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Vitamin C May Reduce Chemotherapy Effectiveness

Results may be due to protective effect of supplemental vitamin on cells' mitochondria

THURSDAY, Oct. 2 (HealthDay News) -- Vitamin C supplementation may reduce the efficacy of a wide range of chemotherapy agents by protecting mitochondria within the cells from damage, according to research published in the Oct. 1 issue of Cancer Research.

Mark L. Heaney, M.D., Ph.D., of Memorial Sloan-Kettering Cancer Center in New York City, and colleagues tested doxorubicin, cisplatin, vincristine, methotrexate and imatinib on leukemia and lymphoma cell lines that were either pretreated with dehydroascorbic acid or left untreated. The cytotoxicity of all the drugs was reduced in pretreated cells, with relative reductions in cytotoxicity of 30 to 70 percent, and less cytotoxicity in cells with higher concentrations of vitamin C.

The researchers report that, in mice given tumors with lymphoma cells, those treated with dehydroascorbic acid two hours before doxorubicin administration had substantially larger tumors at 32 days than mice given doxorubicin alone. Further experimentation found that vitamin C can inhibit mitochondrial membrane depolarization, which the tested antineoplastic agents cause.

"It was notable that the concentration of vitamin C measured in the tumors of the mice in this study was similar to the concentration of vitamin C that can be achieved in human leukocytes with oral vitamin C supplementation, suggesting that our study conditions were relevant to clinical conditions. Therefore, it is possible that vitamin C supplementation may alter the effectiveness of commonly used chemotherapy agents and adversely influence treatment outcome," the authors conclude.

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