Landscape of Somatic Alterations in Thai Pediatric Hepatoblastoma: Implications for Clinical Outcomes and Therapeutic Opportunities.

Background and Objectives: Hepatoblastoma (HB) is a rare pediatric liver cancer. Complete resection and chemotherapy are standard treatments, but many patients in developing countries present with unresectable tumors and show poor responses to conventional chemotherapy. Identifying somatic alterations in HB may help develop targeted molecular therapies. Materials and Methods: Exome sequencing was conducted on 34 HB patient samples to identify somatic mutations and copy number variations (CNVs) and to evaluate their relationships with clinical outcomes, including survival. Results: HB tumors showed a low mutational burden but a high rate of CNVs, averaging 181.5 CNVs compared to 3.6 somatic mutations per tumor. CNVs were enriched in pathways involved in transcription, differentiation, and development. The most common alterations were missense mutations in KMT2D (18%), CTNNB1 (12%), and MUC16 (3%). KMT2D mutations occurred more frequently than CTNNB1 mutations in this cohort. Patients with KMT2D or CTNNB1 mutations generally had better overall survival and longer disease-free intervals. Deletions of ZNF429 or FGD4 were linked to shorter survival in the cohort. Validation with an external dataset confirmed significant downregulation of FGD4 expression in HB samples, correlating with poorer survival. Conclusions: This study broadens the understanding of somatic alterations in HB patients, offering insights into the molecular mechanisms behind HB development and highlighting the potential of CNV profiling and FGD4 deletions as prognostic factors in HB.