DCOG/PMC RETRAITE 2015 SYLLABUS. 2 nd Retrait of Dutch Childhood Oncology Group and Prinses Maxima Centre for Pediatric Oncology

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1 DCOG/PMC RETRAITE 2015 SYLLABUS 2 nd Retrait of Dutch Childhood Oncology Group and Prinses Maxima Centre for Pediatric Oncology Hotel Biltsche Hoek, de Bilt 19th and 20th of March

2 Introduction The Princess Máxima Center (PMC) for pediatric oncology aims to contribute to improving the treatment of childhood cancer with the following objectives: o >90% survival in 2025 o <50% incidence of late effects of treatment in 2025 The PMC aims to improve the outcome for these children by bringing together in one center the treatment and research expertise to create synergies that will accelerate progress in discovering and delivering cures. Research Vision: In the Research Institute of the PMC pre-clinical and clinical researchers work together on the most urgent patient-relevant topics. The choices of research topics are mainly determined by the relevance of the subject for the patient group. The most urgent patient-relevant issues will be particularly identified by development of evidence-based guidelines for treatment and follow-up, and by direct input from patients and parents. The (fundamental) tumor-biological research will also lead to new possibilities for patient application. With this annual retrait, we hope to have a forum for researchers, to exchange knowledge, to exchange idea s and to get inspired by people who are working in the same field, but maybe with different expertise. In the last months, many researchers have given input to give an overview about the current research in the PMC. This inspired also finetune our research vision, in collaboratorion with different partners. Hopefully, this meeting will add a new chapter to this. I wish you a fruitful meeting, leading to new research, as well as making a strong basis for the Research Institute of the PMC. Valérie de Haas 2

3 INDEX Page Program 4 Acute lymphoblastic leukemia 8 Lymphomas 47 Myeloid Malignancies 51 Solid Tumors 68 Brain tumors 86 Immunotherapy 97 Late Effects 112 Phase I-II studies 131 Oncogenomics 137 Supportive Care 145 Psycho-Oncology 166 Outreach 178 List of Participans 180 3

4 Final Program DCOG/PMC Retrait 2015 Thursday 19th of March u u Welcome Valérie de Haas Acute Lymphoblastic Leukemia Frank van Leeuwen: Overview molecular research ALL 1. Kirsten Canté: Mousemodels in T-ALL 2. Mark Kerstjens: MEK inhibition is a Promising Therapeutic Strategy for MLL-rearranged Infant ALL Patients Carrying RAS Mutations 3. Laurens van der Meer: Reverse genetic screens using Crispr/Cas9 4. Roel Polak & Bob de Rooij: B-cell precursor acute lymphoblastic leukemia cells use tunneling nanotubes to orchestrate their microenvironment u Lymphoma Auke Beishuizen: Overview Lymphoma 1. Jan Loeffen: Lymphoma & Genetics 2. Friederieke Meijer-Wentrup: Identification of pediatric Hodgkin Lymphoma biomarkers and novel therapeutics u u u u Quick Coffee/Tea, followed by. Rob Pieters: Update Research in PMC; subsequently discussion: Development of research in the PMC: how to organize? LUNCH BRAIN TUMORS Dannis van Vuurden: Pediatric Neuro-Oncology Research High Priority! 1. Avanita Prabowo: Characterization of genetic aberrations in pediatric low-grade glioneuronal tumors 2. Sophie Veldhuijzen Van Zanten: Molecular imaging in diffuse intrinsic pontine glioma 3. Walderik Zomerman: Kinome profiling of pediatric medulloblastoma 4. Lot Sewing: Liquid biopsies 4

