Investigating the importance of lipid metabolism in liver cancer

Obesity and its associated complications are an increasing global problem and are responsible for a huge burden of morbidity and mortality. Non-alcoholic fatty liver disease (NAFLD), the hepatic component of the metabolic syndrome, currently affects an estimated 25% of the world’s population, with 2% of those affected dying from a NAFLD-related cause, such as hepatocellular carcinoma (HCC) (Younossi et al. 2016). We reported recently that activation of AMP-activated protein kinase (AMPK) protects against NAFLD by inhibiting lipogenesis (Woods et al. 2017). We have extended these studies to show that in addition AMPK activation protects against tumor development in mouse models of HCC. An attractive hypothesis is that reduced lipid synthesis plays a major role in protection against NAFLD and subsequent cancer development. We aim to tackle this directly by using mice expressing a knock-in mutant of acetyl-CoA carboxylase (the rate limiting enzyme in fatty acid synthesis), which cannot be phosphorylated and inactivated by AMPK. The outcome of these studies will allow us to determine the importance of inhibiting lipogenesis in the protective effect of AMPK activation.

We will use metabolomic and lipidomic approaches to measure changes in both polar and lipid metabolites in normal and tumour liver tissue. Even when tumours are large enough to be dissected out separately, they may still include normal tissue, and so bulk-tissue measurements lose critical spatial information. To bridge this gap, we will make use of matrix assisted laser desorption ionisation (MALDI) mass spectrometry imaging (MSI), a transformative technique capable of the spatial mapping of biomolecules in a variety of tissue types with high sensitivity and resolution (Kompauer et al. 2017). Lipids in particular are well suited to analysis by MSI, due to their abundance in the cell and their propensity to ionise. We will therefore exploit this technology to explore metabolic heterogeneity within the tumour microenvironment and its surrounding tissue; and between tumours of different degrees of aggressiveness and/or stages of progression. In addition to studying the tumour microenvironment of liver cancer, we plan to identify the preferred carbon sources for lipid biosynthesis with and without AMPK activation. We will use stable isotope labelling of key carbon sources (e.g. glucose, glutamine, acetate) or labelled fatty acids to determine the incorporation of labelled building blocks in lipid biosynthesis across different time-points.

The ability to spatially and temporally visualise lipids across tissue, and overlay these “metabolic maps” with more traditional biochemical markers, offers tremendous potential for gaining novel insights into the protective mechanisms behind AMPK activation in liver cancer. Alongside these in vivo studies, human liver cell lines will be used to explore the underlying molecular mechanisms leading to key metabolic changes in response to AMPK activation. Changes in both polar and lipid metabolites will be determined using MS-based approaches, and respiration measured using the Seahorse XFe96 Analyser following modulation of AMPK (e.g. activation using pharmacological activators, inhibition by deletion of AMPK subunits by siRNA and/or CRISPR Cas9). Changes in expression and/or phosphorylation of candidate proteins will be monitored by Western blotting, together with corresponding measurement of gene expression determined by RT-PCR. These studies will complement the in vivo studies and establish whether the pathways are conserved in human cells.

To Apply: Please visit our website (https://lms.mrc.ac.uk/study-here/phd-studentships/lms-3-5yr-studentships/) to download an application form.