Characterisation of Aberrant Metabolic Pathways in Hepatoblastoma Using Liquid Chromatography and Tandem Mass Spectrometry (LC-MS/MS)

SIMPLE SUMMARY: Hepatoblastoma is a rare childhood liver cancer with poor outcomes for high-risk patients. Better treatments and better ways of identifying patients who respond poorly to treatment are needed. This paper uses new methods for identifying chemicals or metabolites produced in the tumour. By comparing the profiles of these metabolites in tumour tissue versus normal liver tissue taken from the same patient, we demonstrated that some metabolites differ significantly in hepatoblastoma. This correlates with gene expression data, suggesting that we identified the metabolites correctly. We also stained tumour tissues for proteins (enzymes) that regulate transport of fatty acids into the mitochondria, which are the cell’s powerhouses. Taken together, our results indicate that tumour cells change the energy sources they use and rewire the cellular systems accordingly. Further work is required to verify this, but these leads could improve our understanding of the disease and lead to the development of novel therapies. ABSTRACT: Hepatoblastoma (HB) is a rare childhood tumour with an evolving molecular landscape. We present the first comprehensive metabolomic analysis using untargeted and targeted liquid chromatography coupled to high-resolution tandem mass spectrometry (LC-MS/MS) of paired tumour and non-tumour surgical samples in HB patients (n = 8 pairs). This study demonstrates that the metabolomic landscape of HB is distinct from that of non-tumour (NT) liver tissue, with 35 differentially abundant metabolites mapping onto pathways such as fatty acid transport, glycolysis, the tricarboxylic acid (TCA) cycle, branched-chain amino acid degradation and glutathione synthesis. Targeted metabolomics demonstrated reduced short-chain acylcarnitines and a relative accumulation of branched-chain amino acids. Medium- and long-chain acylcarnitines in HB were similar to those in NT. The metabolomic changes reported are consistent with previously reported transcriptomic data from tumour and non-tumour samples (49 out of 54 targets) as well as metabolomic data obtained using other techniques. Gene set enrichment analysis (GSEA) from RNAseq data (n = 32 paired HB and NT samples) demonstrated a downregulation of the carnitine metabolome and immunohistochemistry showed a reduction in CPT1a (n = 15 pairs), which transports fatty acids into the mitochondria, suggesting a lack of utilisation of long-chain fatty acids in HB. Thus, our findings suggest a reduced metabolic flux in HB which is corroborated at the gene expression and protein levels. Further work could yield novel insights and new therapeutic targets.