Altered expression of members of the IGF-axis in hepatoblastomas

Hepatoblastoma: From Molecular Mechanisms to Therapeutic Strategies

Hepatoblastoma (HB) is the most common malignant liver tumor in children under five years of age. Although globally rare, it accounts for a large proportion of liver cancer in children and has poor survival rates in high-risk and metastatic cases. This review discusses the molecular mechanisms, diagnostic methods, and therapeutic strategies of HB. Mutations in the CTNNB1 gene and the activation of the Wnt/β-catenin pathway are essential genetic factors. Furthermore, genetic syndromes like Beckwith-Wiedemann syndrome (BWS) and Familial Adenomatous Polyposis (FAP) considerably heighten the risk of associated conditions. Additionally, epigenetic mechanisms, such as DNA methylation and the influence of non-coding RNAs (ncRNAs), are pivotal drivers of tumor development. Diagnostics include serum biomarkers, immunohistochemistry (IHC), and imaging techniques. Standard treatments are chemotherapy, surgical resection, and liver transplantation (LT). Emerging therapies like immunotherapy and targeted treatments offer hope against chemotherapy resistance. Future research will prioritize personalized medicine, novel biomarkers, and molecular-targeted therapies to improve survival outcomes.

Whole-genome sequencing and RNA sequencing analysis reveals novel risk genes and differential expression patterns in hepatoblastoma

Hepatoblastoma (HB) is an uncommon malignant liver cancer primarily affecting infants and children, characterized by the presence of tissue that resembling fetal hepatocytes, mature liver cells or bile duct cells. The primary symptom in affected children is abdominal lumps. HB constitutes approximately 28% of all liver tumors and two-thirds of liver malignancies in the pediatric and adolescent population. Despite its high prevalence, the underlying mechanism of HB pathogenesis remain largely unknown. To reveal the genetic alternations associated with HB, we conducted a comprehensive genomic study using whole-genome sequencing (WGS) and RNA sequencing (RNA-seq) techniques on five HB patients. We aimed to use WGS to identify somatic variant loci associated with HB, including single nucleotide polymorphisms (SNPs), insertions and deletions (Indels), and copy number variations (CNVs). Notably, we found deleterious mutation in CTNNB1, AXIN2 and PARP1, previously implicated in HB. In addition, we discovered multiple novel genes potentially associated with HB, including BRCA2 and GPC3 which require further functional validation to reveal their contributions to HB development. Furthermore, the American College of Medical Genetics and Genomics (ACMG) analysis identified the ABCC2 gene was the pathogenic gene as a potential risk gene linked with HB. To study the gene expression patterns in HB, we performed RNA-seq analysis and qPCR validation to reveal differential expression of four candidate genes (IGF1R, METTL1, AXIN2 and TP53) in tumors compared to nonneoplastic liver tissue in HB patients (P-Val < 0.01). These findings shed lights on the molecular mechanisms underlying HB development and facilitate to advance future personalized diagnosis and therapeutic interventions of HB.

Identification of IGF2 as Genomic Driver and Actionable Therapeutic Target in Hepatoblastoma

Management of hepatoblastoma (HB), the most frequent pediatric liver cancer, is based on surgical resection and perioperative chemotherapy regimens. In this study, we aimed to identify actionable targets in HB and assess the efficacy of molecular therapies in preclinical models of HB. Paired tumor and adjacent tissues from 31 HBs and a validation set of 50 HBs were analyzed using RNA-seq, SNP, and methylation arrays. IGF2 overexpression was identified as the top targetable HB driver, present in 71% of HBs (22/31). IGF2high tumors displayed progenitor cell features and shorter recurrence-free survival. IGF2 overexpression was associated in 91% of cases with fetal promoter hypomethylation, ICR1 deregulation, 11p15.5 loss of heterozygosity or miR483-5p overexpression. The antitumor effect of xentuzumab (a monoclonal antibody targeting IGF1/2) alone or in combination with the conventional therapeutic agent cisplatin was assessed in HB cell lines, in PDX-derived HB organoids and in a xenograft HB murine model. The combination of xentuzumab with cisplatin showed strong synergistic antitumor effects in organoids and in IGF2high cell lines. In mice (n = 55), the combination induced a significant decrease in tumor volume and improved survival compared with cisplatin alone. These results suggest that IGF2 is an HB actionable driver and that, in preclinical models of HB, the combination of IGF1/2 inhibition with cisplatin induces superior antitumor effects than cisplatin monotherapy. Overall, our study provides a rationale for testing IGF2 inhibitors in combination with cisplatin in HB patients with IGF2 overexpression.

Hepatoblastoma in molecularly defined, congenital diseases

Beckwith-Wiedemann spectrum, Simpson-Golabi-Behmel syndrome, familial adenomatous polyposis and trisomy 18 are the most common congenital conditions associated with an increased incidence of hepatoblastoma (HB). In patients with these genetic disorders, screening protocols for HB are proposed that include periodic abdominal ultrasound and measurement of alpha-fetoprotein levels. Surveillance in these children may contribute to the early detection of HB and possibly improve their chances of overall survival. Therefore, physicians must be aware of the high HB incidence in children with certain predisposing genetic diseases.

The Curious Case of the HepG2 Cell Line: 40 Years of Expertise

Liver cancer is the third leading cause of cancer death worldwide. Representing such a dramatic impact on our lives, liver cancer is a significant public health concern. Sustainable and reliable methods for preventing and treating liver cancer require fundamental research on its molecular mechanisms. Cell lines are treated as in vitro equivalents of tumor tissues, making them a must-have for basic research on the nature of cancer. According to recent discoveries, certified cell lines retain most genetic properties of the original tumor and mimic its microenvironment. On the other hand, modern technologies allowing the deepest level of detail in omics landscapes have shown significant differences even between samples of the same cell line due to cross- and mycoplasma infection. This and other observations suggest that, in some cases, cell cultures are not suitable as cancer models, with limited predictive value for the effectiveness of new treatments. HepG2 is a popular hepatic cell line. It is used in a wide range of studies, from the oncogenesis to the cytotoxicity of substances on the liver. In this regard, we set out to collect up-to-date information on the HepG2 cell line to assess whether the level of heterogeneity of the cell line allows in vitro biomedical studies as a model with guaranteed production and quality.