5 u PSYCHO-ONCOLOGY Martha Grootenhuis: Overview Pediatric Psycho-Oncology Research 1. Sasja Schepers: From research to standard care: studying implementation of patient reported outcomes in pediatric oncology practice using 2. Raphaele van Litsenburg: The importance of studying Sleep u SUPPORTIVE CARE Marianne van de Wetering: Overview supportive care research 1. Wim Tissing: Preclinical research 2. Mischa Keizer: Efficacy of asparaginase on the complement system 3. Erik Loeffen: Significance of establishing supportive care guidelines 4. Hester Blufpand: Renal toxicity in pediatric oncology and ways of monitoring u u Coffee/Tea KIKA Tom Voûte Award 16.00u Introduction 16.15u Saskia Gooskens: TCF21 hypermethylation in genetically quiescent clear cell sarcoma of the kidney 16.30u Tim van Groningen: Neuroblastoma is biphasic with classical neuroepithelial cells and chemo-resistant mesenchymal cells controlled by PRRX1-NOTCH signaling 16.45u Saskia Hopman: The development of a clinical screening instrument for tumor predisposition syndromes in childhood cancer patients 17.00u Marieke de Ruiter: Neurofeedback in pediatric brain tumor survivors 17.15u Anna Wojtuszkiewicz: Alternative splicing in acute leukemia: the relevance for drug resistance and treatment u DRINKS 18.30u Announcement of winners Tom Voûte Award 19.00u DINNER 5

6 Friday 20 th of March u SOLID TUMORS Jan Molenaar: Overview Solid Tumors 1. Jan Koster: R2; a biologist friendly genomic analysis platform 2. Lieve Tytgat: MRD markers in Solid Tumors 3. Marc Wijnen: Surgical complications in Pediatric solid tumors 4. Marry van de Heuvel Eibrink: Overview research in Renal Tumors u MYELOID MALIGNANCIES Maarten Fornerod: Overview myeloid malignancies 1. Marije Bartels: The role of epigenetic regulators in chemotherapy resistance in pediatric AML 2. Nicole Larmonie: Methylation patterns in pediatric AML subgroups 3. Kim Klein: Translational research in Pediatric AML 4. Edwin Sonneveld: Molecular MRD in AML u u Coffee/Tea LATE EFFECTS Leontien Kremer: LATER: a nationwide collaboration 1. Ellen Kilsdonk: Late mortality in childhood cancer survivors : a DCOG LATER study 2. Marleen van den Berg: Reproductive function, ovarian reserve, and risk of menopause in female CCS VeVo DCOG LATER study 3. Lieke Feijen: Cardiac Disease in childhood cancer survivors: a DCOG LATER study 4. Eva Clemens: PanCare Studies in Fertility and Ototoxicity to improve Quality of Life After Cancer During Childhood u FASE I-II STUDIES Michel Zwaan: Overview fase I-II studies 1. Natasja van Eijkelenburg: MIBG-Gemcitabine in pediatric neuroblastoma patients 2. Sebastiaan Sassen: Towards evidence-based use of ciprofloxacin prophylaxis and glucocorticoids for children with cancer u LUNCH 6

7 u IMMUNOTHERAPY Jaap Jan Boelens: Overview Immunotherapy 1. Ingrid Brok: A transplantable tumor model to develop Immunocombination therapy of Neuroblastoma 2. Astrid van Halteren/Cor van den Bos: Langerhans Cell Histiocytosis: targetting neo antigen-specific T cells in Langerhans Cel Histiocytosis 3. Maarten Schilham/Arjan Lankester: Natural Killer cell biology and immunotherapy 4. Rick Admiraal: Towards Predictable Immune-Reconstitution after Hematopoietic Cell Transplantation 5. Stefan Nierkens: WT-1 Cord Blood derived Dendritic Cell Vaccin for AML /Harmonized (Immuno)-monitoring protocols u OUTREACH Gertjan Kaspers: Introduction Dutch Outreach Pediatric Oncology 1. Trijn Israels: SIOP Africa/PODC Collaborative Wilms Tumour Project 2. Saskia Mostert: Adherence with childhood cancer treatment in Indonesia and Kenya u u u Keynote lecture Edwin Cuppen: Genome analyses within the Centre for Personalized Cancer Treatment Bill Evans: The St Jude Example Closing remarks 16.00u END of meeting 7

