Exome array analysis identifies ETFB as a novel susceptibility gene for anthracycline-induced cardiotoxicity in cancer patients.

PURPOSE: Anthracyclines are widely used chemotherapeutic drugs that can cause progressive and irreversible cardiac damage and fatal heart failure. Several genetic variants associated with anthracycline-induced cardiotoxicity (AIC) have been identified, but they explain only a small proportion of the interindividual differences in AIC susceptibility. METHODS: In this study, we evaluated the association of low-frequency variants with risk of chronic AIC using the Illumina HumanExome BeadChip array in a discovery cohort of 61 anthracycline-treated breast cancer patients with replication in a second independent cohort of 83 anthracycline-treated pediatric cancer patients, using gene-based tests (SKAT-O). RESULTS: The most significant associated gene in the discovery cohort was ETFB (electron transfer flavoprotein beta subunit) involved in mitochondrial ß-oxidation and ATP production (P = 4.16 × 10-4) and this association was replicated in an independent set of anthracycline-treated cancer patients (P = 2.81 × 10-3). Within ETFB, we found that the missense variant rs79338777 (p.Pro52Leu; c.155C > T) made the greatest contribution to the observed gene association and it was associated with increased risk of chronic AIC in the two cohorts separately and when combined (OR 9.00, P = 1.95 × 10-4, 95% CI 2.83-28.6). CONCLUSIONS: We identified and replicated a novel gene, ETFB, strongly associated with chronic AIC independently of age at tumor onset and related to anthracycline-mediated mitochondrial dysfunction. Although experimental verification and further studies in larger patient cohorts are required to confirm our finding, we demonstrated that exome array data analysis represents a valuable strategy to identify novel genes contributing to the susceptibility to chronic AIC.

Extracellular matrix composition defines an ultra-high-risk group of neuroblastoma within the high-risk patient cohort.

BACKGROUND: Although survival for neuroblastoma patients has dramatically improved in recent years, a substantial number of children in the high-risk subgroup still die. METHODS: We aimed to define a subgroup of ultra-high-risk patients from within the high-risk cohort. We used advanced morphometric approaches to quantify and characterise blood vessels, reticulin fibre networks, collagen type I bundles, elastic fibres and glycosaminoglycans in 102 high-risk neuroblastomas specimens. The Kaplan-Meier method was used to correlate the analysed elements with survival. RESULTS: The organisation of blood vessels and reticulin fibres in neuroblastic tumours defined an ultra-high-risk patient subgroup with 5-year survival rate <15%. Specifically, tumours with irregularly shaped blood vessels, large sinusoid-like vessels, smaller and tortuous venules and arterioles and with large areas of reticulin fibres forming large, crosslinking, branching and haphazardly arranged networks were linked to the ultra-high-risk phenotype. CONCLUSIONS: We demonstrate that quantification of tumour stroma components by morphometric techniques has the potential to improve risk stratification of neuroblastoma patients.

A systematic review and meta-analysis of MDM2 polymorphisms in osteosarcoma susceptibility.

Two polymorphisms in the murine double minute 2 (MDM2) gene (rs1690916 and rs2279744) have been associated with the risk of osteosarcoma (OS). When we analyzed these two polymorphisms in two new independents cohorts (Spanish and Slovenian), we found no association. In order to clarify this, we conducted a meta-analysis including six populations, with a total of 246 OS patients and 1,760 controls for rs1690916; and 433 OS patients and 1,959 controls for rs2279744. Pooled odds ratio risks and corresponding 95% CI were estimated to assess the possible associations. Our results showed that these two polymorphisms were not associated with the susceptibility of OS under any genetic model studied. In conclusion, the present meta-analysis indicates that MDM2 rs1690916 and rs2279744 cannot be considered as genetic risk factors for OS susceptibility in the different populations. Therefore, the influence of these two polymorphisms on the risk of OS may be less important than previously suggested. Future studies are needed to confirm these results.

Vincristine pharmacokinetics pathway and neurotoxicity during early phases of treatment in pediatric acute lymphoblastic leukemia.