The Curious Case of the HepG2 Cell Line: 40 Years of Expertise

Liver cancer is the third leading cause of cancer death worldwide. Representing such a dramatic impact on our lives, liver cancer is a significant public health concern. Sustainable and reliable methods for preventing and treating liver cancer require fundamental research on its molecular mechanisms. Cell lines are treated as in vitro equivalents of tumor tissues, making them a must-have for basic research on the nature of cancer. According to recent discoveries, certified cell lines retain most genetic properties of the original tumor and mimic its microenvironment. On the other hand, modern technologies allowing the deepest level of detail in omics landscapes have shown significant differences even between samples of the same cell line due to cross- and mycoplasma infection. This and other observations suggest that, in some cases, cell cultures are not suitable as cancer models, with limited predictive value for the effectiveness of new treatments. HepG2 is a popular hepatic cell line. It is used in a wide range of studies, from the oncogenesis to the cytotoxicity of substances on the liver. In this regard, we set out to collect up-to-date information on the HepG2 cell line to assess whether the level of heterogeneity of the cell line allows in vitro biomedical studies as a model with guaranteed production and quality.

The Curious Case of the HepG2 Cell Line: 40 Years of Expertise

Liver cancer is the third leading cause of cancer death worldwide. Representing such a dramatic impact on our lives, liver cancer is a significant public health concern. Sustainable and reliable methods for preventing and treating liver cancer require fundamental research on its molecular mechanisms. Cell lines are treated as in vitro equivalents of tumor tissues, making them a must-have for basic research on the nature of cancer. According to recent discoveries, certified cell lines retain most genetic properties of the original tumor and mimic its microenvironment. On the other hand, modern technologies allowing the deepest level of detail in omics landscapes have shown significant differences even between samples of the same cell line due to cross- and mycoplasma infection. This and other observations suggest that, in some cases, cell cultures are not suitable as cancer models, with limited predictive value for the effectiveness of new treatments. HepG2 is a popular hepatic cell line. It is used in a wide range of studies, from the oncogenesis to the cytotoxicity of substances on the liver. In this regard, we set out to collect up-to-date information on the HepG2 cell line to assess whether the level of heterogeneity of the cell line allows in vitro biomedical studies as a model with guaranteed production and quality.

High expression of IGF2-derived intronic miR-483 predicts outcome in hepatoblastoma

BACKGROUND

The role of microRNAs (miRs) as biomarkers to predict outcome in hepatoblastoma (HB), the most common malignant liver tumor in childhood, has still to be determined. Recently, the so-called four-miR signature has been described to efficiently stratify HB patients according to their prognosis.

OBJECTIVE

We examined the recently described four-miR signature for its clinical relevance in an independent validation cohort of HB patients and tried to optimize its predictive value by analyzing four additional miRs involved in HB biology.

METHODS

Expression of eight miR was determined in 29 tumor and 10 normal liver samples by TaqMan assays and association studies and Kaplan-Meier estimators determined their clinical relevance.

RESULTS

Stratifying HB patients by the four-miR signature showed no difference in patients' outcome, which was also reflected by the lack of association with any clinical risk parameter. Adding miR-23b-5p and miR-23b-3p did also not increase its discriminating power. However, the integration of miR-483-5p and miR-483-3p into the four-miR signature could predict patients with poor outcome that were associated with large tumors and vessel invasive growth with high accuracy.

CONCLUSIONS

The expansion of the four-miR signature by miR-483 serves as a useful biomarker to predict outcome of HB patients.

Molecular Mechanisms of Hepatoblastoma

Hepatoblastoma (HB) is the predominant primary liver tumor in children. While the prognosis is favorable when the tumor can be resected, the outcome is dismal for patients with progressed HB. Therefore, a better understanding of the molecular mechanisms responsible for HB is imperative for early detection and effective treatment. Sequencing analysis of human HB specimens unraveled the pivotal role of Wnt/β-catenin pathway activation in this disease. Nonetheless, β-catenin activation alone does not suffice to induce HB, implying the need for additional alterations. Perturbations of several pathways, including Hippo, Hedgehog, NRF2/KEAP1, HGF/c-Met, NK-1R/SP, and PI3K/AKT/mTOR cascades and aberrant activation of c-MYC, n-MYC, and EZH2 proto-oncogenes, have been identified in HB, although their role requires additional investigation. Here, we summarize the current knowledge on HB molecular pathogenesis, the relevance of the preclinical findings for the human disease, and the innovative therapeutic strategies that could be beneficial for the treatment of HB patients.

Human amniotic mesenchymal stem cells inhibit hepatocellular carcinoma in tumour-bearing mice

Hepatocellular carcinoma (HCC) is the third leading cause of the cancer-related death in the world. Human amniotic mesenchymal stem cells (hAMSCs) have been characterized with a pluripotency, low immunogenicity and no tumorigenicity. Especially, the immunosuppressive and anti-inflammatory effects of hAMSCs make them suitable for treating HCC. Here, we reported that hAMSCs administrated by intravenous injection significantly inhibited HCC through suppressing cell proliferation and inducing cell apoptosis in tumour-bearing mice with Hepg2 cells. Cell tracking experiments with GFP-labelled hAMSCs showed that the stem cells possessed the ability of migrating to the tumorigenic sites for suppressing tumour growth. Importantly, both hAMSCs and the conditional media (hAMSC-CM) have the similar antitumour effects in vitro, suggesting that hAMSCs-derived cytokines might be involved in their antitumour effects. Antibody array assay showed that hAMSCs highly expressed dickkopf-3 (DKK-3), dickkopf-1 (DKK-1) and insulin-like growth factor-binding protein 3 (IGFBP-3). Furthermore, the antitumour effects of hAMSCs were further confirmed by applications of the antibodies or the specific siRNAs of DKK-3, DKK-1 and IGFBP-3 in vitro. Mechanically, hAMSCs-derived DKK-3, DKK-1 and IGFBP-3 markedly inhibited cell proliferation and promoted apoptosis of Hepg2 cells through suppressing the Wnt/β-catenin signalling pathway and IGF-1R-mediated PI3K/AKT signalling pathway, respectively. Taken together, our study demonstrated that hAMSCs possess significant antitumour effects in vivo and in vitro and might provide a novel strategy for HCC treatment clinically.

