Optimization of Natural Killer Cell Expansion Technology for Immunotherapy
Introduction. To increase the effectiveness of antitumor adoptive immunotherapy using natural killer (NK) cells, it is crucial to get a sufficient NK cell number. There are various cell expansion devices, ranging from standard culture flasks to closed automatic systems. Each of them has its own characteristics, advantages and disadvantages. Purpose. Optimization of NK cell expansion technology using flasks containing gas- permeable membranes, followed by scaling for immunotherapy purposes. Materials and methods. NK cells were obtained by expanding donor peripheral blood mononuclear cells in the presence of interleukin (IL) 2 and irradiated feeder cells K-562-4-1BBL-mIL-21 in standard T-flasks and flasks with a gas-permeable membrane (G-Rex). Number of cells, viability, subpopulation composition, and the concentration of metabolites in the growth medium were evaluated during expansion. Results. As a result of scaling of NK cell expansion process for G-Rex100M flasks we obtained product with an absolute (1.55×109) and relative (95.3%) content of CD3-CD56+ lymphocytes comparable to the product acquired from T-flask. We observed that culture in G-Rex flasks allowed more efficient and rapid NK cell expansion compared with T-flasks (551 in 11 days vs 130 in 16 days). The following criteria were established for expansion process completion in G-Rex: glucose level less than 2 mmol/L and lactate level more than 12 mmol/L. Conclusion. The conditions for NK cell expansion in G-Rex100M flasks have been optimized to provide the required number of target cells for clinical use.