Concurrent chromothripsis events in a case of TP53 depleted acute myeloid leukemia with myelodysplasia-related changes.

Acute myeloid leukemia with myelodysplasia-related changes (AML-MRC) is a heterogeneous hematological disorder defined by morphological, genetic, and clinical features. Patients with AML-MRC often show cytogenetic changes, which are associated with poor prognosis. Straightforward criteria for AML-MRC diagnosis and a more rigorous characterization of the genetic abnormalities accompanying this disease are needed. Here we describe an informative AML-MRC case, showing two separate, but concurrent, chromothripsis events, occurred at the onset of the tumor, and originating an unbalanced t(5;7) translocation and a derivative chromosome 12 with a highly rearranged short arm. Conversely, despite chromothripsis has been often associated with genomic amplification in cancer, in this case a large marker chromosome harboring amplified sequences from chromosomes 19 and 22 arose from a stepwise mechanism. Notably, the patient also showed a TP53 mutated status, known to be associated with an increased susceptibility towards chromothripsis and a poor prognosis. Our results indicate that multiple chromothripsis events may occur early in neoplastic transformation and act in a synergistic way with progressive chromosomal alterations to determine a dramatic impact on disease outcome, as suggested by the gene expression profile analysis.

A novel fusion 5'AFF3/3'BCL2 originated from a t(2;18)(q11.2;q21.33) translocation in follicular lymphoma.

Follicular lymphoma is the second most frequent type of non-Hodgkin's lymphoma in adults. The basic molecular defect consists of the t(14;18)(q32;q21) translocation, juxtaposing the B-cell lymphoma protein 2 gene BCL2 to the immunoglobulin heavy chain locus IGH@, and leading to the antiapoptotic BCL2 protein overproduction. Variations in the t(14;18) are rare and can be classified into two categories: (i) simple variants, involving chromosomes 18 and 2, or 22, in which the fusion partner of BCL2 is the light-chain IGK@ or IGL@; (ii) complex variant translocations occurring among chromosomes 14, 18 and other chromosomes. We report a follicular lymphoma case showing BCL2 overexpression, detected by immunohistochemistry and real-time quantitative PCR, consequently to the formation of a novel fusion gene between the 5' of the lymphoid nuclear transcriptional activator gene AFF3 at 2q11.2, and the 3' of BCL2. This case shows evidence, for the first time, of BCL2 overexpression consequently to the fusion of BCL2 to a non-IG partner locus.

Stage-independent expression and genetic analysis of tp73 in neuroblastoma.

The tp73 gene, a tp53 homologue, has been sub-regionally mapped at 1p36.3, a chromosomal region frequently deleted in neuroblastoma. Due to its chromosomal localization and to the mono-allelic expression observed in some neuroblastoma cell lines, it was proposed that tp73 might be involved in the pathogenesis of neuroblastoma. Functional assays have demonstrated that tp73 can inhibit cell proliferation and induce apoptosis. The role of this gene in tumorigenesis, however, is still unclear. We analyzed tp73 expression in 95 sporadic neuroblastoma samples by RT-PCR and we detected the tp73 transcript in 46 cases (48.4%), without significant correlation with age, clinical stage or 3-year overall survival. A genetic polymorphism in the 2nd exon of tp73 was utilized to identify the transcribed allele in tumor-cell samples. Expression from only one of the tp73 alleles was found in 13 out of 16 heterozygous tumors, while in 3 samples both alleles were present. Genotype analysis of 73 patients and 150 controls showed a significant deviation (p = 0.0308) from the Hardy-Weinberg equilibrium for a tp73 allele only among neuroblastoma patients. The absence of correlation between tp73 expression and clinical stage, age and survival suggests that this gene does not play an essential function in the clinical course of the disease. However, the distribution of genomic tp73 alleles in patients indicates that a role of this gene in the development of neuroblastoma cannot be completely ruled out. Int. J. Cancer (Pred. Oncol.) 84:365-369, 1999.

Neuroblastoma in two siblings supports the role of 1p36 deletion in tumor development.

Familial neuroblastoma occurs rarely. We studied a family with three children; one of them has a disseminated (stage 4) and another has a localized (stage 2) neuroblastoma. We observed subtelomeric locus D1Z2 (1p36) deletion in both tumors by using double-color fluorescence in situ hybridization. The MYNC gene was found in single copy in both tumors. Loss of heterozygosity (LOH) and restriction fragment length polymorphism analyses were performed by using DNA from frozen tumor cells and from microdissected tumor areas excised from paraffin-embedded sections. We detected somatic LOH at locus D1S468 (1p36) in a tumor-cell population with a trisomy 1 of the stage-2 patient. Neuroblastoma cells of the stage-4 patient were diploid and showed allelic loss at the following loci: D1S172, D1S80, D1S94, D1S243, D1S468, D1S214, D1S241, and D1S164. Haplotype study showed that the siblings inherited the same paternal 1p36-->pter chromosome region by homologous recombination and that, in the two tumors, arm 1p of different chromosomes of maternal origin was damaged. Our results suggest that the siblings inherited the predisposition to neuroblastoma associated with paternal 1p36 region and that tumors developed as a consequence of somatic loss of the maternal 1p36 allele.

Refined chromosomal localization of the putative tumor suppressor gene TP73.