AIM: Vincristine is an important component of acute lymphoblastic leukemia (ALL) treatment protocols that can cause neurotoxicity. Patients treated with LAL/SHOP protocols often suffer from vincristine-related neurotoxicity in early phases of treatment. Recently, a genome-wide association study connected a SNP in CEP72, involved in vincristine pharmacodynamics, with neurotoxicity during later phases of therapy, which was not replicated during induction phase. These results, together with previous studies indicating that polymorphisms in pharmacokinetic genes are associated with drug toxicity, suggest that changes in the activity or levels of vincristine transporters or metabolizers could work as predictors of vincristine-related neurotoxicity in early phases of treatment in pediatric ALL. PATIENTS & METHODS: We analyzed 150 SNPs in eight key genes involved in vincristine pharmacokinetics and in 13 miRNAs that regulate them. We studied their correlation with neurotoxicity during induction phase in 152 ALL patients treated with LAL/SHOP protocols. RESULTS: The strongest associations with neurotoxicity were observed for two SNPs in ABCC2. The genotypes rs3740066 GG and rs12826 GG were associated with increased neurotoxicity. CONCLUSION: Polymorphisms in ABCC2 could be novel markers for vincristine-related neurotoxicity in pediatric ALL in early phases.

Array CGH Analysis of Paired Blood and Tumor Samples from Patients with Sporadic Wilms Tumor.

Wilms tumor (WT), the most common cancer of the kidney in infants and children, has a complex etiology that is still poorly understood. Identification of genomic copy number variants (CNV) in tumor genomes provides a better understanding of cancer development which may be useful for diagnosis and therapeutic targets. In paired blood and tumor DNA samples from 14 patients with sporadic WT, analyzed by aCGH, 22% of chromosome abnormalities were novel. All constitutional alterations identified in blood were segmental (in 28.6% of patients) and were also present in the paired tumor samples. Two segmental gains (2p21 and 20q13.3) and one loss (19q13.31) present in blood had not been previously described in WT. We also describe, for the first time, a small, constitutive partial gain of 3p22.1 comprising 2 exons of CTNNB1, a gene associated to WT. Among somatic alterations, novel structural chromosomal abnormalities were found, like gain of 19p13.3 and 20p12.3, and losses of 2p16.1-p15, 4q32.5-q35.1, 4q35.2-q28.1 and 19p13.3. Candidate genes included in these regions might be constitutively (SIX3, SALL4) or somatically (NEK1, PIAS4, BMP2) operational in the development and progression of WT. To our knowledge this is the first report of CNV in paired blood and tumor samples in sporadic WT.

Impact of NGS in the medical sciences: Genetic syndromes with an increased risk of developing cancer as an example of the use of new technologies.

The increased speed and decreasing cost of sequencing, along with an understanding of the clinical relevance of emerging information for patient management, has led to an explosion of potential applications in healthcare. Currently, SNP arrays and Next-Generation Sequencing (NGS) technologies are relatively new techniques used to scan genomes for gains and losses, losses of heterozygosity (LOH), SNPs, and indel variants as well as to perform complete sequencing of a panel of candidate genes, the entire exome (whole exome sequencing) or even the whole genome. As a result, these new high-throughput technologies have facilitated progress in the understanding and diagnosis of genetic syndromes and cancers, two disorders traditionally considered to be separate diseases but that can share causal genetic alterations in a group of developmental disorders associated with congenital malformations and cancer risk. The purpose of this work is to review these syndromes as an example of a group of disorders that has been included in a panel of genes for NGS analysis. We also highlight the relationship between development and cancer and underline the connections between these syndromes.

Noncoding RNA-related polymorphisms in pediatric acute lymphoblastic leukemia susceptibility.

