IKZF1 gene deletions drive resistance to cytarabine in B-cell precursor acute lymphoblastic leukemia.

IKZF1-deletions occur in 10-15% of patients with B-cell precursor acute lymphoblastic leukemia (BCP-ALL) and predict a poor outcome. However, the impact of IKZF1-loss on sensitivity to drugs used in contemporary treatment protocols has remained underexplored. Here we show in experimental models and in patients that loss of IKZF1 promotes resistance to AraC, a key component of both upfront and relapsed treatment protocols. We attribute this resistance, in part, to diminished import and incorporation of cytarabine (AraC) due to reduced expression of the solute carrier hENT1. Moreover, we find elevated mRNA expression of Evi1, a known driver of therapy resistance in myeloid malignancies. Finally, a kinase directed CRISPR/Cas9-screen identified that inhibition of either mediator kinases CDK8/19 or casein kinase 2 can restore response to AraC. We conclude that this high-risk patient group could benefit from alternative antimetabolites, or targeted therapies that resensitize the cells to AraC.

Clonal dynamics in pediatric B-cell precursor acute lymphoblastic leukemia with very early relapse.

INTRODUCTION: One-quarter of the relapses in children with B-cell precursor acute lymphoblastic leukemia (BCP-ALL) occur very early (within 18 months, before completion of treatment), and prognosis in these patients is worse compared to cases that relapse after treatment has ended. METHODS: In this study, we performed a genomic analysis of diagnosis-relapse pairs of 12 children who relapsed very early, followed by a deep-sequencing validation of all identified mutations. In addition, we included one case with a good initial treatment response and on-treatment relapse at the end of upfront therapy. RESULTS: We observed a dynamic clonal evolution in all cases, with relapse almost exclusively originating from a subclone at diagnosis. We identified several driver mutations that may have influenced the outgrowth of a minor clone at diagnosis to become the major clone at relapse. For example, a minimal residual disease (MRD)-based standard-risk patient with ETV6-RUNX1-positive leukemia developed a relapse from a TP53-mutated subclone after loss of the wildtype allele. Furthermore, two patients with TCF3-PBX1-positive leukemia that developed a very early relapse carried E1099K WHSC1 mutations at diagnosis, a hotspot mutation that was recurrently encountered in other very early TCF3-PBX1-positive leukemia relapses as well. In addition to alterations in known relapse drivers, we found two cases with truncating mutations in the cohesin gene RAD21. CONCLUSION: Comprehensive genomic characterization of diagnosis-relapse pairs shows that very early relapses in BCP-ALL frequently arise from minor subclones at diagnosis. A detailed understanding of the therapeutic pressure driving these events may aid the development of improved therapies.

Multiclonal complexity of pediatric acute lymphoblastic leukemia and the prognostic relevance of subclonal mutations

Genomic studies of pediatric acute lymphoblastic leukemia (ALL) have shown remarkable heterogeneity in initial diagnosis, with multiple (sub)clones harboring lesions in relapse-associated genes. However, the clinical relevance of these subclonal alterations remains unclear. We assessed the clinical relevance and prognostic value of subclonal alterations in the relapse-associated genes IKZF1, CREBBP, KRAS, NRAS, PTPN11, TP53, NT5C2, and WHSC1 in 503 ALL cases. Using Molecular Inversion Probe sequencing and breakpoint-spanning PCR we reliably detected alterations below 1% allele frequency. We identified 660 genomic alterations in 285 diagnosis samples of which 495 (75%) were subclonal. RAS pathway mutations were common, particularly in minor subclones, and comparisons between RAS hotspot mutations revealed differences in their capacity to drive clonal expansion in ALL. We did not find an association of subclonal alterations with unfavorable outcome. Particularly for IKZF1, an established prognostic marker in ALL, all clonal but none of the subclonal alterations were preserved at relapse. We conclude that, for the genes tested, there is no basis to consider subclonal alterations detected at diagnosis for risk group stratification of ALL treatment.

Use of quality indicators in neuroblastoma treatment: A feasibility assessment.

