Experiment research of natural killer cells amplification in vitro and the killing effect on ovarian cancer cells

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Objective: To amplify natural killer (NK) cells in vitro and explore its killing effect on ovarian cancer cells. Methods: (1) The separation of NK cells and identification. A total of 20 ml peripheral blood of one healthy volunteer was collected in Nov. 2015, Peking University People's Hospital. The peripheral blood mononuclear cells of normal volunteers were isolated, cultured in vitro and amplificated cultivation for 14 days with K562 cells transfected and expressing interleukin 21 (IL-21-K562) as nourish cells. The number and dynamic state of the growth cells were monitored during the cultured process. Cells were harvested and counted after 14 days cultured. The NK cells phenotypes were detected by flow cytometry. (2) The killing effect of NK cells on ovarian cancer cells: the ratio of effector cells (NK cells) and target cells (ovarian cancer cells and its control) was 50∶1, 20∶1, 10∶1, 5∶1 or 1∶1, NK cells killing effect on ovarian cancer cells was detected by the lactate dehydrogenase (LDH) release experiments. Results: (1) The results of NK cells establishment and phenotypic characterization: the cells were induced in vitro for 14 days by amplification culture. With the extension of incubation time, the number of NK cells increased constantly, from 2.0×10(7) on day 0 to 5.1×10(9) on day 14. Obvious amplification of the total number of cells were detected for 255 times. Living cells unstained by trypan blue eventually reached 95% above. Before and after the induction and amplification in vitro, the percentage of NK cells(CD(3)(-)CD(5)(6+)cells) in CD(3)- cells were 2.33% and 85.32%, respectively (P<0.01), which covered the whole lymphocytes 1.06% and 69.42%, respectively (P<0.01), which showed that NK was the main cell type in the amplificated lymphocytes. (2) The killing rate of NK cells on ovarian cancer cells in vitro: the results detected by LDH release experiments showed that NK cells could performed strong nonspecific killing effect on ovarian cancer cell lines SKOV3, HOC1A, 3AO and CAOV3, as well the normal ovarian cell line T29 and NK sensitive cell line K562, and the killing effect increased significantly along with the increase of effector cells and target cells ratio (P<0.01). When the ratio was 1∶1, the killing rate was 37% for K562, while the rate of killing of other cells was around 10% (P<0.05). When the effect-target ratio was 20∶1 and 50∶1, in addition to CAOV3 cells (more than 70%), NK cells had a kill rate of more than 80% for other ovarian cancer cells lines and their control cell K562 and T29 cells (P>0.05). Conclusion: NK cells could be established in vitro and have a good non-specific killing effect on ovarian cancer cells.