EXPRESSION OF MANGANESE SUPEROXIDE-DISMUTASE IN ESOPHAGEAL AND GASTRIC CANCERS

The tumor-killing activity of radiotherapy and chemotherapy for cancer is closely associated with the production of active oxygen, and the r elation between therapeutic resistance and active oxygen scavengers pr oduced by the tumor itself is gaining more attention. It is considered that manganese superoxide dismutase (MnSOD) protects host cells from oxidative stress, in synergy with other antioxidant enzymes. In this s tudy, we used a quantitative polymerase chain reaction assay to measur e MnSOD mRNA in resected specimens from patients with esophageal and g astric cancers. In both esophageal and gastric cancers, the level of M nSOD mRNA was significantly elevated in cancer tissue compared to non- cancer tissue (P < 0.01). In gastric cancer tissue, the MnSOD mRNA lev el was significantly higher than in esophageal cancer tissue (P < 0.01 ). The significance of MnSOD in cancer tissue was investigated further by measuring MnSOD content in resected specimens using an enzyme-link ed immunosorbent assay, and by examining its location by an immunohist ochemical method. Upregulation of MnSOD in cancer tissue most likely s erves as a protective mechanism against anti-cancer therapies known to produce superoxide radicals as a key component of their rumor-killing activity.