Loss of alleles on the short arm of chromosome 11 in a hepatoblastoma from a child with Beckwith-Wiedemann syndrome

Achaete-scute family bHLH transcription factor 2 activation promotes hepatoblastoma progression

Achaete-scute family bHLH transcription factor 2 (ASCL2) is highly expressed in hepatoblastoma (HB) tissues, but its role remains unclear. Thus, biological changes in the HB cell line HepG2 in response to induced ASCL2 expression were assessed. ASCL2 expression was induced in HepG2 cells using the Tet-On 3G system, which includes doxycycline. Cell viability, proliferation activity, mobility, and stemness were evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, colony-formation, migration, invasion, and sphere-formation assays. Quantitative reverse-transcription polymerase chain reaction was used to assess the expression of markers for proliferation (CCND1 and MYC), epithelial-mesenchymal transition (EMT; SNAI1, TWIST1, and ZEB1), mesenchymal-epithelial transition (CDH1), and stemness (KLF4, POU5F1, and SOX9). Compared with the non-induced HepG2 cells, cells with induced ASCL2 expression showed significant increases in viability, colony number, migration area (%), and sphere number on days 7, 14, 8, and 7, respectively, and invasion area (%) after 90 h. Furthermore, induction of ASCL2 expression significantly upregulated CCND1, MYC, POU5F1, SOX9, and KLF4 expression on days 2, 2, 3, 3, and 5, respectively, and increased the ratios of SNAI1, TWIST1, and ZEB1 to CDH1 on day 5. ASCL2 promoted the formation of malignant phenotypes in HepG2 cells, which may be correlated with the upregulation of the Wnt signaling pathway-, EMT-, and stemness-related genes. ASCL2 activation may therefore be involved in the progression of HB.

Targeting G9a/DNMT1 methyltransferase activity impedes IGF2-mediated survival in hepatoblastoma

BACKGROUND

As the variable clinical outcome of patients with hepatoblastoma (HB) cannot be explained by genetics alone, the identification of drugs with the potential to effectively reverse epigenetic alterations is a promising approach to overcome poor therapy response. The gene ubiquitin like with PHD and ring finger domains 1 (UHRF1) represents an encouraging epigenetic target due to its regulatory function in both DNA methylation and histone modifications and its clinical relevance in HB.

METHODS

Patient-derived xenograft in vitro and in vivo models were used to study drug response. The mechanistic basis of CM-272 treatment was elucidated using RNA sequencing and western blot experiments.

RESULTS

We validated in comprehensive data sets that UHRF1 is highly expressed in HB and associated with poor outcomes. The simultaneous pharmacological targeting of UHRF1-dependent DNA methylation and histone H3 methylation by the dual inhibitor CM-272 identified a selective impact on HB patient-derived xenograft cell viability while leaving healthy fibroblasts unaffected. RNA sequencing revealed downregulation of the IGF2-activated survival pathway as the main mode of action of CM-272 treatment, subsequently leading to loss of proliferation, hindered colony formation capability, reduced spheroid growth, decreased migration potential, and ultimately, induction of apoptosis in HB cells. Importantly, drug response depended on the level of IGF2 expression, and combination assays showed a strong synergistic effect of CM-272 with cisplatin. Preclinical testing of CM-272 in a transplanted patient-derived xenograft model proved its efficacy but also uncovered side effects presumably caused by its strong antitumor effect in IGF2-driven tumors.

CONCLUSIONS

The inhibition of UHRF1-associated epigenetic traces, such as IGF2-mediated survival, is an attractive approach to treat high-risk HB, especially when combined with the standard-of-care therapeutic cisplatin.

Occurrence of Hepatoblastomas in Patients with Beckwith-Wiedemann Spectrum (BWSp)

Patients with Beckwith-Wiedemann syndrome (BWS), an epigenetic imprinting disorder involving alterations in genes at the 11p15 chromosomal location, are predisposed to develop hepatoblastomas (HBs), which are rare embryonal liver tumors. Tumors can develop after a BWS diagnosis or, conversely, can be the presenting feature leading to a subsequent diagnosis. While HBs are the cardinal tumors of BWS, not all patients with the BWS spectrum will develop HBs. This observation has led to many hypotheses, including genotype-associated risk, tissue mosaicism, and tumor-specific second hits. To explore these hypotheses, we present the largest cohort of patients with BWS and HBs to date. Our cohort comprised 16 cases, and we broadened our sample size by searching the literature for all cases of BWS with HBs. From these isolated case studies, we amassed another 34 cases, bringing the total number to 50 cases of BWS-HB. We observed that paternal uniparental isodisomy (upd(11)pat) was the most common genotype, representing 38% of cases. The next most common genotype was IC2 LOM, representing 14% of cases. Five patients had clinical BWS without a molecular diagnosis. To investigate the potential mechanism of HBs in BWS, we analyzed normal liver and HB samples from eight cases and isolated tumor samples from another two cases. These samples underwent methylation testing, and 90% of our tumor samples underwent targeted cancer next-generation sequencing (NGS) panels. These matched samples provided novel insights into the oncogenesis of HBs in BWS. We found that 100% of the HBs that underwent NGS panel testing had variants in the CTNNB1 gene. We further identified three distinct groups of BWS-HB patients based on epigenotype. We also demonstrated epigenotype mosaicism, where 11p15 alterations can differ between the blood, HB, and normal liver. In light of this epigenotype mosaicism, tumor risk assessment based on blood profiling may not be accurate. Therefore, universal screening is recommended for all patients with BWS.