We report the refined chromosomal localization of the putative tumor suppressor gene TP73 (alias p73) within the genomic region between the anonymous loci D1Z2 and D1S47. The region measures less than 6 Mb and covers a genetic distance of 16 cM. The present mapping considerably restricts the previous cytogenetic localization of TP73.

Interstitial and large chromosome 1p deletion occurs in localized and disseminated neuroblastomas and predicts an unfavourable outcome.

We studied chromosome 1p loss of heterozygosity (1p-LOH) in 53 neuroblastomas (NBs) using 15 (CA)n repeat loci, which covered a region of 90 cM. We also assessed chromosome 1p36 deletion by fluorescence in situ hybridization (FISH) on interphase nuclei. 1p-LOH was found in 19 (36%, 95% confidence interval (CI) 23-50%) NBs. We detected interstitial and large deletion in both localized and disseminated tumours and in one tumour of a patient at stage 4S. Allelic loss was frequently observed in 1p36 and 1p32 regions. In patients older than 1 year of age (53 versus 13%, P < 0.002) we detected significant chromosome 1p deletion and it was associated with MYCN amplification (P = 0.001). Overall survival (OS) analysis showed that 1p-LOH is predictive of a poor outcome (odds ratio 16.5, 95% CI 5.4-50.9%); therefore, 1p-LOH should be regarded as an additional tumour progression marker in neuroblastoma.

Structural and functional analysis of cyclin-dependent kinase inhibitor genes (CDKN2A, CDKN2B, and CDKN2C) in neuroblastoma.

The status of the CDKN2A gene family, including CDKN2A, CDKN2B, and CDKN2C, was investigated in 24 cases of neuroblastoma. These genes were selected on the basis of 1) high incidence of their inactivation in several human cancers and 2) their localization on chromosomal regions (9p and 1p) frequently rearranged in neuroblastomas. Detailed molecular analyses indicated the absence of homozygous deletions and point mutations involving these genes in all investigated tumor samples. However, when loss of heterozygostity for chromosome 9p21 (the region where CDKN2A and CDKN2B are localized) was investigated, 16% of cases showed abnormalities in an area telomeric to the CDKN2A locus. To study transcriptional silencing of the CDKN2A gene, the methylation status of exon 1 was examined. In about 35% of cases, a partial methylation was evidenced. Analysis of the CDKN2A mRNA expression, however, did not show any relationship between methylation status and gene transcription. Finally, expression of the CDKN2B gene was demonstrated in all stage IV neuroblastomas, whereas none of stage I tumors expressed this gene. This finding suggests the occurrence of a correlation between CDKN2B transcription and tumor phenotype.

MYCN oncogene amplification in neuroblastoma is associated with worse prognosis, except in stage 4s: the Italian experience with 295 children.

PURPOSE: To evaluate the prognostic role of MYCN oncogene amplification in children with neuroblastoma. PATIENTS AND METHODS: Of 694 children (age, 0 to 15 years) with previously untreated neuroblastoma, 295 (42%) were evaluated at diagnosis for MYCN gene amplification. RESULTS: Clinical characteristics and survival results of 295 patients studied and 399 not studied for MYCN were comparable. In 48 of 295 patients studied for MYCN (16%), the gene was amplified (> or = three gene copies). Amplification was more frequent in children older than 1 year, with abdominal tumor (18% v 7%), advanced disease, normal vanillylmandelic (VMA) urinary excretion, and high lactate dehydrogenase (LDH), ferritin, and neuron-specific enolase (NSE) serum levels. In patients studied for MYCN, the 5-year overall survival (OS) rate was higher for children aged less than 1 year (90% v 44%), with extraabdominal tumor, stage 1 or 2 versus 3 versus 4, and normal NSE, LDH, and ferritin serum levels. Patients with amplified MYCN had a worse OS (odds ratio [OR], 3.38; confidence interval [CI], 2.22 to 5.16). This association held after adjustment for other characteristics. The impact of MYCN amplification was greater in patients with favorable characteristics, in particular age (OR, 10.28 for infants; 2.08 for older children) and stage (OR, 35.3 for stage 1 to 2; 8.41 for stage 3; 1.76 for stage 4). However, of 29 children with stage 4s, all three with amplified MYCN survive. In a multivariate analysis, the prognostic role of MYCN amplification, age, and stage was confirmed, but the size of the effect of MYCN was dependent on age and stage. CONCLUSION: MYCN amplification is associated with a worse prognosis in children with neuroblastoma at all ages and stages except 4s. This association is most pronounced in children with otherwise favorable prognostic indicators, and in these children should be considered as an indication for more intensive intervention.

Loss of heterozygosity for chromosome 1p in familial neuroblastoma.

Loss of heterozygosity (LOH) and deletion of chromosome 1p are very often found in sporadic neuroblastoma. Nevertheless, very few data are available concerning 1p LOH in familial neuroblastoma. Families with recurrent neuroblastoma are rare and analysis of chromosome 1p in these families might give useful information for identifying the putative neuroblastoma suppressor gene. We used combined cytogenetic and molecular techniques to study 1p LOH in two neuroblastoma families. Family M has 2 out of 3 children with neuroblastoma and family C has 2 children, 1 of whom has neuroblastoma and type 1 neurofibromatosis (NF1). All patients of both families showed tumour cells with chromosome 1p deletion (1pdel), but only the patient from family C also had MYCN gene amplification. In all cases the deleted chromosome 1 was of maternal origin.