Pharmacological Vitamin C Plus Oncolytic Adenoviruses Orchestrate Immunogenic Tumor Ferroptosis

High-dose Vitamin C (VitC) substantially boosts the anti-tumor effect of oncolytic adenoviruses (oAds), but optimizing its therapeutic potential remains to be fully explored. This study aims to investigate the synergistic effects of VitC and oAds on tumor cell viability and the underlying mechanisms. The CCK-8 assay and Flow cytometry were employed to detect the viability and apoptosis of tumor cells treated with VitC, oAds and VitC plus oAds. The combination therapy increased the oncolytic effect by 25-fold in CT26 cells and 10-fold in 4T1 cells, highlighting that VitC could enhance the oncolytic effect of oAds. Intermittent injection of VitC, rather than continuous injection, combined with oAds, was applied to examine the anti-tumor effect in vivo. Tumor-bearing mice receiving intermittent VitC alongside oAds showed smaller tumor volume, tumor weight and longer survival compared to those receiving the monotherapy. Additionally, no remarkable side effects were observed, as indicated by H&E staining of vital organs. Mechanistically, VitC synergized with oAds to recruit CD8⁺ effector T cells. These lymphocytes released IFN-γ, which reduced the expression of SLC7A11, a subunit of cystine/glutamate antiporter, and ultimately triggered ferroptosis by the reduced GSH. In conclusion, our findings propose a novel administration strategy for VitC that effectively augments the oncolytic effect of oAds, thereby warranting further investigation into its potential clinical applications.