NAMPT inhibition induces ferroptosis via mitochondrial metabolic reprogramming to enhance tumour immunogenicity in glioblastoma.

Ferroptosis has recently been recognised as an immunogenic form of regulated cell death. Nicotinamide phosphoribosyltransferase (NAMPT), a key enzyme in the NAD+ salvage pathway, is highly expressed in glioblastoma and represents a promising metabolic target. We investigated the effects of the NAMPT inhibitor GMX1778 on ferroptosis and tumour immunogenicity in glioblastoma cells. Mitochondrial NAD+ levels, SIRT3 activity, and ferroptosis-related markers were analysed by biochemical assays and western blotting. The PERK-CHOP pathway and markers of enhanced immunogenicity (calreticulin exposure, ATP release, HMGB1 release) were evaluated. The role of ferroptosis was verified using inducers and inhibitors. Macrophage polarisation was assessed in co-culture with treated tumour cells. In vivo immune responses were examined using a prophylactic vaccination model in GL261 glioma-bearing mice. NAMPT inhibition by GMX1778 depleted mitochondrial NAD+, suppressed SIRT3, and induced ROS accumulation with downregulation of GPX4, leading to ferroptosis. This was accompanied by strong activation of ER stress and increased markers of immunogenicity. Ferroptosis inducers amplified, while inhibitors suppressed, these responses. GMX1778-treated glioma cells promoted macrophage polarisation from an M2 to M1 phenotype. In vivo, GMX1778 pre-treatment significantly reduced intracranial tumour incidence and enhanced anti-tumour immune responses in mice. NAMPT inhibition induces ferroptosis via mitochondrial metabolic reprogramming and subsequently enhances tumour immunogenicity through ER stress activation. These findings highlight a novel metabolic-immune mechanism and suggest that NAMPT inhibitors could serve as promising agents for glioblastoma therapy.