BACKGROUND: Quality indicators (QIs) may be used to monitor the quality of neuroblastoma (NBL) care during treatment, in addition to survival and treatment toxicity, which can only be evaluated in the years after treatment. The present study aimed to assess the feasibility of a new set of indicators for the quality of NBL therapy. PROCEDURE: Seven QIs have been proposed based on literature and consensus of experts: (a) duration of complete diagnostic work-up, (b) prescription of thyroid prophylaxis before metaiodobenzylguanidine imaging, (c) treatment intensity, (d) use of tumor board meetings, (e) number of outpatient visits and sedation procedures during follow-up, (f) protocolled follow-up, and (g) required apheresis sessions. A retrospective data analysis from October 2014 to November 2017 including all patients with NBL in the centralized Princess Máxima Center in the Netherlands was performed to assess these parameters and determine practicality of measurement. RESULTS: A total number of 72 patients (aged between 2 weeks and 15 years) were analyzed. Adherence to all QIs could be determined for all eligible patients using their electronic medical records. Three indicators were compared over time, and an increase in adherence was observed. CONCLUSIONS: Assessment of QIs in neuroblastoma treatment is feasible. Seven new QIs were found to be feasible to measure and showed improvement over time for three indicators. Monitoring of these QIs during treatment may provide tools for quality improvement activities and comparisons of treatment quality over time or between centers. Further study is required to investigate their association with long-term outcomes.

Examining the Potential Relationship Between Multidisciplinary Team Meetings and Patient Survival in Pediatric Oncology Settings: A Systematic Review.

The organization of multidisciplinary team meetings (MTMs) has become standard practice in pediatric oncology and is widely felt to improve communication, knowledge, and patient care. Although the impact of MTMs on survival in adult oncology has been extensively researched, the potential benefits of survival for pediatric cancer patients are still unclear. This systematic review aimed to examine the impact of MTMs on survival in pediatric oncology settings. Relevant studies were identified by searching MEDLINE/PubMed, EMBASE, and the Cochrane Library databases up to January 2020, resulting in 325 unique records. After the title/abstract and full-text screening, 5 studies were included. All of the included studies (one prospective and 4 retrospective cohort studies) described a difference in overall or event-free survival when comparing patients who were discussed in MTMs with non-MTM patients. This association was statistically significant in 3 studies. The quality of the studies was strongly affected by their design. Because of the small number of studies in combination with high clinical and methodological heterogeneity, this review was unable to definitively assert a causal relationship between MTMs and survival in pediatric cancer patients. Further research is needed to explore this relationship and allow cost-benefit analyses, so that time and resources are optimally spent to deliver the best possible care to childhood cancer patients.

Combined sialic acid and histone deacetylase (HDAC) inhibitor treatment up-regulates the neuroblastoma antigen GD2.

Neuroblastoma cells highly express the disialoganglioside GD2, a tumor-associated carbohydrate antigen, which is only sparsely expressed on healthy tissue. GD2 is a primary target for the development of immunotherapy for neuroblastoma. Immunotherapy with monoclonal anti-GD2 antibodies has proven safety and efficacy in clinical trials and is included in the standard treatment for children with high-risk neuroblastoma. Strategies to modulate GD2 expression in neuroblastoma could further improve anti-GD2-targeted immunotherapy. Here, we report that the cellular sialylation pathway, as well as epigenetic reprogramming, strongly modulates GD2 expression in human and mouse neuroblastoma cell lines. Recognition of GD2 by the 14G2a antibody is sialic acid-dependent and was blocked with the fluorinated sialic acid mimetic Ac53FaxNeu5Ac. Interestingly, sialic acid supplementation using a cell-permeable sialic acid analogue (Ac5Neu5Ac) boosted GD2 expression without or with minor alterations in overall cell surface sialylation. Furthermore, sialic acid supplementation with Ac5Neu5Ac combined with various histone deacetylase (HDAC) inhibitors, including vorinostat, enhanced GD2 expression in neuroblastoma cells beyond their individual effects. Mechanistic studies revealed that Ac5Neu5Ac supplementation increased intracellular CMP-Neu5Ac concentrations, thereby providing higher substrate levels for sialyltransferases. Furthermore, HDAC inhibitor treatment increased mRNA expression of the sialyltransferases GM3 synthase (ST3GAL5) and GD3 synthase (ST8SIA1), both of which are involved in GD2 biosynthesis. Our findings reveal that sialic acid analogues and HDAC inhibitors enhance GD2 expression and could potentially be employed to boost anti-GD2 targeted immunotherapy in neuroblastoma patients.

