 children with first ALL recurrence at diagnosis. These patients were enrolled in the ALL-REZ 95-96 disease recurrence trials of the Berlin-Frankurt-Munster study group. C/CR gene expression (interleukin [IL]-7, IL-10, IL-12p40, IL-15, IL-18, IL-7Ralpha, IL-10R1, IL-15Ralpha, interferon-gamma [IFN-gamma], vascular epithelial growth factor [VEGF], Flt1, and transforming growth factor-beta) was quantified by real-time reverse transcriptase-polymerase chain reaction and correlated with protein expression by immunofluorescence.

RESULTS

In comparison with T-lineage ALL specimens, expression of IL-10, IFN-gamma, IL-15Ralpha, and Flt1 was significantly higher in B-cell precursor (BCP) ALL specimens (P <0.01). Among BCP ALL samples, gene expression of IL-7Ralpha and Flt1 was higher in pre-B than in common or pro-B leukemic cells. Moreover, expression levels of VEGF, IL-7Ralpha, IL-10R1, and IL-15Ralpha were lower in lymphoblasts of patients with a combined BM recurrence than in those with an isolated recurrence (P <0.05). Children with IL-15Ralpha expression above the median level had a significantly better probability of event-free survival (0.65 vs. 0.34, P=0.04) and survival (0.71 vs. 0.37, P=0.02) at 5 years.

CONCLUSIONS

Expression of distinct C/CR in ALL cells was associated with lineage commitment and differentiation of leukemic cells, as well as with prognosis. It remains to be evaluated whether these prognostic and biologic findings of distinct C/CR expression in leukemic cells also have therapeutical implications for future antileukemic strategies.

Equal frequency of TEL/AML1+ acute lymphoblastic leukemia in children with and without Down syndrome

Constitutional trisomy 21 is the most prominent predisposing factor to childhood leukemia, whereas the t(12;21)(p13;q22) with its molecular genetic counterpart, the TEL/AML1 fusion gene, is the most common acquired chromosomal rearrangement in childhood B-cell precursor (BCP) acute lymphoblastic leukemia (ALL). Thus, it was somewhat surprising that according to the currently available literature the incidence of TEL/AML1+ BCP ALL is extremely low in patients with Down syndrome (DS). To further investigate this issue in a population-based fashion, the authors retrospectively assessed the number of DS patients with a TEL/AML1+ ALL in two consecutive Austrian ALL multicenter trials. Accordingly, they were able to analyze 8 of 10 individuals with DS and a BCP ALL, including 2 who suffered from a TEL/AML1+ leukemia. Based on this observation we concluded that individuals with a constitutional trisomy 21 may have the similar likelihood to develop a TEL/AML1+ leukemia as BCP ALL patients without this specific predisposingfactor.

TEL-AML1 frequency in multi-ethnic Malaysian pediatric acute lymphoblastic leukemia

Eighty-eight multi-ethnic Malaysian pediatric acute lymphoblastic leukemia (ALL) patients were screened for the TEL-AML1 rearrangement by reverse transcription-polymerase chain reaction (RT-PCR). Fluorescence in situ hybridization (FISH) was used as an independent screen for 30 cases and to confirm RT-PCR positive cases. Seventeen patients, or 19%, were found to be t(12;21) positive. Ethnically the group comprised 12 Malays, 4 Chinese, and 1 Indian. All patients, including 1 with an unusual blast cell morphology who suffered an early relapse and death, were characteristic TEL-AML1 cases in cell count, age, ALL subset classification, and fusion transcript expressed. This study shows that in Malaysia, TEL-AML1 is found in the same distinct ALL subset and at a similar frequency as in other diverse childhood ALL cohorts.

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.

