Background: Leukaemia is an aggressive cancer of haematopoiesis. Despite increasing treatment success, the relapse rate is still high. Natural killer (NK) cells play a key role in the immune response to malignancies; thus, it is conceivable that NK cell-based immunotherapy may control relapses, while extending the disease-free survival. In our study, we investigated whether cryopreserved NK cells are able to kill the leukaemic K562 cell line, the necessity of IL-2 co-application and the association of activation marker expression (NKp44, NKG2D and CD25) with cytotoxic potential.
Materials and methods: K562 cells were added to NK cell cultures in different ratios, i.e. 1:5, 1:10 and 1:20 (K562/NK), immediately after thawing NK cells or after 3-6-12-24 h of re-cultivation with or without IL-2.
Results: Our results demonstrated the ability of cryopreserved NK cells to kill K562 in all ratios, times and culture conditions. The number of dead K562 cells depended on the number of NK cells and on the presence of IL-2. NK cells cytotoxic potential decreased gradually in the culture without IL-2. In contrast, NK cell-mediated cytotoxicity remained the same during the entire re-culture period after IL-2 re-application.
Conclusion: Our study proved the efficacy of using cryopreserved ready-for-use NK cells in relapse treatment and the need for simultaneous administration of IL-2.
Keywords: Cryopreservation; Cytotoxic potential; Leukaemia; Medical product; NK cells.