Genetic and epigenetic basis of hepatoblastoma diversity

Hepatoblastoma (HB) is the most common pediatric liver malignancy; however, hereditary predisposition and acquired molecular aberrations related to HB clinicopathological diversity are not well understood. Here, we perform an integrative genomic profiling of 163 pediatric liver tumors (154 HBs and nine hepatocellular carcinomas) based on the data acquired from a cohort study (JPLT-2). The total number of somatic mutations is precious low (0.52/Mb on exonic regions) but correlated with age at diagnosis. Telomerase reverse transcriptase (TERT) promoter mutations are prevalent in the tween HBs, selective in the transitional liver cell tumor (TLCT, > 8 years old). DNA methylation profiling reveals that classical HBs are characterized by the specific hypomethylated enhancers, which are enriched with binding sites for ASCL2, a regulatory transcription factor for definitive endoderm in Wnt-pathway. Prolonged upregulation of ASCL2, as well as fetal-liver-like methylation patterns of IGF2 promoters, suggests their "cell of origin" derived from the premature hepatoblast, similar to intestinal epithelial cells, which are highly proliferative. Systematic molecular profiling of HB is a promising approach for understanding the epigenetic drivers of hepatoblast carcinogenesis and deriving clues for risk stratification.

Establishment and characterization of a cancer cell line derived from an aggressive childhood liver tumor

BACKGROUND

Hepatoblastoma is a rare malignancy of childhood. The scarcity of adequate cell models has limited our understanding of this tumor. Here we describe and characterize a new human liver tumor cell line, Hep293TT, derived from an aggressive childhood hepatoblastoma.

PROCEDURES

Hep293TT cells were established using primary tumor tissues from a 5-year-old Caucasian female child. This cell line has been maintained for more than 34 months and over 20 subcultures, and was characterized by histopathology, ELISA, genotype, cytogenetics, CGH array, immunohistochemistry, and molecular sequence analyses.

RESULTS

Cells were confirmed to originate from parental tumor cells, secrete alpha-fetoprotein, and express hepatic markers and beta-catenin. Hep293TT cells were able to form colonies in soft agar. Tumorigenicity was demonstrated by induction of solid tumors after subrenal capsule injection in immunodeficient mice. Hep293TT cells demonstrated a highly aneuploid karyotype, and a whole genome CGH analysis revealed chromosomal imbalances in every chromosome. Allelotype analysis demonstrated loss of alleles at distal 11p15.5 as is typical of embryonal tumors. Both Hep293TT cells and the primary tumor contain a deletion of 351 nucleotides in beta-catenin, as has been seen in other hepatoblastoma tumors. The cell line expressed beta-catenin protein in both full-length and partially deleted forms, and expressed NOTCH2 protein characteristic of hepatoblasts. No mutation was detected in the APC, MYH, MLH1, or MSH2 genes.

CONCLUSION

This cell line, Hep293TT, is a valuable resource for the study of childhood liver cancer and may potentially provide a tool in the development of new agents.

Whole-genome profiling of chromosomal aberrations in hepatoblastoma using high-density single-nucleotide polymorphism genotyping microarrays

To identify the genomic profile and elucidate the pathogenesis of hepatoblastoma (HBL), the most common pediatric hepatic tumor, we performed high-density genome-wide single-nucleotide polymorphism (SNP) microarray analyses of 17 HBL samples. The copy number analyzer for GeneChip(R) (CNAG) and allele-specific copy number analysis using anonymous references (AsCNAR) algorithms enabled simple but sensitive inference of allelic composition without using paired normal DNA. Chromosomal aberrations were observed in 15 cases (88%). Gains in chromosomes 1q, 2 (or 2q), 8, 17q, and 20 and losses in chromosomes 4q and 11q were frequently identified. High-grade amplifications were detected at 7q34, 14q11.2, and 11q22.2. Several types of deletions, except homozygous deletion, were identified. Most importantly, copy-neutral loss of heterozygosity (uniparental disomy [UPD]) at 11p15 was detected in four of the 17 HBL samples. Insulin-like growth factor II (IGF2) and H19 genes were located within this region. The methylated status of this region indicated the paternal origin of the UPD. The expression patterns of IGF2 and H19 were opposite between genes with and without the UPD. This difference in the expression patterns might influence the clinical features of HBL.

