Oxidative DNA Lesion (8-hydroxydeoxyguanosine), 8-Oxoguanine DNA Glycosylase 1, and Antioxidant Status in Iranian Patients Diagnosed with High-grade Oral Squamous Cell Carcinoma
Introduction: This study reports the changes in serum total antioxidant status and tissue levels of oxidatively modified deoxyribonucleic acid (DNA) lesion (8-hydroxydeoxyguanosine [8-OHdG]) and 8-oxoguanine DNA glycosylase 1 (OGG1) in oral squamous cell carcinoma (OSCC). Materials and methods: Oral squamous cell carcinoma patients (n = 40) comprising of 80% pathologically well-differentiated and moderately differentiated and 20% poorly differentiated tumors were taken. Besides, blood samples and gingival biopsies (n = 35) from normal individuals were processed accordingly and considered as control. Plasma antioxidant capacity was estimated using ferric reducing antioxidant power (FRAP) assay. Tissue biopsies were processed for ribonucleic acid (RNA) expression of OGG1-specific messenger RNA (mRNA), and DNA samples were isolated for estimation of 8-OHdG levels using enzymelinked immunosorbent assay. Results: Results showed that the total antioxidant capacity (TAC) of plasma in OSCC patients was significantly depleted (reduced to about 25%) compared with normal individuals. 8-Oxoguanine DNA glycosylase 1 expression at mRNA levels showed that there is a twofold increase in OGG1 expression in oral cancer tissues compared with normal samples. The 8-OHdG formation in DNA showed that in DNA isolated from tumors, 8-OHdG was also increased (four- to fivefold; p = 0.03) compared with normal samples. However, there was a significant decline in TAC of plasma in one-third of OSCC patients compared with normal individuals. Conclusion: Overall results suggest that 8-OHdG level and OGG1 expression in OSCC patients are highly associated (r = 0.8; p = 0.001). A decline in FRAP in patients may also suggest that antioxidant factors play a major role in attenuation of DNA damage-repair system leading to progression of OSCC.
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