BACKGROUND: Evidence for an inherited genetic risk for pediatric acute lymphoblastic leukemia has been provided in several studies. Most of them focused on coding regions. However, those regions represent only 1.5% of the entire genome. In acute lymphoblastic leukemia (ALL), it has been suggested that the expression of microRNAs (miRNAs) is dysregulated, which suggests that they may have a role in ALL risk. Changes in miRNA function may occur through single-nucleotide polymorphisms (SNPs). Therefore, the aim of this study was to evaluate whether polymorphisms in pre-miRNAs, and/or miRNA-processing genes, contribute to a predisposition for childhood ALL. METHODS: In this study, we analyzed 118 SNPs in pre-miRNAs and miRNA-processing genes in 213 B-cell ALL patients and 387 controls. RESULTS: We found 11 SNPs significantly associated with ALL susceptibility. These included three SNPs present in miRNA genes (miR-612, miR-499, and miR-449b) and eight SNPs present in six miRNA biogenesis pathway genes (TNRC6B, DROSHA, DGCR8, EIF2C1, CNOT1, and CNOT6). Among the 118 SNPs analyzed, rs12803915 in mir-612 and rs3746444 in mir-499 exhibited a more significant association, with a P value <0.01. CONCLUSION: The results of this study indicate that SNP rs12803915 located in pre-mir-612, and SNP rs3746444 located in pre-mir-499, may represent novel markers of B-cell ALL susceptibility.

Pharmacogenetics of microRNAs and microRNAs biogenesis machinery in pediatric acute lymphoblastic leukemia.

Despite the clinical success of acute lymphoblastic leukemia (ALL) therapy, toxicity is frequent. Therefore, it would be useful to identify predictors of adverse effects. In the last years, several studies have investigated the relationship between genetic variation and treatment-related toxicity. However, most of these studies are focused in coding regions. Nowadays, it is known that regions that do not codify proteins, such as microRNAs (miRNAs), may have an important regulatory function. MiRNAs can regulate the expression of genes affecting drug response. In fact, the expression of some of those miRNAs has been associated with drug response. Genetic variations affecting miRNAs can modify their function, which may lead to drug sensitivity. The aim of this study was to detect new toxicity markers in pediatric B-ALL, studying miRNA-related polymorphisms, which can affect miRNA levels and function. We analyzed 118 SNPs in pre-miRNAs and miRNA processing genes in association with toxicity in 152 pediatric B-ALL patients all treated with the same protocol (LAL/SHOP). Among the results found, we detected for the first time an association between rs639174 in DROSHA and vomits that remained statistically significant after FDR correction. DROSHA had been associated with alterations in miRNAs expression, which could affect genes involved in drug transport. This suggests that miRNA-related SNPs could be a useful tool for toxicity prediction in pediatric B-ALL.

Intron 3 of the ARID5B gene: a hot spot for acute lymphoblastic leukemia susceptibility.

PURPOSE: Single-nucleotide polymorphisms (SNPs) in AT-rich interactive domain 5B (ARID5B) have been associated with risk for pediatric acute lymphoblastic leukemia (ALL). After reviewing previous studies, we realized that the most significant associations were restricted to intron 3, but the mechanism(s) by which those SNPs affect ALL risk remain to be elucidated. Therefore, the aim of this study was to analyze the association between genetic variants of the intron 3 region of ARID5B and the incidence of B-ALL in a Spanish population. We also aimed to find a functional explanation for the association, searching for copy number variations (CNVs), and changes in ARID5B expression associated with the genotypes of the SNPs. METHODS: We analyzed 10 SNPs in intron 3 of ARID5B in a Spanish population of 219 B-ALL patients and 397 unrelated controls with the Taqman Open Array platform. CNVs were analyzed in 23 patients and 17 controls using the Cytogenetics Whole-genome 2.7 M platform. Expression of ARID5B transcript 1 was quantified by qPCR and related to SNPs genotype in seven ALL cell lines. RESULTS: Association between intron 3 and B-ALL risk was confirmed for all of the SNPs evaluated in our Spanish population. We could not explain this association by the presence of CNVs. We neither detected changes in the expression of ARID5B isoform associated with the genotype of the SNPs. CONCLUSIONS: The intron 3 of ARID5B gene was found to be strongly associated with B-ALL risk in the Spanish population examined. However, neither CNVs nor changes in mRNA expression were found to be responsible for this association.

Polymorphisms in the methotrexate transport pathway: a new tool for MTX plasma level prediction in pediatric acute lymphoblastic leukemia.