Risk of tumorigenesis in overgrowth syndromes: a comprehensive review

Overgrowth syndromes (OGS) comprise a heterogeneous group of disorders in which the main characteristic is that either weight, height, or head circumference is 2-3 standard deviations (SD) above the mean for sex and age. A striking feature of OGS is the risk of neoplasms. Here, the relative frequency of specific tumors in each OGS, topographic location, and age of appearance is determined by reviewing published cases. In some OGS (Perlman, Beckwith-Wiedemann, and Simpson-Golabi-Behmel syndromes and hemihyperplasia) more than 94% of tumors appeared in the abdomen usually before 10 years of age, mainly embryonal in type. In Perlman syndrome, only Wilms tumor has been recorded, whereas in Sotos syndrome, lympho-hematologic tumors are most frequent. Based on literature review, a specific schedule protocol for tumor screening is suggested for each OGS. A schedule with different intervals and specific tests is proposed for a more rational cost/benefit program for these disorders.

Beckwith-Wiedemann syndrome: historical, clinicopathological, and etiopathogenetic perspectives

Macroglossia, prenatal or postnatal overgrowth, and abdominal wall defects (omphalocele, umbilical hernia, or diastasis recti) permit early recognition of Beckwith-Wiedemann syndrome. Complications include neonatal hypoglycemia and an increased risk for Wilms tumor, adrenal cortical carcinoma, hepatoblastoma, rhabdomyosarcoma, and neuroblastoma, among others. Perinatal mortality can result from complications of prematurity, pronounced macroglossia, and rarely cardiomyopathy. The molecular basis of Beckwith-Wiedemann syndrome is complex, involving deregulation of imprinted genes found in 2 domains within the 11p15 region: telomeric Domain 1 (IGF2 and H19) and centromeric Domain 2 (KCNQ1, KCNQ1OT1, and CDKN1C). Topics discussed in this article are organized as a series of perspectives: general, historical, epidemiologic, clinical, pathologic, genetic/molecular, diagnostic, and differential diagnostic.

Fluorescent in situ hybridization (FISH) reveals frequent and recurrent numerical and structural abnormalities in hepatoblastoma with no informative karyotype

BACKGROUND

Hepatoblastoma (HB) is the most frequent malignant liver tumor in children. The few cytogenetic studies available indicate that HB is associated with recurring trisomies of chromosomes 2, 8, and 20; recurrent t(1;4) (q12;q34) has been reported in few cases. The abnormalities of chromosome 1q are relatively frequent and usually lead to overexpression of 1q material. A cluster of breakpoints is located at the level of bands 1q12 and 1q21. More work is needed to clarify their real incidence and prognostic significance. Cytogenetic analysis is limited by the requirement of suitable cells in metaphase. A different method that increases analysis sensitivity is fluorescent in situ hybridization (FISH).

PROCEDURE

We studied 10 cases of HB with no informative karyotype (normal karyotype or no metaphases). FISH was performed by the standard method, using cytospins and imprints obtained from frozen or cytogenetic samples of direct cultures. Alpha-satellite probes for centromeric DNA were used for chromosomes 2, 8, and 20 analysis; rearrangement of region 1q12-21 was detected with BAC (bacterial artificial chromosome) probe bA79E5.

RESULTS

We detected at least one trisomic clone in 5/10 of these cases. Trisomy 20 was the most frequently detected abnormality, followed by trisomy of the chromosomes 2 and 8. Analysis of 1q12 band revealed that the rearrangement of 1q usually is in pericentromeric heterochromatin, it was present in 5/10 of studied cases.

CONCLUSION

FISH analysis is recommended in all cases of HB with no informative karyotype to gain more information regarding the frequent trisomies encountered and their significance.

Liver tumors

Liver tumors in children are rare, potentially complex, and encompass a broad spectrum of disease processes. Any age group may be affected, including the fetus. Most present with abdominal distension and/or a mass. Accurate preoperative diagnosis is usually possible using a combination of ultrasound scanning and cross-sectional imaging techniques (CT and/or MR), supplemented by liver biopsy and measurement of tumor markers. The most common benign tumors are hemangiomas, but mesenchymal hamartoma, focal nodular hyperplasia, and adenoma also are found. In Western countries, hepatoblastoma is the most common primary malignant liver tumor; disease-free survival is now possible in more than 80% of affected patients because of advances in combination chemotherapy, improved techniques of surgical resection, and the selective use of liver transplantation. In contrast, there has been less progress in the management of hepatocellular cancer, which still poses many therapeutic challenges.