Cost-effectiveness of Anti-CD19 chimeric antigen receptor T-Cell therapy in pediatric relapsed/refractory B-cell acute lymphoblastic leukemia. A societal view.

INTRODUCTION: In several studies, the chimeric antigen receptor T-cell therapy tisagenlecleucel demonstrated encouraging rates of remission and lasting survival benefits in pediatric patients with relapsed/refractory (r/r) acute lymphoblastic leukemia (ALL). We assessed the cost-effectiveness of tisagenlecleucel (list price: 320 000 EUR) among these patients when compared to clofarabine monotherapy (Clo-M), clofarabine combination therapy (Clo-C), and blinatumomab (Blina) from both a healthcare and a societal perspective. We also assessed future medical and future non-medical consumption costs. METHODS: A three-state partitioned survival model was used to simulate a cohort of pediatric patients (12 years of age) through different disease states until the end of life (lifetime horizon). Relevant outcomes were life years, quality-adjusted life years (QALYs), healthcare costs, societal costs, and the incremental cost-effectiveness ratio (ICER). Uncertainty was explored through deterministic and probabilistic sensitivity analyses as well as through several scenario analyzes. RESULTS: Total discounted costs for tisagenlecleucel were 552 679 EUR from a societal perspective, which was much higher than the total discounted costs from a healthcare perspective (ie, 409 563 EUR). Total discounted societal costs for the comparator regimens ranged between 160 803 EUR for Clo-M and 267 259 EUR for Blina. Highest QALYs were estimated for tisagenlecleucel (11.26), followed by Blina (2.25), Clo-C (1.70) and Clo-M (0.74). Discounted societal ICERs of tisagenlecleucel ranged between 31 682 EUR/QALY for Blina and 37 531 EUR/QALY for Clo-C and were considered cost-effective with a willingness-to-pay (WTP) threshold of 80 000 EUR/QALY. None of the scenarios exceeded this threshold, and more than 98% of the iterations in the probabilistic sensitivity analysis were cost-effective. DISCUSSION: At the current price and WTP threshold, tisagenlecleucel is cost-effective from both a healthcare and a societal perspective. Nevertheless, long-term effectiveness data are needed to validate the several assumptions that were necessary for this model.

Integration of genetic and clinical risk factors improves prognostication in relapsed childhood B-cell precursor acute lymphoblastic leukemia.

Somatic genetic abnormalities are initiators and drivers of disease and have proven clinical utility at initial diagnosis. However, the genetic landscape and its clinical utility at relapse are less well understood and have not been studied comprehensively. We analyzed cytogenetic data from 427 children with relapsed B-cell precursor ALL treated on the international trial, ALLR3. Also we screened 238 patients with a marrow relapse for selected copy number alterations (CNAs) and mutations. Cytogenetic risk groups were predictive of outcome postrelapse and survival rates at 5 years for patients with good, intermediate-, and high-risk cytogenetics were 68%, 47%, and 26%, respectively (P < .001). TP53 alterations and NR3C1/BTG1 deletions were associated with a higher risk of progression: hazard ratio 2.36 (95% confidence interval, 1.51-3.70, P < .001) and 2.15 (1.32-3.48, P = .002). NRAS mutations were associated with an increased risk of progression among standard-risk patients with high hyperdiploidy: 3.17 (1.15-8.71, P = .026). Patients classified clinically as standard and high risk had distinct genetic profiles. The outcome of clinical standard-risk patients with high-risk cytogenetics was equivalent to clinical high-risk patients. Screening patients at relapse for key genetic abnormalities will enable the integration of genetic and clinical risk factors to improve patient stratification and outcome. This study is registered at www.clinicaltrials.org as #ISCRTN45724312.

