Natural killer-92 cells maintain cytotoxic activity after long-term cryopreservation in novel DMSO-free media

Natural killer (NK) cells are a critical part of the innate immune system, and have emerged as attractive targets for immunotherapies for various malignancies. Alongside the need for expansion of NK cells to reach clinically useful numbers, a critical component in the availability of NK cells for allogeneic therapy is cryopreservation. While a continuously-growing cell line such as NK-92 can avoid issues associated with isolating, activating, expanding, and manufacturing large numbers of peripheral blood-derived NKs, cryopreservation of these cells has not made much progress. NK cells are highly sensitive to freezing and thawing, while the use of DMSO during cryopreservation raises serious safety concerns. In this work, we evaluated a number of cryoprotectants that do not contain DMSO for their capacity to cryopreserve NK-92 cells over long-term while retaining their cytotoxic activity and viability, with the aim of identifying potential replacements to DMSO for safe clinical use of these cells.