Frequency and Prognostic Impact of ALK Amplifications and Mutations in the European Neuroblastoma Study Group (SIOPEN) High-Risk Neuroblastoma Trial (HR-NBL1)

PURPOSE

In neuroblastoma (NB), the ALK receptor tyrosine kinase can be constitutively activated through activating point mutations or genomic amplification. We studied ALK genetic alterations in high-risk (HR) patients on the HR-NBL1/SIOPEN trial to determine their frequency, correlation with clinical parameters, and prognostic impact.

MATERIALS AND METHODS

Diagnostic tumor samples were available from 1,092 HR-NBL1/SIOPEN patients to determine ALK amplification status (n = 330), ALK mutational profile (n = 191), or both (n = 571).

RESULTS

Genomic ALK amplification (ALKa) was detected in 4.5% of cases (41 out of 901), all except one with MYCN amplification (MNA). ALKa was associated with a significantly poorer overall survival (OS) (5-year OS: ALKa [n = 41] 28% [95% CI, 15 to 42]; no-ALKa [n = 860] 51% [95% CI, 47 to 54], [P < .001]), particularly in cases with metastatic disease. ALK mutations (ALKm) were detected at a clonal level (> 20% mutated allele fraction) in 10% of cases (76 out of 762) and at a subclonal level (mutated allele fraction 0.1%-20%) in 3.9% of patients (30 out of 762), with a strong correlation between the presence of ALKm and MNA (P < .001). Among 571 cases with known ALKa and ALKm status, a statistically significant difference in OS was observed between cases with ALKa or clonal ALKm versus subclonal ALKm or no ALK alterations (5-year OS: ALKa [n = 19], 26% [95% CI, 10 to 47], clonal ALKm [n = 65] 33% [95% CI, 21 to 44], subclonal ALKm (n = 22) 48% [95% CI, 26 to 67], and no alteration [n = 465], 51% [95% CI, 46 to 55], respectively; P = .001). Importantly, in a multivariate model, involvement of more than one metastatic compartment (hazard ratio [HR], 2.87; P < .001), ALKa (HR, 2.38; P = .004), and clonal ALKm (HR, 1.77; P = .001) were independent predictors of poor outcome.

CONCLUSION

Genetic alterations of ALK (clonal mutations and amplifications) in HR-NB are independent predictors of poorer survival. These data provide a rationale for integration of ALK inhibitors in upfront treatment of HR-NB with ALK alterations.

Incorporation of somatic panels for the detection of haematopoietic transformation in children and young adults with leukaemia predisposition syndromes and with acquired cytopenias

Detection of somatic mutations may help verify the diagnosis of myelodysplastic syndrome (MDS) in patients with persistent cytopenias or with MDS-predisposition syndromes, prior to the development of overt leukemia. However, the spectrum and consequences of acquired changes in paediatric patients have not been fully evaluated, and especially not in the context of an underlying syndrome. We incorporated a targeted next-generation-sequencing panel of 54 genes for the detection of somatic mutations in paediatric and young adult patients with inherited or acquired cytopenias. Sixty-five patients were included in this study, of whom 17 (26%) had somatic mutations. We detected somatic mutations in 20% of individuals with inherited MDS-predisposition syndromes, including in patients with severe congenital neutropenia and Fanconi anaemia, and with germline mutations in SAMD9L. Thirty-eight per cent of children with acquired cytopenias and suspected MDS had somatic changes, most commonly in genes related to signal transduction and transcription. Molecularly abnormal clones often preceded cytogenetic changes. Thus, routine performance of somatic panels can establish the diagnosis of MDS and determine the optimal timing of haematopoietic stem cell transplantation, prior to the development of leukaemia. In addition, performing somatic panels in patients with inherited MDS-predisposition syndromes may reveal their unique spectrum of acquired mutations.

Age Dependency of the Prognostic Impact of Tumor Genomics in Localized Resectable MYCN-Nonamplified Neuroblastomas. Report From the SIOPEN Biology Group on the LNESG Trials and a COG Validation Group

For localized, resectable neuroblastoma without MYCN amplification, surgery only is recommended even if incomplete. However, it is not known whether the genomic background of these tumors may influence outcome.

