Table 4 Summary of NK expansion and activation strategies
From: NK cell-based cancer immunotherapy: from basic biology to clinical development
Stimulation substance | Expansion criteria | Used clinically | Reference | Considerations |
|---|---|---|---|---|
Cytokines alone: applied separately or in combinations of two IL-2, IL-15, IL-2/IL-15, IL-2/IL-21 |  ~ 5 (two weeks) | Yes | Generate highly activated NK cells Possibility of dependence on cytokine Expansion is facilitated in the presence of autologous PBMC | |
IL-2/IL-15/IL-21 |  ~ 8 (two weeks) | No | Lower rate of NK cell expansion compared to feeder cell Only IL-2 cytokine is GMP-grade | |
IL-15/IL-18/IL-27 |  ~ 17 (two weeks) | No | [122] |  |
IL-2, IL-18 |  ~ 500 (two weeks) | No | [123] |  |
Autologous feeder cells OK432, RN-T cells |  ~ 600 (three weeks) | Yes | [4] | RN-T cells were established by activation PBMC with OKT-3 and RetroNectin FN-CH296 |
Autologous feeder + Activating Abs Anti-CD335 (NKp46) and anti-CD2 |  ~ 3800 (three weeks) | No | Patent, 2013, EP2824112B [153] | CD2 and CD335 coated nanomatrices with commercially available cell stimulation beads (Miltenyi Biotec Kit) |
OKT-3 (Anti CD3), anti-CD 52 | 1,537 (18Â days) | Yes | [146] | PBMCs are typically irradiated 25Â Gy or more GMP-grade antibody Anti CD3 is available |
OKT-3 (Anti CD3) |  ~ 1000 (two weeks) | Yes |  | |
Anti CD16 |  > 500 (two weeks) | No | [147] |  |
Allogeneic feeder cells PBMC  + PHA, Ionomycin |  ~ 100 | No | [139] | Without selection final product may contain up to 40% T cell PBMCs are typically irradiated 25 Gy or more |
 + ConA |  ~ 100 | Yes | [138] |  |
 + anti CD3 |  ~ 300 | Yes | [144] |  |
Allogeneic feeder cells (tumor) Wilms tumor cell line (HFWT), |  ~ 113 (two weeks) | Yes | [134] | Feeder can be genetically modified to enhance activation Feeder cells require irradiation and GMP-grade production Final product needs to be feeder free assured |
Jurkat |  ~ 100 (two weeks) | No | [135] | Risk of bacterial and viral contamination derived from feeder cells |
Transformed feeder cells Epstein-Barr lymphoblastoid cell line (EBV-LCL), |  ~ 3000 (two weeks) | Yes | [136] | Feeder cells require irradiation Safety considerations associated with feeder |
Engineered feeder K562 4-1BB + IL15 |  ~ 1200 (two weeks) | Yes | Increased apoptosis of NK cells noted after extensive expansion | |
Engineered feeder K562 4-1BB + IL21 |  ~ 30,000 (three weeks) | Yes | Greatest rate of expansion reported so far Lower dose of supportive IL-2 required | |
Feeder particles K562 4-1BB + IL21 |  ~ 250 (two weeks) |  | [141] | Avoids the safety considerations associated with feeder cells Laborious to produce |
Group A-Streptococcus and zoledronate |  ~ 1,560 (three weeks) | No | [107] |  > 90% of NK cells. May not require magnetic cell sorting Components IL2, streptococcus and zoledronate are FDA approved |