Karyotypic analyses of hepatoblastoma. Report of two cases and review of the literature suggesting chromosomal loci responsible for the pathogenesis of this disease

Two cases of fetal hepatoblastoma with unique karyotypic changes are described. One was a 17-month-old boy with multiple unbalanced chromosomal translocations, resulting in four types of derivative chromosomes involving chromosomal loci at 1q21, 1q32, 2q23, 6q27, 7p22, and 21p12, partial tetrasomy of 1q, partial trisomy of 2q, and partial monosomy of 21p. The clonal karyotype of this tumor was 46,XY,der(2)t(1;2)(q32;q37), der(6)t(1;6)(q12;q27), der(7)t(2;7)(q23;p22), der(21)t(2;21) (q23;p12). In the other case, a 4-year-old girl, karyotypic analyses revealed trisomy 2 and 8, and the clonal karyotype of this case was 48,XX,+2,+8. Review of these cases together with previous reports suggested the significance of chromosomal changes including numerical abnormalities of 1q, 2(or 2q), 20, and 8 (or 8q), and breakage of 1q and 2q in the development of hepatoblastoma. The results presented herein underscore the significance of numerical abnormalities of chromosomal regions 1q and 2q and of chromosome 8 in the development of hepatoblastoma, in addition to abnormalities of 6q27, 7p22, and 21p12-13 as other chromosomal loci that may be responsible for the pathogenesis of this embryonal type of tumor.

Genomic imprinting and cancer

Genomic imprinting is the phenomenon by which individual alleles of certain genes are expressed differentially according to their parent of origin. The alleles appear to be differentially marked during gametogenesis or during the early part of development. This mark is heritable but reversible from generation to generation, implying a stable epigenetic modification. Approximately 25 imprinted genes have been identified to date, and dysregulation of a number of these has been implicated in tumour development. The normal physiological role of many imprinted genes is in the control of cell proliferation and fetal growth, indicating potential mechanisms of action in tumour formation. Both dominant and recessive modes of action have been postulated for the role of imprinted genes in neoplasia, as a result of effective gene dosage alterations by epigenetic modification of the normal pattern of allele specific transcription. The aim of this review is to assess the importance of imprinted genes in generating tumours and to discuss the implications for novel mechanisms of transforming mutation.

Cytogenetic analysis of hepatoblastoma: hypothesis of cytogenetic evolution in such tumors and results of a multicentric study

Hepatoblastoma is a rare pediatric malignant tumor of the liver. Previous cytogenetic reports are sporadic. We karyotyped nine consecutive hepatoblastomas from the Italian centers participating in a multicentric study on hepatic tumors (SIOPEL 1). Six cases showed abnormal karyotypes. The most common abnormalities were trisomies of chromosomes 2 and 20. Four cases showed abnormalities of chromosome 1. On the basis of findings, we speculate the possibility of a cytogenetic evolutive pattern of hepatoblastomas.

DUB-2 is a member of a novel family of cytokine-inducible deubiquitinating enzymes

Cytokines regulate cell growth by inducing the expression of specific target genes. We have recently identified a cytokine-inducible, immediate-early gene, DUB-1, that encodes a deubiquitinating enzyme with growth regulatory activity. In the current study, we have isolated a highly related gene, DUB-2, that is induced by interleukin-2. The DUB-2 mRNA was induced in T cells as an immediate-early gene and was rapidly down-regulated. Like DUB-1, the DUB-2 protein had deubiquitinating activity in vitro. When a conserved cysteine residue of DUB-2, required for ubiquitin-specific thiol protease activity, was mutated to serine (C60S), deubiquitinating activity was abolished. DUB-1 and DUB-2 proteins are highly related throughout their primary amino acid sequence except for a hypervariable region at their COOH terminus. Moreover, the DUB genes co-localize to a region of mouse chromosome 7, suggesting that they arose by a tandem duplication of an ancestral DUB gene. Additional DUB genes co-localize to this region, suggesting a larger family of cytokine-inducible DUB enzymes. We propose that different cytokines induce specific DUB genes. Each induced DUB enzyme thereby regulates the degradation or the ubiquitination state of an unknown growth regulatory factor, resulting in a cytokine-specific growth response.

Hepatoblastoma in an adult associated with c-met proto-oncogene imbalance

A rare case of hepatoblastoma in a 61-year-old Japanese housewife is described. This liver tumor mainly consisted of two tissue components: embryonal hepatocytes and primitive mesenchymal tissue. Fetal hepatocytes with alpha-fetoprotein production, gland formation, cartilage and osteoid were also found in a small portion. Molecular analysis by slot blot method revealed increased copy numbers of c-met and K-sam proto-oncogenes and cyclin D1 genes. These findings suggest that alterations of these oncogenes might play a role in the development of adult hepatoblastoma.