Real-time quantification of TEL-AML1 fusion transcripts for MRD detection in relapsed childhood acute lymphoblastic leukaemia. Comparison with antigen receptor-based MRD quantification methods

Response to therapy of ALL assessed by molecular methods has been proved to be a predictor of outcome. Alternatively to established but very labour-intensive DNA-based PCR-techniques the TEL-AML1 fusion transcript can serve as a marker for MRD monitoring. MRD quantification using TEL-AML1 is of particular interest if the results are directly comparable to data obtained by established DNA-based assays. Investigation of the potential of MRD monitoring using LightCycler technology for TEL-AML1 real-time quantification and comparison to results from established DNA-based MRD assays revealed corresponding results. Accordingly, TEL-AML1 MRD quantification is a sensitive, specific and rapid method that can supplement clone-specific MRD detection.

Prevalence of TEL/AML1 fusion gene in Brazilian pediatric patients with acute lymphoblastic leukemia

We studied 58 childhood B-lineage acute lymphoblastic leukemia (B-ALL) in Brazilian sample patients at the time of diagnosis to investigate the prevalence of the cryptic t(12;21)(p13;q22). All bone marrow specimens were G-band karyotyped, and commercial dual-color DNA probes were used to search for fusion signals in nuclei. The karyotype analysis showed hyperdiploidy as the most frequent abnormality. The frequency of patients with TEL/AML1 gene fusion was 19% (11 out of 58 cases). Six of the positive samples had normal karyotypes. Deletion of the wild-type TEL allele was observed in 27.3% of TEL/AML1 fusion-positive cases, but it was also identified in 4.2% of the negative cases. Three cases presented two fusion signals, indicating possible duplication of the der(21). The mean age of the patients with TEL/AML1 fusion was 4.8 years and the mean amount of peripheral leukocytes was 44,270 x 10(6)/L. The higher frequency of females with B-ALL (33/58 cases) observed in our sample was probably due to the selection mode of the study cases. The prevalence of TEL/AML1 fusion in Brazilian children in our study is similar to that found in other populations.

TEL/AML1 Overcomes Drug Resistance Through Transcriptional Repression of Multidrug Resistance-1 Gene Expression

The t(12;21)(p12;q22) chromosomal aberration, which is frequently observed in pediatric precursor B-cell acute lymphoblastic leukemia (ALL), generates the TEL/AML1 chimeric gene and protein. TEL/AML1-positive ALL has a favorable prognosis, and one possible reason is that this subtype of ALL rarely shows drug resistance. AML1/ETO, another AML1-containing chimeric protein, has been shown to transcriptionally repress the activity of the multidrug resistance-1 (MDR-1) gene promoter; thus, we examined whether TEL/AML1 also represses MDR-1 gene expression, possibly preventing the emergence of multidrug resistance. In this study, we show that the TEL/AML1 protein binds to the consensus AML1 binding site in the MDR-1 promoter and transcriptionally represses its activity. Following transient transfection of TEL/AML1 protein into Adriamycin-resistant K562/Adr cells, we also demonstrate that TEL/AML1 can down-regulate the expression of P-glycoprotein, a product of the MDR-1 gene, and restore the chemosensitivity to the cells. Furthermore, we report that MDR-1 mRNA levels in leukemic cells obtained from TEL/AML1-positive ALL patients are lower than those from TEL/AML1-negative ALL patients. Thus, TEL/AML1 protein acts as a transcriptional repressor of MDR-1 gene expression, and although TEL/AML1 has been implicated in leukemogenesis, its effects on the MDR-1 gene may contribute to the excellent prognosis of TEL/AML1-positive ALL with current therapy.

Mechanism, detection and clinical significance of the reciprocal translocation t(12;21)(p12;q22) in the children suffering from acute lymphoblastic leukaemia

The t(12;21)(p12;q22) is the most frequent chromosomal rearrangement observed in acute lymphoblastic leukaemia (ALL) and is associated with favourable prognosis and good response to initial treatment. The translocation-Ets-leukaemia (TEL) and AML1 genes are very often involved in chromosomal translocations in haematopoietic malignancies. This review presents the structure, roles of TEL and AML1 genes, and their proteins in haematopoiesis and in leukaemiogenesis as well. Aspects such as: the mechanism of translocation t(12;21)(p12;q22), function of TEL/AML1 fusion gene and chimeric protein, clinical significance of this abnormality and methods allowing to detect this translocation and its transcript are also discussed in this paper.

