[Changes of superoxide dismutase (SOD) and metallothionien (MT) before, during, and after radiotherapy for nasopharyngeal carcinoma and their significance].
The superoxide anion and the hydroxyl radical (OH.) play an important role in the radiotherapy of tumors. The superoxide dismutase (SOD) and the metallothionien (MT) are the main enzymes to clear the superoxide anion and OH. Up to now, there are few reports on the relationship between the nasopharyngeal carcinoma (NPC) and SOD or MT. This study was conducted to observe the dynamic changes of the activity of total superoxide dismutase (T-SOD) in the serum and the expression of MT in the tissue from the NPC patients treated with radiotherapy. From December 2000 to January 2002, 46 patients with NPC were selected randomly to test the activity of T-SOD in serum using xanthine oxidase method and the expression of MT in tissue using immunohistochemistry before, during, and after radiotherapy. And 26 persons without cancer were enrolled as normal control. Thirty-two patients were performed 3 times of examinations of T-SOD activity. The activity of T-SOD before radiotherapy (83.9+/-19.6 U(N)/ml) was lower than normal control (96.8+/-23.6 U(N)/ml) (P< 0.05). The activities of T-SOD in the serum samples before, during, and after the radiotherapy were 77.6+/-19.1, 87.1+/-18.6, and 96.3+/-31.6 in the NPC patients at stage I(P >0.05); 80.1+/-15.0, 78.0+/-35.4, and 110.6+/-72.0 in the NPC patients at stage IV(P >0.05); 79.8+/-18.2, 87.2+/-31.7, and 94.8+/-36.3 in the patients with complete response to radiotherapy (P >0.05); 98.5+/-18.6, 62.9+/-35.3, and 79.2+/-27.3 in the patients with part response to radiotherapy (P >0.05). Among the 32 patients, 27 patients were performed 3 times of tests of MT expression. The expression rate of MT in NPC tissues was 39.8+/-37.8% before radiotherapy, and markedly higher than the normal control 12.1+/-22.4% (P< 0.05). The expression rates of MT before, during, and after radiotherapy were 33.0+/-42.2%, 21.3+/-36.1%, and 5.0+/-10.0% in the tissues from the patients at stage I(P< 0.05); 62.2+/-40.5%, 9.2+/-12.8%, and 9.2+/-15.0% in the patients at stage IV( P< 0.05); 42.5+/-38.6%, 19.8+/-27.5%, and 10.0+/-13.9% in the patients with complete response to radiotherapy (P< 0.05); 32.3+/-37.2%, 1.43+/-2.43%, and 5.4+/-9.1% in the patients with part response to radiotherapy (P< 0.05). The test of T-SOD in serum may be helpful for the diagnosis of initial NPC. But the dynamic change of the activity of total T-SOD in radiotherapy was not obvious. The expression rates of MT in NPC tissues increased markedly before radiotherapy, and decreased obviously after radiotherapy.