B3GNT9-mediated O-glycosylation reprograms fatty acid metabolism in peroxisomes to promote invasion progression of peritumoral glioma cells.

Glioblastoma (GBM) is a highly aggressive brain tumor characterized by rapid recurrence and invasion, particularly in the peritumoral brain zone (PBZ), a critical site for tumor spread. Through RNA-seq of tumor core and PBZ tissues from GBM patients, we identified B3GNT9 as significantly upregulated in tumor cells within the PBZ. Bioinformatics analysis revealed that elevated B3GNT9 expression is associated with poor prognosis. Functional studies in glioblastoma cell lines, patient-derived cells, and animal models showed that B3GNT9 overexpression promotes cell proliferation, migration, and invasion. Mechanistically, RNA-seq and in vitro experiments demonstrated that B3GNT9 enhances glioma invasiveness by regulating the fatty acid metabolism gene ACOX1. Quantitative proteomics further identified PPARD as a key transcription factor mediating the B3GNT9-ACOX1 signaling axis. B3GNT9 increases mucin-type O-glycosylation in glioblastoma cells, facilitating O-GalNAc glycosylation of PPARD, which enhances its transcriptional activity and drives ACOX1 expression. High-throughput metabolomics and cellular, organoid, and animal studies revealed that activation of the B3GNT9-PPARD-ACOX1 axis reduces intracellular eicosapentaenoic acid (EPA) levels, promoting GBM invasiveness. These findings highlight the critical role of B3GNT9 and O-glycosylation in GBM progression, suggesting that targeting the B3GNT9-PPARD-ACOX1 axis could offer a promising therapeutic strategy to suppress GBM invasion and recurrence.