OBJECTIVES: Methotrexate (MTX) is an important component of therapy for pediatric acute lymphoblastic leukemia (ALL). Treatment with MTX often causes toxicity, which can necessitate dose reduction or treatment cessation. Interindividual differences in adverse reactions can be due to different factors, including polymorphisms in key genes. Recently, we confirmed the association between SLCO1B1 rs11045879 polymorphism and toxicity previously proposed by Treviño and colleagues. As SLCO1B1 is a transporter involved in MTX elimination, other polymorphisms in genes from this pathway could also have a role in MTX toxicity. The aim of the present study was to analyze in depth the role of polymorphisms in the genes of the MTX transport pathway as putative toxicity predictors in pediatric ALL. METHODS: We analyzed 384 single nucleotide polymorphisms in 12 transporter genes (SLCO1B1, SLCO1B3, SLCO1A2, ABCB1, ABCG2, ABCC1, ABCC2, ABCC3, ABCC4, SLC19A1, SLC22A6 and SLC22A8) and their correlation with different toxicity parameters in 151 pediatric ALL patients treated using the LAL/SHOP protocol. RESULTS: A significant association with MTX plasma levels was found for 21 polymorphisms from seven genes and 15 haplotypes. After correction, rs9516519 in ABCC4, rs3740065 in ABCC2, and haplotype GCGGG in ABCC2 remained significantly associated. CONCLUSION: Our results suggest that polymorphisms in ABCC4 and ABCC2 could be novel markers for MTX toxicity in pediatric ALL.

[T-cell pediatric acute lymphoblastic leukemia: analysis of survival and prognostic factors in 4 consecutive protocols of the Spanish cooperative study group SHOP]. / Leucemia linfoblástica aguda T pediátrica: análisis de supervivencia y factores pronósticos en 4 protocolos consecutivos del grupo cooperativo multicéntrico SHOP.

BACKGROUND AND OBJECTIVES: Acute lymphoblastic leukemia (ALL) is the most frequent cancer in childhood, with cure rates of 80-85%. In T-cell ALL (15% of ALL), prognostic factors are ill defined. We aimed to describe the event-free survival (EFS) and analyze clinical prognostic factors in a series of pediatric T-ALL of 4 consecutive clinical trials. PATIENTS AND METHODS: Children with T-ALL aged 1-18 years treated in 37 institutions in Spain were enrolled in 4 consecutive trials from February-1989 to November-2009. RESULTS: A total of 218 T-ALL patients out of 1,652 pediatric ALL were evaluable during the study period (SHOP/ALL-89: 35, ALL-94: 63, ALL-99: 62, ALL-2005: 58). There were 164 boys (75%). Median age (years) was 7.8 range (1.3-18.6). Median leukocytes (10(9)/L) was 78.2, range 0.8-930. Fifteen (6.8%) children had central nervous system (CNS) involvement at diagnosis. Regarding response to induction treatment, 150 (75%) patients had less than 5% blasts on day-14 bone marrow and 199 achieved complete remission at the end of induction. Overall survival (OS) at 60 months for SHOP/ALL-89, ALL-94, ALL-99 was 48 (8), 49 (6), 70 (6) %, respectively, and at 48 months for SHOP/ALL-2005 (ongoing protocol) was 74 (8) %. Median follow-up (months) was 206, 152, 74 and 17 respectively. Analysis of prognostic factors revealed no statistical differences regarding sex or age. Leukocyte count over 200×10(9)/l (P=.024), CNS infiltration at diagnosis (P<.006) and treatment response had prognostic significance (end-induction complete remission) (P=.0000), day 14-bone marrow (P=.005). CONCLUSIONS: Results for the SHOP/ALL-89 and ALL-94 protocols were inferior to other contemporary protocols but there has been an improvement in survival in the 2 last trials. In line with other T-ALL series, response to treatment had the strongest prognostic impact.

Polymorphisms of the SLCO1B1 gene predict methotrexate-related toxicity in childhood acute lymphoblastic leukemia.