Validation of the United Kingdom copy-number alteration classifier in 3239 children with B-cell precursor ALL

Genetic abnormalities provide vital diagnostic and prognostic information in pediatric acute lymphoblastic leukemia (ALL) and are increasingly used to assign patients to risk groups. We recently proposed a novel classifier based on the copy-number alteration (CNA) profile of the 8 most commonly deleted genes in B-cell precursor ALL. This classifier defined 3 CNA subgroups in consecutive UK trials and was able to discriminate patients with intermediate-risk cytogenetics. In this study, we sought to validate the United Kingdom ALL (UKALL)-CNA classifier and reevaluate the interaction with cytogenetic risk groups using individual patient data from 3239 cases collected from 12 groups within the International BFM Study Group. The classifier was validated and defined 3 risk groups with distinct event-free survival (EFS) rates: good (88%), intermediate (76%), and poor (68%) (P < .001). There was no evidence of heterogeneity, even within trials that used minimal residual disease to guide therapy. By integrating CNA and cytogenetic data, we replicated our original key observation that patients with intermediate-risk cytogenetics can be stratified into 2 prognostic subgroups. Group A had an EFS rate of 86% (similar to patients with good-risk cytogenetics), while group B patients had a significantly inferior rate (73%, P < .001). Finally, we revised the overall genetic classification by defining 4 risk groups with distinct EFS rates: very good (91%), good (81%), intermediate (73%), and poor (54%), P < .001. In conclusion, the UKALL-CNA classifier is a robust prognostic tool that can be deployed in different trial settings and used to refine established cytogenetic risk groups.

Circulating microRNA biomarkers for metastatic disease in neuroblastoma patients

In this study, the circulating miRNome from diagnostic neuroblastoma serum was assessed for identification of noninvasive biomarkers with potential in monitoring metastatic disease. After determining the circulating neuroblastoma miRNome, 743 miRNAs were screened in 2 independent cohorts of 131 and 54 patients. Evaluation of serum miRNA variance in a model testing for tumor stage, MYCN status, age at diagnosis, and overall survival revealed tumor stage as the most significant factor impacting miRNA abundance in neuroblastoma serum. Differential abundance analysis between patients with metastatic and localized disease revealed 9 miRNAs strongly associated with metastatic stage 4 disease in both patient cohorts. Increasing levels of these miRNAs were also observed in serum from xenografted mice bearing human neuroblastoma tumors. Moreover, murine serum miRNA levels were strongly associated with tumor volume. These findings were validated in longitudinal serum samples from metastatic neuroblastoma patients, where the 9 miRNAs were associated with disease burden and treatment response.

Heterogeneous MYCN amplification in neuroblastoma: a SIOP Europe Neuroblastoma Study

Background

In neuroblastoma (NB), the most powerful prognostic marker, the MYCN amplification (MNA), occasionally shows intratumoural heterogeneity (ITH), i.e. coexistence of MYCN-amplified and non-MYCN-amplified tumour cell clones, called heterogeneous MNA (hetMNA). Prognostication and therapy allocation are still unsolved issues.

Methods

The SIOPEN Biology group analysed 99 hetMNA NBs focussing on the prognostic significance of MYCN ITH.

Results

Patients <18 months (18 m) showed a better outcome in all stages as compared to older patients (5-year OS in localised stages: <18 m: 0.95 ± 0.04, >18 m: 0.67 ± 0.14, p = 0.011; metastatic: <18 m: 0.76 ± 0.15, >18 m: 0.28 ± 0.09, p = 0.084). The genomic 'background’, but not MNA clone sizes, correlated significantly with relapse frequency and OS. No relapses occurred in cases of only numerical chromosomal aberrations. Infiltrated bone marrows and relapse tumour cells mostly displayed no MNA. However, one stage 4s tumour with segmental chromosomal aberrations showed a homogeneous MNA in the relapse.

Conclusions

This study provides a rationale for the necessary distinction between heterogeneous and homogeneous MNA. HetMNA tumours have to be evaluated individually, taking age, stage and, most importantly, genomic background into account to avoid unnecessary upgrading of risk/overtreatment, especially in infants, as well as in order to identify tumours prone to developing homogeneous MNA.

miR expression profiling at diagnosis predicts relapse in pediatric precursor B-cell acute lymphoblastic leukemia

Our aim was to identify miRNAs that can predict risk of relapse in pediatric patients with acute lymphoblastic leukemia (ALL). Following high-throughput miRNA expression analysis (48 samples), five miRs were selected for further confirmation performed by real time quantitative PCR on a cohort of precursor B-cell ALL patients (n = 138). The results were correlated with clinical parameters and outcome. Low expression of miR-151-5p, and miR-451, and high expression of miR-1290 or a combination of all three predicted inferior relapse free survival (P = 0.007, 0.042, 0.025, and <0.0001, respectively). Cox regression analysis identified aberrant expression of the three miRs as an independent prognostic marker with a 10.5-fold increased risk of relapse (P = 0.041) in PCR-MRD non-high risk patients. Furthermore, following exclusion of patients harboring IKZF1 deletion, the aberrant expression of all three miRs could identify patients with a 24.5-fold increased risk to relapse (P < 0.0001). The prognostic relevance of the three miRNAs was evaluated in a non-BFM treated precursor B-cell ALL cohort (n = 33). A significant correlation between an aberrant expression of at least one of the three miRs and poor outcome was maintained (P < 0.0001). Our results identify an expression profile of miR-151-5p, miR-451, and miR-1290 as a novel biomarker for outcome in pediatric precursor B-cell ALL patients, regardless of treatment protocol. The use of these markers may lead to improved risk stratification at diagnosis and allow early therapeutic interventions in an attempt to improve survival of high risk patients.

