Acyl-CoA thioesterase 9 promotes tumour growth and metastasis through reprogramming of fatty acid metabolism in hepatocellular carcinoma

Acyl-CoA thioesterase 9 (ACOT9) is a critical regulator of cellular utilization of fatty acids by catalysing the hydrolysis of acyl-CoA thioesters to non-esterified fatty acid and coenzyme A (CoA). Recently, ACOT9 was reported to participate in the pathogenesis of non-alcoholic liver disease (NAFLD), which arises from aberrant lipid metabolism and serves as a risk factor for hepatocellular carcinoma (HCC). However, the functions of ACOT9 in carcinogenesis and aberrant lipid metabolism in HCC remain unexplored. Here, we found that ACOT9 expression is significantly elevated in HCC at least partially due to the down-regulation of miR-449c-3p. Upregulation of ACOT9 is closely associated with poor prognosis for patients with HCC. Knockdown of ACOT9 expression in HCC cells significantly decreased cell proliferation, colony formation, migration and invasion, mainly through suppression of G1-to-S cell cycle transition and epithelial-to-mesenchymal transition (EMT). By contrast, forced ACOT9 expression promoted HCC growth and metastasis. In addition, we found that ACOT9 reprogrammed lipid metabolism in HCC cells by increasing de novo lipogenesis. Furthermore, we demonstrated that increased lipogenesis was involved in ACOT9-promoted HCC growth and metastasis. Altogether, we demonstrate that ACOT9 plays a critical oncogenic role in the promotion of tumour growth and metastasis by reprogramming lipid metabolism in HCC, indicating ACOT9 as a potential therapeutic target in treatment of HCC.