BACKGROUND: Methotrexate (MTX) is an important component of the therapy for childhood acute lymphoblastic leukemia. Treatment with high-dose MTX often causes toxicity, recommending a dose reduction and/or cessation of treatment. Polymorphisms in genes involved in the MTX metabolism have been associated with toxicity with controversial results. The discrepancies could be due to differences in treatment protocols among studies, small, or non-homogeneous populations or the use of different toxicity criteria. The aim of the present study was to analyze the possible correlation of polymorphisms of genes involved in the MTX metabolism with the toxicity during therapy with the well-established LAL/SHOP protocol. PROCEDURE: We analyzed 10 polymorphisms in seven genes (MTHFR, TS, SHMT1, RFC1, ABCB1, ABCG2, and SLCO1B1) from the MTX metabolism in 115 Spanish pediatric B-ALL patients, using MTX plasma concentration as an objective and quantifiable marker of toxicity. RESULTS: We confirmed the suitability of MTX plasma levels as a toxicity marker. We found a statistically significant association between MTX plasma concentration and the SLCO1B1 rs11045879 CC genotype (P = 0.030). The rs4149081 AA genotype, in the same gene, could also be an indicator for high-MTX plasma concentrations. We did not find any significant association in the other genetic polymorphisms analyzed. CONCLUSIONS: Identification of the rs4149081 and rs11045879 SLCO1B1 polymorphisms in children with ALL could be a useful tool for monitoring patients at risk of low-MTX clearance in order to avoid MTX-related toxicity.

Long-term results of the Spanish Protocol SO-95 for the treatment of non-metastatic high-grade osteosarcoma of the extremities in children.

INTRODUCTION: The long-term results of the Spanish Study Protocol SEOP-SO-95 for treatment of localised osteosarcoma of the extremities in children were evaluated. PATIENTS AND METHODS: One hundred consecutive patients under 18 years of age from 22 institutions were enrolled from January 1995 to December 2000. Immunohistochemical expression of p53, HER/erbB-2 and P-glycoprotein were retrospectively studied in 27 patients. Treatment consisted of: preoperative chemotherapy with doxorubicin, cisplatin, high-dose methotrexate with leucovorin rescue and ifosfamide for 14 weeks; surgery of primary tumour in week 16; postoperative chemotherapy with the above-mentioned drugs for 25 weeks. RESULTS: With a median follow-up of 124 months (range 84-158 months), 69 patients (69%) were continuously event-free survivors; the 10-year probability of event-free survival (EFS) was 62%. Conservative surgery was performed in 85% of patients. Twenty-six patients had local recurrence or distant relapse. The median time to recurrence/ relapse was 27 months (range 17-93 months). The local recurrence rate was 7% (7 of the 100 patients); 4 had wide surgical margins, 2 marginal and 1 intralesional. Four patients died as a result of chemotherapy-related toxicity and 1 developed a second neoplasia (acute myeloid leukaemia). p53 expression and HER2/erbB-2 expression showed no effect on survival or EFS. CONCLUSIONS: This therapeutic protocol achieved good oncologic and orthopaedic results. We observed a significant treatment-related toxicity.

Pathogenic validation of unique germline intronic variants of RB1 in retinoblastoma patients using minigenes.

Precise identification of the pathogenic character of germline mutations in the retinoblastoma gene (RB1) is fundamental to provide genetic counselling to patients at risk of developing retinoblastoma. In contrast to bona fide oncogenic RB1 mutations like nonsense or frameshift mutations, and those affecting invariant dinucleotides at splice sites, intronic variants affecting less conserved splice motifs require additional analysis to ascertain whether splicing is altered. Although the frequency of these variations is low, their impact on genetic counselling is high, since they are usually associated with low penetrance phenotypes and unaffected carriers. In this work, we used minigene assays to study infrequent germline intronic variations for which functional data were not available. Using this approach, the aberrant splicing and the resulting oncogenic nature of three intronic RB1 mutations was established (c.501-15T>G, c.719-9C>G, c.2326-8T>A). Conversely, the intronic variant c.1961-12T>C was categorized by minigene assay as a very infrequent neutral polymorphism. To our knowledge this is the first report describing the use of minigene constructs to study the oncogenic character of intronic RB1 variants detected during mutational screening and show the utility of this approach to ascertain the oncogenic nature of unique RB1 intronic variants for which no previous functional and clinical data are available. Minigene assay can be especially useful when lymphocyte RNA is not available for study, or when aberrant mRNA can not be detected as a consequence of nonsense mediated decay. Since RB1 minigene are time-consuming assays, owing to the genomic organization of the RB1 gene, it should be welcome the design of new expression vectors that make this type of studies more straightforward.

