Glutathione, ascorbic acid and antioxidant enzymes in the tumor tissue and blood of patients with oral squamous cell carcinoma.

BACKGROUND Oral squamous cell carcinoma is one of the most common cancers in the world. Reactive oxygen species are postulated to be involved in neoplastic transformation. The antioxidant defence system limits cell injury induced by reactive oxygen species. Oxidative stress occurs when there is an imbalance between the production of reactive oxygen species and a cell's oxidant capacity or when there is a decrease in this capacity. This stress may cause mutagenesis, cytotoxicity and changes in gene expression that initiate or promote carcinogenesis. OBJECTIVES The present study was conducted to investigate whether tumor tissue and blood of patients with oral squamous cell carcinoma have altered antioxidants levels. METHODS Levels of antioxidants such as reduced glutathione (GSH) and ascorbic acid (AA) and the activities of antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase (GPx), glutatione reductase (GR), were estimated in the tumor tissue and blood of 18 oral squamous cell carcinoma patients and in 20 healthy subjects as control. RESULTS Significantly increased levels of GSH, GPx, GR and AA and significantly decreased activity of SOD were observed in tumor tissue (p < 0.001) and in tumor-free tissue of oral cancer patients as compared with healthy subjects. In contrast, decrease in antioxidants (GSH, GPx, GR and AA p < 0.001, SOD p < 0.05 respectively) was observed in the blood of oral cancer patients, as compared with healthy subjects. CONCLUSION The low levels of antioxidants in the blood of oral cancer patients may be due to their increased utilization to scavenge lipid peroxides as well as their sequestration by tumor cells. The enhanced antioxidant capacities in tumor tissues can make them less susceptible to oxidative stress, conferring a selective growth advantage on tumor cells. These finding suggest that normalization of the levels of these antioxidants might be used to reduce oral tumor malignancy.