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.

Effect of curcumin on vascular endothelial growth factor in hypoxic HepG2 cells via the insulin-like growth factor 1 receptor signaling pathway

To investigate the anti-angiogenic effect and underlying molecular mechanisms of curcumin on HepG2 cells under hypoxic conditions, insulin-like growth factor 1 receptor (IGF-1R) knockout HepG2 cells were constructed using a clustered regularly interspaced short palindromic repeats/Cas9 genome-editing system. Hypoxic conditions were generated using cobalt chloride (CoCl₂). An MTT assay was performed to measure the effects of curcumin on cell viability in hypoxia-induced IGF-1R knockout HepG2 cells, while western blot analysis was used to detect the expression of IGF-1R, phosphorylated (p)-protein kinase B (Akt), p-extracellular signal-regulated kinases (Erk)1/2, hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF). The results revealed that CoCl₂ at low concentrations (50 and 100 µM) had no significant inhibitory effects on IGF-1R knockout HepG2 cells. However, with increasing concentrations of CoCl₂ and treatment time, cell viability decreased and was significantly reduced at 150, 200 and 400 µM compared with the control group (P<0.05). The expression of HIF-1α and VEGF were significantly increased when the cells were treated with 150 or 200 µM CoCl₂ compared with the control (P<0.05). With the increase of CoCl₂ concentration or the treatment time, the expression of HIF-1α and VEGF were upregulated gradually. Additionally, curcumin significantly inhibited the expression of p-Akt, p-Erk1/2, HIF-1α and VEGF in hypoxia-induced IGF-1R knockout HepG2 cells. In conclusion, the findings of the present study suggest that curcumin may serve a pivotal role in tumor suppression via the inhibition of IGF-1R-mediated angiogenesis under hypoxic conditions.

Glomerulocystic Kidney Disease and Hepatoblastoma in an Infant: A Rare Presentation

Glomerulocystic kidney disease (GCKD) is a rare condition comprising heritable and non-heritable types [Oh et al.: Nephron 1986;43:299–302]. Hepatoblastoma is a sporadically occurring tumor of embryonal origin that is associated with overgrowth syndrome and renal cysts. A concurrent presentation of GCKD with hepatoblastoma was first described in 1989 [Rao et al.: Jpn J Surg 1989;19:583–585]. We report the simultaneous presentation of hepatoblastoma and GCKD in a 5-month-old child and explore the probability of insulin-like growth factors, insulin-like growth factor-binding protein and Beckwith-Wiedemann gene mutation as a putative cause.

Upregulated genes at 2q24 gains as candidate oncogenes in hepatoblastomas

AIM

Cytogenetic data of hepatoblastomas, a rare embryonal tumor of the liver, mostly consist of descriptions of whole-chromosome aneuploidies and large chromosome alterations. High-resolution cytogenetics may provide clues to hepatoblastoma tumorigenesis and indicate markers with clinical significance.

PATIENTS & METHODS

We used array-CGH (180K) to screen for genomic imbalances in nine hepatoblastomas. Additionally, we investigated the expression pattern of selected genes exhibiting copy number changes.

RESULTS

Analysis showed mainly whole-chromosome or chromosome-arm aneuploidies, but some focal aberrations were also mapped. Expression analysis of 48 genes mapped at one 10 Mb amplification at 2q24 revealed upregulation of DAPL1, ERMN, GALNT5, SCN1A and SCN3A in the set of tumors compared with differentiated livers.

CONCLUSION

These genes appear as candidates for hepatoblastoma tumorigenesis.

A pleiotropic effect of the single clustered hepatic metastamiRs miR-96-5p and miR-182-5p on insulin-like growth factor II, insulin-like growth factor-1 receptor and insulin-like growth factor-binding protein-3 in hepatocellular carcinoma

MicroRNAs (miRs) have a major role in the pathogenesis of hepatocellular carcinoma (HCC). As the insulin-like growth factor (IGF) axis is a highly tumorigenic pathway in HCC, the present study attempted to target it with miRs. Potential targeting of crucial members of the IGF axis by miRNAs at the 3'-untranslated region (3'-UTR) was predicted using bioinformatic tools, such as microrna.org, Diana lab and Targetscan, while 5'-UTR targeting was predicted using bibiserv software. Expression profiling of obtained miRNAs was performed using quantitative polymerase chain reaction (qPCR) in 22 non-metastatic HCC biopsy samples and 10 healthy tissues. To investigate the impact of miRNAs on their potential downstream targets, transfection of miRNAs was performed in HuH-7 cells and the targets' expression was quantified using qPCR. Transcripts of insulin-like growth factor-1 receptor (IGF-1R), insulin-like growth factor binding protein-3 (IGFBP-3) and IGF-II were found to be potentially targeted at the 5'-UTR and 3'-UTR regions by the single clustered hepatic metastamiRs miR-96-5p and miR-182-5p. The two miRNAs showed a similar expression pattern in HCC tissues compared to those in healthy tissues. Forced expression of miR-96-5p and miR-182-5p in the HCC cell line HuH-7 had inducing effects on IGFBP-3 and IGF-II transcripts. Of note, the two miRs had differential effects on IGF-1R, where miR-96-5p induced IGF-1R mRNA expression and miR-182-5p inhibited its expression. The present study revealed the pleiotropic impact of the single clustered hepatic metastamiRs miR-96-5p and miR-182-5p on IGF-1R, and an inducing effect on IGF-II and IGFBP-3 in hepatocellular carcinoma.

A Phase I Study of Cixutumumab (IMC-A12) in Combination with Temsirolimus (CCI-779) in Children with Recurrent Solid Tumors: A Children's Oncology Group Phase I Consortium Report

PURPOSE

To determine the MTD, dose-limiting toxicities (DLT), pharmacokinetics, and biologic effects of cixutumumab administered in combination with temsirolimus to children with refractory solid tumors.

EXPERIMENTAL DESIGN

Cixutumumab and temsirolimus were administered intravenously once every 7 days in 28-day cycles. Pharmacokinetic and biology studies, including assessment of mTOR downstream targets in peripheral blood mononuclear cells, were performed during the first cycle.

