DNA damage of tumor-associated lymphocytes and total antioxidant capacity in cancerous patients.

The purpose of this study was to assess DNA damage of tumor-associated lymphocytes (TALs) in malignant pleural effusion (MPE), the total antioxidant capacity (TAC) of plasma and MPE from patients with carcinoma, and DNA repair effect of melatonin. TAC of plasma was measured in 28 cancer patients with MPE and in 33 healthy persons, and also TAC of MPE supernatant was measured in these patients. DNA damages of peripheral blood mononuclear cells (PBMCs) and of TALs were assessed using comet assay. The TAC of plasma was remarkably lower in cancer patients (8.41+/-1.78 U/ml) than that in healthy persons (10.52+/-1.64 U/ml, P<0.001). The TAC of MPE supernatant (6.34+/-1.57 U/ml) was significantly lower than that of plasma in cancer patients (8.41+/-1.78 U/ml, P<0.001). The comet percentage of PBMCs was higher in cancer patients (16.8+/-7.9) than that in healthy persons (10.4+/-4.9, P<0.01). Within cancer patients, the comet percentage of TALs (41.9+/-11.7) was significantly higher than that of PBMCs (16.8+/-7.9, P<0.001). A negative correlation was observed between the TAC of MPE supernatant and the comet percentage of TALs in patients (r=-0.538, P<0.01). After treatment with melatonin, comet percentage of TALs declined significantly from 42.6+/-12.8 to 27.1+/-9.9 (P<0.001). These data show that lower TAC of MPE supernatant may be related to higher degree of DNA damage of TALs and that melatonin may facilitate the repair of the damaged DNA.