Favorable outcome in 20-year follow-up of children with very-low-risk ALL and minimal standard therapy, with special reference to TEL-AML1 fusion

BACKGROUND

As the treatment results of childhood ALL have improved, avoidance of late effects has become increasingly important. Identification of favorable prognostic factors helps to achieve this goal.

PROCEDURE

We studied the prognostic value of TEL-AML1 fusion and a risk factor composed of age, white blood cell count (WBC), lymphomatous features, and hemoglobin level (Hb). We also compared outcome between two cohorts; cohort 1 (n=100) diagnosed 1975-1981, and cohort 2 (n=102) 1989-1991. Both cohorts were retrospectively divided in two groups: very-low-risk (WBC <10 x 10(9)/L, age 2 to <10 years, no lymphomatous features, Hb <90 g/L), and non-low-risk (=the remainder). We performed fluorescent in situ hybridization (FISH) of TEL-AML1 fusion of the marrow samples obtained at diagnosis.

RESULTS

The median follow-up is 20 years in cohort 1, and 8 years in cohort 2. In both cohorts, the very-low-risk category comprised one-fourth of the children. TEL-AML1 fusion was more frequent in the very-low-risk (35%) than in the non-low-risk group (17%) (P=0.03). The 8-year event-free survival (EFS) of children with the fusion was better than of those without, 74 vs. 54% (P=0.040). The 8-year EFS in the very-low-risk group was 76% in cohort 1, and 79% in cohort 2 (n.s.). In the non-low-risk groups, EFS was 39 vs. 64% (P=0.02), respectively.

CONCLUSIONS

Our data support the reported association of TEL-AML1 fusion with a favorable outcome although the risk group had a greater impact. These very-long-term follow-up data also indicate that children with very-low-risk ALL (slow disease) had a favorable outcome already in the late 1970s, and may be over treated with the contemporary ALL protocols.

Conversion of childhood acute lymphocytic leukemia (L2) with a double t(12;21) to juvenile myelomonocytic leukemia with a novel t(4;11)(p12;q23): a cytogenetic, morphologic, and immunophenotypic study

Here we describe a cytogenetic and flow-cytometric study of a case in which a conversion of childhood acute lymphocytic leukemia (ALL) into juvenile myelomonocytic leukemia (JMML) occurred. A 3-year-old boy diagnosed CALLA+, pre-B-ALL with double t(12;21) (by fluorescence in situ hybridization analysis), was treated as per the BFM protocol. A cytogenetic analysis performed at 17 months into treatment showed no t(12;21) in bone marrow (BM) cells; however, a novel translocation, namely, t(4;11), involving the p12 locus on chromosome 4 and the MLL gene at 11q23 was detected in monocytes. No cytogenetic abnormalities were found either in Epstein-Barr virus-transformed B cells or in phytohemagglutinin-stimulated T-lymphoid cells. Flow-cytometric analysis demonstrated an asynchronous expression of the antigenic determinants in populations of granulocytic and monocytoid cells: 60% of monocytes expressed low levels of CD14, an unusually high level of CD15, and no CD13 or HLA-DR antigens; 74% of myeloid cells expressed no CD13. Our results indicate that the transformation from B-cell ALL to JMML in this case occurred most probably in the granulocyte-erythroid-macrophage-megakaryocyte progenitor cells without involving the lymphoid cell line. To date, the child is 10 months off therapy and asymptomatic, with t(4;11) in only 3% of the cells.

