First Transcriptome Analysis of Hepatoblastoma in Brazil: Unraveling the Pivotal Role of Noncoding RNAs and Metabolic Pathways

Hepatoblastoma stands as the most prevalent liver cancer in the pediatric population. Characterized by a low mutational burden, chromosomal and epigenetic alterations are key drivers of its tumorigenesis. Transcriptome analysis is a powerful tool for unraveling the molecular intricacies of hepatoblastoma, shedding light on the effects of genetic and epigenetic changes on gene expression. In this study conducted in Brazilian patients, an in-depth whole transcriptome analysis was performed on 14 primary hepatoblastomas, compared to control liver tissues. The analysis unveiled 1,492 differentially expressed genes (1,031 upregulated and 461 downregulated), including 920 protein-coding genes (62%). Upregulated biological processes were linked to cell differentiation, signaling, morphogenesis, and development, involving known hepatoblastoma-associated genes (DLK1, MEG3, HDAC2, TET1, HMGA2, DKK1, DKK4), alongside with novel findings (GYNG4, CDH3, and TNFRSF19). Downregulated processes predominantly centered around oxidation and metabolism, affecting amines, nicotinamides, and lipids, featuring novel discoveries like the repression of SYT7, TTC36, THRSP, CCND1, GCK and CAMK2B. Two genes, which displayed a concordant pattern of DNA methylation alteration in their promoter regions and dysregulation in the transcriptome, were further validated by RT-qPCR: the upregulated TNFRSF19, a key gene in the embryonic development, and the repressed THRSP, connected to lipid metabolism. Furthermore, based on protein-protein interaction analysis, we identified genes holding central positions in the network, such as HDAC2, CCND1, GCK, and CAMK2B, among others, that emerged as prime candidates warranting functional validation in future studies. Notably, a significant dysregulation of non-coding RNAs (ncRNAs), predominantly upregulated transcripts, was observed, with 42% of the top 50 highly expressed genes being ncRNAs. An integrative miRNA-mRNA analysis revealed crucial biological processes associated with metabolism, oxidation reactions of lipids and carbohydrates, and methylation-dependent chromatin silencing. In particular, four upregulated miRNAs (miR-186, miR-214, miR-377, and miR-494) played a pivotal role in the network, potentially targeting multiple protein-coding transcripts, including CCND1 and CAMK2B. In summary, our transcriptome analysis highlighted disrupted embryonic development as well as metabolic pathways, particularly those involving lipids, emphasizing the emerging role of ncRNAs as epigenetic regulators in hepatoblastomas. These findings provide insights into the complexity of the hepatoblastoma transcriptome and identify potential targets for future therapeutic interventions.

Quantitative expression evaluation of PRAME gene in osteosarcoma

BACKGROUND

In a previous study, our group observed that 68% of the osteosarcoma (OS) samples presented PRAME (Preferentially Expressed Antigen in Melanoma) gene expression. In this work, we propose to investigate quantitatively gene expression of PRAME in distinct patients groups.

METHODS AND RESULTS

61 osteosarcoma samples, from 3 distinct patients groups were selected for this study: (1) Patients younger than 10 years old at diagnosis, (2) Patients that had poor evolution of disease and (3) Patients that were in remission of disease and had treatment with no intercurrences) PRAME gene expression levels were obtained using quantitative Real-Time Polymerase Chain Reaction method (qRT-PCR). Clinical parameters were collected from patient's medical charts. Results demonstrated an increase in PRAME gene expression in all samples, with high variation in expression levels, when considering all samples and when analyzed in each group. In addition, no statistical difference was found when considering clinical data collected or patients groups.

CONCLUSION

PRAME gene expression quantitative investigation did not bring any complementary information beyond of what had already been observed in other qualitative investigations published by our group, there is no relation between PRAME gene expression levels and disease evolution. However, the findings in this work contribute for validation PRAME gene expression as a good biomarker to OS, which, in the future, may allow identification circulating tumor cell or molecules to contribute with early diagnostic of metastasis, a genuine problem in OS that determinate flattening in survival curves.

Unraveling the Genetic Architecture of Hepatoblastoma Risk: Birth Defects and Increased Burden of Germline Damaging Variants in Gastrointestinal/Renal Cancer Predisposition and DNA Repair Genes

The ultrarare hepatoblastoma (HB) is the most common pediatric liver cancer. HB risk is related to a few rare syndromes, and the molecular bases remain elusive for most cases. We investigated the burden of rare damaging germline variants in 30 Brazilian patients with HB and the presence of additional clinical signs. A high frequency of prematurity (20%) and birth defects (37%), especially craniofacial (17%, including craniosynostosis) and kidney (7%) anomalies, was observed. Putative pathogenic or likely pathogenic monoallelic germline variants mapped to 10 cancer predisposition genes (CPGs: APC, CHEK2, DROSHA, ERCC5, FAH, MSH2, MUTYH, RPS19, TGFBR2 and VHL) were detected in 33% of the patients, only 40% of them with a family history of cancer. These findings showed a predominance of CPGs with a known link to gastrointestinal/colorectal and renal cancer risk. A remarkable feature was an enrichment of rare damaging variants affecting different classes of DNA repair genes, particularly those known as Fanconi anemia genes. Moreover, several potentially deleterious variants mapped to genes impacting liver functions were disclosed. To our knowledge, this is the largest assessment of rare germline variants in HB patients to date, contributing to elucidate the genetic architecture of HB risk.

Gliomas in children and adolescents: investigation of molecular alterations with a potential prognostic and therapeutic impact

PURPOSE

Gliomas represent the most frequent central nervous system (CNS) tumors in children and adolescents. However, therapeutic strategies for these patients, based on tumor molecular profile, are still limited compared to the wide range of treatment options for the adult population. We investigated molecular alterations, with a potential prognostic marker and therapeutic target in gliomas of childhood and adolescence using the next-generation sequencing (NGS) strategy.

METHODS

We selected 95 samples with initial diagnosis of glioma from patients treated at Pediatric Oncology Institute-GRAACC/UNIFESP. All samples were categorized according to the 2021 World Health Organization Classification of Tumors of the CNS, which included 39 low-grade gliomas (LGGs) and 56 high-grade gliomas (HGGs). Four HGG samples were classified as congenital glioblastoma (cGBM). NGS was performed to identify somatic genetic variants in tumor samples using the Oncomine Childhood Cancer Research Assay^® (OCCRA^®) panel, from Thermo Fisher Scientific^®.

