High-dose ascorbic acid prolongs the suppression of cell proliferation by enhancing intracellular oxidative stress-induced damage and inhibits invasion and adhesion in human fibrosarcoma HT-1080 cells.

Pharmacological vitamin C (VC) infusion therapy has shown efficacy against various cancer types; however, there are few reports on its effects on fibrosarcoma. This study investigated the impact of high-dose ascorbic acid (AsA), the reduced form of VC, on human fibrosarcoma HT-1080 cells. High-dose AsA (2-5 mM) markedly decreased HT-1080 cell viability compared with normal fibroblasts, indicating cancer cell selectivity. In contrast, dehydroascorbic acid (DehAsA), the oxidized form of AsA, exhibited no cytotoxicity toward cancer cells. Studies using D-AsA and AsA transport inhibitors demonstrated that intracellular AsA transport was not required for cytotoxicity in HT-1080 cells. Our results showed that high-dose AsA induced extracellular H₂O₂ production and increased intracellular H₂O₂, reactive oxygen species (ROS), and Fe2+ levels in HT-1080 cells compared with normal fibroblasts, suggesting that strong oxidative stress triggers actin disruption, ATP depletion, DNA damage, and reduced DNA synthesis. Additionally, a 1-h AsA exposure produced a sustained inhibitory effect on cell proliferation lasting at least 72 h. Moreover, high-dose AsA inhibited HT-1080 cell invasion and adhesion, with increased intracellular ROS likely contributing to these effects. These results indicate that high-dose AsA generates extracellular H₂O₂ and subsequently induces cancer cell-specific oxidative damage due to differences in intracellular H₂O₂ and Fe2+ levels, which differ between normal fibroblasts and HT-1080 cells. These actions lead to cancer cell-selective toxicity and prolonged growth-suppressive effects induced by high-dose AsA.