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"The natural killer (NK) cells differentiated from umbilical cord blood (UCB) hematopoietic stem cells (HSCs) may be more suitable for cell-based immunotherapy compared to the NK cells from adult donors. This is due to the possibility to choose alloreactive donors and potentially more robust in vivo expansion. However, the cytotoxicity of UCB-HSC-derived NK cells against cancer cells might be suboptimal. To overcome this obstacle, we attempted to generate NK cells with potent antitumor activity by targeting RAS/MAPK, IGF-1R and TGF-β signaling pathways using IL-15, IGF-1 and SIS3 respectively. The CD34 + cells were isolated from human UCB mononuclear cells through magnetic activation cell sorting (MACS) with purity of (≥ 90%) and were subjected to differentiate into NK cells. After 21 days of induction with SFTG36 (SCF, FLt-3L, TPO, GM-CSF, IL-3 and IL-6), IS721 (IGF-1, SIS3, IL-7 and IL-21) and IL-15/Hsp70 media, NK cells phenotypes were studied and their cytotoxicity against K562 human erythroleukemia cells and SKOV3 ovarian carcinoma cells was analyzed. The NK cells induced in SFTG36/IS721 medium were selected for activation due to their higher expression of CD56 + 16 + CD3 −  (93.23% ± 0.75) and mean fluorescence intensity (MFI) of NKG2D + (168.66 ± 20.00) and also a higher fold expansion potential (11.893 ± 1.712) compared to the other groups. These cells once activated with IL-15, demonstrated a higher cytotoxicity against K562 (≥ 90%; P ≤ 0.001) and SKOV3 tumor cells (≥ 65%; P ≤ 0.001) compared to IL-15/Hsp70-activated NK cells. The differentiation of ex vivo expanded CD34 + cells through manipulation of RAS/MAPK, IGF-1R and TGF-β signaling pathways is an efficient approach for generating functional NK cells that can be used for cancer immunotherapy."
<https://cancerci.biomedcentral.com/articles/10.1186/s12935-021-01983-z/figures/4>