RESULTS

Genetic variants were identified in 76 of 95 (80%) tumors. In HGGs, the most common molecular alteration detected was H3F3A c.83A > T variant (H3.3 K27M) and co-occurring mutations in ATRX, TP53, PDGFRA, MET, and MYC genes were also frequently observed. One HGG sample was reclassified as supratentorial ependymoma ZFTA-fusion positive after NGS was performed. In LGGs, four KIAA1549-BRAF fusion transcripts were detected and this alteration was the most recurrent genetic event and favorable prognostic factor identified. Additionally, genetic variants in ALK and NTRK genes, which provide potential targets for therapy with Food and Drug Administration-approved drugs, were identified in two different cases of cGBM that were classified as infant-type hemispheric glioma, a newly recognized subgroup of pediatric HGG.

CONCLUSION

Molecular profiling by the OCCRA^® panel comprehensively addressed the most relevant genetic variants in gliomas of childhood and adolescence, as these tumors have specific patterns of molecular alterations, outcomes, and effectiveness to therapies.

Molecular profiling of pediatric and adolescent ependymomas: identification of genetic variants using a next-generation sequencing panel

PURPOSE

Ependymoma (EPN) accounts for approximately 10% of all primary central nervous system (CNS) tumors in children and in most cases, chemotherapy is ineffective and treatment remains challenging. We investigated molecular alterations, with a potential prognostic marker and therapeutic target in EPNs of childhood and adolescence, using a next-generation sequencing (NGS) panel specific for pediatric neoplasms.

METHODS

We selected 61 samples with initial diagnosis of EPN from patients treated at Pediatric Oncology Institute-GRAACC/UNIFESP. All samples were divided according to the anatomical compartment of the CNS - 42 posterior fossa (PF), 14 supratentorial (ST), and five spinal (SP). NGS was performed to identify somatic genetic variants in tumor samples using the Oncomine Childhood Cancer Research Assay® (OCCRA®) panel, from Thermo Fisher Scientific®.

RESULTS

Genetic variants were identified in 24 of 61 (39.3%) tumors and over 90% of all variants were pathogenic or likely pathogenic. The most commonly variants detected were in CIC, ASXL1, and JAK2 genes and have not been reported in EPN yet. MN1-BEND2 fusion, alteration recently described in a new CNS tumor type, was identified in one ST sample that was reclassified as astroblastoma. Additionally, YAP1-MAMLD1 fusion, a rare event associated with good outcome in ST-EPN, was observed in two patients diagnosed under 2 years old.

CONCLUSIONS

Molecular profiling by the OCCRA® panel showed novel alterations in pediatric and adolescent EPNs, which highlights the clinical importance in identifying genetic variants for patients' prognosis and therapeutic orientation.

Abstract 2167: Genomic profiling of pediatric and adolescent ependymomas: Underlying genetic alterations for prognosis and therapeutic orientation

Background: Ependymoma (EPN) is the third most common brain tumor in children and adolescents and is incurable in up to 40% cases, as chemotherapy is ineffective in most individuals and treatment remains challenging. A genetic panel based on next-generation sequencing (NGS) technology and developed exclusively for pediatric neoplasms is essential in order to determine prognosis and therapeutic managements in EPN, as this tumor comprise several molecular subgroups with unique clinical characteristics. We aimed to detect and investigate molecular alterations, with potential prognostic marker and therapeutic target in childhood and adolescence EPN, using the NGS strategy.

Methods: We selected 59 EPN samples from patients diagnosed and treated at Pediatric Oncology Institute-GRAACC/UNIFESP. All 59 EPN samples were divided according to the anatomical compartment of the Central Nervous System: 41 samples from the posterior fossa (PF), 13 supratentorial (ST) and 5 spinal (SP). NGS was performed to identify somatic genetic alterations in tumor samples using Oncomine Childhood Cancer Research Assay (OCCRA) panel, from Thermo Fisher, designed specifically for childhood and adolescence neoplasms. Our molecular findings were correlated with clinical and histopathological characteristics of the patients analyzed.

Results: A total of 59 EPN samples were sequenced in our institution and we identified somatic alterations in 24 of 59 (40.7%) tumors. We observed 14 altered genes and 16 genetic variants, which 43.8% were pathogenic and 37.5% have not been reported yet. The most commonly detected genetic alterations were involving ASXL1, CIC, JAK2, ABL2 and MDM4 genes. SNVs were the majority of all genetic alterations detected, accounting for 10 of 20 cases (50%). The pathogenic and synonymous mutation c.4533C>T of CIC gene, previously reported as SNP, was the most frequent variant observed in EPN samples. CNVs were observed in ABL2 and MDM4 genes and were exclusively identified in PF-EPN samples. Gene fusions were found in 3 alive patients with age to diagnosis under 5 years and with ST-EPN and SP-EPN.

Conclusions: Molecular profile investigation, based on NGS panel specific for pediatric tumors, can provide information about potential prognostic biomarkers for EPN. Thus, genomic profiling of childhood and adolescence EPN that appropriately integrate the clinical, radiologic, and histologic aspects of this tumor, is essential in order to define therapeutic strategies.

Funding Source: São Paulo Research Foundation (FAPESP no. 2019/12074-5)

Citation Format: Débora Cabral de Corrêa, Indhira Dias Oliveira, Francine Tesser-Gamba, Maria Teresa de Seixas Alves, Nasjla Saba-Silva, Andrea Maria Capellano, Patrícia Dastoli, Sergio Cavalheiro, Silvia Regina Caminada de Toledo. Genomic profiling of pediatric and adolescent ependymomas: Underlying genetic alterations for prognosis and therapeutic orientation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2167.

Frequency of Pathogenic Germline Variants in Cancer-Susceptibility Genes in Patients With Osteosarcoma

Importance

Osteosarcoma, the most common malignant bone tumor in children and adolescents, occurs in a high number of cancer predisposition syndromes that are defined by highly penetrant germline mutations. The germline genetic susceptibility to osteosarcoma outside of familial cancer syndromes remains unclear.

Objective

To investigate the germline genetic architecture of 1244 patients with osteosarcoma.