Influence of segmental chromosome abnormalities on survival in children over the age of 12 months with unresectable localised peripheral neuroblastic tumours without MYCN amplification

Background:

The prognostic impact of segmental chromosome alterations (SCAs) in children older than 1 year, diagnosed with localised unresectable neuroblastoma (NB) without MYCN amplification enrolled in the European Unresectable Neuroblastoma (EUNB) protocol is still to be clarified, while, for other group of patients, the presence of SCAs is associated with poor prognosis.

Methods:

To understand the role of SCAs we performed multilocus/pangenomic analysis of 98 tumour samples from patients enrolled in the EUNB protocol.

Results:

Age at diagnosis was categorised into two groups using 18 months as the age cutoff. Significant difference in the presence of SCAs was seen in tumours of patients between 12 and 18 months and over 18 months of age at diagnosis, respectively (P=0.04). A significant correlation (P=0.03) was observed between number of SCAs per tumour and age. Event-free (EFS) and overall survival (OS) were calculated in both age groups, according to both the presence and number of SCAs. In older patients, a poorer survival was associated with the presence of SCAs (EFS=46% vs 75%, P=0.023; OS=66.8% vs 100%, P=0.003). Moreover, OS of older patients inversely correlated with number of SCAs (P=0.002). Finally, SCAs provided additional prognostic information beyond histoprognosis, as their presence was associated with poorer OS in patients over 18 months with unfavourable International Neuroblastoma Pathology Classification (INPC) histopathology (P=0.018).

Conclusions:

The presence of SCAs is a negative prognostic marker that impairs outcome of patients over the age of 18 months with localised unresectable NB without MYCN amplification, especially when more than one SCA is present. Moreover, in older patients with unfavourable INPC tumour histoprognosis, the presence of SCAs significantly affects OS.

Abstract B34: Increased risk of relapse in non-high-risk children with pediatric B-lineage acute lymphoblastic leukemia can be predicted at diagnosis by microRNA expression

Aim: microRNAs (miRNAs) have been implicated in many malignancies. Our aim was to identify specific miRNAs that can predict risk of relapse in pediatric acute lymphoblastic leukemia (ALL) patients treated on BFM protocols, better than the current risk group stratification. Currently, the main method for risk group stratification is based on the amount of minimal residual disease (MRD) assessed at specific time points by real time quantitative PCR (RQ-PCR).

Material and methods: Following microRNA expression analysis, we decided to focus on miR-151-5p and miR-451 that significantly correlated with known prognostic factors in ALL. Validation was performed by measuring the expression levels of miR-151-5p and miR-451 by RQ- PCR on a cohort of B-lineage ALL patients treated by a Berlin-Frankfurt-Munster (BFM) protocol following exclusion of Philadelphia positive patients (n=123).

Results: Low expression of miR-151-5p, miR-451 or of both together resulted in significantly worse relapse free survival (RFS) (61%, 64% and 43%, respectively) compared to RFS rates when either or both miRNAs were highly expressed (83%, 82% and 82%, respectively) (p=0.023, 0.03 and 0.0001, respectively). Multivariate Cox regression analysis identified low expression of both miRNAs as an independent prognostic marker. Patients expressing low expression levels of both miRs had a 8.8-fold increased risk for relapse (p=0.003). Deletion of IKZF1 gene is a known adverse prognostic marker in B-lineage ALL. In 88 patients, IKZF1 status was analyzed and 9 patients were found to harbor the deletion. The expression of both miRs could still identify an adverse group of patients with only 50% RFS within the group with no deletion (p&lt;0.0003).

Even in a non-BFM treated B-lineage ALL cohort from The Netherlands, the expression levels of both miRs significantly correlated with outcome (p=0.003).

Conclusion: Our results identify miR-151-5p and miR-451 as novel biomarkers for outcome in pediatric B-lineage ALL patients, regardless of treatment protocol. This may lead to improved risk group stratification and better RFS.

