TMET-03. Inhibition of pentose phosphate pathway sensitized gliomas to temozolomide

Temozolomide (TMZ) is a standard chemotherapeutic agent used in combination with radiotherapy for glioblastoma. However, its therapeutic efficacy remains limited, and strategies to enhance TMZ sensitivity are needed. The pentose phosphate pathway (PPP), which is upregulated in glioblastoma, plays a critical role in maintaining redox homeostasis via NADPH production and supports tumor growth through nucleotide biosynthesis. We hypothesized that inhibition of the PPP would disrupt these functions and enhance the cytotoxic effect of TMZ. We investigated this hypothesis using glioblastoma cell lines. PPP inhibition was achieved using two agents: 6-aminonicotinamide (6AN), a glucose-6-phosphate dehydrogenase inhibitor, and oxythiamine (OT), a transketolase inhibitor. Antitumor effects were assessed by colony formation assays. Mechanistic studies evaluated intracellular NADPH levels, reactive oxygen species (ROS) production, and ferroptosis induction. Both 6AN and OT reduced colony formation as monotherapies. Notably, OT significantly potentiated TMZ-induced growth inhibition. This enhancement was associated with decreased NADPH levels, increased ROS production, and elevated lipid peroxidation indicative of ferroptosis. The addition of N-acetylcysteine (NAC), a ROS scavenger, attenuated the combined antitumor effect, supporting the role of oxidative stress in mediating the observed synergy. These findings suggest that inhibition of PPP can sensitize glioma cells to TMZ via ROS-mediated mechanisms, including ferroptosis. Targeting metabolic pathways such as the PPP may offer a promising approach to augment the therapeutic effects of TMZ in glioblastoma treatment.