Design, Setting, and Participants

Whole-exome sequencing (n = 1104) or targeted sequencing (n = 140) of the DNA of 1244 patients with osteosarcoma from 10 participating international centers or studies was conducted from April 21, 2014, to September 1, 2017. The results were compared with the DNA of 1062 individuals without cancer assembled internally from 4 participating studies who underwent comparable whole-exome sequencing and 27 173 individuals of non-Finnish European ancestry who were identified through the Exome Aggregation Consortium (ExAC) database. In the analysis, 238 high-interest cancer-susceptibility genes were assessed followed by testing of the mutational burden across 736 additional candidate genes. Principal component analyses were used to identify 732 European patients with osteosarcoma and 994 European individuals without cancer, with outliers removed for patient-control group comparisons. Patients were subsequently compared with individuals in the ExAC group. All data were analyzed from June 1, 2017, to July 1, 2019.

Main Outcomes and Measures

The frequency of rare pathogenic or likely pathogenic genetic variants.

Results

Among 1244 patients with osteosarcoma (mean [SD] age at diagnosis, 16 [8.9] years [range, 2-80 years]; 684 patients [55.0%] were male), an analysis restricted to individuals with European ancestry indicated a significantly higher pathogenic or likely pathogenic variant burden in 238 high-interest cancer-susceptibility genes among patients with osteosarcoma compared with the control group (732 vs 994, respectively; P = 1.3 × 10-18). A pathogenic or likely pathogenic cancer-susceptibility gene variant was identified in 281 of 1004 patients with osteosarcoma (28.0%), of which nearly three-quarters had a variant that mapped to an autosomal-dominant gene or a known osteosarcoma-associated cancer predisposition syndrome gene. The frequency of a pathogenic or likely pathogenic cancer-susceptibility gene variant was 128 of 1062 individuals (12.1%) in the control group and 2527 of 27 173 individuals (9.3%) in the ExAC group. A higher than expected frequency of pathogenic or likely pathogenic variants was observed in genes not previously linked to osteosarcoma (eg, CDKN2A, MEN1, VHL, POT1, APC, MSH2, and ATRX) and in the Li-Fraumeni syndrome-associated gene, TP53.

Conclusions and Relevance

In this study, approximately one-fourth of patients with osteosarcoma unselected for family history had a highly penetrant germline mutation requiring additional follow-up analysis and possible genetic counseling with cascade testing.

Abnormal spindle-like microcephaly-associated (ASPM) gene expression in posterior fossa brain tumors of childhood and adolescence

PURPOSE

In neurogenesis, ASPM (abnormal spindle-like microcephaly-associated) gene is expressed mainly in the ventricular zone of posterior fossa and is the major determinant in the cerebral cortex. Besides its role in embryonic development, ASPM overexpression promotes tumor growth, including central nervous system (CNS) tumors. This study aims to investigate ASPM expression levels in most frequent posterior fossa brain tumors of childhood and adolescence: medulloblastoma (MB), ependymoma (EPN), and astrocytoma (AS), correlating them with clinicopathological characteristics and tumor solid portion size.

METHODS

Quantitative reverse transcription (qRT-PCR) is used to quantify ASPM mRNA levels in 80 pre-treatment tumor samples: 28 MB, 22 EPN, and 30 AS. The tumor solid portion size was determined by IOP-GRAACC Diagnostic Imaging Center. We correlated these findings with clinicopathological characteristics and tumor solid portion size.

RESULTS

Our results demonstrated that ASPM gene was overexpressed in MB (p = 0.007) and EPN (p = 0.0260) samples. ASPM high expression was significantly associated to MB samples from patients with worse overall survival (p = 0.0123) and death due to disease progression (p = 0.0039). Interestingly, two patients with AS progressed toward higher grade showed ASPM overexpression (p = 0.0046). No correlation was found between the tumor solid portion size and ASPM expression levels in MB (p = 0.1154 and r = - 0.4825) and EPN (p = 0.1108 and r = - 0.3495) samples.

CONCLUSION

Taking in account that ASPM gene has several functions to support cell proliferation, as mitotic defects and premature differentiation, we suggest that its overexpression, presumably, plays a critical role in disease progression of posterior fossa brain tumors of childhood and adolescence.

Hepatoblastomas exhibit marked NNMT downregulation driven by promoter DNA hypermethylation

Hepatoblastomas exhibit the lowest mutational burden among pediatric tumors. We previously showed that epigenetic disruption is crucial for hepatoblastoma carcinogenesis. Our data revealed hypermethylation of nicotinamide N-methyltransferase, a highly expressed gene in adipocytes and hepatocytes. The expression pattern and the role of nicotinamide N-methyltransferase in pediatric liver tumors have not yet been explored, and this study aimed to evaluate the effect of nicotinamide N-methyltransferase hypermethylation in hepatoblastomas. We evaluated 45 hepatoblastomas and 26 non-tumoral liver samples. We examined in hepatoblastomas if the observed nicotinamide N-methyltransferase promoter hypermethylation could lead to dysregulation of expression by measuring mRNA and protein levels by real-time quantitative polymerase chain reaction, immunohistochemistry, and Western blot assays. The potential impact of nicotinamide N-methyltransferase changes was evaluated on the metabolic profile by high-resolution magic angle spinning nuclear magnetic resonance spectroscopy. Significant nicotinamide N-methyltransferase downregulation was revealed in hepatoblastomas, with two orders of magnitude lower nicotinamide N-methyltransferase expression in tumor samples and hepatoblastoma cell lines than in hepatocellular carcinoma cell lines. A specific TSS1500 CpG site (cg02094283) of nicotinamide N-methyltransferase was hypermethylated in tumors, with an inverse correlation between its methylation level and nicotinamide N-methyltransferase expression. A marked global reduction of the nicotinamide N-methyltransferase protein was validated in tumors, with strong correlation between gene and protein expression. Of note, higher nicotinamide N-methyltransferase expression was statistically associated with late hepatoblastoma diagnosis, a known clinical variable of worse prognosis. In addition, untargeted metabolomics analysis detected aberrant lipid metabolism in hepatoblastomas. Data presented here showed the first evidence that nicotinamide N-methyltransferase reduction occurs in hepatoblastomas, providing further support that the nicotinamide N-methyltransferase downregulation is a wide phenomenon in liver cancer. Furthermore, this study unraveled the role of DNA methylation in the regulation of nicotinamide N-methyltransferase expression in hepatoblastomas, in addition to evaluate the potential effect of nicotinamide N-methyltransferase reduction in the metabolism of these tumors. These preliminary findings also suggested that nicotinamide N-methyltransferase level may be a potential prognostic biomarker for hepatoblastoma.