8 ACUTE LYMPHOBLASTIC LEUKEMIA 8

9 NAAM: Judith M. Boer Postdoc Naam Centrum: Erasmus MC-Sophia Children s Hospital, Dept. of Pediatric Oncology Naam Research groep: B-cell precursor-all, PI: Prof.dr. Monique L. den Boer Abstract: Key-words: pathobiology BCP-ALL, oncogenomics, data-integration, next-gen sequencing, bio-informatics Major breakthroughs in studying diseases can only be achieved by integration of multiple life science technologies in scientific research. We aim to discover novel abnormalities at the genomic, transcriptomic and proteomic level that have the potential to improve diagnostics and offer therapeutic targets in childhood ALL. Analyses of RNA expression as well as DNA copy number profiles, generated in our group and in others, have given valuable insights in molecular changes in childhood acute lymphoblastic leukemia (ALL). Our collection of different types of molecular profiling data from the same pediatric ALL patients now offers a unique opportunity to study the integrated effect of abnormalities at multiple omics levels simultaneously. We have developed a novel integration method that increases the discrimination between causative and bystander molecular changes. Our integration method is based on gene set testing to detect consistent effects across multiple genes with great sensitivity. We apply this systematic and unbiased approach to identify key genomic and mirna expression abnormalities that affect the expression and function of downstream genes in childhood ALL. Molecular abnormalities that affect downstream gene and protein expression are the most likely causative drivers of leukemogenesis. The embedding in a multidisciplinary research group ensures effective experimental validation of novel aberrations to answer these relevant biological and clinical questions in childhood ALL. 9

10 NAAM: Aurélie Boeree Technician Naam Centrum: Erasmus MC-Sophia Children s Hospital, Dept. of Pediatric Oncology Naam Research groep: B-cell precursor-all, PI: Prof.dr. Monique L. den Boer Abstract Key-words: Pathobiology ALL, oncogenomics, drug interference studies, targeted drugs, ALL xenograft Work description I work as a technician in the group of Monique den Boer on the research laboratory of pediatric oncology. As technician we isolate leukemic cells from bone marrow and/or peripheral blood for further experiments. For example, I am testing patients leukemic cells for the presence of different tyrosine kinase gene fusions and whether these cells are sensitive to chemotherapeutic drugs and inhibitors. Together with dr. C. van de Ven I will soon start with a proof-of-concept study in mice. In vitro results show that the TCF3-PBX1 positive leukemic cells are very sensitive to the BTK inhibitor Ibrutinib. To rationally re-design therapies for this good prognostic group, more proof is needed. To this aim, we determine the anti-leukemic effect and specificity of the inhibitor in vivo. After an intrafemural injection with patients leukemic cells the mice develop leukemia. Subsequently, these mice are treated with Ibrutinib and the antileukemic effect is being monitored by measuring the amount of human leukemic cells in the blood of the mouse and by determining the effect of Ibrutinib on downstream effectors of BTK. 10

11 NAAM: Prof.dr. Monique den Boer hoofd researchlaboratorium, principal investigator Naam Centrum: Erasmus MC-Sophia Children s Hospital, Dept. of Pediatric Oncology Naam Research groep: B-cell precursor-all Key-words: Pathobiology B-cell precursor ALL, oncogenomics, BCR-ABL1 like ALL, subclonality of disease, predictive biomarkers, drug resistance mechanisms, microenvironment, targeted drugs, ALL xenografts, humanized scaffold models, early clinical trials, translational research, personalized medicine. The major aims of Monique s research program Molecular Markers and Targets are: 1) To decipher the pathobiology of ALL in order to find new molecular markers (at DNA, RNA and/or protein level) that can be used for a better risk stratification and application of personalized medicine (targeted drugs) in pediatric B-cell precursor ALL. 2) To study the leukemic niche in order to circumvent microenvironmental induced quiescence of leukemic cells and escape from chemotherapy. Main topics that are being studied: oncogenomics of B-other, BCR-ABL1-like and known cytogenetic subtypes. Finding mutations/genetic abnormalities in leukemic cells and study the clinical relevance of these lesions and synergy with recurrent cytogenetic lesions in the right cellular context. causes of cellular drug resistance and how to sensitize to chemotherapeutic drugs, mainly focused on glucocorticoids and L-asparaginase. subclonality of leukemia and how to eradicate these subclones more effective. interaction between leukemic cells and the bone marrow microenvironment and how to interfere with this niche to prevent outgrowth of resistant subclones. exploring drugable targets and targeted drugs (including mouse models) and provide an evidence-based rationale for predictive biomarkers and eligibility criteria to select patients for early clinical trials. 11