RESULTS

Thirty-nine patients, median age 11.8 years (range, 1-21.5), with recurrent solid or central nervous system tumors were enrolled, of whom 33 were fully assessable for toxicity. There were four dose levels, which included two dose reductions and a subsequent intermediated dose escalation: (i) IMC-A12 6 mg/kg, temsirolimus 15 mg/m(2); (ii) IMC-A12 6 mg/kg, temsirolimus 10 mg/m(2); (iii) IMC-A12 4 mg/kg, temsirolimus 8 mg/m(2); and (iv) IMC-A12 6 mg/kg, temsirolimus 8 mg/m(2). Mucositis was the predominant DLT. Other DLTs included hypercholesterolemia, fatigue, thrombocytopenia, and increased alanine aminotransferase. Target inhibition (decreased S6K1 and PAkt) in peripheral blood mononuclear cells was noted at all dose levels. Marked interpatient variability in temsirolimus pharmacokinetic parameters was noted. At 8 mg/m(2), the median temsirolimus AUC was 2,946 ng • h/mL (range, 937-5,536) with a median sirolimus AUC of 767 ng • h/mL (range, 245-3,675).

CONCLUSIONS

The recommended pediatric phase II doses for the combination of cixutumumab and temsirolimus are 6 mg/kg and 8 mg/m(2), respectively.

Hepatoblastoma state of the art: pathology, genetics, risk stratification, and chemotherapy

PURPOSE OF REVIEW

As a rare pediatric tumor, hepatoblastoma presents challenges to the individual practitioner as no center will see more than a handful of cases each year.

RECENT FINDINGS

The Children's Hepatic tumor International Collaborative (CHIC) effort has fostered international cooperation in this rare children's tumor, leading to the establishment of a large international collaborative dataset, the CHIC database, which has been interrogated to refine risk stratification and inform treatment options. Apace with this effort has been the international collaboration of pediatric pathologists working together to establish a new international histopathologic consensus classification for pediatric liver tumors as a whole, with particular focus on the histological subtypes of hepatoblastoma.

SUMMARY

International collaborative efforts in hepatoblastoma have led to a new international histopathologic consensus classification, refinements in risk stratification, advances in chemotherapy, and a better understanding of surgical resection options forming the foundation for the development of an upcoming international therapeutic trial.

Genetics and epigenetics of hepatoblastoma

A number of unique genetic features are observed in hepatoblastoma that have provided insights into the origins of hepatoblastoma. Hallmark cytogenetic changes in hepatoblastoma include the acquisition of additional copies of whole chromosomes and a recurring unbalanced translocation involving 1q. Genetic syndromes are associated with approximately 15% of hepatoblastoma and the understanding and recognition of these syndromes will be important in determining future surveillance studies needed to prevent additional cancers in survivors as well as in some case guide the care of family members. This article will review the genetic changes, both germ line and acquired, that are recurring events in hepatoblastoma, with emphasis on how these genetic changes could work together with other developmental factors and influence cancer predisposition, tumor growth, as well as aid in prognosis. Tumor-specific signatures based on transcriptional or epigenetic alterations will be reviewed that might be used in the future to better diagnose and subtype the disease as well as predict prognosis and response to therapy.

Current and future management strategies for relapsed or progressive hepatoblastoma

Hepatoblastoma is the most common primary malignant neoplasm of the liver in children. Improvements in chemotherapy and surgical techniques have increased survival rates for those with localized disease. The prognosis for patients with progressive or relapsed disease continues to be dismal. Complete resection by surgery or liver transplantation is necessary for cure. Few conventional chemotherapy agents have demonstrated activity in progressive or relapsed hepatoblastoma. Irinotecan has shown activity in relapsed and progressive hepatoblastoma. The efficacy of high-dose chemotherapy in this setting is unknown. Newer targeted agents that 'selectively' interfere with pathway targets involved in tumor growth and progression such as insulin-like growth factor, phosphatidylinositol 3-kinase (PI3K), Akt, and mammalian target of rapamycin (mTOR) are currently under development. Because of the rarity of hepatoblastoma, only a small minority of these agents will ever be evaluated in children with this disorder. Gene-directed therapy and immunotherapy have shown promising results in the preclinical setting, and should be investigated as future treatment options for advanced hepatoblastoma.

IGFBP3 impedes aggressive growth of pediatric liver cancer and is epigenetically silenced in vascular invasive and metastatic tumors

Background

Hepatoblastoma (HB) is an embryonal liver neoplasm of early childhood with a poor prognosis for patients with distant metastases and vascular invasion. We and others have previously shown that the overexpression of insulin-like growth factor 2 (IGF2), loss of imprinting at the IGF2/H19 locus, and amplification of pleomorphic adenoma gene 1 (PLAG1) are common features in HB, suggesting a critical role of the IGF axis in hepatoblastomagenesis. In this study, we investigated the role of the insulin-like growth factor binding protein 3 (IGFBP3), a known competitor of the IGF axis, in pediatric liver cancers.

Results

The IGFBP3 gene was highly expressed in normal pediatric livers but was heavily downregulated in four HB cell lines and the majority of HB primary tumors (26/36). Detailed methylation analysis of CpG sites in the IGFBP3 promoter region by bisulfite sequencing revealed a high degree of DNA methylation, which is causatively associated with the suppression of IGFBP3 in HB cell lines. Consequently, the treatment of HB cell lines with 5-aza-2'-deoxycytidine resulted in DNA demethylation and reactivation of the epigenetically silenced IGFBP3 expression. Interestingly, IGFBP3 promoter methylation predominantly occurred in metastatic HB with vascular invasion. Restoring IGFBP3 expression in HB cells resulted in reduced colony formation, migration, and invasion.

Conclusion

This study provides the first direct evidence that the reactivation of IGFBP3 decreases aggressive properties of pediatric liver cancer cells and that IGFBP3 promoter methylation might be used as an indicator for vessel-invasive tumor growth in HB patients.