Standardization and quality control studies of ‘real-time’ quantitative reverse transcriptase polymerase chain reaction of fusion gene transcripts for residual disease detection in leukemia – A Europe Against Cancer Program

Detection of minimal residual disease (MRD) has proven to provide independent prognostic information for treatment stratification in several types of leukemias such as childhood acute lymphoblastic leukemia (ALL), chronic myeloid leukemia (CML) and acute promyelocytic leukemia. This report focuses on the accurate quantitative measurement of fusion gene (FG) transcripts as can be applied in 35-45% of ALL and acute myeloid leukemia, and in more than 90% of CML. A total of 26 European university laboratories from 10 countries have collaborated to establish a standardized protocol for TaqMan-based real-time quantitative PCR (RQ-PCR) analysis of the main leukemia-associated FGs within the Europe Against Cancer (EAC) program. Four phases were scheduled: (1) training, (2) optimization, (3) sensitivity testing and (4) patient sample testing. During our program, three quality control rounds on a large series of coded RNA samples were performed including a balanced randomized assay, which enabled final validation of the EAC primer and probe sets. The expression level of the nine major FG transcripts in a large series of stored diagnostic leukemia samples (n=278) was evaluated. After normalization, no statistically significant difference in expression level was observed between bone marrow and peripheral blood on paired samples at diagnosis. However, RQ-PCR revealed marked differences in FG expression between transcripts in leukemic samples at diagnosis that could account for differential assay sensitivity. The development of standardized protocols for RQ-PCR analysis of FG transcripts provides a milestone for molecular determination of MRD levels. This is likely to prove invaluable to the management of patients entered into multicenter therapeutic trials.

The biology and therapy of adult acute lymphoblastic leukemia

BACKGROUND

Much progress has been made in understanding the biology of acute lymphoblastic leukemia (ALL). This has translated into the recognition of several subgroups of ALL and the institution of risk-adapted therapies. New therapies are emerging based on the definition of specific cytogenetic-molecular abnormalities.

METHODS

A review from the English literature, including original articles and related reviews from Medline (Pubmed) and abstracts based on publication of meeting material, was performed.

RESULTS

Changes in the pathologic classification of ALL have led to therapeutic consequences. Adaptation of successful treatment strategies in children with ALL has resulted in similar complete response rates in adults. Prognosis has especially improved in mature-B-cell and T-lineage ALL. The role of tyrosine kinase inhibitors in Philadelphia chromosome-positive ALL was evaluated in the current study. However, regardless of the ALL subgroup, long-term survival of adults is still inferior to that in children.

CONCLUSIONS

Intense clinical and laboratory research is attempting to close the gap in outcome between children and adults with ALL. Investigations are focusing on 1) refinement of the basic treatment stratagem of induction, consolidation, and maintenance; 2) expansion of risk-based, subgroup-oriented therapies; 3) assessment of minimal residual disease, its impact on disease recurrence, and its practical implications in clinical practice; 4) salvage strategies; 5) the role of stem cell transplantation in ALL; and 6) the development of new drugs based on a better understanding of disease biology.

Levels of the soluble, 55-kilodalton isoform of tumor necrosis factor receptor in bone marrow are correlated with the clinical outcome of children with acute lymphoblastic leukemia in first recurrence

BACKGROUND

It has been shown that the soluble, 55-kilodalton isoform of tumor necrosis factor receptor (sTNFRp55) enhances tumor survival by exhibiting competitive ligand binding. The objective of the current study was to determine the levels of sTNFRp55 and their impact on outcome in 106 children with acute lymphoblastic leukemia (ALL) in first recurrence.

METHODS

Between January 1997 and December 2001, bone marrow (BM) samples were collected from 106 children with a first recurrence of ALL at diagnosis. These patients were enrolled in the Berlin-Frankfurt-Münster (BFM) ALL recurrence trial, ALL-REZ BFM 90-96. Levels of sTNFRp55 in BM samples were determined with a commercially available enzyme-linked immunosorbent assay kit. Event-free survival (EFS) and overall survival were assessed from the date of study entry or the date of randomization, as appropriate.