A common region of loss of heterozygosity in Wilms' tumor and embryonal rhabdomyosarcoma distal to the D11S988 locus on chromosome 11p15.5

The development of Wilms' tumor has been associated with two genetic loci on chromosome 11: WT1 in 11p13 and WT2 in 11p15.5. Here, we have used loss of heterozygosity (LOH) in Wilms' tumors to narrow the WT2 locus distal to the D11S988 locus. A similar region was apparent for the clinically associated tumor, embryonal rhabdomyosarcoma. We have also demonstrated that a constitutional chromosome translocation breakpoint associated with Beckwith-Wiedemann syndrome and an acquired somatic chromosome translocation breakpoint in a rhabdoid tumor each occur in the same chromosomal interval as the smallest region of LOH in Wilms' tumors and embryonal rhabdomyosarcoma. Finally, we report the first Wilms' tumor without a cytogenetic deletion that shows targeted LOH for 11p15 and 11p13 while maintaining germline status for 11p14.

Insulin-like growth factor 2 and insulin-like growth factor binding protein 2 expression in hepatoblastoma

The expression of insulin-like growth factor 2 (IGF2) and insulin-like growth factor binding protein 2 (IGFBP2) in 11 cases of hepatoblastoma was studied by means of in situ mRNA hybridization using digoxigenin (DIG)-labeled riboprobes. The results showed that both IGF2 and IGFBP2 transcripts are present in hepatoblastoma and that their expression is inversely correlated with the degree of tumor cell differentiation. The data suggested that IGF2 and IGFBP2 gene expression could be regarded as a marker for assessment of the degree of differentiation in hepatoblastoma.

Expression of a high molecular weight form of insulin-like growth factor II in a Beckwith-Wiedemann syndrome associated adrenocortical adenoma

Beckwith-Wiedemann syndrome is a rare condition (1/13,700 live births) occurring in both inherited and sporadic forms in the population. It is manifest as a fetal overgrowth syndrome, in which hypertrophy dominates the clinical picture. An additional complication is that these children are predisposed to a specific subset of childhood neoplasms, amongst which are Wilms' tumour and adrenocortical carcinoma. We report here the synthesis by an associated adrenal tumour of large quantities of a high molecular weight form of insulin-like growth factor II (IGF-II), associated with profound suppression of circulating IGFs in the patient's serum. As with other tumours of this type, the tumours showed loss of material on chromosome 11p.

Genetic mosaicism at the insulin locus in liver associated with childhood hepatoblastoma

Hepatoblastoma is commonly associated with loss of heterozygosity (LOH) involving chromosome region 11p15.5. This region may contain an as yet unidentified tumor suppressor gene relevant to this and other tumors associated with the Beckwith-Wiedemann syndrome. Using the insulin (INS) locus as a marker for this region we have identified two of three patients with hepatoblastoma whose livers demonstrated genetic mosaicism. One tumor arose from the clone demonstrating LOH in the liver while the other arose from the clone without LOH.

A constitutional BWS-related t(11;16) chromosome translocation occurring in the same region of chromosome 16 implicated in Wilms' tumors

Beckwith-Wiedemann syndrome (BWS) is a congenital overgrowth disorder with a varying spectrum of clinical manifestations including macroglossia, omphalocele, hemihypertrophy, and a predisposition to a subset of embryonal tumors, most frequently Wilms' tumor (WT). A variety of cytogenetic, genetic linkage, and molecular mapping data implicate a gene or genes on chromosome band 11p15.5 in BWS and its related tumors. However, some families with BWS do not show linkage to 11p15, and other alterations have been found in Wilms' tumors as well. One such alteration is loss of heterozygosity (LOH) for chromosome arm 16q. Here we have analyzed a balanced t(11;16)(p15;q13) chromosomal translocation associated with the BWS phenotype and mapped the breakpoint positions for both chromosomes 11 and 16 by using somatic cell hybrids and polymorphic markers. The chromosome 11 breakpoint was found to lie distal to the D11S12 locus, but proximal to TH on 11p15.5, a region shown previously to contain other BWS-related chromosomal events. The chromosome 16 breakpoint was distal to D16S290 in 16q13, but proximal to loci D16S265, D16S267, and D16S164 in band 16q21. This area encompasses the region of LOH occurring through mitotic recombination in sporadic WT. This raises interesting possibilities for the genetic and epigenetic involvement of both chromosomal regions (11p15 and 16q13) in the pathogenesis of BWS and Wilms' tumor.

Occasional loss of constitutive heterozygosity at 11p15.5 and imprinting relaxation of the IGFII maternal allele in hepatoblastoma

The 11p15.5 chromosomal region contains one or more loci involved in congenital developmental abnormalities and in the genesis of embryonal tumors, such as Wilms' tumor, embryonal rhabdomyosarcoma, and hepatoblastoma. In these tumors, a loss of constitutive heterozygosity, selectively involving a specific parental allele, suggests both the presence of onco-suppressor genes and a phenomenon of genomic imprinting. We present evidence that both genetic events could be occasionally involved in hepatoblastoma. In fact, loss of heterozygosity at 11p15.5 could be documented in 3 of 13 patients with hepatoblastoma, and in 2 cases the paternal origin of the residual allele in the tumor was assessed. Moreover, imprinting of the paternal IGFII allele and the maternal H19 allele was confirmed in normal tissues of 5 informative patients. Finally, imprinting relaxation of IGFII was detected in the tumor tissue of 1 patient.