12 NAAM: Miriam Butler Promovendus Naam Centrum: Radboud umc Naam Research groep: Laboratory of Pediatric Oncology Abstract Although it is now possible to predict poor response based on tumor genetics, translating this into alternative therapeutic strategies remains a challenge. For example, loss of IKZF1 predicts a poor outcome. Similarly, deletion of BTG1 is associated with a poor response in a subgroup of patients. How the genetic lesions that are associated with poor outcome affect the cellular response to chemotherapy, is currently unknown. We combine the overexpression of oncogenes with RNAi or CRISPR/Cas9 based loss-offunction of tumor suppressors to model a relevant genetic context in both cell line as well as mouse models. Using this approach, we have successfully induced resistance towards the tyrosine-kinase inhibitor imatinib by generating a genetic knockout of NF1, a member of the RAS pathway. Next, we aim to define the molecular pathways that are altered in the modeled resistant cells using both biochemical studies (looking for pathway activation) as well as expression analysis (expression arrays). Alternatively, because not every poorly responding can be identified using genetic stratifiers, we are performing an unbiased genome-wide CRISPR/Cas9 based loss and gainof-function screen to identify pathways that can be linked to therapy resistance. These combined approached will not only lead to more insight into the mechanisms of therapy resistance in pediatric ALL, but can identify potential therapeutic targets that can be exploited in a strategy to overcome resistance. 12

13 NAAM: J.G.C.A.M. Buijs-Gladdines Research Analist Naam Centrum: Department of Pediatric Oncology/Hematology, Erasmus MC Rotterdam-Sophia Children s Hospital, Rotterdam, the Netherlands Naam Research groep: T cell-acute Lymphoblastic Leukemia Research Group (Principal Investigator: Dr. J.P.P. Meijerink) Abstract Key-words: T cell-acute Lymphoblastic Leukemia, support of PhD students and postdocs, Whole genome sequencing project, patient care I am working since 2001 as a research technician at the T-ALL group led by Dr. J.P.P. Meijerink. As a research technician, I especially support the PhD students and postdocs in our group. In these 14 years, I have gained a lot of experience in various cellular and molecular techniques such as DNA / RNA isolation, FISH (self-optimized in our department), ELISA (RTQ) PCR, sequencing, array CGH, DNA microarray, flow cytometry, western blotting, hybridoma technology, recombinant protein production and isolation and cell culture. By gaining these experiences, I joined a few years to become chief technician within our group. The project, for which I currently offer support, is the Whole genome sequencing project together with Yunlei li (Bioinformatician within the T-ALL group). For this project, we hope to find by means of High through-put sequencing, new genes, which may be important in the development of T-ALL and possibly important new targets for the development of a targeted therapy. High through-put sequencing was carried out on DNA from both diagnosis and remission material of a large cohort of T-ALL patients. Based on the results we are now working with functional validation experiments found to be able to prove functional associations. In addition to the research, I am also involved in the reprocessing of patient material. During this procedure, the blasts from the bone marrow and / or blood of leukemia patients will be isolated, characterized and viable frozen, which can be used for various research questions. 13

14 NAAM: Kirsten Canté-Barrett, PhD Postdoc Naam Centrum: Erasmus MC, Rotterdam Naam Research groep: T-ALL (Dr. J.P.P. Meijerink) Research interesses/expertises (trefwoordsgewijs, max.50 woorden): Early T cell progenitor ALL (ETP-ALL) Xenografting human (leukemic) cells in immunocompromised mice Knock-out and Knock-in mouse models Relating T-ALL oncogene function to normal T cell development Beschrijving eigen research project Pediatric T-cell acute lymphoblastic leukemia (T-ALL) is a cancer of developing T-cells in the thymus. Genetic aberrations can lead to oncogenic transformation and differentiation arrest of thymocytes. Transformed thymocytes acquire pathogenic mutations that further contribute to uncontrolled thymocyte expansion and T-ALL, therapy resistance and relapse. T-ALL subgroups are classified by the activation of oncogenes that facilitate T-cell developmental arrest. Our group identified a novel genetic T-ALL subgroup that overexpresses the transcription factor MEF2C and that is associated with the high-risk early thymocyte progenitor ALL (ETP-ALL). Moreover, my work using Mef2c conditional knock-out mice points to an important role for MEF2C in normal T-cell development, and deletion of this gene early in T-cell development results in severely reduced T-cell numbers. To further prove MEF2C as a pathogenic driver for ETP- ALL, we have developed a conditional transgenic knock-in mouse model in which the human MEF2C gene can be activated exclusively and ectopically in early developing thymocytes. Preliminary results again demonstrate T-cell developmental defects by arresting differentiation of early thymocytes. Current aging cohorts and bone marrow transplantation experiments are ongoing to model MEF2C-driven T-cell leukemia. We further aim to compare gene expression signatures and immunophenotype of mouse leukemia cells with primary leukemia cells from ETP-ALL patients to pionpoint conserved pathogenic mechanisms of MEF2C. This way, we aim to identify potential drug targets for future patient-tailored therapies for ETP-ALL. This system can be exploited as a novel in vivo model to study MEF2C-driven ETP-ALL and in-vivo drug-testing. 14

