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Several studies have demonstrated that the direct cytotoxic effect of ascorbic acid on various types of cancer cells is mediated through a chemical reaction that generates hydrogen peroxide.[1,7,13,14] Treating colon cancer cells with 2 m M to 3 m M of ascorbic acid resulted in downregulation of specificity protein (Sp) transcription factors, iron metabolism disruption, and Sp-regulated genes involved in cancer progression.[10,15] One study suggested that ascorbate-mediated prostate cancer cell death may occur through activation of an autophagy pathway. Differences in chemosensitivity to ascorbate treatment in breast cancer cell lines may depend on expression of the sodium -dependent vitamin C transporter 2 (SVCT-2). Research has suggested that pharmacological doses of ascorbic acid enhance the effects of arsenic trioxide on ovarian cancer cells, gemcitabine on pancreatic cancer cells, and combination treatment of gemcitabine and epigallocatechin-3-gallate (EGCG) on mesothelioma cells. Findings from one study reported in 2012 suggested that high-dose ascorbate increases radiosensitivity of glioblastoma multiforme cells, resulting in more cell death than from radiation alone. However, not all studies combining vitamin C with chemotherapy have shown improved outcomes.
Treating leukemia and lymphoma cells with dehydroascorbic acid (the oxidized form of vitamin C that increases levels of intracellular ascorbic acid) reduced the cytotoxic effects of various antineoplastic agents tested, including doxorubicin, methotrexate, and cisplatin (relative reductions in cytotoxicity ranged from 30% to 70%). In another study, multiple myeloma cells were treated with bortezomib and/or plasma obtained from healthy volunteers who had taken vitamin C supplements.
This summary contains the following key information: Many of the medical and scientific terms used in this summary are hypertext linked (at first use in each section) to the NCI Dictionary of Cancer Terms, which is oriented toward nonexperts.
During vitamin C therapy, the patients used additional treatments, including vitamins, minerals, and botanicals.
A case report published in 1975 detailed one of the patients who had experienced tumor regression. Diagnosed with reticulum cell sarcoma, the patient exhibited improvement in well-being and resolution of lung masses after being treated with ascorbic acid.
When the patient's daily dose of ascorbic acid was reduced, some of signs of the disease returned; however, remission was achieved again after the patient reverted to the higher initial dose.
Fourteen subjects entered the study and planned to receive IV gemcitabine (1,000 mg /m over 30 minutes, once a week for 7 weeks), oral erlotinib (100 mg daily for 8 weeks), and IV ascorbate (50 g/infusion, 75 g/infusion, or 100 g/infusion 3 times per week for 8 weeks).
Minimal adverse effects were reported for ascorbic acid treatment.