[Results of the SHOP LNHB98 (LMB89) trial in pediatric patients with B-cell non-Hodgkin's lymphoma]. / Resultados del protocolo SHOP LNHB98 (LMB89) en pacientes de edad pediátrica afectados de linfoma no hodgkiniano de células B.

BACKGROUND AND OBJECTIVE: After the good results obtained by the Société Française d'Oncologie Pédiatrique (SFOP) regarding the pediatric B-type non-Hodgkin's (Burkitt and large B-cell) lymphoma and L3 leukemia, the Sociedad Española de Hematología y Oncología Pediátricas (SHOP) decided to use the same treatment protocol. PATIENTS AND METHOD: Pediatric patients diagnosed with B-type non-Hodgkin's lymphoma without a previous history of malignant diseases were eligible for this study. They were classified in 3 groups of risk: group A (resected stage I and abdominal stage II), group B (not eligible for groups A or C), and group C (with central nervous system involvement and L3 leukemia). All received treatment according to the SFOP's LMB89 protocol. RESULTS: A total of 153 patients were considered in this multicenter, prospective and non-randomized trial (1997-2005). The global and event-free survival (EFS) were found to be of 88% (0.88; 95% confidence interval [CI], 0.83-0.93) and 85% (0.85; 95% CI, 0.79-0.90), respectively. The EFS was 100% for the group A (n = 16), 86% (0.86; 95% CI, 0.79-0.92) for the group B (n = 113), and 68% (0.68; 95% CI, 0.49-0.86) for the group C (n = 24). CONCLUSIONS: The results confirm the good efficiency of the LMB89 protocol for treating B-cell lymphoma and L3 leukemia, despite having diminished the treatment intensity in the less risk groups. The worst prognostic factor was found to be a central nervous system involvement, whereas being younger than 10 years was confirmed to be a favorable prognostic factor. In addition, no differences were evidenced between Burkitt and large B-cell lymphoma.

Cholecystokinin down-regulation by RNA interference impairs Ewing tumor growth.

PURPOSE: Tumors of the Ewing family are characterized by chromosomal translocations that yield chimeric transcription factors, such as EWS/FLI1, which regulate the expression of specific genes that contribute to the malignant phenotype. In the present study, we show that cholecystokinin (CCK) is a new target of the EWS/FLI1 oncoprotein and assess its functional role in Ewing tumor pathogenesis. EXPERIMENTAL DESIGN: Relevant EWS/FLI1 targets were identified using a combination of cell systems with inducible EWS/FLI1 expression, Ewing tumors and cell lines, microarrays, and RNA interference with doxycycline-inducible small hairpin RNA (shRNA) vectors. A doxycycline-inducible CCK-shRNA vector was stably transfected in A673 and SK-PN-DW Ewing cell lines to assess the role of CCK in cell proliferation and tumor growth. RESULTS: Microarray analysis revealed that CCK was up-regulated by EWS/FLI1 in HeLa cells. CCK was overexpressed in Ewing tumors as compared with other pediatric malignancies such as rhabdomyosarcoma and neuroblastoma, with levels close to those detected in normal tissues expressing the highest levels of CCK. Furthermore, EWS/FLI1 knockdown in A673 and SK-PN-DW Ewing cells using two different doxycycline-inducible EWS/FLI1-specific shRNA vectors down-regulated CCK mRNA expression and diminished the levels of secreted CCK, showing that CCK is a EWS/FLI1 specific target gene in Ewing cells. A doxycycline-inducible CCK-specific shRNA vector successfully down-regulated CCK expression, reduced the levels of secreted CCK in Ewing cell lines, and inhibited cell growth and proliferation in vitro and in vivo. Finally, we show that Ewing cell lines and tumors express CCK receptors and that the growth inhibition produced by CCK silencing can be rescued by culturing the cells with medium containing CCK. CONCLUSIONS: Our data support the hypothesis that CCK acts as an autocrine growth factor stimulating the proliferation of Ewing cells and suggest that therapies targeting CCK could be promising in the treatment of Ewing tumors.

