Glioblastoma is the most lethal intracranial malignant tumor, for which the five-year overall survival rate is approximately 5%. Here we explored the therapeutic combination of vitamin C and plasma-conditioned medium on glioblastoma cells in culture and as subcutaneous or intracranial xenografts in mice. The combination treatment reduced cell viability and proliferation while promoting apoptosis, and the effects were significantly stronger than with either treatment on its own. Similar results were obtained in the two xenograft models. Vitamin C appeared to upregulate aquaporin-3 and enhance the uptake of extracellular H 2 O 2 , while the combination treatment increased intracellular levels of reactive oxygen species including H 2 O 2 and activated the JNK signaling pathway. The cytotoxic effects of the combination treatment were partially reversed by the specific JNK signaling inhibitor SP600125. Our results suggest that the combination of vitamin C and plasma-conditioned medium has therapeutic potential against glioblastoma, and they provide mechanistic insights that may help investigate this and other potential therapies in greater depth. Our results lead us to propose a model in which vitamin C upregulates aquaporin-3, which drives uptake of extracellular H 2 O 2 from vitamin C oxidation and plasma-conditioned medium. [Display omitted] • Vitamin C and plasma-conditioned medium combined to inhibit glioblastoma via H 2 O 2. • 2.Vitamin C and plasma-conditioned medium combination treatment upregulated aquaporin-3. • 3.Combined effects involves activation of the JNK signaling path. [ABSTRACT FROM AUTHOR]