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

Background: The association of birth defects and developmental alterations with pediatric cancer is a recognized long-standing global observation, although very few syndromes confer a high risk of hepatoblastoma development. Procedures: Here we describe the results of germline exome analysis of two syndromic patients with Hirschsprung disease who developed hepatoblastoma. Results: Germline variants of uncertain clinical significance (VUS) were disclosed in 28 genes that might be related to patients’ phenotypes. More importantly, germline VUS were detected in eight known cancer predisposition genes (APC, BRCA1, ERBB2, ERCC2, HRAS, ODC1, SERPINA6, and MCC). Additionally, our data disclosed two candidate genes with germline variants potentially contributing to the phenotype of these patients, namely, CEP164 and CYP1A1. The last one was the only gene presenting variants of uncertain significance in both patients. This gene encodes the most important xenobiotic-metabolizing enzyme of the placenta for which relevant inducible activity has been demonstrated throughout pregnancy. Conclusion: our data pointed out a set of genes that are enriched for pathways already related to cancer and developmental biology, suggesting they could have a broader role in cancer and congenital abnormalities. These results can help future studies to understand the biology of Hirschsprung disease and its association with hepatoblastoma.

Background: Hepatoblastoma (HB) is a rare embryonal liver tumor occurring in the pediatric population, and although intrinsic biological differences between tumors can impact HBs prognosis, few groups have studied this aspect. Given the crescent relevance of epigenetic mechanisms in the genesis and progression of these tumors, we aim to classify HB samples according to the different stages of liver development as well as DNA methylation machinery. Procedures: Using bioinformatics tools, we evaluate the expression of 24 genes associated with epigenetics and stages of hepatocyte differentiation as well as global DNA methylation to propose a stratification model for HB. Results: Based on the gene expression profiles of DNA methylation machinery and hepatocyte differentiation markers, HBs were clustered into three groups. Besides reinforcing the molecular heterogeneity of these embryonal tumors, our data propose that a panel of 13 genes can be used for HB stratification (TET1, TET2, TET3, DNMT1, DNMT3A, UHRF1, ALB, CYP3A4, TDO2, UGT1A1, AFP, HNF4A, and FOXA2). DNA methylation machinery exerts a key role in the characterization of HBs, directly reflected in diverse DNA methylation content. Moreover, we suggest that the group of HBs presenting similarity with differentiated livers, such as upregulation of mature hepatocyte markers, decreased expression of DNA methylation enzymes and higher global methylation levels are associated with a worse prognosis. Conclusions: HBs are heterogeneous tumors and our findings point out the role of the epigenetic machinery in the samples characterization, suggesting the need of new stratification system for patients with HBs.