Table 1.

The challenge of designing UCB-derived NK cell adoptive therapy.

Challenges	Possible Improvements/Resolutions
Low numbers of NK cells	Purification and in-vitro expansion of mature NK cells with IL-2/IL-15 ± irradiated feeder cells Exploitation of approved GMP protocols for large scale generation of NK cells from UCB CD34+ HSPC Generation of UCB-iPSC-derived NK cells (iNK)
Low expression of activating receptors, adhesion molecules and Granzyme B	In-vitro activation with IL-15 plus IL-12/IL-18
In-vitro survival and sustained activation of infused NK cells	IL-15 administration Generation of UCB-CAR NK cells equipped with IL-15 construct IL-15 superagonist/IL-15Rα fusion construct in iNK Deleting in iNK cells the CISH gene coding for CIS protein, a negative regulator of IL-15 signaling
Improvement of NK cell homing in tumor nest and of their antitumor activity	Generation of UCB CAR NK cells equipped with CD16/NKG2D/chemokine receptors/tumor specific antigens Generation of BIKE/TRIKE molecules Use of anti-CD94/NKG2A antibodies