Biozentrum (M. Hall group): The role of arginine metabolism in mTOR signaling during ageing and cancer
i. Objective of research: To dissect the role of arginine metabolism in mTOR signaling during ageing and cancer.
ii. Current state of the art: The mTOR signaling pathway controls cell growth and organismal ageing but is also frequently activated in hepatocellular carcinoma (HCC). Activation of mTOR requires amino acid sufficiency, in particular arginine. Alterations in amino acid metabolism in multiple cancers are increasingly apparent. However, how arginine metabolism is deregulated in and impacts HCC is not characterized. To better understand changes in amino acid metabolism, we profiled amino acid levels in tumors from an HCC mouse model with liver-specific deletion of the two tumor suppressors and mTOR inhibitors PTEN and TSC1 (L-dKO)1. While the levels of several amino acids were found to be decreased, arginine levels were specifically increased in the tumors, as compared to control liver tissue. Subsequent proteomic and transcriptomic analyses of L-dKO tumors and of HCC biopsies from human patients2 revealed deregulation of arginine metabolism. Arginine uptake was increased while arginine catabolism was decreased, thereby explaining the observed high levels of arginine. We will investigate how arginine metabolism changes affect tumor progression in vivo and how these alterations can be exploited for therapy.
iii. Research methodology and approach: We will perform tissue microarray analysis to determine how common the alterations of arginine metabolic enzymes are in HCC patients. To investigate how changes in expression of arginine metabolic enzymes affect arginine-related metabolites, we will perform metabolomic analyses of L-dKO tumors and human HCC biopsies. We will use liver cancer cell lines to investigate the effect of alterations in arginine metabolic enzymes on cancer cell growth, metabolism and mTORC1 activity. Our preliminary findings suggest that that changes in the expression of arginine metabolism enzymes are at the transcriptional level. We aim to explore which transcription factors and signaling pathways regulate arginine metabolic enzymes. Finally, to validate the role of arginine metabolic enzymes in HCC, we will overexpress or silence candidate genes in young L-dKO and control animals using liver-specific adeno-associated viruses and monitor tumor burden and mTORC1 activity. In particular, we aim to test the hypothesis that arginine metabolism is altered in HCC to sustain mTORC1 activity.
iv. Originality and innovative aspects of the ESR project: Using high-throughput proteomics and genomics approaches, we will dissect the role of arginine metabolism in HCC in mouse and human HCC allowing us to reveal new strategies in the treatment of HCC.
v. Integration of the ESR project to the overall research programme: Our ESR will work with the Amazentis group to test new nutraceuticals on L-dKO, with ProtATonce on the evaluation of proteomics markers and with the Garinis group to evaluate the arginine metabolism on NER progeroid animals.