The discovery and validation of metabolites as candidate biomarkers for the diagnosis of hepatocellular carcinoma

Abstract

Hepatocellular carcinoma (HCC) constitutes a major disease burden worldwide. Much of its high mortality-to-incidence ratio can be attributed to late diagnosis, resulting in poor survival. Motivated by the need to develop a novel non-invasive diagnostic test to improve the chances of early diagnosis, this thesis makes use of metabonomic technologies to discover and validate metabolites as potential novel diagnostic markers for HCC. First, a systematic review of the literature on the topic was conducted to collate all published evidence of metabolites that were reported to be discriminatory for HCC. A bespoke risk of bias assessment tool was developed for metabonomic studies and a weighted score system was implemented to rank metabolites based on the strength of evidence. This resulted in a ranked list of metabolites with the greatest potential to be followed up for validation for each of the sample types (tissue, blood and urine). Then, validation of urinary metabolites with the greatest potential concluded from the systematic review was performed using data acquired from a UK cohort. None of the previously reported difference between HCC and cirrhosis groups could be reproduced, indicating the current lack of candidate markers specific for HCC detectable in urine. Finally, an exploratory analysis of serum 1H-NMR data from a UK and a Nigerian cohort was performed. Common and different alterations in metabolite levels between the two cohorts were compared. Glutamine-to-glutamate ratio was identified as a potential marker with the best discriminatory power between HCC and cirrhosis patients and this was validated using an independent cohort from the Gambia. This work adds to the ongoing effort to elucidate metabolites with the best potential to be further validated with the goal of developing a novel diagnostic test for HCC.