Tumor suppressors BTG1 and IKZF1 cooperate during mouse leukemia development and increase relapse risk in B-cell precursor acute lymphoblastic leukemia patients.

Deletions and mutations affecting lymphoid transcription factor IKZF1 (IKAROS) are associated with an increased relapse risk and poor outcome in B-cell precursor acute lymphoblastic leukemia. However, additional genetic events may either enhance or negate the effects of IKZF1 deletions on prognosis. In a large discovery cohort of 533 childhood B-cell precursor acute lymphoblastic leukemia patients, we observed that single-copy losses of BTG1 were significantly enriched in IKZF1-deleted B-cell precursor acute lymphoblastic leukemia (P=0.007). While BTG1 deletions alone had no impact on prognosis, the combined presence of BTG1 and IKZF1 deletions was associated with a significantly lower 5-year event-free survival (P=0.0003) and a higher 5-year cumulative incidence of relapse (P=0.005), when compared with IKZF1-deleted cases without BTG1 aberrations. In contrast, other copy number losses commonly observed in B-cell precursor acute lymphoblastic leukemia, such as CDKN2A/B, PAX5, EBF1 or RB1, did not affect the outcome of IKZF1-deleted acute lymphoblastic leukemia patients. To establish whether the combined loss of IKZF1 and BTG1 function cooperate in leukemogenesis, Btg1-deficient mice were crossed onto an Ikzf1 heterozygous background. We observed that loss of Btg1 increased the tumor incidence of Ikzf1+/- mice in a dose-dependent manner. Moreover, murine B cells deficient for Btg1 and Ikzf1+/- displayed increased resistance to glucocorticoids, but not to other chemotherapeutic drugs. Together, our results identify BTG1 as a tumor suppressor in leukemia that, when deleted, strongly enhances the risk of relapse in IKZF1-deleted B-cell precursor acute lymphoblastic leukemia, and augments the glucocorticoid resistance phenotype mediated by the loss of IKZF1 function.

Real-world implementation of electronic patient-reported outcomes in outpatient pediatric cancer care.

OBJECTIVE: The KLIK method is an online tool that monitors and discusses electronic patient-reported outcomes (ePROs), which has been shown to enhance outcomes. This study aimed (1) to determine the fidelity (ie, extent to which used as intended) of the KLIK method as implemented in outpatient pediatric cancer care and (2) to study health care professional (HCP)-reported barriers and facilitators for implementation. METHODS: Two hundred five children with newly diagnosed cancer (enrollment rate 85%) participated. At 1 (T1), 3 (T2), and 6 (T3) months after diagnosis, patients (8-18 years) or parents (of patients 0-7 years) completed health-related quality of life (HRQoL) questionnaires, which were transformed into an ePROfile and discussed by their HCP during consultations. Fidelity was determined by the following: percentage of website registrations, HRQoL questionnaires completed, and ePROfiles discussed. Implementation determinants were assessed with HCPs after the final T3 with the Measurement Instrument for Determinants of Innovations. RESULTS: Depending on the time point (T1-T3), fidelity was 86% to 89% for website registration, 66-85% for completed HRQoL questionnaires, and 56% to 62% for ePROfile discussion. Barriers were mainly related to organizational issues (eg, organizational change) and less frequently to users (eg, motivation to comply) or the intervention (compatibility). Facilitators were related to the user (eg, positive outcome expectations) and intervention (simplicity) but not to the organization. CONCLUSIONS: When implementing ePROs in outpatient pediatric oncology practice, HCPs report determinants that influence ePRO integration. To improve implementation and outcomes, tailored organizational (eg, formal ratification by management and time) and specific local (eg, individualized assessments) strategies should be developed to achieve optimal ePRO discussion.

AGORA, a data- and biobank for birth defects and childhood cancer.