Rapamycin blocks hepatoblastoma growth in vitro and in vivo implicating new treatment options in high-risk patients

Activation of the protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signalling pathway plays a central role in the formation of hepatoblastoma (HB), the most common liver cancer in childhood. Blocking this pathway with specific mTOR inhibitors such as the immunosuppressant rapamycin is being currently tested for a variety of cancers. Here, we report that rapamycin treatment induced a significant dose-dependent inhibition of cell viability and promoted apoptosis in HB cells in vitro. Moreover, rapamycin inhibited AKT/mTOR signalling by dephosphorylation of the downstream target p70S6 kinase (p70S6K). Most importantly, treating subcutaneous HUH6 xenograft tumour bearing mice orally with 5mg/kg/day rapamycin for three weeks resulted in a striking reduction of tumour growth, as evidenced by reduced volume and weight, and moderately lowered tumour-specific alpha-fetoprotein (AFP) serum levels. The anti-tumourigenic effect was primarily ascribed to a significantly reduced proliferation rate upon p70S6K dephosphorylation, as microvascular density of rapamycin-treated compared to vehicle-treated tumours stayed grossly unchanged. Of uttermost clinical importance, we found no evidence for a feedback-loop activation of AKT in vivo. In conclusion, we demonstrate that rapamycin effectively inhibits HB growth both in vitro and in vivo by blocking AKT/mTOR signalling at the level of p70S6K and that rapamycin should be considered to treat HB patients especially those to be indicated for liver transplantation to benefit from its anti-tumourigenic and immunosuppressive properties.

Insulin-like growth factors and hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most malignant types of cancer. It has a rapid course and carries a poor prognosis. Hepatocarcinogenesis is a complex multi-step and multi-factorial process. Recent studies have discovered the association between the dysregulation of insulin-like growth factor (IGF)-related signaling pathways and pathogenesis of liver cancer. IGFs are multifunctional cell proliferation regulatory factors and play an important role in fetal development, central nervous system development and cancer cell proliferation. The biological activity of IGFs is regulated by a complex regulatory network which consists of different types of receptors, IGF-binding proteins and IGF binding-related proteins. This review focuses on the changes in the IGF axis and IGF-related signaling pathways in liver tumorigenesis and their application in targeted therapy for liver cancer.

Altered microRNA Expression Patterns in Hepatoblastoma Patients

Liver cancers in children are rare representing only 1.1% of malignancies, with an annual incidence rate of 1.5 cases per million. Hepatoblastoma and hepatocellular carcinomas are the most common malignancies of the liver occurring in young people aged 15 years or younger. Molecular basis of both tumors are still unclear, and common markers (i.e., CTNNB1, APC, IGF-2) are not always useful in the characterization of sporadic forms; in this respect, microRNA recently associated with carcinogenesis could play a pivotal role in their onset. CTNNB1 and APC were analyzed by sequencing, and IGF-2 promoter methylation status was assessed by methylation-specific polymerase chain reaction. MicroRNA expression was assayed by microarray and quantitative reverse transcription-polymerase chain reaction in hepatoblastoma samples. Although few genomic alterations were detected in ours samples, an altered expression of somemicroRNA in hepatoblastoma was observed. Unsupervised clustering shows that microRNA profile can distinguish tumor from nontumor tissues. Further analyses of microRNA contents in hepatoblastoma compared with hepatocellular carcinoma highlighted four upregulated microRNA (miR-214, miR-199a, miR-150 [P < .01], and miR-125a [P < .05]) and one downregulated microRNA (miR-148a [P < .01]). In conclusion, although our samples were poorly informative from a genetic point of view, they showed a peculiar microRNA expression pattern compared with nontumor tissues and hepatocellular carcinoma. MicroRNA could represent valid markers for the classification of pediatric liver tumors.

Involvement of the IGF system in fetal growth and childhood cancer: an overview of potential mechanisms

Fetal growth is determined by a complex interplay of genetic, nutritional, environmental, and hormonal factors. Greater than expected fetal growth has been positively associated with the risk of the development of some cancers in childhood, particularly acute lymphoblastic leukemia, and the biological mechanisms underlying such associations are thought to involve insulin-like growth factors (IGFs). Circulating IGF levels are highly correlated with fetal growth, and IGFs are believed to play an important role in carcinogenesis; however, these two bodies of evidence have not been well integrated and, as a result, the potential underlying biological mechanisms linking the IGF system with the development of specific childhood cancers have not been elucidated. This review aims to draw together and summarize the literature linking the IGF system, rapidity of fetal growth, and risk of some specific childhood cancers; suggest explanations for some of the inconsistencies observed in previous studies of these associations; and propose an integrated framework for the putative involvement of the IGF system in the development of at least some childhood cancers. If the challenges involved in studying the complex IGF system can be overcome, this field presents an exciting opportunity to elucidate etiological pathways to childhood malignancies.

The role of IGF-1R in pediatric malignancies

The insulin-like growth factor (IGF) family consists of ligands (IGF-I, IGF-II, insulin), several receptors (including IGF-1R), and six binding proteins (IGFBP-1 through IGFBP-6). Members of this family regulate key cellular activities and they also play an important role in the development and progression of both adult and childhood cancers. Binding of a ligand to the receptor leads to its activation, followed by signal transduction along several pathways. In some childhood malignancies, IGF-1R can be activated by endocrine, autocrine, or paracrine mechanisms. Although mutations in IGF-1R have not been identified, this signaling pathway is upregulated in many childhood cancers. These findings have led to the development of a host of IGF-1R signaling modulators that are currently being tested in clinical trials. This review explores the role of IGF-1R in a range of childhood malignancies.

Loss of imprinting of IGF2 correlates with hypermethylation of the H19 differentially methylated region in hepatoblastoma

IGF2, a maternally imprinted foetal growth factor gene, is implicated in many childhood tumours including hepatoblastoma (HB); however, the genetic and epigenetic alterations have not comprehensively been studied. We analysed the methylation status of the H19 differentially methylated region (DMR), loss of heterozygosity (LOH) and allelic expression of IGF2 in 54 HB tumours, and found that 12 tumours (22%) with LOH, 9 (17%) with loss of imprinting (LOI) and 33 (61%) with retention of imprinting (ROI). Biallelic and monoallelic IGF2 expressions correlated with hypermethylation and normal methylation of H19 DMR, respectively, in two tumours with LOI and seven tumours with ROI. Quantitative RT–PCR analysis showed minimal expression of H19 mRNA and substantial expression of IGF2 mRNA in tumours with LOH or LOI, and substantial expression of both H19 and IGF2 mRNAs in tumours with ROI. Increased IGF2 expression with predominant embryonic P3 transcript was found in the majority of HBs with ROI and foetal livers. In contrast to the earlier reports, our findings suggest that the disruption of the enhancer competition model reported in Wilms' tumour may also occur in HB. Both frequencies of LOH and LOI seem to be lower in HB than in Wilms' tumour, reflecting the different tissue origins.

