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1.  ESF-EMBO Symposium “Molecular Biology and Innovative Therapies in Sarcomas of Childhood and Adolescence” Sept 29–Oct 4, Polonia Castle Pultusk, Poland 
Frontiers in Oncology  2013;3:142.
Rhabdomyosarcoma (RMS) and Ewing sarcoma (ES) are among the most common pediatric sarcomas (Arndt et al., 2012). Despite sarcomas representing a highly heterogeneous group of tumors, ES and alveolar RMS (ARMS) typically share one common genetic characteristic, namely a specific chromosomal translocation (Helman and Meltzer, 2003; Lessnick and Ladanyi, 2012). These translocations generate fusion proteins, which are composed of two transcription factors (TF). Typically, one TF is a developmentally regulated factor that is essential for proper specification of a given lineage and provides the DNA-binding domain, while the partner TF contributes a transactivation domain that drives aberrant expression of target genes. Based on these common genetic characteristics, the first ESF-EMBO research conference entitled “Molecular Biology and Innovative Therapies in Sarcomas of Childhood and Adolescence” with special focus on RMS and ES was held at the Polonia Castle in Pultusk, Poland. The conference gathered 70 participants from more than 15 countries and several continents representing most research groups that are active in this field.
PMCID: PMC3671287  PMID: 23761860
Rhabdomyosarcoma; Ewing sarcoma; therapeutics; PAX3/FOXO1; EWS/Fli1
2.  Cell-Based Small-Molecule Compound Screen Identifies Fenretinide as Potential Therapeutic for Translocation-Positive Rhabdomyosarcoma 
PLoS ONE  2013;8(1):e55072.
A subset of paediatric sarcomas are characterized by chromosomal translocations encoding specific oncogenic transcription factors. Such fusion proteins represent tumor specific therapeutic targets although so far it has not been possible to directly inhibit their activity by small-molecule compounds. In this study, we hypothesized that screening a small-molecule library might identify already existing drugs that are able to modulate the transcriptional activity of PAX3/FOXO1, the fusion protein specifically found in the pediatric tumor alveolar rhabdomyosarcoma (aRMS). Towards this end, we established a reporter cell line based on the well characterized PAX3/FOXO1 target gene AP2ß. A library enriched in mostly FDA approved drugs was screened using specific luciferase activity as read-out and normalized for cell viability. The most effective inhibitor identified from this screen was Fenretinide. Treatment with this compound resulted in down-regulation of PAX3/FOXO1 mRNA and protein levels as well as in reduced expression of several of its direct target genes, but not of wild-type FOXO1, in a dose- and time-dependent manner. Moreover, fenretinide induced reactive oxygen species and apoptosis as shown by caspase 9 and PARP cleavage and upregulated miR-9. Importantly, it demonstrated a significant anti-tumor effect in vivo. These results are similar to earlier reports for two other pediatric tumors, namely neuroblastoma and Ewing sarcoma, where fenretinide is under clinical development. Our results suggest that fenretinide might represent a novel treatment option also for translocation-positive rhabdomyosarcoma.
PMCID: PMC3555977  PMID: 23372815
3.  The First European Interdisciplinary Ewing Sarcoma Research Summit 
The European Network for Cancer Research in Children and Adolescents (ENCCA) provides an interaction platform for stakeholders in research and care of children with cancer. Among ENCCA objectives is the establishment of biology-based prioritization mechanisms for the selection of innovative targets, drugs, and prognostic markers for validation in clinical trials. Specifically for sarcomas, there is a burning need for novel treatment options, since current chemotherapeutic treatment protocols have met their limits. This is most obvious for metastatic Ewing sarcoma (ES), where long term survival rates are still below 20%. Despite significant progress in our understanding of ES biology, clinical translation of promising laboratory results has not yet taken place due to fragmentation of research and lack of an institutionalized discussion forum. To fill this gap, ENCCA assembled 30 European expert scientists and five North American opinion leaders in December 2011 to exchange thoughts and discuss the state of the art in ES research and latest results from the bench, and to propose biological studies and novel promising therapeutics for the upcoming European EWING2008 and EWING2012 clinical trials.
PMCID: PMC3361960  PMID: 22662320
Ewing sarcoma; animal models; sarcomagenesis; genomics; epigenetics; biomarkers; drug screen; prognosis
4.  CD133 Positive Embryonal Rhabdomyosarcoma Stem-Like Cell Population Is Enriched in Rhabdospheres 
PLoS ONE  2011;6(5):e19506.
Cancer stem cells (CSCs) have been identified in a number of solid tumors, but not yet in rhabdomyosarcoma (RMS), the most frequently occurring soft tissue tumor in childhood. Hence, the aim of this study was to identify and characterize a CSC population in RMS using a functional approach. We found that embryonal rhabdomyosarcoma (eRMS) cell lines can form rhabdomyosarcoma spheres (short rhabdospheres) in stem cell medium containing defined growth factors over several passages. Using an orthotopic xenograft model, we demonstrate that a 100 fold less sphere cells result in faster tumor growth compared to the adherent population suggesting that CSCs were enriched in the sphere population. Furthermore, stem cell genes such as oct4, nanog, c-myc, pax3 and sox2 are significantly upregulated in rhabdospheres which can be differentiated into multiple lineages such as adipocytes, myocytes and neuronal cells. Surprisingly, gene expression profiles indicate that rhabdospheres show more similarities with neuronal than with hematopoietic or mesenchymal stem cells. Analysis of these profiles identified the known CSC marker CD133 as one of the genes upregulated in rhabdospheres, both on RNA and protein levels. CD133+ sorted cells were subsequently shown to be more tumorigenic and more resistant to commonly used chemotherapeutics. Using a tissue microarray (TMA) of eRMS patients, we found that high expression of CD133 correlates with poor overall survival. Hence, CD133 could be a prognostic marker for eRMS. These experiments indicate that a CD133+ CSC population can be enriched from eRMS which might help to develop novel targeted therapies against this pediatric tumor.