BACKGROUND: Research regarding the etiology of birth defects and childhood cancer is essential to develop preventive measures, but often requires large study populations. Therefore, we established the AGORA data- and biobank in the Netherlands. In this study, we describe its rationale, design, and ongoing data collection. METHODS: Children diagnosed with and/or treated for a structural birth defect or childhood cancer and their parents are invited to participate in the AGORA data- and biobank. Controls are recruited through random sampling from municipal registries. The parents receive questionnaires about demographics, family and pregnancy history, health status, prescribed medication, lifestyle, and occupational exposures before and during the index pregnancy. In addition, blood or saliva is collected from children and parents, while medical records are reviewed for diagnostic information. RESULTS: So far, we have collected data from over 6,860 families (3,747 birth defects, 905 childhood cancers, and 2,208 controls). The types of birth defects vary widely and comprise malformations of the digestive, respiratory, and urogenital tracts as well as facial, cardiovascular, kidney, skeletal, and central nervous system anomalies. The most frequently occurring childhood cancer types are acute lymphatic leukemia, Hodgkin and non-Hodgkin lymphoma, Wilms' tumor, and brain and spinal cord tumors. Our genetic and/or epidemiologic studies have been focused on hypospadias, anorectal malformations, congenital anomalies of the kidney and urinary tract (CAKUT), and orofacial clefts. CONCLUSION: The large AGORA data- and biobank offers great opportunities for investigating genetic and nongenetic risk factors for disorders in children and is open to collaborative initiatives. Birth Defects Research (Part A) 106:675-684, 2016. © 2016 Wiley Periodicals, Inc.

Predicting trajectories of behavioral adjustment in children diagnosed with acute lymphoblastic leukemia.

PURPOSE: Previous research showed that children with cancer are at risk for developing behavioral adjustment problems after successful treatment; however, the course of adjustment remains unclear. This study focuses on adjustment trajectories of children during treatment for acute lymphoblastic leukemia (ALL) and aims to distinguish subgroups of patients showing different trajectories during active treatment, and to identify sociodemographic, medical, and psychosocial predictors of the distinct adjustment trajectories. METHODS: In a multicenter longitudinal study, 108 parents of a child (response rate 80 %) diagnosed with ALL were assessed during induction treatment (T0), after induction/consolidation treatment (T1), and after end of treatment (T2). Trajectories of child behavioral adjustment (Child Behavior Checklist; CBCL) were tested with latent class growth modeling (LCGM) analyses. RESULTS: For internalizing behavior, a three-trajectory model was found: a group that experienced no problems (60 %), a group that experienced only initial problems (30 %), and a group that experienced chronic problems (10 %). For externalizing behavior, a three-trajectory model was also found: a group that experienced no problems (83 %), a group that experienced chronic problems (12 %), and a group that experienced increasing problems (5 %). Only parenting stress and baseline QoL (cancer related) were found to contribute uniquely to adjustment trajectories. CONCLUSIONS: The majority of the children (77 %) showed no or transient behavioral problems during the entire treatment as reported by parents. A substantial group (23 %) shows maladaptive trajectories of internalizing behavioral problems and/or externalizing behavioral problems. Screening for risk factors for developing problems might be helpful in early identification of these children.

Illness cognitions and family adjustment: psychometric properties of the Illness Cognition Questionnaire for parents of a child with cancer.