Citation Format: Smadar Avigad, Iedan RN Verly, Gertjan JL Kaspers, Jacqueline Cloos, Anat Ohali, Michal Hameiri-Grossman, Keren Shichrur, Eva Fronkova, Jan Trka, Drorit Luria, Yona Kodman, Hadar Mirsky, Dafna Gaash, Marta Jeison, Galia Avrahami, Sarah Elitzur, Gil Gilad, Batia Stark, Isaac Yaniv. Increased risk of relapse in non-high-risk children with pediatric B-lineage acute lymphoblastic leukemia can be predicted at diagnosis by microRNA expression. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B34.

Novel SMARCAL1 bi-allelic mutations associated with a chromosomal breakage phenotype in a severe SIOD patient

PURPOSE

Chromosomal instability syndromes include a group of rare diseases characterized by defective DNA-damage-response and increased risk of chromosomal breakage. Patients display defects in the recognition and/or repair of DNA damage, with a subsequent high rate of malignancies and abnormal gene rearrangements. Other clinical manifestations, such as immunodeficiency, neurodevelopmental delay and skeletal abnormalities, are present in some of these syndromes. We studied a patient with profound T-lymphocyte defect, neurodevelopmental delay, facial dysmorphism, nephrotic syndrome and spondyloepiphyseal bone dysplasia typical of SIOD.

METHODS

Karyotype and chromosome fragility assays on patients' peripheral blood mononuclear cells showed an abnormal rate of spontaneous breaks. Cell cycle analysis of patient's fibroblasts following replication stress induced by hydroxyhurea revealed a delay in their release from S-phase to G2. When using higher concentrations of hydroxyhurea no patient fibroblast colonies could survive, compared with control fibroblasts. Whole-exome sequencing revealed novel compound heterozygote mutations in SMARCAL1 gene, resulting in putative frame shifts of encoded SMARCAL1 from each allele and no detected protein in patient's cells. The patient's youngest brother was found to have similar manifestations of SIOD but of less severity, including short stature, facial dysmorphism and typical osseous dysplasia, but no clinical findings suggestive of immunodeficiency and no chromosomal fragility. Similar to his sister, the brother carries both bi-allelic mutations in SMARCAL1 gene.

CONCLUSIONS

We present here the first evidence of intrinsic chromosomal instability in a severe SMARCAL1-deficient patient with a clinical picture of SIOD. Our results are consistent with the recently outlined role of SMARCAL1 protein in DNA damage response.

Genetic stratification of neuroblastoma for treatment tailoring

Neuroblastoma is the most common extracranial tumor of childhood. The clinical behavior is variable, ranging from spontaneous regression to fatal progression despite aggressive therapy. The most highly statistically significant and clinically relevant factors that are currently used for classification include stage, age, histopathologic category, MYCN oncogene status, chromosome 11q status and DNA ploidy. These genetic markers were analyzed separately by classical methods until recently: mainly fluorescence in situ hybridization or loss of heterozygosity. The development of genome-wide techniques such as comparative genomic hybridization, array comparative genomic hybridization and single nucleotide polymorphism allows the analysis of copy number variations through the whole genome in one step. This enabled the investigators to refine different genetic subtypes for the better comprehension of neuroblastoma tumor behavior and reach the conclusion that these data together with a genomic profile based on gene expression should be included in future treatment stratification.

2p24 Gain region harboring MYCN gene compared with MYCN amplified and nonamplified neuroblastoma: biological and clinical characteristics

Although the role of MYCN amplification in neuroblastoma is well established, the biological and clinical characteristics of the 2p gain region harboring the MYCN gene remain unclear. The aim of this study was to compare the biological and clinical characteristics of these tumors with MYCN amplified and nonamplified neuroblastoma and to determine their impact on disease outcome. Samples from 177 patients were analyzed by fluorescence in situ hybridization, including MYCN, 1p, 17q, and 11q regions; 2p gain was identified in 25 patients, MYCN amplification in 31, and no amplification in 121 patients. Patients with 2p gain had a significantly worse 5-year event-free survival rate than patients with no MYCN amplified (P < 0.001), and an intermediate 5-year overall survival rate difference existed between the MYCN amplified tumors (P = 0.025) and nonamplified (P = 0.003) groups. All of the 2p gain samples were associated with segmental and/or numerical alterations in the other tested regions. The presence of segmental alterations with or without MYCN amplification was recently found to be the strongest predictor of relapse in a multivariate analysis. The results of the present study suggest that the determination of MYCN gene copy number relative to chromosome 2, when evaluating MYCN status at diagnosis, may help to reveal the underlying genetic pattern of these tumors and better understand their clinical behavior.

