FTO ‐mediated m6A modification of protein disulfide‐isomerase activates VEGFA – VEGFR2 to suppress programmed cell death in osteosarcoma

Osteosarcoma (OS) is a primary bone malignancy, and its progression can be hindered by inducing programmed cell death (PCD). Protein disulfide-isomerase (PDI) regulates cancer cell death; however, its functional role in OS remains unclear. P4HB expression was assessed in tumor tissues and cells from patients with OS using RT-qPCR. The effects of P4HB on OS cell lines were evaluated. Western blotting was used to assess the impact of P4HB on various forms of PCD (apoptosis, ferroptosis, and pyroptosis). Bioinformatics analysis identified the upstream and downstream mechanisms of P4HB in OS progression. A xenograft tumorigenesis study was performed to elucidate the role and mechanism of P4HB in OS progression. Elevated P4HB expression was observed in OS tissue samples and cell lines. Downregulation of P4HB suppressed OS cell growth, migration, and invasiveness and induced PCD. Functional enrichment analysis and experimental validation revealed that PDI upregulated vascular endothelial growth factor A (VEGFA) vascular endothelial growth factor receptor 2 (VEGFR2) signaling. Methylation analysis showed that the m6A demethylase fat mass and obesity-associated protein (FTO) decreased P4HB m6A levels and enhanced VEGFA-VEGFR2 signaling in OS cells. Moreover, FTO overexpression enhanced the proliferative, migratory, and invasive capabilities of OS cells and decreased PCD. Finally, FTO knockdown inhibited tumor growth and lung metastasis of OS by decreasing the activity of the PDI/VEGFA-VEGFR2 signaling axis. Mechanistically, FTO-mediated m6A modification of P4HB regulates PCD in OS through activation of this axis. © 2026 The Pathological Society of Great Britain and Ireland.