Title: Oncometabolism
Funder: Cancer Research UK

Abstract: Glutamine and glutamate metabolism in brain and liver cancer: Glutamine and glutamate are instrumental to physiological processes, such as neurotransmission in the brain and ammonia homeostasis in the liver. At the same time, they are obligate substrates for anabolism of tumours originating in these organs, such as glioma and hepatocellular carcinoma. In particular, we are investigating the role of glutamine synthetase (GS) in the biology of glioblastoma and hepatocellular carcinoma. GS catalyses the ligation of glutamate and ammonia, and is the only known enzyme able to synthesise glutamine in mammalian cells. We previously showed that GS-derived glutamine provides the nitrogen required for nucleotide biosynthesis in glutamine-restricted glioblastoma, the most aggressive type of glioma. Currently, we are assessing the effects of GS interference on the metabolism and growth of human glioblastoma xenografts implanted orthotopically While in normal liver the expression of GS is strictly confined to pericentral hepatocytes, in liver tumours this metabolic zonation is disrupted. Liver tumours such as hepatoblastoma and hepatocellular carcinoma (HCC) with an overactive WNT/β-catenin signalling pathway show widespread and sustained GS expression. Based on this clinical observation, we are developing a β-catenin- and c-Myc-driven mouse model of HCC, in which the gene encoding glutamine synthetase is deleted conditionally. Of note, the amplification of c-Myc is an aberrant genetic event frequently occurring in HCC, and both β-catenin and c-Myc control glutamine metabolism. While an active β-catenin promotes the expression of GS in HCC, in various types of cancer c-Myc drives the expression of glutaminase (GLS), which catalyses glutaminolysis. By means of HPLC–mass-spectrometry–based metabolomics and cell biology approaches, we are studying the rewiring of carbon and nitrogen metabolism imposed by high GS expression, in murine and human models of liver cancer. This study will shed light on the metabolic features imposed by specific oncogenic mutations in liver cancer, and it will pave the way for the identification of metabolic targets with therapeutic potential in a genetically defined subset of patients with liver tumours. Rethinking cell culture media to achieve more physiologically relevant in vitro results: Despite it seeming obvious that the nutrient composition of culture medium affects the phenotypic behaviour of cells, as well as their response to the environment, and their epigenotype and genotype, very little attention has been focused on perfecting the formulation of historic media in recent years. Indeed, the vast majority of biomedical research employs commercially available growth media, based on the pioneering work done 60 years ago by Harry Eagle. However, these formulations were not designed to reproduce the physiological cellular environment, but rather to enable the continued culture of cells with minimal amount of serum (i.e. Minimal Essential Medium). Consequently, a standard culture medium known as DMEM is far apart from the nutrient levels found in normal human blood; for example, glucose in DMEM is at fivefold the normal glycaemia. A similar ratio applies to glutamine, the most abundant amino acid in circulation. Conversely, five non-essential amino acids normally circulating in blood are missing from DMEM. On this basis, we designed, developed and produced a cell culture medium with 53 nutrients and metabolites at the concentration normally found in human blood. This is among the first examples of cell culture medium formulated on physiological criteria. The newly formulated medium allows the culture of mammalian cells with reduced supplementation of FBS. It has been successfully tested in a variety of cell culture systems, including murine normal, stem and cancer cells, as well as established and primary human cancer cells derived from several tumour types. The availability of a physiologically relevant cell culture medium will reduce the inconsistency between in vitro and in vivo results, thus favouring more translational biomedical research.


Research activity codes: 2.1 BIOLOGICAL AND ENDOGENOUS FACTORS
Health categories: CANCER AND NEOPLASMS