Reduced levels of miR-34a in neuroblastoma are not caused by mutations in the TP53 binding site

Neuroblastoma (NB) is the most common extracranial solid tumor in children below the age of 5 years. miR-34a, located in chromosome band 1p36, has been recently implicated as a tumor suppressor gene in NB. In addition, it has been shown that miR-34a is activated by TP53 by binding to a TP53 binding site upstream to the mature miR-34a. We studied NB tumors from 57 patients for miR-34a expression levels, 1p status, mutations in the TP53 coding region and mutations of the TP53 binding site. Reduced expression levels of miR-34a were identified in tumors harboring 1p36.3 Loss (P = 0.028). No mutations were identified in the coding region of TP53, or in the TP53 binding site. Thus, mutations in the binding site are not an additional mechanism for the inactivation of miR-34a in NB. Other regulatory mechanisms controlling miR-34a expression and its relationship to TP53 should be further explored.

Short telomeres: a novel potential predictor of relapse in Ewing sarcoma

PURPOSE

Despite advances in therapy, >50% of patients with Ewing sarcoma will relapse. The current prognostic factors are not optimal for risk prediction. Studies have shown that telomere length could predict outcome in different malignancies. Our aim was to evaluate whether telomere length could be a better prognostic factor in Ewing sarcoma and correlate the results with clinical variables, outcome, and chromosomal instability.

EXPERIMENTAL DESIGN

Telomere length was determined in the primary tumor and peripheral blood of 32 patients with Ewing sarcoma. Chromosomal instability was evaluated by combining classical cytogenetics, comparative genomic hybridization and random aneuploidy. Telomere length was correlated to clinical variables, chromosomal instability, and outcome.

RESULTS

In 75% of the tumors, changes in telomere length, when compared with the corresponding peripheral blood lymphocytes, were noted. The majority of changes consisted of a reduction in telomere length. Patients harboring shorter telomeres had a significantly adverse outcome (P = 0.015). Chromosomal instability was identified in 65% of tumors, significantly correlating with short telomeres (P = 0.0094). Using multivariate analysis, telomere length remained the only significant prognostic variable (P = 0.034). Patients with short telomeres had a 5.3-fold risk of relapse as compared to those with unchanged or longer telomeres.

CONCLUSION

We have shown that tumors with telomere length reduction result in genomic instability. In addition, telomere length reduction was the only significant predictor of outcome. We suggest that reduction of telomere length in tumor cells at diagnosis could serve as a prognostic marker in Ewing sarcoma.

Micro-RNA deletion in neuroblastoma: A possible alternative mechanism of MYCN overexpression

9052

Background: Micro-RNAs (miRNAs) are small noncoding RNAs of 18 to 25 nucleotides that regulate protein expression. The biological functions of miRNAs are not yet fully understood. miRNA genes were recently found to be abnormally expressed in several types of cancer. By negatively regulating proto-oncogenes, miRNAs could act as tumor suppressors and conversely, by inhibiting tumor suppressors function as oncogenes. Neuroblastoma (NB) is the most common solid tumor in children under 5 years of age. Major adverse prognostic factors include: age over 1 year, advanced stages, adrenal primary site, MYCN amplification, diploid or tetraploid DNA content (DI), and chromosomal aberrations - including 1p deletions. We studied a possible involvement of miRNAs in neuroblastoma. Methods: The cohort consisted of 72 patients: 65% of them were above 1 year of age, 72% with advanced stages, 33% of the patients progressed. Median follow up was 60 months (ranging 1–221). Genomic DNA from 72 tumors were analyzed for the presence of 7 miRNAs located on chromosome 1p, ranging from 1p36.33 to 1p31.1 by PCR. Results: Deletion of one or more of the miRNAs was identified in 50% of the tumors.The most prevalent deletions were of two miRNAs: miR 30e located on 1p34.2 (29%) and miR 34a on 1p 36.23 (22%), accounting for 40% of the patients with a deletion of one or both of these miRs. Interestingly, miR 30e and miR 34a are known to negatively regulate the oncogene MYCN. MYCN protein expression is currently being evaluated in this cohort. Conclusions: The deletions of these miRNAs in neuroblastoma tumors suggest their involvement as tumor suppressor genes. This implies a new mechanism for the overexpression of MYCN. Discovery of the miRNAs and their targets involved in neuroblastoma has a therapeutic potential, for the development of new targeted therapies.

No significant financial relationships to disclose.