Analysis of paediatric tumour types associated with hemihyperplasia in childhood

In order to further explore the relationship between hemihyperplasia in children and the occurrence of embryonal tumours of childhood, the records at St Jude Children's Research Hospital were examined for patients who presented with a malignant tumour and hemihyperplasia. Of 27 evaluable patients, 19 had Wilm's tumour and one had massive bilateral nephroblastomatosis. The tumours were more likely to occur on the side affected by hemihyperplasia than to be found contralaterally. All but five of these patients developed the tumours before the age of six. Twenty-two of the 27 patients developed tumours associated with allelic loss on chromosome band 11p15, suggesting that the locus associated with hemihyperplasia may be also located at chromosome band 11p15.

Three non-overlapping regions of chromosome arm 11p allele loss identified in infantile tumors of adrenal and liver

Tumor and constitutional chromosome arm 11p genotypes were compared in 6 hepatoblastoma (HB) patients and 2 adrenal adenoma (AA) patients, with one HB patient and both AA patients displaying clinical features associated with the Beckwith-Wiedemann syndrome (BWS). Using up to 14 chromosome 11 polymorphic markers, loss of constitutional heterozygosity (LOH) was demonstrated in both AA patients and in 4 of 6 HB patients. This identified three distinct and non-overlapping regions of 11p within which LOH occurred, which were defined as lying distal to the gamma-globin locus (11p15.5), proximal to the gamma-globin locus but distal to 11p13 (LOH being detected at 11p15.1), and restricted to the 11p13 region. Specific LOH within each 11p15 region was observed in HB, and this represents the first demonstration by a single study of LOH clearly affecting separate regions of chromosome band 11p15 in a particular tumor type. One AA showed LOH restricted to 11p13 loci, implicating the involvement of the WT1 gene. The second AA patient presented with genitourinary abnormalities and we therefore examined sequences coding for 3 zinc finger domains of WT1 in both AAs. No point mutations were identified in sequence from either patient. Nonetheless our results indicate that 3 separate 11p loci may be significant in the development of tumors which arise in association with BWS.

Systemic effects of insulin-like growth factor-II produced and released from Wilms tumour tissue

The concentration of mRNA of insulin-like growth factor-II is (IGF-II) much elevated in some embryonic tumours such as Wilms tumour (nephroblastoma). In order to prove whether or not IGF-II is produced by the tumour tissue, IGF-II was extracted from freshly frozen tissue of Wilms tumour and hepatoblastoma. Normal adjacent tissue of kidney and liver was used as a control. The total IGF-II in Wilms tumour was 548.4 +/- 77.4 ng/g (n = 7) compared to 112.8 +/- 38.2 ng/g (n = 5) in kidney. In two hepatoblastomas, it was 96.1 +/- 22.8 ng/g compared to 30.1 +/- 14.2 ng/g in normal liver. Small pieces of fresh primary tissue of several Wilms tumours were successfully transplanted into immunodeficient nude mice. In serum of tumour-bearing mice IGF-II was elevated compared to normal mice. Liver weight of tumour bearing mice was higher than that of control mice (2.29 +/- 0.4 g and 2.02 +/- 0.06 g; P < 0.005). This was also found for kidney weight (0.58 +/- 0.01 g vs. 0.51 +/- 0.01 g in controls, P < 0.001). In contrast, serum glucose (9.73 +/- 0.29 mmol/l compared to 11.80 +/- 0.42 mmol/l in controls, P < 0.0005) was decreased. However, there was no significant difference in nose-tail length of tumour-bearing compared to control mice. These results demonstrate that besides the highly increased IGF-II-mRNA, the synthesis of the peptide IGF-II and its release into circulation are also elevated in Wilms tumour transplanted into nude mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytogenetic abnormalities in mesoblastic nephroma: a link to Wilms' tumour?

Cytogenetic analysis of tumour material from a congenital mesoblastic nephroma is reported. Two cell lines were found, one with a normal 46,XY karyotype and the other with a hyperdiploid 51,XY karyotype, including a rearrangement of chromosome 11 at 11p15. This finding is of interest since loss of allelic heterozygosity at polymorphic 11p15 loci has been described in sporadic Wilms' tumour [1], and both cytogenetic [2] and molecular [3] changes of 11p15 are found in the Wiedemann-Beckwith syndrome, a condition with a predisposition to embryonal tumours, particularly Wilms' tumour. Our results lead us to speculate on the implications relating to the pathogenesis of this relatively benign tumour variant with respect to the current understanding of the genetics of Wilms' tumour.

