Glycosyltransferase B4GALNT1 promotes immunosuppression in hepatocellular carcinoma via the HES4-SPP1-TAM/Th2 axis

β-1,4-N-acetylgalactosaminyltransferase I (B4GALNT1) is a key glycosyltransferase for gangliosides. Its aberrant expression has been observed in various cancers, and its potential roles in tumor immunity were suggested recently. However, how B4GALNT1 regulate tumor progression and tumor immunity remains largely unknown. In this study, we aimed to investigate the roles of B4GALNT1 in hepatocellular carcinoma (HCC), particularly in reshaping the tumor immune microenvironment, and evaluate the potential beneficial effects of targeting B4GALNT1 in immunotherapy. Our data verified the aberrant upregulation of B4GALNT1 in HCC tumor tissues and tumor cells, which could be utilized as an independent prognostic factor and improve the predicting performance of traditional tumor node metastasis (TNM) system. We also demonstrated that B4GALNT1 increased the phosphorylation of Hes Family BHLH Transcription Factor 4 (HES4) via p38 mitogen-activated protein kinase (p38)/ c-Jun N-terminal kinase (JNK) signaling in tumor cells, thus increasing the transcriptional activity of HES4, which upregulated the synthesis and secretion of secreted phosphoprotein 1 (SPP1), modulated the composition of tumor-associated macrophages (TAMs) and T helper type 2 (Th2) cells, and eventually reshaped the immunosuppressive microenvironment. In addition, silencing B4GALNT1 was proved to enhance the tumor-killing efficiency of the programmed cell death protein 1 (PD-1)-targeting strategy in mouse model. In conclusion, this study evaluated B4GALNT1 as a prognostic predictor for HCC patients and revealed the mechanism of B4GALNT1 in microenvironmental remodeling, which extends the understanding of HCC progression and provides a novel auxiliary strategy for HCC immunotherapy.