Abstract
Problem
To assess levels of oxidative damage: DNA adduct (8 oxo dG) and lipid peroxidation (4HNE) in follicular carcinomas (FTC), papillary carcinomas (PTC) and follicular adenomas (FTA) and their corresponding matched normal tissue.
Methods
Using tissue microarrays and immunohistochemistry, we examined expression levels of nuclear and cytoplasmic (mitochondrial) 8 oxo dG and 4HNE in matched tumor and normal tissues from 16 FTC's, 15 PTC's and 39 FTA's.
Results
There were higher levels of mitochondrial 8 oxo dG expression in the FTA, FTC and PTC tissue compared to matched normal tissue (p values <0.001, <0.001, <0.03, respectively). This trend remained significant for the levels of mitochondrial 4HNE expression in these groups. (All p values < 0.01.) The levels of nuclear 4HNE expression were elevated in FTA and FTC compared to matched normal tissue (p values <0.001, <0.01, respectively). In contrast, the levels of nuclear 8 oxo dG expression was only statistically significant in the FTA group compared to matched normal tissue. Comparing all three groups to each other, there were higher levels of nuclear 8 oxo dG expression in FTA compared to FTC (p<0.01). This difference was not detected for 4HNE expression.
Conclusion
Oxidative stress is a key feature of benign and malignant thyroid neoplasms. Interestingly, levels of oxidative damage are higher in adenoma compared to the carcinoma groups.
Significance
The higher levels of oxidative damage in thyroid adenoma compared to carcinoma groups indicates the accumulation of this damage is an early event which could promote further genomic instability with subsequent risk of mutational events.
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