Background Due to their powerful immune surveillance activity and ability to kill and clear cancer cells, natural killer (NK) cells are an emerging anticancer immunotherapeutic agent.1,2 Therefore, there is much interest in developing efficient technologies that further enhance the therapeutic antitumor efficacy of NK cells. One of these technologies is a priming strategy that pre-activates NK cells using a cytokine cocktail or cancer cell lysates.3,4
Methods Chem_NK refers to ex vivo NK92MI or primary NK cells that have been chemically primed by 25KDa branched polyethylenimine (25KbPEI). The priming activity of 25KbPEI was evaluated by receptor expression, perforin accumulation, chemotaxis and the antitumor efficacy of Chem_NK. The priming mechanism was studied regarding 25KbPEI mediated calcium influx and subsequent activation of multiple signaling pathways.
Results Chem_NK showed increased perforin accumulation, interferon-γ expression and activating/adhesion/chemokine related receptor expression. In line with these phenotypes, Chem_NK had potent in vivo antitumor efficacy toward ovarian cancers and triple negative breast cancers. The major mechanism for 25KbPEI to prime NK cells was identified as a calcium influx via the Ca2+-permeable nonselective cation channel transient receptor potential melastatin 2 (TRPM2). We confirmed that 25KbPEI mediated calcium-influx is associated with activation of ERK and mTOR signaling, which is directly linked to the translational initiation of immune response-related proteins of NK cells (figure 1).
Conclusions NK cells can be chemically primed with 25KbPEI to become ‘ready to fight’ state. Because PEI is a biocompatible and FDA-approved chemical for biomedical use, our results suggest a cost-effective and simple method of producing therapeutic NK cells.
Acknowledgements This work was supported by Samsung Research Funding & Incubation Center of Samsung Electronics under Project Number SRFC_MA2102_06.
Lanier, L.L. Up on the tightrope: natural killer cell activation and inhibition. Nat Immunol 9, 495-502 (2008).
Lusty, E. et al. IL-18/IL-15/IL-12 synergy induces elevated and prolonged IFN-gamma production by ex vivo expanded NK cells which is not due to enhanced STAT4 activation. Mol Immunol 88, 138-147 (2017).
Ni, J. et al. Sustained effector function of IL-12/15/18-preactivated natural killer cells against established tumors. J Exp Med 209, 2351-2365 (2012)
North J. et al. Tumor-priming human natural killer cells lyse NK-resistant tumor targets: evidence of a two-stage process in resting NK cell activation. J Immunol 178, 85-94 (2007)
Ethics Approval All animal experiments were approved by the Institutional Animal Care and Use Committee of the laboratory animal research center at CHA University. Primary NK cells were isolated from peripheral blood mononuclear cells obtained from healthy donors. This research was reviewed and approved by the institutional review board of CHA University.
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.