Targeting nitrogen metabolism in hepatocellular carcinoma.

Abstract

e15101 Background: Hepatocellular carcinoma (HCC) commonly develops in patients with cirrhosis, a condition associated with impaired hepatic ammonia clearance and systemic hyperammonemia. Although ammonia has traditionally been considered a byproduct of liver dysfunction, its direct role in tumor biology remains incompletely understood. We hypothesized that ammonia functions as an active metabolic substrate that promotes HCC aggressiveness through tumor-intrinsic mechanisms. Methods: Metabolic, molecular, and functional assays were performed in human and murine HCC models to evaluate ammonia uptake, downstream metabolic utilization, and effects on cancer stem cell phenotypes. Nitrogen isotope tracing was used to define the metabolic fate of ammonia-derived nitrogen. Genetic and pharmacologic approaches were employed to disrupt ammonia transport and metabolism. Clinical relevance was assessed using multivariable analyses of a large, clinically annotated HCC cohort with adjustment for liver function. Results: Ammonia was actively imported into HCC cells via the transporter SLC4A11 and utilized as a nitrogen source to support tumor metabolism. Ammonia uptake promoted cancer stem cell properties, including enhanced sphere formation, tumor initiation, and growth in vivo. Isotope tracing demonstrated incorporation of ammonia-derived nitrogen into downstream amino acid and nucleotide metabolic pathways. Disruption of ammonia transport or metabolism suppressed stemness and tumor growth. Clinically, elevated serum ammonia levels were independently associated with worse overall survival in HCC patients, even after controlling for liver function and disease stage. Conclusions: These findings redefine ammonia from a consequence of cirrhosis to an active, tumor-intrinsic metabolic driver of HCC progression. Ammonia import and utilization sustain cancer stem cell phenotypes and aggressive tumor behavior, identifying ammonia metabolism as a previously unrecognized and therapeutically actionable vulnerability in HCC. Given the availability of clinically approved ammonia-lowering agents, targeting ammonia may offer a novel strategy to improve outcomes in patients with HCC.