Identification of genetic alterations in childhood and adolescence glioblastoma (GBM) using next generation sequencing strategy

e14547

Background: Glioblastoma (GBM) is the most aggressive brain malignancy with a heterogeneity molecular profile and accounts for no more than 3-5% of Central Nervous System tumors in children. Despite its rarity, pediatric GBM pertain different molecular genetics, outcome and effectiveness to therapies and remains an equally lethal tumor in children. Identification of genetic alterations in GBM of childhood and adolescence is important to refine molecular classification, define prognosis and therapeutic strategies. We aimed to detect and investigate molecular changes with potential prognostic marker and therapeutic target in GBM, using next generation sequencing (NGS) strategy. Methods: We selected 41 GBM samples from patients treated at Pediatric Oncology Institute/GRAACC. NGS was performed to identified genetic alterations in tumor samples using Oncomine Childhood Cancer Research Assay (OCCRA) panel, specific genetic panel for childhood and adolescence neoplasms. Results: We selected 41 GBM samples and identified 33 mutated genes. The most commonly detected genetic alterations were involving TP53, PDGFRA, PIK3CA, NF1, MYC, MET and genes with histone-related functions, including H3F3A and ATRX. Mutations in H3F3A K28M, ATRX and TP53 were most recurrent. ATRX alterations, either nonsense substitution or frameshift deletion, were exclusively found in patients with H3F3A K28M mutations. TP53 loss-of-function was exclusive in 9 of 41 (22%) tumors. In 7 of 9 cases (78%) harboring both H3F3A and TP53 mutations, patients died due to disease progression . In these patients, H3F3A-TP53 mutation is suggested to be unfavorable prognostic factor. Copy number alterations were found in 30% of GBM cases and PDGFRA-amplifications were the most frequent. PDGFRA-amplification was exclusively found in patients with H3F3A K28M mutations and 75% of these patients did not survived longer than two years. Conclusions: Molecular profiling based on NGS genetic panel, specific for pediatric tumors, can provide information about potential prognostic biomarkers for GBM of childhood and adolescence. Thus, wider understanding about GBM biologic heterogeneity may lead to personalized therapeutic strategies for pediatric patients.

Insights Into the Somatic Mutation Burden of Hepatoblastomas From Brazilian Patients

Hepatoblastoma is a very rare embryonal liver cancer supposed to arise from the impairment of hepatocyte differentiation during embryogenesis. In this study, we investigated by exome sequencing the burden of somatic mutations in a cohort of 10 hepatoblastomas, including a congenital case. Our data disclosed a low mutational background and pointed out to a novel set of candidate genes for hepatoblastoma biology, which were shown to impact gene expression levels. Only three recurrently mutated genes were detected: CTNNB1 and two novel candidates, CX3CL1 and CEP164. A relevant finding was the identification of a recurrent mutation (A235G) in two hepatoblastomas at the CX3CL1 gene; evaluation of RNA and protein expression revealed upregulation of CX3CL1 in tumors. The analysis was replicated in two independents cohorts, substantiating that an activation of the CX3CL1/CX3CR1 pathway occurs in hepatoblastomas. In inflammatory regions of hepatoblastomas, CX3CL1/CX3CR1 were not detected in the infiltrated lymphocytes, in which they should be expressed in normal conditions, whereas necrotic regions exhibited negative labeling in tumor cells, but strongly positive infiltrated lymphocytes. Altogether, these data suggested that CX3CL1/CX3CR1 upregulation may be a common feature of hepatoblastomas, potentially related to chemotherapy response and progression. In addition, three mutational signatures were identified in hepatoblastomas, two of them with predominance of either the COSMIC signatures 1 and 6, found in all cancer types, or the COSMIC signature 29, mostly related to tobacco chewing habit; a third novel mutational signature presented an unspecific pattern with an increase of C>A mutations. Overall, we present here novel candidate genes for hepatoblastoma, with evidence that CX3CL1/CX3CR1 chemokine signaling pathway is likely involved with progression, besides reporting specific mutational signatures.

TET Upregulation Leads to 5-Hydroxymethylation Enrichment in Hepatoblastoma

Hepatoblastoma is an embryonal liver tumor carrying few genetic alterations. We previously disclosed in hepatoblastomas a genome-wide methylation dysfunction, characterized by hypermethylation at specific CpG islands, in addition to a low-level hypomethylation pattern in non-repetitive intergenic sequences, in comparison to non-tumoral liver tissues, shedding light into a crucial role for epigenetic dysregulation in this type of cancer. To explore the underlying mechanisms possibly related to aberrant epigenetic modifications, we evaluated the expression profile of a set of genes engaged in the epigenetic machinery related to DNA methylation (DNMT1, DNMT3A, DNMT3B, DNMT3L, UHRF1, TET1, TET2, and TET3), as well as the 5-hydroxymethylcytosine (5hmC) global level. We observed in hepatoblastomas a general disrupted expression of these genes from the epigenetic machinery, mainly UHRF1, TET1, and TET2 upregulation, in association with an enrichment of 5hmC content. Our findings support a model of active demethylation by TETs in hepatoblastoma, probably during early stages of liver development, which in combination with UHRF1 overexpression would lead to DNA hypomethylation and an increase in overall 5hmC content. Furthermore, our data suggest that decreased 5hmC content might be associated with poor survival rate, highlighting a pivotal role of epigenetics in hepatoblastoma development and progression.

Intravenous Grafts of Human Amniotic Fluid-Derived Stem Cells Reduce Behavioral Deficits in Experimental Ischemic Stroke

Amniotic fluid has been investigated as new cell source for stem cells in the development of future cell-based transplantation. This study reports isolation of viable human amniotic fluid-derived stem cells, labeled with multimodal iron oxide nanoparticles, and its effect on focal cerebral ischemia–reperfusion injury in Wistar rats. Middle cerebral artery occlusion of 60 min followed by reperfusion for 1 h, 6 h, and 24 h was employed in the present study to produce ischemia and reperfusion-induced cerebral injury in rats. Tests were employed to assess the functional outcome of the sensorimotor center activity in the brain, through a set of modified neurological severity scores used to assess motor and exploratory capacity 24 h, 14, and 28 days after receiving cellular therapy via tail vein. In our animal model of stroke, transplanted cells migrated to the ischemic focus, infarct volume decreased, and motor deficits improved. Therefore, we concluded that these cells appear to have beneficial effects on the ischemic brain, possibly based on their ability to enhance endogenous repair mechanisms.