Duplication of paternal IGF2 or loss of maternal IGF2 imprinting occurs in half of Wilms tumors with various structural WT1 abnormalities

The WT1 gene essential for the embryonic kidney development is mutated in 15-25% of Wilms tumors (WTs). To clarify whether genetic subtypes of WT1 abnormalities are correlated with IGF2 or CTNNB1 alterations or clinicopathological characteristics, we performed comprehensive WT1, IGF2, and CTNNB1 analyses of 36 WTs with WT1 abnormalities using single nucleotide polymorphism arrays, and methylation analysis of the IGF2-H19 differentially methylated region. The tumors were classified into three subtypes based on WT1 abnormalities: 13 with WT1 deletion, 12 with WT1 mutation, and 11 with both deletion and mutation. IGF2 alterations were found in 50% (18/36), paternal uniparental disomy (UPD) of 11p13-11p15 in 13 tumors, UPD limited to 11p15 in 3, and loss of IGF2 imprinting in 2. Quantitative RT-PCR analysis showed that tumors with IGF2 alteration had higher levels of IGF2 mRNA than tumors without IGF2 alteration (P = 0.02). WT1 mRNA levels were very low in six of eight WTs with WT1 deletion, whereas four of eight WTs with WT1 mutation or both deletion and mutation showed higher levels of WT1 mRNA than fetal kidneys. WTs with WT1 mutations occurred in younger patients (P < 0.01), and WTs with mutations or both deletion and mutation (12/23) were more frequent in syndromic patients than WTs (1/13) with the deletion (P = 0.02). WTs with WT1 mutations or both deletion and mutation had the triphasic histological-type (15/23; P = 0.03) and CTNNB1 mutation (17/23; P = 0.03) more frequently than WTs with the deletion (2/13 and 4/13). Thus, three WT1 subtypes were correlated with certain genetic and clinicopathological characteristics.

Signaling pathway of insulin-like growth factor-II as a target of molecular therapy for hepatoblastoma

AIM

To address the possibility that insulin-like growth factor (IGF)-II is a growth factor and its signaling pathway so as to develop a molecular therapy for hepatoblastoma.

METHODS

Huh-6 and HepG2, human hepatoblastoma cell lines, were used. IGF-II was added to the medium deprived of serum. Western blot analysis was performed to clarify the expression of IGF-I receptor (IGF-IR). Inhibitors of IGF-IR (piclopodophyllin, PPP), phosphatidyl-inositol (PI) 3-kinase (LY294002 and Wortmannin), or mitogen-activated protein (MAP) kinase (PD98059) were added to unveil the signaling pathway of IGF-II. Cells were analyzed morphologically with hematoxylin-eosin staining to reveal the mechanism of suppression of cell proliferation.

RESULTS

IGF-II stimulated cells proliferated to 2.7 (269%+/-76%) (mean+/-SD) (Huh-6) and 2.1 (211%+/-85%) times (HepG2). IGF-IR was expressed in Huh-6 and HepG2. PPP suppressed the cell number to 44%+/-11% (Huh-6) and 39%+/-5% (HepG2). LY294002 and Wortmannin suppressed the cell number to 30%+/-5% (Huh-6), 44%+/-0.4% (HepG2), 49%+/-1.0% (Huh-6) and 46%+/-1.1% (HepG2), respectively. PD98059 suppressed the cell number to 33%+/-11% for HepG2 but not for Huh-6. When cell proliferation was prohibited, many Huh-6 and HepG2 cells were dead with pyknotic or fragmented nuclei, suggesting apoptosis.

CONCLUSION

IGF-II was shown to be a growth factor of hepatoblastoma via IGF-I receptor and PI3 kinase which were good candidates for target of molecular therapy.

An evaluation of the role of insulin-like growth factors (IGF) and of type-I IGF receptor signalling in hepatocarcinogenesis and in the resistance of hepatocarcinoma cells against drug-induced apoptosis

Strong evidence emphasizes the role of the insulin-like growth factor (IGF) system and of type-I IGF receptor (IGF-IR) signalling in tumourigenesis. In this connection: (i) changes in the expression pattern of components of the IGF system (autocrine/paracrine expression of IGF-I and -II, overexpression of IGF-IR, decreased expression of IGF-binding proteins (IGFBPs) and of type-II IGF receptor/cation-independent mannose-6-phosphate receptor (IGF-II/M6PR) and (ii) increased serum concentrations of proteases that cleave the IGFBPs (e.g., cathepsin D) were observed in patients with hepatocellular carcinomas (HCC), in human hepatoma cell lines and in their conditioned culture medium, as well as in rodent models of hepatocarcinogenesis. Accordingly, studies carried out with animal models do suggest that the IGF system and IGF-IR signalling may play a role in hepatocarcinogenesis and in deregulated proliferation and apoptosis of HCC cells. Finally the instrumental role of Raf/MEK/ERK, one of the signalling cascades stimulated by IGF-IR, in anthracycline-induced apoptosis of HepG2 and Huh-7 human hepatoma cell lines emphasizes that care must be taken when designing combinations of antitumoural molecules for antineoplastic treatment. This review addresses the putative roles of the IGF system in primary HCC, with a special focus on the underlying molecular mechanisms. In a second part it emphasizes the putative interference of IGF-IR signalling with chemotherapeutic drug-induced apoptosis in human hepatoma cells.