Classical and molecular cytogenetic abnormalities and outcome of childhood acute myeloid leukaemia: report from a referral centre in Israel

The incidence of cytogenetic abnormalities in childhood de novo acute myeloid leukaemia (AML) and its prognostic significance was assessed in an Israeli paediatric referral centre. Cytogenetic analysis was successful in 86 of 97 children (< 20 years of age) diagnosed between 1988 and 2002 with de novo AML. Fluorescence in situ hybridization analysis detected new information in 11 of them, leading to reassignment in cytogenetic group classification. The incidence of the various cytogenetic subgroups was as follows: normal - 9%; t(11q23) - 22%; t(8;21) - 13%; t(15;17) - 8%; inv(16) - 3.4%; abn(3q) - 4.6%; 7/7q-(sole or main) - 5.8%; del(9q)(sole) and +21(sole) - 4.6% each; t(8;16) - 2.3%; t(6;9), t(1;22), +8(sole) - 1.1% each; and miscellaneous - 18%. The overall survival (OS) and event-free survival (EFS) (4 years) for 94 patients treated with the modified Berlin-Frankfürt-Münster (BFM) AML protocols (non-irradiated) were 59.9% (SE = 5%) and 55.7% (SE = 5%), respectively, and for the favourable t(8;21), t(15;17) and inv(16), OS was 60% (SE = 15%), 83% (SE = 15%) and 100% respectively. For the normal group it was 62% (SE = 17%), miscellaneous 64% (SE = 12%), t(11q23) 44.6% (SE = 11%) and of the -7/7q-, del(9q)(sole) or t(6;9), none had survived at 4 years. The incidence of cytogenetic subgroups in the Israeli childhood AML population and their outcome were similar to other recently reported paediatric series. Cytogenetic abnormalities still carry clinical relevance for treatment stratification in the context of modern chemotherapy.

der(11)t(11;17): a distinct cytogenetic pathway of advanced stage neuroblastoma (NBL) - detected by spectral karyotyping (SKY)

Conventional cytogenetic, molecular cytogenic and genetic methods disclosed a broad spectrum of genetic abnormalities leading to gain and loss of chromosomal segments in advanced stage neuroblastoma (NBL). Specific correlation between the genetic findings could delineate distinct genetic pathways, of which the biology and prognostic significance is as yet undetermined. Using spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH) on metaphases from 16 patients with advanced stage NBL, it was possible to explore the whole spectrum of rearrangement within complex karyotypes and to detect hidden recurrent translocations. All translocations were unbalanced. The most prevalent recurrent unbalanced translocations resulted in 17q gain in 12 patients (75%), 11q loss in nine patients (56%), and 1p deletion/imbalance in eight patients (50%). The most frequent recurrent translocation was der(11)t(11;17) in six patients. Three cytogenetic pathways could be delineated. The first, with six patients, was characterized by the unbalanced translocation der(11)t(11;17), detected only by SKY, resulting in the concomitant 17q gain and 11q loss. No MYCN amplification or 1p deletion (except one patient with 1p imbalance) were found, while 3p deletion, and complex karyotypes were common. The second subgroup, with four patients, had 17q gain and 1p deletion, and in two patients 11q loss, that was apparent only by FISH. 1p deletion occurred through der(1)t(1;17) or del(1p). The third subgroup of four patients was characterized by MYCN amplification with 17q gain and 1p deletion, very rarely with 11q loss (one patient) through a translocation with a non-17q partner. The SKY subclassifications were in accordance with the findings reported by molecular genetic techniques, and may indicate that distinct oncogenes and suppressor genes are involved in the der(11)t(11;17) pathway of advanced stage NBL.

Acquired trisomy 21 and distinct clonal evolution in acute megakaryoblastic leukaemia in young monozygotic twins

An intrauterine origin of childhood acute lymphoblastic leukaemia (ALL) was proven by the identical clonotypic gene rearrangement in the concordant leukaemias of monozygotic twins, arising from a single clonogenic progeny. The monozygotic twins, presented at the age of 22 months with acute megakaryoblastic leukaemia (AML-M7) in one and myelodysplasia transformed to AML-M7 in the other. Leukaemic cells in both twins carried trisomy 21 and additional different clonal evolution changes of del(20q) in the first twin and trisomy 8 in the second. AML-M7 of late infancy with trisomy 21 may be included in the leukaemias of intrauterine origin, possibly a result of genotoxic insult.

Distinct cytogenetic pathways of advanced-stage neuroblastoma tumors, detected by spectral karyotyping

