SOD1 and neoplasm: CTX chemotherapy further intensifies oxidative stress in tumor-bearing mice as it furthers reduces serum/tissue SOD activity (which is consistent with a previous report that CTX can decrease activity of SOD of liver34), increases serum LDH activity (which has been associated with more serious toxicity of CTX35), and elevates serum MDA contents (which is consistent with a previous finding of increased levels of MDA following CTX treatment32).