Expression profiling and differential screening between hepatoblastomas and the corresponding normal livers: identification of high expression of the PLK1 oncogene as a poor-prognostic indicator of hepatoblastomas

Hepatoblastoma is one of the most common malignant liver tumors in young children. Recent evidences have suggested that the abnormalities in Wnt signaling pathway, as seen in frequent mutation of the beta-catenin gene, may play a role in the genesis of hepatoblastoma. However, the precise mechanism to cause the tumor has been elusive. To identify novel hepatoblastoma-related genes for unveiling the molecular mechanism of the tumorigenesis, a large-scale cloning of cDNAs and differential screening of their expression between hepatoblastomas and the corresponding normal livers were performed. We constructed four full-length-enriched cDNA libraries using an oligo-capping method from the primary tissues which included two hepatoblastomas with high levels of alpha-fetoprotein (AFP), a hepatoblastoma without production of AFP, and a normal liver tissue corresponded to the tumor. Among the 10,431 cDNAs randomly picked up and successfully sequenced, 847 (8.1%) were the genes with unknown function. Of interest, the expression profile among the two subsets of hepatoblastoma and a normal liver was extremely different. A semiquantitative RT-PCR analysis showed that 86 out of 1188 genes tested were differentially expressed between hepatoblastomas and the corresponding normal livers, but that only 11 of those were expressed at high levels in the tumors. Notably, PLK1 oncogene was expressed at very high levels in hepatoblastomas as compared to the normal infant's livers. Quantitative real-time RT-PCR analysis for the PLK1 mRNA levels in 74 primary hepatoblastomas and 29 corresponding nontumorous livers indicated that the patients with hepatoblastoma with high expression of PLK1 represented significantly poorer outcome than those with its low expression (5-year survival rate: 55.9 vs 87.0%, respectively, p=0.042), suggesting that the level of PLK1 expression is a novel marker to predict the prognosis of hepatoblastoma. Thus, the differentially expressed genes we have identified may become a useful tool to develop new diagnostic as well as therapeutic strategies of hepatoblastoma.

Pilot study of elevated levels of insulin-like growth factor-binding protein-2 as indicators of hepatocellular carcinoma

BACKGROUND/AIMS

Insulin-like growth factor-binding protein-2 (IGFBP-2) is expressed in many malignant tissues, and elevated serum levels can be indicators of tumour activity in addition to conventional tumour markers. Our aim was to evaluate the role of IGFBP-2 levels together with insulin-like growth factor (IGF)-I, IGF-II and IGFBP-3 in the diagnostic work-up of patients with hepatocellular carcinoma (HCC).

METHODS

In 50 (39 males, 11 females) histologically confirmed and TNM-graded patients with HCC who had not received adjuvant chemotherapy, the basal serum levels of IGF-I, IGF-II, IGFBP-3, IGFBP-2 and alpha-fetoprotein (AFP) were measured. The median age of the patients was 66 (37-84) years, body mass index was normal (25 (35-16) kg/m2).

RESULTS

The levels of IGF-I, IGF-II and IGFBP-3 were diminished, as is the case when nutrition, hepatic function and growth hormone (GH) secretion are decreased. The levels of AFP and IGFBP-2 were markedly high. In 37 cases, IGFBP-2 levels were above the age-related norm, and in 40 cases AFP levels were also elevated. In 3 cases, both AFP and IGFBP-3 were normal, and in 4 cases AFP was high but IGFBP-2 normal, whereas in 10 cases AFP was normal but IGFBP-2 was high.

CONCLUSIONS

In addition to AFP, IGFBP-2 appears to be a suitable marker for the evaluation of the serological status of HCC patients. A longitudinal study during disease management is required to assess the full potential of IGFBP-2 measurements as a marker.

Elevated insulin, proinsulin and insulin-like growth factor-binding protein-1 in liver disease

Insulin-like growth factor-binding protein-1 (IGFBP-1) is one of six soluble binding proteins that regulate the actions of the insulin-like growth factors (IGFs). Liver is the major source of IGFBP-1 in non-pregnant humans. In normal physiology, IGFBP-1 transcription is potently inhibited by insulin and serum levels are limited by a rapid clearance rate. Elevated levels of IGFBP-1 in liver disease have been attributed to insulin resistance; however, the relationships between these analytes have not been defined. We studied insulin, proinsulin and IGFBP-1 in normal subjects (NL, N=47, 43+/-12 yr), cirrhosis (CIR, N=29, 54+/-14 yr), hepatocellular carcinoma (HCC, N=42, 61+/-11 yr), and other liver tumors (TUM, N=8, 60+/-17 yr). All three analytes were significantly increased in liver disease (mean+/-SEM; p-values relative to normals): IGFBP-1 (NL 24+/-4 ng/ml; CIR 235+/-53, p<0.0001; HCC 505+/-105, p<0.0001; TUM 118+/-36, p<0.0001), insulin (NL 72+/-4 pM; CIR 261+/-62, p<0.0002; HCC 180+/-25, p<0.0001; TUM 189+/-58, p<0.0001), proinsulin (NL 6.5+/-0.7 pM; CIR 36.8+/-7.7, p<0.0001; HCC 26.2+/-3.8, p<0.0001; TUM 32.1+/-9.7, p<0.0001). The ratio of proinsulin to insulin was also significantly elevated in liver disease. A typical curvilinear inverse relationship of insulin and IGFBP-1 was observed, but was shifted several fold higher for the liver disease groups. Our results demonstrate that insulin and proinsulin are elevated in liver disease. However, these elevations are paradoxically accompanied by elevated IGFBP-1 levels, indicating disruption of normal regulatory mechanisms. IGFBP-1 is postulated to play a dynamic role in metabolic substrate utilization via regulation of free IGF. Therefore, inappropriate elevation of IGFBP-1 could play an important role in the metabolic disturbances associated with liver disease.