RESULTS

The mean sTNFRp55 level (+/- standard deviation) was 3.40 +/- 2.57 ng/mL. High levels of sTNFRp55 were associated with shorter duration of first complete remission and observation time as well as poor response to chemotherapy. Most importantly, the probability of EFS (pEFS) at 3 years was significantly worse for children with recurrent ALL who had sTNFRp55 levels greater than the median value (> 2.77 ng/mL) compared with patients who had levels that were less than the median value (pEFS: 0.44 +/- 0.10 ng/mL vs. 0.12 +/- 0.10 ng/mL; P = 0.006). It is noteworthy that the sTNFRp55 levels in 22 children with recurrent, TEL-AML1-positive ALL ([t(12;21)(p13;q22)]; 2.69 +/- 1.05 ng/mL) were significantly lower compared with the levels in children who had TEL-AML1-negative ALL (3.34 +/- 1.49 ng/mL; P < 0.05).

CONCLUSIONS

The results indicated that a high sTNFRp55 level represents a negative prognostic factor for children with recurrent ALL in terms of EFS and overall survival.

Minimal residual disease detection in childhood precursor-B-cell acute lymphoblastic leukemia: relation to other risk factors. A Children's Oncology Group study

Minimal residual disease (MRD) can be detected in the marrows of children undergoing chemotherapy either by flow cytometry or polymerase chain reaction. In this study, we used four-color flow cytometry to detect MRD in 1016 children undergoing therapy on Children's Oncology Group therapeutic protocols for precursor-B-cell ALL. Compliance was excellent, with follow-up samples received at the end of induction on nearly 95% of cases; sensitivity of detection at this time point was at least 1/10,000 in more than 90% of cases. Overall, 28.6% of patients had detectable MRD at the end of induction. Patients with M3 marrows at day 8 were much more likely to be MRD positive (MRD+) than those with M2 or M1 marrows. Different genetically defined groups of patients varied in their prevalence of MRD. Specifically, almost all patients with BCR-ABL had high levels of end-of-induction MRD. Only 8.4% of patients with TEL-AML1 were MRD+>0.01% compared with 20.3% of patients with trisomies of chromosomes 4 and 10. Our results show that MRD correlates with conventional measures of slow early response. However, the high frequency of MRD positivity in favorable trisomy patients suggests that the clinical significance of MRD positivity at the end of induction may not be the same in all patient groups.

[Cytogenetic abnormalities in acute lymphoblastic leukemia]

Acute lymphoblastic leukemias (ALL) represent malignant clonal proliferations of stem cells committed in lymphoid differentiation, B or T-cell ALL. Clonal chromosomal abnormalities are found in 80% children and 70% adult cases. They are associated with an independent prognostic value which modifies the therapeutic approach and therefore karyotyping at diagnosis is mandatory. Molecular techniques such as FISH and RT-PCR are very helpful too as cryptic chromosomal abnormalities have been described. In this review, numerical and structural abnormalities are described: frequency, diagnosis and prognosis value as well as genes involved in structural abnormalities.

Preponderant mitotic activity of nonleukemic cells plays an important role in failures to detect abnormal clone in childhood acute lymphoblastic leukemia

At diagnosis, clonal chromosomal abnormalities are found in the bone marrow blasts in more than two thirds of children with acute lymphoblastic leukemia (ALL). Practically, however, failure to detect these abnormalities is frequent and usually attributed to poor marrow sampling, inadequate metaphases, and/or a preponderant mitotic activity among nonleukemic cells. The authors applied fluorescence in situ hybridization (FISH) techniques to re-examine 30 cases of karyotypically "normal" childhood ALL to explore the role of preponderant mitotic activities of nonleukemic cells in failures to detect clonal abnormalities. The FISH test were performed using TEL/AML1 fusion gene probe and the centromere probes for chromosome 8 and 10 to detect the t(12;21) translocation and/or hyperdiploidy. Half of the karyotypically "normal" ALL cases examined have been found to have abnormal clones with t(12;21) rearrangement and/or hyperdiploidy by this specially designed FISH assay. Contrary to expectation, the authors found a higher incidence (52%) of clonal abnormalities in cases where over 20 metaphases had been examined than in cases (44%) where fewer than 20 metaphases had been analyzed. These findings suggest that a preponderant mitotic activity of nonleukemic cells plays an important role in failures to detect an abnormal clone by conventional cytogenetic studies. Therefore, karyotypically "normal" childhood ALL patients should undergo FISH studies to rule out the presence of t(12;21) and/or hyperdiploid clone.