PURPOSE: Illness cognitions are an important mediator between disease and psychological adjustment. This study assessed the psychometric properties of the Illness Cognition Questionnaire (ICQ), adjusted for the parents of an ill child. METHODS: Participants were recruited from two multicenter studies: sample 1 included 128 parents of a child diagnosed with acute lymphoblastic leukemia (ALL) (response rate 82 %) and sample 2 included 114 parents of a child diagnosed with cancer (response rate 74 %). Parents completed an adapted version of the ICQ (Illness Cognition Questionnaire-Parent version (ICQ-P)), together with the Profile of Mood States (POMS; sample 1) or the Hospital Anxiety and Depression Scale (HADS; sample 2). The factor structure of the ICQ-P was examined by means of principal component analysis. Cronbach's alpha for each subscale and correlations between the ICQ-P scales and the HADS and POMS were calculated. The illness cognitions of parents with and without psychological distress were compared. RESULTS: Factor analysis confirmed the hypothesized structure of the ICQ-P in our sample (n = 242). The three scales Helplessness, Acceptance, and Perceived Benefits explained 9.8, 31.4, and 17.9 % of the variance, respectively. Cronbach's alpha showed adequate internal consistency (.80-.88). Concurrent and criterion-related validity were appropriate. CONCLUSIONS: The results confirm that the ICQ-P reliably assesses the illness cognitions of the parents of a child with cancer. Psychologically distressed parents showed less acceptance and more helplessness. The availability of a short and valid illness cognition questionnaire will help clinicians gain insight into parental cognitions regarding the illness of their child, information that might be helpful for targeting interventions.

Screening for Psychosocial Risk in Dutch Families of a Child With Cancer: Reliability, Validity, and Usability of the Psychosocial Assessment Tool.

OBJECTIVE: The Psychosocial Assessment Tool (PAT) was developed to screen for psychosocial risk in families of a child diagnosed with cancer. The current study is the first describing the cross-cultural adaptation, reliability, validity, and usability of the PAT in an European country (Dutch translation). METHODS: A total of 117 families (response rate 59%) of newly diagnosed children with cancer completed the PAT2.0 and validation measures. RESULTS: Acceptable reliability was obtained for the PAT total score (α = .72) and majority of subscales (0.50-0.82). Two subscales showed inadequate internal consistency (Social Support α = .19; Family Beliefs α = .20). Validity and usability were adequate. Of the families, 66% scored low (Universal), 29% medium (Targeted), and 5% high (Clinical) risk. CONCLUSIONS: This study confirms the cross-cultural applicability, reliability, and validity of the PAT total score. Reliability left room for improvement on subscale level. Future research should indicate whether the PAT can be used to provide cost-effective care.

Intra-adrenal murine TH-MYCN neuroblastoma tumors grow more aggressive and exhibit a distinct tumor microenvironment relative to their subcutaneous equivalents.

In around half of the patients with neuroblastoma (NBL), the primary tumor is located in one of the adrenal glands. We have previously reported on a transplantable TH-MYCN model of subcutaneous (SC) growing NBL in C57Bl/6 mice for immunological studies. In this report, we describe an orthotopic TH-MYCN transplantable model where the tumor cells were injected intra-adrenally (IA) by microsurgery. Strikingly, 9464D cells grew out much faster in IA tumors compared to the subcutis. Tumors were infiltrated by equal numbers of lymphocytes and myeloid cells. Within the myeloid cell population, however, tumor-infiltrating macrophages were more abundant in IA tumors compared to SC tumors and expressed lower levels of MHC class II, indicative of a more immunosuppressive phenotype. Using 9464D cells stably expressing firefly luciferase, enhanced IA tumor growth could be confirmed using bioluminescence. Collectively, these data show that the orthotopic IA localization of TH-MYCN cells impacts the NBL tumor microenvironment, resulting in a more stringent NBL model to study novel immunotherapeutic approaches for NBL.

Independent prognostic value of BCR-ABL1-like signature and IKZF1 deletion, but not high CRLF2 expression, in children with B-cell precursor ALL.