Latent hepatitis B virus infection in childhood hepatocellular carcinoma. Analysis by polymerase chain reaction

The presence of hepatitis B virus (HBV) has been evaluated in liver specimens from 11 children with primary liver tumors and negative results of serologic testing for HBV markers. HBV-DNA sequences were detected by the polymerase chain reaction procedure, using different sets of oligonucleotide primers from highly conserved regions of HBV genome. Two of three children with histologic diagnosis of hepatocellular carcinoma were positive for HBV-DNA in the liver, whereas the remaining children, including six patients with hepatoblastoma, one patient with hemangioma, and one patient with hamartoma, were negative. These findings support the hypothesis of a primary role of HBV in the development of hepatocellular carcinoma in children from nonendemic areas and without overt HBV infection.

The M1 subunit of ribonucleotide reductase refines mapping of genetic rearrangements at chromosome 11p15

We report the first use of the ribonucleotide reductase M1 subunit (RRM1) locus as a marker to assist in defining genetic rearrangements at 11p15. Our sample consisted of 21 Wilms' tumors from 18 patients, and one adrenal adenoma from a patient with Beckwith-Wiedemann syndrome, preexisting chromosome 11 maps being refined by the use of the RRM1 locus in all cases. Significantly, one Wilms' tumor showed loss of heterozygosity at the RRM1 locus only, whereas the adrenal adenoma showed a maintenance of heterozygosity at the RRM1 locus, loss having been previously demonstrated at the c-Ha-ras locus. The relevance of this finding to the location of one or more disease-associated loci at 11p15 is discussed.

Suppression of tumorigenicity in Wilms tumor by the p15.5-p14 region of chromosome 11

Wilms tumor has been associated with genomic alterations at both the 11p13 and 11p15 regions. To differentiate between the involvement of these two loci, a chromosome 11 was constructed that had one or the other region deleted, and this chromosome was introduced into the tumorigenic Wilms tumor cell line G401. When assayed for tumor-forming activity in nude mice, the 11p13-deleted, but not the 11p15.5-p14.1-deleted chromosome, retained its ability to suppress tumor formation. These results provide in vivo functional evidence for the existence of a second genetic locus (WT2) involved in suppressing the tumorigenic phenotype of Wilms tumor.

Trisomy 2 and 20 in two hepatoblastomas

Cytogenetic analysis of two pediatric hepatoblastomas is presented, comparing results in primary tumor samples, nude mouse xenographs, and lung metastases in one case. Both tumors had trisomy 2 and 20 in the primary tumors, along with other structural abnormalities. In subsequent passages/metastases, both tumors showed structural changes in one chromosome 2, resulting in partial trisomy 2q, along with structural changes of other chromosomes. Partial trisomy 1q was also common to both tumors in late stages. Results are compared to those of embryonal rhabdomyosarcoma, where trisomy 2 has also been noted.

Microdissection of chromosome band 11p15.5: characterization of probes mapping distal to the HBBC locus

Both cytogenetic and molecular genetic analyses of the 11p15.5 subband suggest it may contain loci important in the genesis of a wide variety of tumors such as rhabdomyosarcomas and Wilms' tumors as well as the congenital tumors associated with the Beckwith-Wiedemann syndrome. As a first step in further defining the involvement of this chromosomal region in these various maladies, a library was constructed from the specific microdissection of chromosomal fragments representing 11p15.5-pter. Of 98 microclones analyzed, 31 identified single copy human DNA sequences, 21 of which mapped to 11p15.5 while 10 mapped proximal to the HBBC locus. Five of the 11p15.5-positioned microprobes detected restriction fragment length polymorphisms at their homologous genomic loci for various enzymes. These microprobes are now being utilized in several ways in order to address the underlying basis of the Beckwith-Wiedemann syndrome and its associated tumors.

Abnormalities of 2q: a common genetic link between rhabdomyosarcoma and hepatoblastoma?

Cytogenetic and restriction fragment length polymorphism (RFLP) analyses were performed on a mediastinal germ cell tumor comprising distinct teratoma and embryonal rhabdomyosarcoma components in a 31-year-old male and a hepatoblastoma in a 2 month-old male child. Clonal relationship between the teratoma and rhabdomyosarcoma of the germ cell tumor was established by the presence in both of i(12p), the characteristic marker of germ cell tumors. Both the rhabdomyosarcoma component of the mediastinal germ cell tumor and the hepatoblastoma exhibited rearrangements of 2q. These data suggest that malignant differentiation of a teratoma is accompanied by the development of chromosome abnormalities specific for the transformed histology and further suggest that 2q abnormalities may be the common genetic link in the development of the two histologically unrelated tumor types, embryonal rhabdomyosarcoma and hepatoblastoma.