Transcriptional profiling in hepatoblastomas using high-density oligonucleotide DNA array

Hepatoblastoma is a common hepatic tumor in children. Although evidence regarding cytogenetic and molecular genetic alterations in hepatoblastomas has been reported, the molecular events affecting the biologic characteristics of this tumor, including alterations of the gene expression profile, are largely unknown. To identify genes differentially expressed between nondiseased liver (NDL) and hepatoblastoma tumor (HBT), we analyzed the gene expression profile in 14 NDL and 16 HBT samples using a high-density oligonucleotide DNA array. Using Mann-Whitney U test followed by the k-nearest neighbor algorithm, we identified 26 genes (predictor genes) that were able to assign unknown samples derived from NDL and HBT to either the NDL group or HBT group with 100% accuracy. Using a cross-validation approach, we confirmed that the k-nearest neighbor algorithm assigned the particular samples derived from NDL and HBT to either the NDL or HBT group with 93.3% (28/30 samples) accuracy. In the 26 predictor genes, we found alteration of the expression of genes regulating cell division (NAP1L1, STMN1, CCNG2, and CDC7L1) and tumor cell growth (IGF2 and IGFBP4) in HBT. Four predictor genes (ETV3, TPR, CD34, and NR1I3) were also found to be mapped to the chromosomal region 1q21 approximately q32, which has been reported to be frequently involved in the development of hepatoblastoma. The findings obtained in this study suggest that alteration of the expression of some genes regulating cell division and tumor cell growth may be characteristics of the gene expression profile in HBT, and that alteration of the expression of the four predictor genes mapped to chromosomal region 1q21 approximately q32 may also contribute to the differences in gene expression profile between NDL and HBT.

Insulin-like growth factor binding protein-1 over-expression in transgenic mice inhibits hepatic preneoplasia

Insulin-like growth factor binding protein-1 (IGFBP-1) is synthesized in the liver and regulates the mitogenic effects of the insulin-like growth factors (IGFs). The evidence that IGFBP-1 plays a role in hepatocarcinogenesis, however, is equivocal. We have, therefore, investigated the development of preneoplastic hepatic lesions in transgenic mice in which the human IGFBP-1 gene is under the control of the mouse metallothionein promoter. The lesions were induced by treating 15-d-old male mice with a single intraperitoneal injection of 5 mg/kg diethylnitrosamine (DENA). Lesions were scored when the mice were 28 wk of age. Quantitative microscopy of liver sections revealed that significantly fewer transgenic mice treated with zinc to activate the transgene had focal lesions compared to either transgenic mice not treated with zinc or wild-type mice treated with zinc (36.4% versus 85.7% and 83.3%, respectively, P < 0.05 in each case). Zinc-treated transgenic mice also had significantly fewer lesions per liver (11.5 +/- 5.0 versus 74.7 +/- 18.4 and 59.4 +/- 15.6, respectively, P < 0.01 in each case) and a smaller percentage of liver volume occupied by lesions (0.2 +/- 0.1 versus 1.4 +/- 0.3 and 1.1 +/- 0.4 respectively, P < 0.05 in each case). Immunohistochemical staining showed that both IGF-I and IGF-II were overexpressed in most of the lesions. These results show that expression of the IGFBP-1 transgene leads to a marked inhibition of hepatic preneoplasia, possibly by decreasing the mitogenic activity of IGF-I and/or IGF-II. This study adds new evidence to the notion that the IGF axis plays an important role in liver cancer development.

Decreased expression of the mannose 6-phosphate/insulin-like growth factor-II receptor promotes growth of human breast cancer cells

BACKGROUND

Loss or mutation of the mannose 6-phosphate/insulin-like growth factor-II receptor (M6P/IGF2R) has been found in breast cancer. However, whether or not decreased levels of functional M6P/IGF2R directly contribute to the process of carcinogenesis needs to be further verified by functional studies.

METHODS

In this study, using viral and ribozyme strategies we reduced the expression of M6P/IGF2R in human breast cancer cells and then examined the effect on growth and apoptosis of these cells.

RESULTS

Our results showed that infection of MCF-7 cells with the adenovirus carrying a ribozyme targeted against the M6P/IGF2R mRNA dramatically reduced the level of transcripts and the functional activity of M6P/IGF2R in these cells. Accordingly, cells treated with a ribozyme exhibited a higher growth rate and a lower apoptotic index than control cells (infected with a control vector). Furthermore, decreased expression of M6P/IGF2R enhanced IGF-II-induced proliferation and reduced cell susceptibility to TNF-induced apoptosis.

CONCLUSIONS

These results suggest that M6P/IGF2R functions as a growth suppressor and its loss or mutation may contribute to development and progression of cancer. This study also demonstrates that adenoviral delivery of the ribozyme provides a useful tool for investigating the role of M6P/IGF2R in regulation of cell growth.

The IGF axis and hepatocarcinogenesis

Deregulation of the insulin-like growth factor (IGF) axis, including the autocrine production of IGFs, IGF binding proteins (IGFBPs), IGFBP proteases, and the expression of the IGF receptors, has been identified in the development of hepatocellular carcinoma (HCC). Characteristic alterations detected in HCC and hepatoma cell lines comprise the increased expression of IGF-II and the IGF-I receptor (IGF-IR), which have emerged as crucial events in malignant transformation and the growth of tumours. Alterations of IGFBP production and the proteolytic degradation of IGFBPs resulting in an excess of bioactive IGFs, as well as the defective function of the IGF degrading IGF-II/mannose 6-phosphate receptor (IGF-II/M6PR), may further potentiate the mitogenic effects of IGFs in the development of HCC.

Expression levels of insulin-like growth factor binding proteins and insulin receptor isoforms in hepatoblastomas

Hepatoblastoma, a rare pediatric liver tumour, is a poorly understood disease. While expression studies for some members of the Insulin-like growth factor axis have been studied in hepatoblastoma, a systematic analysis of the IGF-axis has not been carried out. We have examined a series of hepatoblastomas with matched normal liver tissue for gene expression differences with emphasis on members of the insulin-like growth factor binding proteins. The expression profiles obtained reveal that the expression of these genes are altered in these tumors. The results indicate that the IGF-axis is seriously disturbed in the tumors.

Comparative genomic hybridization reveals population-based genetic alterations in hepatoblastomas

Hepatoblastoma is a malignant paediatric liver tumour. In order to approach the genetic background of this malignancy we have screened a panel of eighteen cases from Europe and Japan for chromosomal imbalances using comparative genomic hybridization (CGH). The most frequent losses included chromosomal regions 13q21-q22 (28%) and 9p22-pter (22%), while the most frequent gains occurred on 2q23-q24 (33%), 20q (28%) and 1q24-q25 (28%). A significant difference in CGH alterations between the tumours from patients of Caucasian and Japanese was revealed where loss of 13q was found only in the Japanese samples. In conclusion, the findings indicate several candidate regions for suppressor genes and oncogenes potentially involved in the hepatoblastomas of different ethnic origin.