Epigenetic footprint enables molecular risk stratification of hepatoblastoma with clinical implications
Background & Aims: Hepatoblastoma (HB) is a rare disease. Nevertheless, it is the predominant pediatric liver cancer, with limited therapeutic options for patients with aggressive tumors. Herein, we aimed to uncover the mechanisms of HB pathobiology and to identify new biomarkers and therapeutic targets in a move towards precision medicine for patients with advanced HB. Methods: We performed a comprehensive genomic, transcriptomic and epigenomic characterization of 159 clinically annotated samples from 113 patients with HB, using high-throughput technologies. Results: We discovered a widespread epigenetic footprint of HB that includes hyperediting of the tumor suppressor BLCAP concomitant with a genome-wide dysregulation of RNA editing and the overexpression of mainly non-coding genes of the oncogenic 14q32 DLK1-DIO3 locus. By unsupervised analysis, we identified 2 epigenomic clusters (Epi-CA, Epi-CB) with distinct degrees of DNA hypomethylation and CpG island hypermethylation that are associated with the C1/C2/C2B transcriptomic subtypes. Based on these findings, we defined the first molecular risk stratification of HB (MRS-HB), which encompasses 3 main prognostic categories and improves the current clinical risk stratification approach. The MRS-3 category (28%), defined by strong 14q32 locus expression and Epi-CB methylation features, was characterized by CTNNB1 and NFE2L2 mutations, a progenitor-like phenotype and clinical aggressiveness. Finally, we identified choline kinase alpha as a promising therapeutic target for intermediate and high-risk HBs, as its inhibition in HB cell lines and patient-derived xenografts strongly abrogated tumor growth. Conclusions: These findings provide a detailed insight into the molecular features of HB and could be used to improve current clinical stratification approaches and to develop treatments for patients with HB. Lay summary: Hepatoblastoma is a rare childhood liver cancer that has been understudied. We have used cutting-edge technologies to expand our molecular knowledge of this cancer. Our biological findings can be used to improve clinical management and pave the way for the development of novel therapies for this cancer. ; Instituto de Salud Carlos III PI09/00751 PI10/02082 PI13/02340 European Union (EU) 668596 826121 Agencia de Gestio D'Ajuts Universitaris de Recerca Agaur (AGAUR) 2019 FI_B01024 Associazione Italiana per la Ricerca sul Cancro (AIRC) C9380/A26813 Gilead Sciences European Union's Horizon 2020 research and innovation programme (HEPCAR) 667273-2 ICREA United States Department of Defense CA150272P3 United States Department of Health & Human Services National Institutes of Health (NIH) - USA NIH National Cancer Institute (NCI) Tisch Cancer Institute P30-CA196521 Samuel Waxman Cancer Research Foundation Spanish National Health Institute SAF2016-76390 Agencia de Gestio D'Ajuts Universitaris de Recerca Agaur (AGAUR) SGR-1358 2017-SGR-490 Ramon y Cajal program of the Ministry of Science and Innovation of Spain RYC-2010-07249 Miguel Servet program of the ISCIII CPII14/00021 CIBERehd CB06/04/0033