Congenital gastric teratoma in Wiedemann-Beckwith syndrome

Wiedemann-Beckwith syndrome (WBS) may be associated with abdominal tumors, including Wilms tumor, adrenocortical carcinoma, hepatoblastoma, gonadoblastoma, rhabdomyosarcoma, and neuroblastoma. We report on a newborn infant with WBS and a congenital teratoma of the stomach. This is the sole report of any teratoma being associated with WBS and also the first report of a tumor present at birth and visible prenatally in WBS. At birth this infant boy had the diagnostic findings of WBS with macroglossia, ear lobule creases and pits, nevus flammeus, and omphalocele, and an abdominal mass. Abnormalities were detected prenatally when ultrasound examination showed placental overgrowth, polyhydramnios, omphalocele, and posterior abdominal calcifications. Resection of the mass and partial gastrectomy were performed at age 10 days; histologic study showed an immature grade-II teratoma containing a mixture of mature and immature tissues from all germ layers. Results of cytogenetic studies of blood and teratoma were normal (46,XY). This congenital gastric teratoma in a newborn boy with classical WBS may represent either a tumor or an included twin. We discuss its implications for the association of WBS with neoplasia and monozygotic (MZ) twinning, review various neoplasias associated with WBS, and consider pathogenetic mechanisms.

Consistent cytogenetic aberrations in hepatoblastoma: a common pathway of genetic alterations in embryonal liver and skeletal muscle malignancies?

Cytogenetic analyses of four consecutive hepatoblastomas revealed near-diploid stemline karyotypes with relatively simple chromosome aberrations. Cytogenetic abnormalities shared by each tumor included trisomy for all of part of chromosome 2 and trisomy for chromosome 20. In two cases, partial trisomy for chromosome 2 resulted from direct duplication of long arm material with the shortest region of overlap being 2q23-2q35. In one tumor, each metaphase also contained a variable number of double minute chromosomes found not to derive from NMYC amplification. Interestingly, trisomy for 2q and trisomy 20 are also characteristic events in pediatric embryonal rhabdomyosarcomas. Furthermore, others have reported loss of heterozygosity for the short arm of chromosome 11 in both hepatoblastoma and childhood embryonal rhabdomyosarcoma, and both these malignant diseases are associated with Beckwith-Wiedemann syndrome. These cytogenetic and molecular findings suggest a parallel pathway of genetic steps in the initiation and/or progression of tumors of embryonal liver and skeletal muscle.

Molecular characterization of Beckwith-Wiedemann syndrome (BWS) patients with partial duplication of chromosome 11p excludes the gene MYOD1 from the BWS region

The molecular characterization of two patients with features of Beckwith-Wiedemann syndrome (BWS) and chromosome abnormalities is consistent with the association of this phenotype with a duplication of a portion of chromosome 11. Quantitative Southern blot analysis of DNA from patient A defines a large inherited duplicated segment of chromosome 11. For patient B, a de novo duplication of unknown origin has been shown to contain a segment of 11p15. This chromosome segment includes the genes for insulin-like growth factor 2, beta-hemoglobin, calcitonin A (CALCA), and parathyroid hormone (PTH). However, the myogenic differentiation factor, MYOD1, is not included in the duplicated segment. This demonstrates that MYOD1 is proximal to CALCA and PTH and excludes MYOD1 as the BWS gene. These data place the BWS gene distal to MYOD1 on 11p15.

Neuroblastoma in a child with Wiedemann-Beckwith syndrome

We report on a patient with Wiedemann-Beckwith syndrome (WBS) who developed abdominal neuroblastoma. Although WBS patients are known to have a higher incidence of embryonal tumors, this is only the 4th known case of neuroblastoma associated with this syndrome. Chromosomes on peripheral lymphocytes and tumor cells were normal. Children with WBS should be screened for a variety of embryonal neoplasms, not only Wilms tumor.

Overgrowth syndromes

The causes of these fascinating conditions and the mechanisms by which infants of such proportions are formed remain generally unknown. Future understanding of the overgrowth syndromes is likely to be gained from studies employing the exciting new methodology of molecular genetics.

A case-control study of risk factors for hepatoblastoma. A report from the Childrens Cancer Study Group

Parents of 75 children with hepatoblastoma, registered with the Childrens Cancer Study Group, and 75 age-matched controls, who had been identified through random digit dialing were interviewed. No evidence was found to support the primary study hypotheses relating to hepatitis infection, maternal estrogen exposure, alcohol consumption, smoking, or potential sources of nitrosamines. Case mothers were more likely to report occupational exposure to metals (odds ratio [OR] = 8.0, P = 0.01), petroleum products (OR = 3.7, P = 0.03), and paints or pigments (OR = 3.7, P = 0.05). Metal exposures were commonly to welding or soldering fumes, and most occurred daily, before and during the index pregnancy. Petroleum product exposures were predominantly to lubricating oils or protective greases. The only significant paternal exposure was to metals (OR = 3.0, P = 0.01) and the risk with exposure to petroleum products was marginally significant (OR = 1.9, P = 0.06). These findings provide further evidence that occupational exposures may increase the risk of cancer in offspring.