Tropism of mesenchymal stem cell toward CD133+ stem cell of glioblastoma in vitro and promote tumor proliferation in vivo

Background

Previous studies have demonstrated remarkable tropism of mesenchymal stem cells (MSCs) toward malignant gliomas, making these cells a potential vehicle for delivery of therapeutic agents to disseminated glioblastoma (GBM) cells. However, the potential contribution of MSCs to tumor progression is a matter of concern. It has been suggested that CD133⁺ GBM stem cells secrete a variety of chemokines, including monocytes chemoattractant protein-1 (MCP-1/CCL2) and stromal cell-derived factor-1(SDF-1/CXCL12), which could act in this tropism. However, the role in the modulation of this tropism of the subpopulation of CD133⁺ cells, which initiate GBM and the mechanisms underlying the tropism of MSCs to CD133⁺ GBM cells and their effects on tumor development, remains poorly defined.

Methods/results

We found that isolated and cultured MSCs (human umbilical cord blood MSCs) express CCR2 and CXCR4, the respective receptors for MCP-1/CCL2 and SDF-1/CXCL12, and demonstrated, in vitro, that MCP-1/CCL2 and SDF-1/CXC12, secreted by CD133⁺ GBM cells from primary cell cultures, induce the migration of MSCs. In addition, we confirmed that after in vivo GBM tumor establishment, by stereotaxic implantation of the CD133⁺ GBM cells labeled with Qdots (705 nm), MSCs labeled with multimodal iron oxide nanoparticles (MION) conjugated to rhodamine-B (Rh-B) (MION-Rh), infused by caudal vein, were able to cross the blood-brain barrier of the animal and migrate to the tumor region. Evaluation GBM tumors histology showed that groups that received MSC demonstrated tumor development, glial invasiveness, and detection of a high number of cycling cells.

Conclusions

Therefore, in this study, we validated the chemotactic effect of MCP-1/CCL2 and SDF-1/CXCL12 in mediating the migration of MSCs toward CD133⁺ GBM cells. However, we observed that, after infiltrating the tumor, MSCs promote tumor growth in vivo probably by release of exosomes. Thus, the use of these cells as a therapeutic carrier strategy to target GBM cells must be approached with caution.

Abstract 2072: Genomic studies of Brazilian patients with hepatoblastoma: Insight into somatic mutations using whole-exome sequencing

Hepatoblastomas (HB) are embryonal tumors of the liver with histological features that resemble different stages of liver differentiation. The identification of molecular pathways involved in HB development can expand the understanding of the connections between disruption of normal differentiation and cancer. Exome sequencing (244K Agilent SureSelect Target Enrichment) analysis was performed for 6 HBs matched with their non tumoral liver tissues (fresh frozen tissues). Bioinformatic analysis of exome data identified somatic variants in 69 genes which were chosen for validation using a target sequencing panel (SureSelectXT Target Enrichment System for Illumina Paired-End Sequencing Library). The gene panel was composed of the detected 69 genes and other 48 genes related with HB or cancer, and it was used to investigated additional 13 HB samples as a validation group. 60% of the patients were male, and the mean age at diagnosis was 36 months. 13% of this cohort presented pulmonary metastasis. All patients received pre-surgery chemotherapy (SIOPEL and COG protocol).

Results: A total of 71 somatic rare coding mutations (missense and loss-of-function) were validated in 53 genes considering the entire HB group. The somatic analysis reveals pathogenic mutations in the CTNNB1 gene and a recurrent missense mutation in the CX3CL1 gene; the role of these mutations was explored by IHQ studies of their proteins as well as by gene expression analysis by RT-PCR. We also used results from Illumina 450k to evaluated the methylation levels of CX3CL1 and CX3CR1 genes. Methylation values for CpG sites in each sample were measured as β-and CpG sites were grouped into categories, promoter (1stExon; 5'UTR; TSS1500; TSS200) or gene body, information provided by Illumina, based on UCSC data (GRhC 37). The methylation level of each category was obtained by averaging the β-values of all CpGs mapped in the category for each gene, followed by Wilcoxon test correction by calculating the false discovery rate (FDR).

Conclusion: Most investigated HBs carry few potentially pathogenic genetic mutations (≤ 5 mutations). This observed low frequency of somatic mutations is a result similar to previous studies. The proposed explanation is based on the fact that pediatric tumors would originate from precursor cells with pluripotent characteristics; therefore, such tumors may require fewer mutations than adult solid tumors to develop. The congenital HB case of our cohort is discrepant from this scenario since a relatively high number of somatic mutations were found compared to the HB group. To our knowledge, this is the first comprehensive genomic characterization of Brazilian HBs. Next steps include expanding the casuistry of exome sequenced tumors, including two cases of HB associated with Hirschprung disease.

Grants: FAPESP (2016/04785-0; 2017/11212-0), FAPESP (2013/08028-1), CNPq (141625/2016-3).

Citation Format: Talita F. Aguiar, Tatiane Rodrigues, Maria Prates, Fernanda Aparecida dos Santos, Gustavo Fernandes, Cecília Maria Lima da Costa, Isabela Werneck da Cunha, Monica Cypriano, Silvia Regina Caminada de Toledo, Jorge Estefano S. de Souza, Eugênia Valadares, Raquel Borges, Vicente Odone, Israel Tojal, Dirce Carraro, Carla Rosenberg, Ana C.V. Krepischi. Genomic studies of Brazilian patients with hepatoblastoma: Insight into somatic mutations using whole-exome sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2072.