Molecular studies of advanced-stage neuroblastoma (NBL) have revealed a marked genetic heterogeneity. In addition to MYCN amplification and chromosome 1 short-arm deletions/translocations detected by conventional cytogenetics, application of fluorescence in situ hybridization has disclosed a high prevalence of 17q gain, whereas allelotyping and comparative genomic hybridization techniques also have revealed loss of 11q and of other chromosomal material. Using the recently developed technique of spectral karyotyping (SKY), we sought to refine the cytogenetic information, identify hidden recurrent structural chromosomal abnormalities, and compare them to the molecular findings. Thirteen samples of metaphase spreads from 11 patients with advanced-stage NBL were analyzed by SKY. Most of them were found to have complex karyotypes (more than three changes per metaphase) and complex unbalanced rearrangements. Recurrent aberrations leading to 17q gain, deletion of 1p, MYCN amplification, and loss of 11q appeared in 7, 4, 4, and 5 patients, respectively, in simple and complex karyotypes. Chromosome 3 changes and gain of 1q and 7q appeared in 6, 5, and 4 patients, respectively, in complex karyotypes only, reflecting later changes. A strikingly high prevalence of the unbalanced translocation der(11)t(11;17), leading to concomitant 11q loss and 17q gain in 4 patients, delineated a distinct cytogenetic group, none having 1p deletion and/or MYCN amplification. der(11)t(11;17) was associated with complex karyotypes with changes in chromosomes 3 and 7q. The 17q translocations with partners other than 11q were associated with 1p deletion and/or MYCN amplification. The distinct cytogenetic subgroups identified by SKY confirm and extend the recent molecular observations, and suggest that different genes may interact in the der(11)t(11;17) pathway of NBL development and progression.

Near haploid childhood acute lymphoblastic leukemia masked by hyperdiploid line: detection by fluorescence in situ hybridization

Near-haploid (<30 chromosomes) acute lymphoblastic leukemia (ALL) is a rare and unique subgroup of childhood common ALL associated with a very poor outcome. It may be underdiagnosed when masked by a co-existing hyperdiploid line, which has to be distinguished from the common good-prognostic hyperdiploid (>50 chromosomes) ALL. We present three children in whom, by conventional cytogenetics, near-haploid ALL was detected on relapse. Using interphase FISH probes of chromosomes X, Y, 4, 12, and 21, we were able, in two cases, to trace the hidden near-haploid lines of approximately 5% and 20% of the cells, masked by hyperdiploid cells of approximately 80% and 70%, respectively; at relapse, the proportion was reversed, with predominant near-haploid lines of over 80% and residual hyperdiploidy of less than 10%. The near-haploid lines consisted of 24 and 27 chromosomes, and always retained the second copy of chromosome 21 or its derivative, as detected in one of our patients by SKY. The hyperdiploid clones were the exact duplicates of the near-haploid ones and contained four and two copies of the chromosomes represented in two and one copies in the near-haploid stem line, respectively. Unlike the common hyperdiploid ALL, no trisomies were observed. The patients were all aged >10 years, with WBC 0.7-30 x 10(9)/L, and a common ALL phenotype. They were treated with the ALL-BFM-95 protocol, medium risk group, and responded well to 8 days of steroid therapy, but relapsed early, within 11 months, and died a few months later. Interphase FISH technique is recommended for the detection of cryptic near-haploid clones in the diagnostic survey of ALL. To assess the prognostic value of near-haploidy in the context of the ALL-BFM protocols, a larger cohort of patients is required.

Apparently unrelated clones shown by spectral karyotyping to represent clonal evolution of cryptic t(10;11)(p13;q23) in a patient with acute monoblastic leukemia

The accurate genetic classification of acute leukemia is of the utmost clinical importance for treatment stratification. In the present study, we report on a young girl with aggressive acute monoblastic leukemia (AML) (M5b) with skin, lymph node, and bone marrow involvement, in whom cytogenetic analysis revealed three clones with different secondary chromosomal changes. Two clones had the secondary +8 and del(9q) aberrations, with the der(11)t(1;11) in the second one; the third clone was apparently unrelated to the others, and had add(7)(p?21),-13,+22. Using the spectral karyotyping (SKY) technique, we found that all three clones originated from a common clone that harbored the hidden primary t(10;11)(p13;q23) or its derivatives, suggesting clonal evolution. The first clone had the balanced t(10;11), the second had its derivative, der(10)t(10;11), and the third had the other derivative, der(11)t(10;11). On fluorescence in situ hybridization (FISH), MLL gene splitting, with translocation of its centromeric portion to 10p, and deletion of its telomeric portion, was demonstrated. In conclusion, the detection of the very poor prognostic t(10;11) aberration in AML, was possible by complementing the traditional cytogenetic analysis with SKY and FISH.

