To investigate the cytotoxic effect of peripheral blood NK cell proliferation in vitro on different tumor cell lines.

Human hepatoma cell strains BEL-7402, HepG2 and SMCC-7721, human lung cancer cell strain A549 and human cervical cancer cell strain Hela were stored and passaged in the laboratory of Biological Treatment Center of Lingnan Hospital, the Third Affiliated Hospital of Sun Yat-sen University. The peripheral blood samples were collected from 10 healthy volunteers, 5 male and 5 female, aged (52±13) years on average, from Lingnan Hospital, the Third Affiliated Hospital ofSun Yat-sen University. The informed consents of all subjects were obtained and the local ethical committee approval was received. Human peripheral blood mononuclear cells were isolated, NK cells were cultured and identified by flow cytometry. The cytotoxic effect of human peripheral blood CD56⁺CD3^-NK cell proliferated in vitro on the tumor cells was evaluated by CCK-8 method. The absorbance (A) value was observed under different conditions of wavelengths, culture time, target cell counts and different effect to target ratio.

After human peripheral blood was cultured for 14 d, CD56⁺CD3^-NK cells accounted for (61±24)%. The optimal absorption wavelength of target cells was 450 nm, the optimal detection time was 1-4 h, and the optimal cell density was (1-4)×10⁴ cells/ml. NK cells exerted different cytotoxic effects on different tumor cell lines. At the effect to target ratio of 40∶1, NK cells had the highest effect on BEL7402, followed by A549, SMMC7721, HepG2 and Hela cell lines. At the effect to target ratio of 20∶1 and 10∶1, NK cells exerted the highest effect on BEL7402, followed by SMMC7721, A549, HepG2 and Hela cell lines. The cytotoxic effects of NK cells on 3 hepatoma cell strains also differed. The effect on BEL7402 was the highest, followed by SMMC7721 and HepG2 cell lines. At the effect to target ratio of 40∶1, the killing probability of NK cells on BEL-7402, SMCC-7721, A549 and Hela cells were significantly higher than those at 10∶1 (LSD-t=2.10, 2.37, 2.26, 5.61; P<0.05). The killing probability of NK cells on A549 cells was significantly higher when the effect to target ratio was 40∶1, compared with 20∶1 (LSD-t=1.14, P<0.05).

NK cells exert the highest cytotoxic effect on the tumor cell lines at the effect to target ratio of 40∶1. NK cells have different cytotoxic effects on different tumor cell lines, and also exert varying cytotoxic effects on different cell strains of the same tumor cell line.