Increased B3GALNT2 in hepatocellular carcinoma promotes macrophage recruitment via reducing acetoacetate secretion and elevating MIF activity.

BACKGROUND: Hepatocellular carcinoma (HCC) ranks as the sixth most prevalent cancer and the third leading cause of tumor-related death, so it is urgently needed to discover efficient markers and targets for therapy. β-1,3-N-acetylgalactosaminyltransferase II (B3GALNT2) belongs to the β-1,3-glycosyltransferases (b3GT) family and has been reported to regulate development of both normal and tumor tissues. However, studies on the functions of B3GALNT2 in cancer are quite limited. Here we investigated the potential role of B3GALNT2 in HCC progression.

METHODS: Western blot, qPCR, and immunohistochemistry assays were performed to quantify the relative expression of B3GALNT2 in HCC. The functions of B3GALNT2 in tumor progression were evaluated in HCC cell lines and nude mice. Metabolomics analysis was applied to detect alternatively expressed small molecules. Enzyme activity assays were employed to determine the tautomerase activity of macrophage inhibitory factor (MIF).

RESULTS: For expression analysis, higher levels of B3GALNT2 were observed in tumor tissues compared with adjacent normal tissues, and upregulation of B3GALNT2 correlated with increased tumor size and worse overall survival. Changing levels of B3GALNT2 did not influence cell viability in vitro but promoted tumor growth via enhancing macrophage recruitment in vivo. Furthermore, acetoacetate was identified as a key molecule in B3GALNT2-mediated macrophage recruitment. Mechanistically, B3GALNT2 downregulated expression of enzymes involved in acetoacetate-related metabolism, and reduction of acetoacetate revived MIF activity, thus promoting macrophage recruitment.

CONCLUSIONS: This study evaluated B3GALNT2 as a tumor marker in HCC and revealed functions of B3GALNT2 in metabolic transformation and microenvironmental remodeling in HCC. Mechanistically, B3GALNT2 reduced expression of some metabolic enzymes and thus downregulated levels of secreted acetoacetate. This relieved the activity of MIF and enhanced macrophage recruitment to promote tumor growth.