Genome-wide association study identifies the GLDC/IL33 locus associated with survival of osteosarcoma patients

Survival rates for osteosarcoma, the most common primary bone cancer, have changed little over the past three decades and are particularly low for patients with metastatic disease. We conducted a multi-institutional genome-wide association study (GWAS) to identify germline genetic variants associated with overall survival in 632 patients with osteosarcoma, including 523 patients of European ancestry and 109 from Brazil. We conducted a time-to-event analysis and estimated hazard ratios (HR) and 95% confidence intervals (CI) using Cox proportional hazards models, with and without adjustment for metastatic disease. The results were combined across the European and Brazilian case sets using a random-effects meta-analysis. The strongest association after meta-analysis was for rs3765555 at 9p24.1, which was inversely associated with overall survival (HR = 1.76; 95% CI 1.41-2.18, p = 4.84 × 10-7 ). After imputation across this region, the combined analysis identified two SNPs that reached genome-wide significance. The strongest single association was with rs55933544 (HR = 1.9; 95% CI 1.5-2.4; p = 1.3 × 10-8 ), which localizes to the GLDC gene, adjacent to the IL33 gene and was consistent across both the European and Brazilian case sets. Using publicly available data, the risk allele was associated with lower expression of IL33 and low expression of IL33 was associated with poor survival in an independent set of patients with osteosarcoma. In conclusion, we have identified the GLDC/IL33 locus on chromosome 9p24.1 as associated with overall survival in patients with osteosarcoma. Further studies are needed to confirm this association and shed light on the biological underpinnings of this susceptibility locus.

CYP genes in osteosarcoma: Their role in tumorigenesis, pulmonary metastatic microenvironment and treatment response

Osteosarcoma (OS) is the most common malignant bone tumor in children and adolescents. The present study investigated the expression of Cytochrome P-450 (CYP) genes: CYP1A2, CYP3A4 and CYP3A5 by qRT-PCR in 135 specimens obtained from OS patients, including biopsy (pre-chemotherapy), tumor resected in surgery (post-chemotherapy), adjacent bone to tumor (nonmalignant tissue), pulmonary metastasis and adjacent lung to metastasis (nonmalignant tissue). Normal bone and normal lung tissues were used as control. We also investigated in five OS cell lines the modulation of CYPs expression by cisplatin, doxorubicin and methotrexate. As result, the adjacent lung specimens presented CYP1A2 overexpression compared to the normal lung (p=0.0256). Biopsy specimens presented lower CYP3A4 expression than normal bone (p=0.0314). The overexpression of both CYP1A2 and CYP3A4 in post-chemotherapy specimens were correlated with better event free-survival (p=0.0244) and good response (p=0.0484), respectively. Furthermore, in vitro assays revealed that CYP1A2 was upregulated by doxorubicin (p=0.0034); CYP3A4 was upregulated by cisplatin, doxorubicin and methotrexate (p=0.0004, p=0.0024, p<0.0001, respectively); and CYP3A5 was downregulated by doxorubicin (p=0.0285) and upregulated in time-dependent manner by methotrexate (p=0.0239). In conclusion, our findings suggest that CYP genes play an important role in OS tumorigenesis, at primary and metastatic sites, as well in treatment response.

Abstract A18: Insights into the somatic mutation burden of hepatoblastomas using whole exome sequencing

Hepatoblastomas (HB) are embryonal tumors of the liver with histologic features that resemble different stages of liver differentiation. Molecular data on HB tumorigenesis are still scarce because of its rarity. The identification of molecular pathways involved in HB development can expand the understanding of the connections between disruption of normal differentiation and cancer. Exome sequencing is a powerful tool to identify somatic mutations in tumors, possibly related to cancer development.

We performed a whole-exome sequencing in a discovery cohort of 6 HBs and their paired non-tumoral adjacent liver tissues (capture method 244K Agilent SureSelect Target Enrichment). Bioinformatic analysis of the exome data identified 76 rare somatic variants in coding sequences of 69 genes, which were validated using a target sequencing panel covering the affected genes (SureSelectXT Target Enrichment System for Illumina Paired-End Sequencing Library). These 69 genes and other 48 genes related with HB or cancer were also investigated, in addition to 13 HBs as a validation group. A total of 64 rare somatic mutations in 53 genes were validated in all hepatoblastomas.

Four different pathogenic mutations in the CTNNB1 gene were disclosed in five tumors.

Immunohistochemistry analysis of β-catenin was carried out in eight of the sequenced tumors as well as in a tissue microarray consisting of 19 novel hepatoblastomas cases. The constitutive activity of Wnt-β-catenin pathway, which is caused by the gain-of-function mutations of CTNNB1, was confirmed by the study of protein expression, which shows the accumulation of β-catenin in the nucleus. In addition, CX3CL1 gene was found to be somatically mutated in two different tumors; however, CX3CL1 gene expression was not altered in mutated tumors. We are currently investigating the possible role of CX3CL1 and its receptor (CX3CR1) in hepatoblastomas. Our data highlighted a relatively stable tumoral genome in this type of pediatric liver tumors, which present a small number of potentially pathogenic mutations, a feature that is also a hallmark of adult liver cancer.

Grants: FAPESP (2016/04785-0), FAPESP (2013/08028-1), CNPq (141625/2016-3).

Citation Format: Talita Aguiar, Tatiane Rodrigues, Cecília Maria Lima da Costa, Isabela Werneck, Monica Cypriano, Silvia Regina Caminada de Toledo, Jorge Estefano Santana de Souza, Israel Tojal, Dirce M Carraro, Carla Rosenberg, Ana Krepischi. Insights into the somatic mutation burden of hepatoblastomas using whole exome sequencing [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr A18.

Abstract 4871: Whole-exome sequencing identifies a high frequency of germline deleterious variants in cancer predisposition genes in individuals with osteosarcoma

In children and adolescents, osteosarcoma (OS) is the most common malignant bone tumor. OS occurs in certain cancer predisposition syndromes at a higher than expected frequency. However, outside of these rare syndromes, OS is significantly more common and its genetic etiology remains poorly understood. We conducted an evaluation of rare exonic variants in 545 unselected OS cases compared with 1061 cancer-free controls using whole-exome sequencing of blood or buccal cell DNA to estimate the prevalence and burden of rare deleterious germline variants.

