Decreased expression of antioxidant enzymes is associated with aggressive features in ependymomas

The purpose of this study was to investigate the relationship between antioxidant enzyme expression and clinicopathological features in 67 ependymal tumors. We included into the analysis antioxidant enzymes (AOEs) and related proteins, such as, manganese superoxide dismutase (MnSOD), gammaglutamylcysteine synthetase catalytic and regulatory subunits (GLCL-C and GLCL-R), thioredoxin (Trx) and thioredoxin reductase (TrxR). Their expression was studied in 46 primary (10 grade I, 30 grade II and 6 grade III) and 21 recurrent (3 grade I, 12 grade II and 6 grade III) tumors. Immunoreactivity for MnSOD was found in 87%, GLCL-C in 74%, GLCL-R in 89%, Trx in 72%, TrxR in 54%, of primary tumors. Lower GLCL-C and GLCL-R expression was associated with higher tumor grade (P = 0.047 and 0.049, respectively). MnSOD, GLCL-C and TrxR expressions were significantly higher in tumors located in the spinal cord compared to those in the brain (P = 0.044, 0.046 and 0.004, respectively). In the primary tumors Trx-positivity was found to correlate significantly with patient survival. In univariate survival analysis patients whose tumors did not express Trx had shorter survival (P = 0.045) and there was even more significant association (P = 0.011) when only adults were included in the analysis (in the total material median follow-up time of Trx-positive tumors was 9.7 years and of Trx-negative 5.4 years). The results indicate that AOEs have several biological functions in ependymal tumors. Trx had important prognostic value: all adults with Trx-positive tumors were alive at follow-up (median 7.8 years).