Minimal residual disease prior to stem cell transplant for childhood acute lymphoblastic leukaemia

Allogeneic stem cell transplantation (SCT) is a highly effective therapy for childhood acute lymphoblastic leukaemia (ALL). Concerns about unnecessary toxicity and expense mean that SCT is currently largely reserved for children who cannot be cured with chemotherapy. Not surprisingly, many such children also fail SCT. Retrospective studies have shown that a single analysis of minimal residual disease (MRD) pre-SCT identified those at highest risk of relapse. It is now appropriate to call for the universal incorporation of standardized MRD testing into SCT protocols as the next step to maximize the clinical impact of this technology in ALL.

Persistence of TEL-AML1 transcript in acute lymphoblastic leukemia in long-term remission

BACKGROUND

It has recently been shown that t (12;21) (p13;q 22) is the most common molecular genetic abnormality in childhood acute lymphoblastic leukemia (ALL). We have analyzed this translocation in an attempt to evaluate its incidence and to monitor minimal residual disease (MRD) with t (12; 21) rearrangement by detection of TEL-AML1 transcript in patients with childhood ALL.

PROCEDURE

All cryopreserved bone marrow samples were analyzed using a nested reverse transcription-polymerase chain reaction (RT-PCR) method. TEL-AML1 transcripts were searched for in 34 ALL patients, including six in relapse consecutively diagnosed at our institution between 1991 and 1997.

RESULTS

TEL-AML1 transcripts were found in five (19%) of 27 patients with B precursor ALL. The patients with BCR-ABL, chromosome 11q23 rearrangement and T-ALL patients did not express TEL-AML1 transcripts. Moreover, MRD in five patients with TEL-AML1 transcripts were analyzed in serial samples. Although TEL-AML1 transcripts disappeared soon after the beginning of chemotherapy in three of the five patients, one patient continued to express them for up to 21 months without recurrence and remained in continuous complete remission for seven years after the cessation of chemotherapy. The remaining patient was admitted to our hospital after the second relapse but died following a failure to induce complete remission.

CONCLUSION

For most patients, the presence of TEL-AML1 transcripts suggests excellent chemosensitivity and a favorable prognosis, but some patients with these transcripts have a different outcome. The present study suggests the possibility that a persistence of MRD is not necessarily related to a relapse of ALL with TEL-AML1 fusion. The prognostic significance of TEL-AML1 transcript remains controversial. Further studies are needed to evaluate the relation between the TEL-AML1 transcript and prognosis.

Prognostic significance of the TEL-AML1 fusion gene in pediatric acute lymphoblastic leukemia in Turkey

PURPOSE

The t(12;21) translocation is the most common reciprocal chromosomal rearrangement in pediatric acute lymphoblastic leukemia (ALL). This translocation fuses two genes, TEL and AML1, and results in the production of the TEL-AML1 fusion protein. The authors investigated the incidence and prognostic significance of the TEL-AML1 fusion gene in patients with ALL in Turkey.

METHODS

The authors analyzed 219 children with ALL using the reverse transcription-polymerase chain reaction.

RESULTS

The TEL-AML1 fusion transcript was detected in 20.1% (44/219) of newly diagnosed children with ALL. -positive patients had precursor B-cell ALL and were 3 to 10 years old at diagnosis. -positive patients had a significantly lower rate of relapse compared with -negative patients. -positive patients have a higher overall survival rate than -negative patients.

CONCLUSIONS

These data support that the presence of at diagnosis is an independent favorable prognostic indicator in patients with ALL in Turkey.