We assessed potentially pathogenic rare variants in 126 established cancer predisposing genes (CPG) and known somatically mutated genes. We also surveyed the exome for genes with a higher burden of rare variants in 342 EUR cases with 994 EUR controls sequenced at the same time. Rare genetic variants, defined by a MAF &lt;0.01 in 1000G, ESP or ExAC, that passed quality control filters were classified based on well-annotated databases (IARC-TP53, Telomerase Database, ARUP, BIC, Insight and COSMIC-hotspots), variant databases (e.g. Clinvar, HGMD and LOVD), and in silico predictions (Sift, Polyphen, Mutation assessor, MutationTaster, FATHMM and LTR). Rare variants matching known pathogenic variants, or inexact matches at the same residue, in selected well-annotated databases were labeled as putative pathogenic variants. High impact variants (frameshift, stop gain/loss, or known splice sites) not matching a previously identified pathogenic variant in the selected databases were categorized as probably pathogenic. Predictions based solely on in silico predictions were categorized as possibly pathogenic, uncertain or likely benign.

A total of 14.5% of cases had a predicted pathogenic or high impact variant in an autosomal dominant CPG. A significantly higher pathogenic rare variant burden was present in EUR cases compared with EUR controls (Pburden=3.7x10-05). TP53 had the highest prevalence of pathogenic mutations (5% of EUR cases; Pburden=1.05x10-09). CDKN2A, MEN1, MLH1, MUTYH, PALB2 and VHL had a significantly higher rare variant burden in the EUR cases. 7.5% of cases had a predicted pathogenic or probably pathogenic variant in an autosomal recessive CPG (Pburden=5.4x10-03). Additionally, two males had a pathogenic variant in the X-linked genes, DKC1 and GPC3. In total, 21% of cases had a predicted pathogenic or high impact variant in a CPG (Pburden=2.4x10-07). Exome-wide analysis identified two novel genes with significantly higher rare variant burdens in the cases compared to controls.

In conclusion, several CPGs and two novel genes, not previously associated with OS, had an enrichment of rare variants in OS and warrant further follow-up. Our results indicate that a clinically significant fraction of OS cases may harbor one or more mutations worthy of consideration for further investigation and genetic counseling.

Citation Format: Roelof Koster, Bin Zhu, Meredith Yeager, Michael Dean, Matthew Gianferante, Lei Song, Joshua Sampson, NCI DCEG Cancer Genomics Research Laboratory, Julie Gastier-Foster, Richard Gorlick, Silvia Regina Caminada de Toledo, Antonio Petrilli, Ana Patiño-Garcia, Fernando Lecanda, Massimo Serra, Claudia Hattinger, Piero Picci, Katia Scotlandi, Adrienne Flanagan, Roberto Tirabosco, Maria Amary, Nilgün Kurucu, Inci Ergurhan Ilhan, Neriman Sari, Mandy Ballinger, David Thomas, Donald Barkauskas, Belynda Hicks, Margaret Tucker, Neil Caporaso, Robert Hoover, Stephen Chanock, Sharon Savage, Lisa Mirabello. Whole-exome sequencing identifies a high frequency of germline deleterious variants in cancer predisposition genes in individuals with osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4871. doi:10.1158/1538-7445.AM2017-4871

DNA methylation landscape of hepatoblastomas reveals arrest at early stages of liver differentiation and cancer-related alterations

Hepatoblastomas are uncommon embryonal liver tumors accounting for approximately 80% of childhood hepatic cancer. We hypothesized that epigenetic changes, including DNA methylation, could be relevant to hepatoblastoma onset. The methylomes of eight matched hepatoblastomas and non-tumoral liver tissues were characterized, and data were validated in an independent group (11 hepatoblastomas). In comparison to differentiated livers, hepatoblastomas exhibited a widespread and non-stochastic pattern of global low-level hypomethylation. The analysis revealed 1,359 differentially methylated CpG sites (DMSs) between hepatoblastomas and control livers, which are associated with 765 genes. Hypomethylation was detected in hepatoblastomas for ~58% of the DMSs with enrichment at intergenic sites, and most of the hypermethylated CpGs were located in CpG islands. Functional analyses revealed enrichment in signaling pathways involved in metabolism, negative regulation of cell differentiation, liver development, cancer, and Wnt signaling pathway. Strikingly, an important overlap was observed between the 1,359 DMSs and the CpG sites reported to exhibit methylation changes through liver development (p<0.0001), with similar patterns of methylation in both hepatoblastomas and fetal livers compared to adult livers. Overall, our results suggest an arrest at early stages of liver cell differentiation, in line with the hypothesis that hepatoblastoma ontogeny involves the disruption of liver development. This genome-wide methylation dysfunction, taken together with a relatively small number of driver genetic mutations reported for both adult and pediatric liver cancers, shed light on the relevance of epigenetic mechanisms for hepatic tumorigenesis.

Genetic and Immunohistochemical Expression of Integrins ITGAV, ITGA6, and ITGA3 As Prognostic Factor for Colorectal Cancer: Models for Global and Disease-Free Survival

Objective

To evaluate the relationship between the expression profiles of 84 extracellular matrix (ECM) genes and the prognosis of patients with colorectal cancer (CRC).

Methods

This retrospective study included 114 patients with stage I–IV CRC who underwent primary tumour resection. Quantitative real-time PCR and immunohistochemistry assays were conducted using primary tumour samples. Kaplan-Meier survival curves were also generated to identify differences in global survival (GS) and disease-free survival (DFS) for the hypo- or hyperexpression status of each marker. The log-rank test was used to verify whether the differences were significant. Stepwise Cox regression models were also used to identify the risk factors associated with GS and DFS in a multivariate mode, and then were used to score the risk of death associated with each marker, either independently or in association.

Results

In the univariate analyses, significant differences in GS in relation to the expression profiles of ITGAV (p = 0.001), ITGA3 (p = 0.002), ITGA6 (p = 0.001), SPARC (p = 0.036), MMP9 (p = 0.034), and MMP16 (p = 0.038) were observed. For DFS, significant differences were observed in associated with ITGAV (p = 0.004) and ITGA3 (p = 0.001). However, only the ITGAV and ITGA6 gene markers for GS (hazard ratio (HR) = 3.209, 95% confidence interval (CI) = 1.412–7.293, p = 0.005 and HR = 3.105, 95% CI = 1.367–7.055, p = 0.007, respectively), and ITGA3 for DFS (HR = 3.806, 95% CI = 1.573–9.209, p = 0.003), remained in the final Cox regression models. A scoring system was developed to evaluate the risk of patient death based on the number of markers for the components of the final GS model. Scores of 0, 1, or 2 were associated with the following mean survival rates [CI]: 47.162 [44.613–49.711], 39.717 [35.471–43.964], 30.197 [24.030–36.327], respectively.