Most relapses in childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL) are not predicted using current prognostic features. Here, we determined the co-occurrence and independent prognostic relevance of 3 recently identified prognostic features: BCR-ABL1-like gene signature, deletions in IKZF1, and high CRLF2 messenger RNA expression (CRLF2-high). These features were determined in 4 trials representing 1128 children with ALL: DCOG ALL-8, ALL9, ALL10, and Cooperative ALL (COALL)-97/03. BCR-ABL1-like, IKZF1-deleted, and CRLF2-high cases constitute 33.7% of BCR-ABL1-negative, MLL wild-type BCP-ALL cases, of which BCR-ABL1-like and IKZF1 deletion (co)occurred most frequently. Higher cumulative incidence of relapse was found for BCR-ABL1-like and IKZF1-deleted, but not CRLF2-high, cases relative to remaining BCP-ALL cases, reflecting the observations in each of the cohorts analyzed separately. No relapses occurred among cases with CRLF2-high as single feature, whereas 62.9% of all relapses in BCR-ABL1-negative, MLL wild-type BCP-ALL occurred in cases with BCR-ABL1-like signature and/or IKZF1 deletion. Both the BCR-ABL1-like signature and IKZF1 deletions were prognostic features independent of conventional prognostic markers in a multivariate model, and both remained prognostic among cases with intermediate minimal residual disease. The BCR-ABL1-like signature and an IKZF1 deletion, but not CRLF2-high, are prognostic factors and are clinically of importance to identify high-risk patients who require more intensive and/or alternative therapies.

The origin and nature of tightly clustered BTG1 deletions in precursor B-cell acute lymphoblastic leukemia support a model of multiclonal evolution.

Recurrent submicroscopic deletions in genes affecting key cellular pathways are a hallmark of pediatric acute lymphoblastic leukemia (ALL). To gain more insight into the mechanism underlying these deletions, we have studied the occurrence and nature of abnormalities in one of these genes, the B-cell translocation gene 1 (BTG1), in a large cohort of pediatric ALL cases. BTG1 was found to be exclusively affected by genomic deletions, which were detected in 65 out of 722 B-cell precursor ALL (BCP-ALL) patient samples (9%), but not in 109 T-ALL cases. Eight different deletion sizes were identified, which all clustered at the telomeric site in a hotspot region within the second (and last) exon of the BTG1 gene, resulting in the expression of truncated BTG1 read-through transcripts. The presence of V(D)J recombination signal sequences at both sites of virtually all deletions strongly suggests illegitimate RAG1/RAG2-mediated recombination as the responsible mechanism. Moreover, high levels of histone H3 lysine 4 trimethylation (H3K4me3), which is known to tether the RAG enzyme complex to DNA, were found within the BTG1 gene body in BCP-ALL cells, but not T-ALL cells. BTG1 deletions were rarely found in hyperdiploid BCP-ALLs, but were predominant in other cytogenetic subgroups, including the ETV6-RUNX1 and BCR-ABL1 positive BCP-ALL subgroups. Through sensitive PCR-based screening, we identified multiple additional BTG1 deletions at the subclonal level in BCP-ALL, with equal cytogenetic distribution which, in some cases, grew out into the major clone at relapse. Taken together, our results indicate that BTG1 deletions may act as "drivers" of leukemogenesis in specific BCP-ALL subgroups, in which they can arise independently in multiple subclones at sites that are prone to aberrant RAG1/RAG2-mediated recombination events. These findings provide further evidence for a complex and multiclonal evolution of ALL.

A transplantable TH-MYCN transgenic tumor model in C57Bl/6 mice for preclinical immunological studies in neuroblastoma.

Current multimodal treatments for patients with neuroblastoma (NBL), including anti-disialoganglioside (GD2) monoclonal antibody (mAb) based immunotherapy, result in a favorable outcome in around only half of the patients with advanced disease. To improve this, novel immunocombinational strategies need to be developed and tested in autologous preclinical NBL models. A genetically well-explored autologous mouse model for NBL is the TH-MYCN model. However, the immunobiology of the TH-MYCN model remains largely unexplored. We developed a mouse model using a transplantable TH-MYCN cell line in syngeneic C57Bl/6 mice and characterized the immunobiology of this model. In this report, we show the relevance and opportunities of this model to study immunotherapy for human NBL. Similar to human NBL cells, syngeneic TH-MYCN-derived 9464D cells endogenously express the tumor antigen GD2 and low levels of MHC Class I. The presence of the adaptive immune system had little or no influence on tumor growth, showing the low immunogenicity of the NBL cells. In contrast, depletion of NK1.1+ cells resulted in enhanced tumor outgrowth in both wild-type and Rag1(-/-) mice, showing an important role for NK cells in the natural anti-NBL immune response. Analysis of the tumor infiltrating leukocytes ex vivo revealed the presence of both tumor associated myeloid cells and T regulatory cells, thus mimicking human NBL tumors. Finally, anti-GD2 mAb mediated NBL therapy resulted in ADCC in vitro and delayed tumor outgrowth in vivo. We conclude that the transplantable TH-MYCN model represents a relevant model for the development of novel immunocombinatorial approaches for NBL patients.

