RESUMO
<p><b>OBJECTIVE</b>To explore the role of oxidative stress and the antioxidant protein thioredoxin in the tumorigenesis and progression of gastric cancer.</p><p><b>METHODS</b>The plasma levels of adenosine deaminase (ADA), glutathione peroxidase (GPX), superoxide dismutase (SOD), and advanced oxidation protein products (AOPP) were determined by colorimetry, and the plasma levels of thioredoxin were determined by enzyme-linked immunosorbent assay (ELISA) in 48 gastric cancer patients and 30 healthy subjects. RT-PCR assay was employed to examine the expression levels of thioredoxin mRNA in the tissue samples of the patients.</p><p><b>RESULTS</b>Compared with the healthy controls, patients with gastric cancer had significantly increased plasma levels of ADA and AOPP (P<0.05), decreased plasma GPX level (P<0.05), and similar plasma SOD levels. The plasma levels of thioredoxin were significantly higher in patients with gastric cancer than in the healthy controls (P<0.05). Thioredoxin levels was not associated with gender, age, degree of tumor cell differentiation, invasion depth, or lymph node metastasis (P>0.05), but was correlated to distant tumor metastasis (P<0.05). The expression of Trx mRNA was significantly higher in gastric carcinoma than in normal gastric tissue (P<0.05).</p><p><b>CONCLUSION</b>Gastric cancer patients have high levels of oxidative stress and thioredoxin expression, and the latter is related to distant metastasis of the tumor.</p>