Monitoring One-carbon metabolism by mass spectrometry for early diagnosis of cirrhosis and HCC

Abstract

Introduction: Liver cancer represents one of the most frequent causes of death by cancer, ranked as the sixth most prevalent and the second in lethality. Hepatocellular carcinoma (HCC) is the predominant type of liver cancer and presents an increasing incidence during the last years. Late diagnosis is one of the reasons explaining the low survival rate of HCC patients (5 years survival after diagnosis below 20%). Remarkably, 80% of HCC cases develop in cirrhotic tissue (1). Main risk factors for HCC are well known and include hepatitis B and C viral infections or abusive alcohol consumption. However, the underlying molecular mechanisms remain unknown and its research will lead to the characterization of new biomolecular markers for the early diagnosis, prognosis and therapy of HCC. Metabolic remodeling is a common feature among several hepatic disorders, from steatosis to HCC (2). Tumoral hepatocytes modify their metabolism to satisfy cancer’s proliferative requirements. One-carbon metabolism (OCM) plays a fundamental role maintaining the differentiation and quiescent state of hepatocytes, and is recognized as the link between intermediate metabolism and epigenetic regulation. Owing to these reasons, it might be a potential source of biomarkers for early diagnosis and prognosis of HCC. Accordingly, it has been demonstrated that some OCM enzymes are differentially expressed in murine HCC models (3). Materials and methods: We have developed a robust targeted mass spectrometry-based method, using SRM mode (Selected Reaction Monitoring), for the systematic quantification of 13 enzymes that participate in OCM. For this purpose, purified synthetic heavy standard peptides, as well as OCM recombinant proteins have been used. Sixty-four human liver samples, including 28 control samples, 21 tumoral samples and15 cirrhotic samples have been used. Results and conclusions: We have demonstrated that there is a profound remodeling of the OCM cycle in HCC versus control samples, while cirrhotic samples tend to show intermediate expression levels between both physiological situations. Machine learning- based analysis of our results suggests that monitoring a panel of functionally related proteins might be useful for future clinical developments and improve the management of HCC patients. However, further experiments with larger cohorts are required to confirm these findings. References 1) Ryerson, A. B., et al (2016). Annual Report to the Nation on the Status of Cancer, 1975-2012, featuring the increasing incidence of liver cancer. Cancer, 122(9), 1312-1337. 2) Vander Heiden, et al (2009). Understanding the Warburg effect: the metabolic requirements of cell proliferation. Science, 324(5930), 1029-1033 3) Mora, M. I., Corrales, F. J., et al (2017). Prioritizing popular proteins in liver cancer: remodelling one-carbon metabolism. Journal of proteome research, 16(12), 4506-4514.