Small Extracellular Vesicle-Derived Nicotinamide Phosphoribosyltransferase (NAMPT) Induces Acyl-Coenzyme A Synthetase...

Tumour-derived small extracellular vesicles (sEV) are critical mediators within the tumour microenvironment (TME) and are known to regulate various metabolic pathways. In metastatic hepatocellular carcinoma (HCC), mass spectrometry protein analysis of HCC-derived sEV (HCC-sEV) identified an upregulation of nicotinamide phosphoribosyltransferase (NAMPT), a key enzyme in maintaining cellular nicotinamide adenine dinucleotide (NAD+) levels. Our study demonstrates that sEV-NAMPT enhances glycolysis, tumorigenesis, and metastasis in HCC. Specifically, sEV-NAMPT activates the NF-κB transcription factor through toll-like receptor 4 (TLR4), leading to elevated SLC27A4 expression. SLC27A4 functions primarily as a long-chain fatty acid transporter and acyl-CoA synthetase. Lipidomic and metabolomic analyses revealed a positive correlation between SLC27A4 and intracellular levels of triacylglycerol (TG) and dihydroxyacetone phosphate (DHAP). Increased TG levels enhance lipolysis via hepatic lipase and facilitate the conversion of glycerol-3-P to DHAP, an intermediate that bridges lipid metabolism and glycolysis. This study uncovers a novel regulatory axis involving sEV-NAMPT and SLC27A4 in glycolysis, independent of traditional fatty acid metabolism pathways. Clinically, targeting sEV-NAMPT with the inhibitor FK866 significantly inhibited tumour growth in various HCC in vivo models, highlighting the potential of sEV-NAMPT as both a biomarker and therapeutic target in HCC.