15 NAAM: Patricia GARRIDO CASTRO Postdoc Naam Centrum: Erasmus MC Sophia Kinderziekenhuis Naam Research groep: MLL-herschikte acute lymfatische leukemie bij zuigelingen. Keywords: MLL-rearranged infant ALL, mirna expression, bone marrow microenvironment, xenograft mouse model, in vivo pre-clinical drug testing. Abstract Both biologically and clinically, MLL-rearranged infant acute lymphoblastic leukemia (ALL) represents a unique malignancy associated with drug resistance to first-line chemotherapeutics, high relapse rates and an unfavorable prognosis. Hence, novel treatment strategies that specifically target the underlying molecular pathobiology of this disease are urgently needed. The majority of the MLL rearrangements involve the translocation partners AF4, AF9 or ENL; the resulting fusion genes, MLL/AF4, MLL/AF9 and MLL/ENL, code for chimeric transcription regulators acting as strong oncogenic drivers, rewriting the epigenetic landscape of the cell and profoundly altering gene expression. In order to gain further molecular understanding, we have already performed patient cohort profiling on both the transcript and epigenetic level. Currently we are completing mirnome screens of primary patient material, as well as hematopoietic precursor cells transduced to ectopically express the MLL fusion genes. This comprehensive approach reveals molecular events associated with MLL fusions on different regulatory levels, highlighting aberrant pathways and networks as putative novel druggable targets. Furthermore, we have established an in vivo xenograft mouse model with MLL-rearranged cells, able to recapitulate the disease observed in humans. Investigating the interactions of these leukemic cells with their microenvironment and how they influence each other on a molecular level, unveils novel points of attack. Consequently, candidate drugs targeting MLL-rearranged ALL cells or their interactions with the microenvironment are tested using this in vivo model. This integrative research approach, including both fundamental target discovery and translational pre-clinical in vivo models, aims to generate novel treatment rationales for this hard to treat disease. 15

16 NAAM: Willemieke de Goffau Nobel Technician Naam Centrum: Erasmus MC-Sophia Children s Hospital, Dept. of Pediatric Oncology Naam Research groep: B-cell precursor-all, PI: Prof.dr. Monique L. den Boer Abstract Key-words: Pathobiology ALL, oncogenomics, drug interference studies, fusion genes, targeted drugs. Patients with B-cell precursor acute lymphoblastic leukemia (BCP-ALL) can be classified in several subtypes, based on their genetic background. Unfortunately, certain cytogenetic subtypes are still associated with a poor prognosis. The overall survival of pediatric BCP- ALL is around 80%. We have identified patients carrying JAK2 mutations or JAK2 rearrangements by Sanger sequencing and RT-PCR/FISH, respectively. Mutations and rearrangements are thougth to activate the JAK-STAT signaling pathway, resulting into survival and proliferation of these leukemic cells. Currently, we are investigating the efficacy and specificity of two JAK2 inhibitors, momelotinib and ruxolitinib, on cell lines and patients leukemic cells. These inhibitors are tested in leukemic cells which are grown in co-culture with mesenchymal stromal cells, since stromal (growth) factors may be essential to (co) activate the JAK- STAT pathway. We compare patients samples with and without the presence of these fusion genes or mutations. Our aim is to identify which JAK2 inhibitor may be most specific against JAK2-aberrant cells, whether JAK2-mutated cells respond different to these inhibitors than JAK2-translocated cells and how these inhibitors affect the response to regular chemotherapeutic drugs (e.g. to prednisolone). 16