[Molecular diagnosis of retinoblastoma: molecular epidemiology and genetic counseling]. / Diagnóstico molecular del retinoblastoma: epidemiología molecular y consejo genético.

BACKGROUND AND OBJECTIVE: Retinoblastoma, a prototype of hereditary cancer, is the most common intraocular tumor in children and a potential cause of blindness from therapeutic eye ablation, second tumors in germ line mutation carriers, and even death when untreated. The molecular scanning of RB1 in search of germ line mutations in 213 retinoblastoma patients from Spain, Cuba, Colombia and Serbia, has led to the detection of 106 mutations whose knowledge is important for genetic counselling and characterization of phenotypic-genotypic relations. PATIENTS AND METHOD: Mutational study (PCR-sequentiation and microsatellites analysis) in patients with retinoblastoma, from Spain, Cuba, Colombia and Serbia. RESULTS: 45% of mutations, including most of the frame shift (FS), missense (MS) and splicing (SP), were new, while all nonsense mutations (NS) corresponded to hypermutable sites in RB1. Germ line mutations were found in 22% of unilateral sporadic patients. The incidence of SP plus MS mutations in this group of patients was greater (p = 0.018) than in bilateral patients. The frequency of SP mutations was higher (p = 0.0003) in Spain and France than in Germany and United Kingdom, while the incidence of NS mutations was lower (p = 0.0006). SP mutations were associated with the low penetrance phenotype and were also overrepresented (p = 0.018) in patients with delayed retinoblastoma onset. CONCLUSIONS: Mutational scanning of unilateral patients is important for genetic counselling and may help decipher the molecular mechanisms leading to low penetrance or expressivity. The functional characterization of mutations associated with low-penetrance or expressivity phenotypes and the molecular classification of tumors using multiple expression profiling is important for a better understanding of the retinoblastoma pathogenesis.

The orphan nuclear receptor DAX1 is up-regulated by the EWS/FLI1 oncoprotein and is highly expressed in Ewing tumors.

The Ewing family of tumors harbors chromosomal translocations that join the N-terminal region of the EWS gene with the C-terminal region of several transcription factors of the ETS family, mainly FLI1, resulting in chimeric transcription factors that play a pivotal role in the pathogenesis of Ewing tumors. To identify downstream targets of the EWS/FLI1 fusion protein, we established 293 cells expressing constitutively either the chimeric EWS/FLI1 or wild type FLI1 proteins and used cDNA arrays to identify genes differentially regulated by EWS/FLI1. DAX1 (NR0B1), an unusual orphan nuclear receptor involved in gonadal development, sex determination and steroidogenesis, showed a consistent up-regulation by EWS/FLI1 oncoprotein, but not by wild type FLI1. Specific induction of DAX1 by EWS/FLI1 was confirmed in two independent cell systems with inducible expression of EWS/FLI1. We also analyzed the expression of DAX1 in Ewing tumors and derived cell lines, as well as in other nonrelated small round cell tumors. DAX1 was expressed in all Ewing tumor specimens analyzed, and in seven out of eight Ewing tumor cell lines, but not in any neuroblastoma or embryonal rhabdomyosarcoma. Furthermore, silencing of EWS/FLI1 by RNA interference in a Ewing tumor cell line markedly reduced the levels of DAX1 mRNA and protein, confirming that DAX1 up-regulation is dependent upon EWS/FLI1 expression. The high levels of DAX1 found in Ewing tumors and its potent transcriptional repressor activity suggest that the oncogenic effect of EWS/FLI1 may be mediated, at least in part, by the up-regulation of DAX1 expression.