Continuous PEGasparaginase Dosing Reduces Hypersensitivity Reactions in Pediatric ALL: A Dutch Childhood Oncology Group ALL11 Randomized Trial.

PURPOSE: The primary objective of this randomized study was to determine whether a continuous dosing schedule (without the asparaginase-free interval) would result in less hypersensitivity reactions to PEGasparaginase (PEGasp) compared with the standard noncontinuous dosing schedule. METHODS: Eight hundred eighteen patients (age 1-18 years) with ALL were enrolled in the Dutch Childhood Oncology Group-ALL11 protocol and received PEGasp. Three hundred twelve patients stratified in the medium-risk arm were randomly assigned to receive 14 individualized PEGasp doses once every two weeks in either a noncontinuous or continuous schedule after the first three doses in induction (EudraCT: 2012-000067-25). Hypersensitivity reactions were defined as allergies, allergic-like reactions, and silent inactivation. Secondary end points were other asparaginase-related toxicities, asparaginase activity and antibody levels, and outcome. RESULTS: During induction, 27 of 818 patients (3.3%) experienced hypersensitivity reactions. After random assignment, 4 of 155 (2.6%) in the continuous treatment arm versus 17 of 157 (10.8%) patients in the noncontinuous treatment arm had hypersensitivity reactions (P < .01), of which two (1.3%) versus 13 (8.3%) were inactivating reactions (P < .01). The occurrence of inactivating hypersensitivity reactions was seven times lower in the continuous arm (odds ratio, 0.15 [0.032-0.653]). In addition, antibody levels were significantly lower in the continuous arm (P < .01). With exception of a lower incidence of increased amylase in the continuous arm, there were no significant differences in total number of asparaginase-associated toxicities between arms. However, the timing of the toxicities was associated with the timing of the asparaginase administrations. No difference in 5-year cumulative incidence of relapse, death, or disease-free survival was found between both treatment arms. CONCLUSION: A continuous dosing schedule of PEGasp is an effective approach to prevent antibody formation and inactivating hypersensitivity reactions. The continuous PEGasp schedule did not increase toxicity and did not affect the efficacy of the therapy.

Sleep, fatigue, depression, and quality of life in survivors of childhood acute lymphoblastic leukemia.

BACKGROUND: With the improved survival of childhood acute lymphoblastic leukemia (ALL), the effect of treatment on psychosocial well-being becomes increasingly relevant. Literature on sleep and fatigue during treatment is emerging. However, information on these subjects after treatment is sparse. This cross-sectional study examined sleep and fatigue in relation to depression and quality of life (QoL) after treatment for childhood ALL. PROCEDURE: Sleep, fatigue, depression, and QoL were evaluated by parent proxy and/or child self-reports of the Children's Sleep Habits Questionnaire, the PedsQL™ multidimensional fatigue scale, the Children's Depression Inventory and the Child Health Questionnaire. All total scores were compared to Dutch norm references. RESULTS: Sixty-two children were included, being 36 (interquartile range 22-62) months after finishing treatment. Parents rated the ALL survivors as having more disturbed sleep, more fatigue and poorer physical QoL compared to the Dutch norm. ALL survivors themselves reported less sleep problems, less depressive symptoms, and better psychosocial QoL than the Dutch norm. More sleep disturbances and fatigue correlated with more symptoms of depression and a worse QoL. CONCLUSIONS: Differences in parental and self-reports, including worse parental ratings, might be explained by worried parents and/or the adaptive style of the children. Impaired sleep and fatigue correlated with more depressive symptoms and a worse QoL.