17 NAAM: Y.M. van Helsdingen Researchanalist Naam Centrum: Department of Pediatric Oncology/Hematology, Erasmus MC Rotterdam- Sophia Children s Hospital, Rotterdam, the Netherlands Naam Research groep: T cell-acute Lymphoblastic Leukemia Research Group (Principal Investigator: Dr. J.P.P. Meijerink) Abstract Als researchanalist in de T-ALL groep van de afdeling kindergeneeskunde, hou ik mij voornamelijk bezig met lentivirale gentherapie technieken om muis stamcellen te transduceren met genexpressie constructen om T-ALL oncogenen geforceerd tot expressie te kunnen brengen. Middels dit model bestuderen we de impact van deze oncogenen op normale T-cel ontwikkeling in de muis alsook het ontstaan van T-ALL na in vivo transplantatie experimenten. Daarnaast willen we synergisme van afwijkingen die vaak gepaard voorkomen in T-ALL patiënten bestuderen in het ontstaan van T-ALL. Middels dit model systeem proberen we meer te weten te komen over de pathogenetische mechanismen van oncogenen waardoor T-ALL ontstaat en waarop we nieuwe therapie zouden kunnen richten. Daarnaast kunnen deze modelsystemen helpen om de effectiviteit van nieuwe middelen (compounds) te testen. Tot mijn dagelijkse werkzaamheden behoren o.a. ook genotyperingen van de muizenlijnen, het produceren van lentivirale virus batches, het isoleren van muis stamcellen en transductie, RNA/DNA isolaties van patiëntmateriaal, kweken van T-ALL cellijnen. Hiervoor gebruik ik diverse technieken zoals o.a. DNA/RNA isolaties, (RTQ)PCR, virusproductie en transductie, kloneren van nieuwe constructen op basis van de Gateway technologie, FACS analyse en cel sorteringen, western blot en diverse dierexperimentele technieken (oogsten van cellen uit muis beenmerg, diverse injectie technieken, etc). 17

18 NAAM: Alex Hoogkamer Bioinformaticion Naam Centrum: Erasmus MC-Sophia Children s Hospital, Dept. of Pediatric Oncology Naam Research groep: B-cell precursor-all, PI: Prof.dr. Monique L. den Boer Abstract Key-words: pathobiology BCP-ALL, oncogenomics, mutation analysis, subclonality of disease, next-gen sequencing, data-integration, bio-informatics Pediatric leukemia is the most common cancer diagnosed in hundred-fifty children each year in the Netherlands. Using techniques such as next generation sequencing we aim to find (sub)clonal mutations in known oncogenic genes such as RAS, RAF and P53. We are sequencing a cohort of over 500 patient samples on the Illumina Miseq platform with 1000x coverage of a custom cancer gene panel in collaboration with the Center for Personalized Cancer Treatment (CPCT). One of the challenges of next generation sequencing is the processing of data. We work on creating bioinformatics workflows that take raw sequencing reads and transform it into a comprehensive and human readable format. This workflow includes quality control, mapping of sequencing reads back to the human genome, variant calling and filtering of the found mutations. A second line of bioinformatics research involves the integration of different types of highthroughput 'omics' data such as mutations, DNA copy number, gene expression and protein expression levels. By integrating these different types of data we prioritize genes and proteins for experimental validation and functional studies in the lab with the aim to identify markers to improve diagnostics and targets for novel treatment strategies. 18

19 NAAM: Peter Hoogerbrugge Klinisch-projectleider Naam Centrum: Naam Research groep: Prinses Máxima Centrum Lab Pediatric Oncology Nijmegen Abstract See summary lab Dr Frank van Leeuwen. In collaboration with the groups of Prof. Den Boer (ErasmusMC, Rotterdam), DCOG (Drs De Haas and Sonneveld) and Dr. R Kuiper (Human genetics, RadboudUMC), research aimed at improving early identification of ALL-patients at high risk for relapse by using the latest genome-analysis techniques is being performed. The mechanisms of the therapy-resistance in these patients is being performed in-vitro and in murine models, e.g. of IKZF-deleted leukemias. The aim of this line of research is developing targeted, more effective treatment. In another line of research in collaboration with Prof. Adema (Tumorimmunology dept, RadboudUMC) relevant murine models of high-risk Neuroblastoma are being used to improve immunotherapy for patients with high-risk neuroblastoma. We focus on the development of more effective, rational combined immunotherapy-chemotherapy regimens. 19