Additional chromosome 1q aberrations and der(16)t(1;16), correlation to the phenotypic expression and clinical behavior of the Ewing family of tumors

The cytogenetic hallmark of the Ewing family of tumors is t(11,22)(q24;q12) in its simple, complex or variant forms and/or its molecular equivalent EWS/FLI, EWS/ERG rearrangement. Additional secondary consistent chromosomal aberrations include the der(16)t(1;16) and frequently, other chromosome 1q abnormalities leading to 1q overdosage. We studied whether these secondary cytogenetic changes are correlated to clinical features and phenotypic expression which may have a prognostic impact. Successful cytogenetic evaluation was performed in eight patients with a Ewing family tumor. In four of these, in addition to the primary aberration, chromosome 1q overdosage (including two with der (16)t(1;16)) was noted. Out of these four patients, two had metastatic disease at the time of evaluation, while in the other four, disease was localized. Morphologically, the tumors with the additional 1q aberration, revealed the pPNET subtype more frequently than the typical Ewing. They also expressed a higher degree of neural differentiation by neural marker immunocytochemistry, in comparison to tumors without the 1q aberration. Determination of the prognostic significance of this finding requires a longer follow-up with a larger group of patients.

Metastatic extraosseous Ewing tumor. Association of the additional translocation der(16)t(1;16) with the variant EWS/ERG rearrangement in a case of cytogenetically inconspicuous chromosome 22

In Ewing sarcoma and related tumors, recently referred to as the Ewing tumors (ET), t(11;22)(q24q12) and its molecular genetic equivalent, the EWS/FLI-1 rearrangement, characterize approximately 85% of cases, while variant aberrations are rare. A second nonrandom aberration in ET is the unbalanced t(1;16) accompanying the t(11;22) in roughly 17% of cases. We present a 17-year-old man with estraosseous ET and multiple metastases, in whom the only cytogenetically detectable chromosomal aberration was der (16)t(1;16)(q12;q11.2). This finding was confirmed by fluorescence in situ hybridization (FISH). Using the RT-PCR technique, a variant EWS/ERG fusion transcript was noted, resulting from a t(21;22) chromosomal rearrangement which recently demonstrated in roughly 10% of ET. However, data on possible biologic differences in EWS/FLI-1 versus EWS/ERG expressing ET are as yet unavailable. This is the first reported combination of t(1;16) with the EWS/ERG rearrangement. A possible significance of this finding for Ewing tumor progression is discussed.

A distinct subtype of M4/M5 acute myeloblastic leukemia (AML) associated with t(8:16)(p11:p13), in a patient with the variant t(8:19)(p11:q13)--case report and review of the literature

Acute myeloblastic leukemia (AML) with t(8:16) or its variant t(8:V) has been rarely reported. A high proportion of patients are infants and children, often with a bleeding tendency and disseminated intravascular coagulopathy (DIC). Only one-third of the de novo patients remain in the first complete remission following multiagent chemotherapy and bone marrow transplantation (BMT). Morphocytochemically, the disorder is classified as an M5, M4, or M4/M5 variant. In the presented case, with the variant t(8:19)(p11:q13), comprehensive light and electron microscopic blast cell characterization showed monocytic and granulocytic features compatible with the M4 subtype (on the monocytic predominance range of the French-American-British classification scale). Although hemophagocytosis, one of the hallmarks of the disease, was rare in our patient, numerous autophagic vacuoles were present. Immuno- and genotyping showed a myelomonocytic phenotype with no evidence of early progenitor antigen expression or mixed leukemia. These results and those of previous reports support the high specificity of t(8:16) or its variants to the unique M4/M5 type leukemia and the role of a gene on 8p11 in this specific transformation.

Involvement of 11p15 and 3q21q26 in therapy-related myeloid leukemia (t-ML) in children. Case reports and review of the literature

The cytogenetic findings of therapy-related myeloid leukemia (t-ML) in three children are presented. These included one male patient with acute lymphoblastic leukemia (ALL) who underwent bone marrow transplantation and developed therapy-related myeloproliferative disease (t-MPD) in the female-donor hematopoietic cells 2.5 years after receiving radiation and epipodophyllotoxin therapy for ALL testicular relapse. Bone marrow leukemic cell karyotype revealed 46,XX,add (11)(p15) and a normal female karyotype in the peripheral blood lymphocytes. The other two children, one with ALL and one with ganglioneuroblastoma, developed fatal t-MPD and therapy-related acute myeloblastic leukemia (t-AML) preceded by myelodysplastic syndrome (t-MDS), respectively, 5 years after diagnosis, following administration of alkylating agents and irradiation. Monosomy 7 was present in both, and was combined with inv(3)(q21q26) in the second patient. Our review of the cytogenetic findings in 91 previously reported pediatric patients with t-ML suggested that the involvement of 11p15 and 3q21-->23, 3q24-q26 with or without a combination of translocation 11q23 and -7/7q-, respectively, are nonrandom aberrations of t-ML in children. Comparison of the chromosomal changes in t-ML between the pediatric and an adult series revealed some differences which may result from differences in treatment modalities and which, in addition, may indicate a possible role of genetic and/or age-dependent factors in the pathogenesis of therapy-related leukemogenesis in children.