Conclusions

Multivariate mathematical models demonstrated an association between hyperexpression of the ITGAV and ITGA6 integrins and GS, and also between the ITGA3 integrin and DFS, in patients with colorectal tumours. A risk scoring system based on detected hyperexpression of 0, 1, or 2 markers (e.g., ITGAV and/or ITGA6) was also found to accurately correlate with the GS curves generated for the present cohort.

A Genome-Wide Scan Identifies Variants in NFIB Associated with Metastasis in Patients with Osteosarcoma

Metastasis is the leading cause of death in patients with osteosarcoma, the most common pediatric bone malignancy. We conducted a multistage genome-wide association study of osteosarcoma metastasis at diagnosis in 935 osteosarcoma patients to determine whether germline genetic variation contributes to risk of metastasis. We identified an SNP, rs7034162, in NFIB significantly associated with metastasis in European osteosarcoma cases, as well as in cases of African and Brazilian ancestry (meta-analysis of all cases: P = 1.2 × 10(-9); OR, 2.43; 95% confidence interval, 1.83-3.24). The risk allele was significantly associated with lowered NFIB expression, which led to increased osteosarcoma cell migration, proliferation, and colony formation. In addition, a transposon screen in mice identified a significant proportion of osteosarcomas harboring inactivating insertions in Nfib and with lowered NFIB expression. These data suggest that germline genetic variation at rs7034162 is important in osteosarcoma metastasis and that NFIB is an osteosarcoma metastasis susceptibility gene.

SIGNIFICANCE

Metastasis at diagnosis in osteosarcoma is the leading cause of death in these patients. Here we show data that are supportive for the NFIB locus as associated with metastatic potential in osteosarcoma.

Investigation of IGF2, Hedgehog and fusion gene expression profiles in pediatric sarcomas

The childhood sarcomas are malignant tumors with high mortality rates. They are divided into two genetic categories: a category without distinct pattern karyotypic changes and the other category showing unique translocations that originate gene rearrangements. This category includes rhabdomyosarcoma (RMS), Ewing's sarcoma (ES) and synovial sarcoma (SS). Diverse studies have related development genes, such as; IGF2, IHH, PTCH1 and GLI1 and sarcomatogenesis.

OBJECTIVE

To characterize the RMS, ES and SS rearrangements, we quantify the expression of IGF2 IHH, PTCH1 and GLI1 genes and correlate molecular data with clinical parameters of patients.

DESIGN

We analyzed 29 RMS, 10 SS and 60 ES tumor samples by RT-PCR (polymerase chain reaction-reverse transcription) and qPCR (quantitative PCR).

RESULTS

Among the samples of ARMS, 50% had rearrangements of PAX3/7-FOXO1, 60% of ES samples were EWS-FLI1 positive and 90% of SS samples were positive for SS18-SSX1/2. In relation to the control reference samples (QPCR Human Reference Total RNA-Stratagene, Human Skeletal Muscle Total RNA-Ambion, Universal RNA Human Normal Tissues-Ambion), RMS samples showed a high IGF2 gene expression (p<0.0001). Moreover, ES samples showed a low IGF2 gene expression (p<0.0001) and high IHH (p<0.0001), PTCH1 (p=0.0173) and GLI1 (p=0.0113) gene expressions.

CONCLUSIONS

The molecular characterization of IGF and Hedgehog pathway in these pediatric sarcomas may collaborate to enable a better understanding of the biological behavior of these neoplasms.

Expression of major vault protein gene in osteosarcoma patients

Osteosarcoma (OS) is a primary malignant tumor of bone. Despite the successful use of multiple chemotherapeutic agents in the treatment of OS, more than 30% of OS tumors remain resistant to treatment. Elucidation of cellular resistance mechanisms may lead to better treatments for cancer patients. In this study, we used the low-density expression cDNA array, GEArray Q Series Human Cancer Drug Resistance and Metabolism Gene Array to screen genes related to drug resistance in 15 OS tumors. Expression patterns of the MPV gene were validated by real time PCR on 45 OS patient tumor samples and correlated with clinical and pathological data. Major vault protein (MVP) expression was present in 24 (53%) tumor samples and absent in 21 (47%). Samples from surgery showed correlation between the expression of MVP, metastatic disease at diagnosis and event free survival (EFS). The MVP gene expression correlates with metastatic disease at diagnosis after neoadjuvant chemotherapy (p=0.048), and is also associated with worse EFS (p=0.036). These findings suggest that MVP expression is involved in one of the mechanisms of drug resistance in OS and is induced by chemotherapy.

TNF-alpha, TNF-beta, IL-6, IL-10, PECAM-1 and the MPO inflammatory gene polymorphisms in osteosarcoma

The inflammatory microenvironment of tumors is characterized by the presence of cytokines and growth factor's network both in the supporting stroma and in tumor areas. These molecules may contribute to tumoral growth and progression, facilitating metastatic process. Therefore, cancer susceptibility and severity may be associated with the functional polymorphisms of inflammatory genes. We hypothesized that inflammatory gene polymorphisms may have important role for osteosarcoma patients. We studied -308G>A TNF-alpha, +252A>G TNF-beta, -174G>C IL-6, -1082A>G IL-10, +125C>G PECAM-1, and the -463A>G MPO inflammatory gene polymorphisms in 80 osteosarcoma patients and 160 control individuals using polymerase chain reaction-restriction-fragment length polymorphism method. We found that the patients with variant genotype (GG) of the +252A>G TNF-beta gene showed an event-free survival rate of 20% at 100 months. We suggest that the presence of the variant genotype (GG) of the +252A>G TNF-beta polymorphism, which leads to higher level of cytokine production, could be a facilitator mechanism in tumor progression leading to a poor event-free survival.

Myelodysplastic syndrome in childhood: report of two cases with deletion of chromosome 4 and the Philadelphia chromosome

We report two pediatric patients with unclassified myelodysplastic syndrome (MDS) by the French-American-British (FAB) group. Both cases had clinical and hematological peculiarities, which had not been described yet. The cytogenetic alterations were 4q deletion and the Philadelphia (Ph) chromosome which appeared at different moments of the disease. One patient showed the Ph chromosome at disease transformation and the other at diagnosis. The different breakpoints at 4q and the presence of Ph could be a marker of this form of MDS. The association of clinical and hematological findings suggests the possibility of a new group of pediatric MDS.