20 NAAM: Adrián Jaramillo Promovendus Naam Centrum: Erasmus MC Sophia Kinderziekenhuis. Naam Research groep: MLL-herschikte acute lymfatische leukemie bij zuigelingen. Keywords: MLL-rearranged infant ALL, MLL-AF4 driven leukemogenesis, MLL-AF4 dependent genes. Abstract : My research work on MLL-rearranged acute lymphoblastic leukemia in infants includes: 1. The contribution of the bone marrow niche to leukemogenesis, and 2. Validation and characterization of genes transcriptionally dependent on the presence of the MLL fusion protein. 1. Despite the aggressive nature of MLL-rearranged infant ALL, it remains difficult to model leukemogenesis in mice by xenotransplanting human hematopoietic stem cells (HSCs) expressing the MLL-AF4 fusion gene. Recent studies have showed that a unique feature of MLL-AF4+ infant ALL is the presence of the MLL-AF4 fusion in the patient s bone marrow mesenchymal cells. This may suggest that a leukemic bone marrow microenvironment may be required for proper transformation. Therefore we are currently conducting experiments in mice in which MLL-AF4 expressing human mesenchymal stem cells (MSCs) are co-injected together with MLL-AF4+ human HSCs. 2. Recently our research group has identified gene signatures that transcriptionally readily respond to sirnamediated knock-down of MLL-AF4. Obviously, these genes potentially represent attractive therapeutic targets. Therefore we are currently in the process of validating and functionally characterizing the effects of gene expression modulation of a selected subset of these genes with respect to drug resistance, proliferation and leukemic cell survival. 20

21 NAAM: Isabel Jerchel PhD student Naam Centrum: Erasmus MC-Sophia Children s Hospital, Dept. of Pediatric Oncology Naam Research groep: B-cell precursor-all, PI: Prof.dr. Monique L. den Boer Abstract Key-words: pathobiology BCP-ALL, oncogenomics, subclonality of ALL, microenvironment, growth factor mediated signaling, cellular drug resistance, targeted drugs. Most pediatric patients with B-cell precursor (BCP) ALL have a good prognosis: the overall survival rate has improved to 80-90%. For certain subgroups of patients the cure rates are considerably lower. Most relapses occur in patients who have been in complete remission for several months up to years and ALL cells from relapsed patients are often intrinsically more resistant to chemotherapy. It is therefore believed that a small number of drug resistant cells can survive chemotherapy and grow out to a relapse. The bone marrow microenvironment that usually supports normal hematopoiesis, is believed to play an important role in supporting the survival of ALL cells: by providing nutrients and growth factors the bone marrow stroma forms a home for the leukemic cells. Our research therefore aims to discover and target the factors and pathways that link the bone marrow stroma to the ALL cells. Interfering with this supportive niche may reduce the amount of chemotherapy needed to eradicate all leukemic cells and may also prevent that resistant subclones reside in the bone marrow during chemotherapy. Furthermore, several recurrent genetic aberrations in growth factor receptors and their associated pathways are indicative of a trend towards niche independence, highlighting the importance of the growth signals initially regulated by the niche. In line with this, our group has recently shown that activating RAS mutations confer cellular resistance towards prednisolone. Importantly, RAS is a cellular hub for relating external growth factor signals into a cellular growth response. In an ongoing study we currently study the subclonality of BCP-ALL for RAS-pathway genes and other candidate genes which are often mutated in other malignancies. To this aim, next generation sequencing (Illumina, MiSeq, paired-end sequencing) of ALL samples is being performed and patients are selected for functional studies addressing the specificity of targeted drugs in combination with prednisolone. Our aim is to elucidate the signal mediators that activate survival pathways, which may lead to drugs/inhibitors which block the vital growth signals and may be of use to kill (subclones of) leukemic cells more specifically. 21