PMCID: PMC3094354  PMID: 21602936
5.  Furin Targeted Drug Delivery for Treatment of Rhabdomyosarcoma in a Mouse Model 
PLoS ONE  2010;5(5):e10445.
Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children. Improvement of treatment efficacy and decreased side effects through tumor-targeted drug delivery would be desirable. By panning with a phage-displayed cyclic random peptide library we selected a peptide with strong affinity for RMS in vitro and in vivo. The peptide minimal binding motif Arg-X-(Arg/Lys)(Arg/Lys) identified by alanine-scan, suggested the target receptor to be a proprotein convertase (PC). Expression profiling of all PCs in RMS biopsies and cell lines revealed consistent high expression levels for the membrane-bound furin and PC7. Direct binding of RMS-P3 peptide to furin was demonstrated by affinity chromatography and supported by activity and colocalization studies. Treatment of RMS in mice with doxorubicin coupled to the targeting peptide resulted in a two-fold increase in therapeutic efficacy compared to doxorubicin treatment alone. Our findings indicate surface-furin binding as novel mechanism for therapeutic cell penetration which needs to be further investigated. Furthermore, this work demonstrates that specific targeting of membrane-bound furin in tumors is possible for and suggests that RMS and other tumors might benefit from proprotein convertases targeted drug delivery.
PMCID: PMC2862740  PMID: 20454619
6.  Induction of autophagy-dependent necroptosis is required for childhood acute lymphoblastic leukemia cells to overcome glucocorticoid resistance 
The Journal of Clinical Investigation  2010;120(4):1310-1323.
In vivo resistance to first-line chemotherapy, including to glucocorticoids, is a strong predictor of poor outcome in children with acute lymphoblastic leukemia (ALL). Modulation of cell death regulators represents an attractive strategy for subverting such drug resistance. Here we report complete resensitization of multidrug-resistant childhood ALL cells to glucocorticoids and other cytotoxic agents with subcytotoxic concentrations of obatoclax, a putative antagonist of BCL-2 family members. The reversal of glucocorticoid resistance occurred through rapid activation of autophagy-dependent necroptosis, which bypassed the block in mitochondrial apoptosis. This effect was associated with dissociation of the autophagy inducer beclin-1 from the antiapoptotic BCL-2 family member myeloid cell leukemia sequence 1 (MCL-1) and with a marked decrease in mammalian target of rapamycin (mTOR) activity. Consistent with a protective role for mTOR in glucocorticoid resistance in childhood ALL, combination of rapamycin with the glucocorticoid dexamethasone triggered autophagy-dependent cell death, with characteristic features of necroptosis. Execution of cell death, but not induction of autophagy, was strictly dependent on expression of receptor-interacting protein (RIP-1) kinase and cylindromatosis (turban tumor syndrome) (CYLD), two key regulators of necroptosis. Accordingly, both inhibition of RIP-1 and interference with CYLD restored glucocorticoid resistance completely. Together with evidence for a chemosensitizing activity of obatoclax in vivo, our data provide a compelling rationale for clinical translation of this pharmacological approach into treatments for patients with refractory ALL.
PMCID: PMC2846044  PMID: 20200450
7.  Dral Is a P53-Responsive Gene Whose Four and a Half Lim Domain Protein Product Induces Apoptosis 
The Journal of Cell Biology  2000;151(3):495-506.
DRAL is a four and a half LIM domain protein identified because of its differential expression between normal human myoblasts and the malignant counterparts, rhabdomyosarcoma cells. In the current study, we demonstrate that transcription of the DRAL gene can be stimulated by p53, since transient expression of functional p53 in rhabdomyosarcoma cells as well as stimulation of endogenous p53 by ionizing radiation in wild-type cells enhances DRAL mRNA levels. In support of these observations, five potential p53 target sites could be identified in the promoter region of the human DRAL gene. To obtain insight into the possible functions of DRAL, ectopic expression experiments were performed. Interestingly, DRAL expression efficiently triggered apoptosis in three cell lines of different origin to the extent that no cells could be generated that stably overexpressed this protein. However, transient transfection experiments as well as immunofluorescence staining of the endogenous protein allowed for the localization of DRAL in different cellular compartments, namely cytoplasm, nucleus, focal contacts, as well as Z-discs and to a lesser extent the M-bands in cardiac myofibrils. These data suggest that downregulation of DRAL might be involved in tumor development. Furthermore, DRAL expression might be important for heart function.
PMCID: PMC2185594  PMID: 11062252
LIM domain protein; transcriptional regulation; p53; apoptosis; subcellular localization

Results 1-7 (7)