**Author details**

effect, by which tumour cells rely mostly on glycolysis for energy production, enables cancer

Tumour cells can also impair dendritic cell (DC) function to prevent NK cell priming, by changing their expressions of IL‐6, IL‐10, vascular epithelial growth factor or GM‐CSF. Finally, tumour cells have also been shown to lower NK cell count by decreasing the numbers of lym‐ phoid progenitor cells [67]. **Figure 3** describes different tumour immune evasion strategies

The ability of NK cells to kill tumour cells has made them very attractive in immunotherapy. NK cell impairments associated with tumour development and progression have been fre‐ quently reported in cancer patients, including weakened effector functions and an altered phenotype with downregulation of activating NK cell receptors [68]. Different strategies have been employed to repair, replace or enhance the biological functions of autologous or

**Figure 3.** Tumour Evasion from NK cells. Tumour cells use direct and indirect mechanisms to evade NK cell attack. Direct mechanisms include A) upregulation of MHC class I expression B) shedding of soluble ligands for NK cell activation receptors and C) release of inhibitory cytokines. Indirect mechanisms include D) activation of inhibitory regulatory T cells E) killing of immature dendritic cells to prevent NK cell priming F) release of phagocyte‐derived inhibitory cytokines and G) reducing the number of NK progenitor cells to lower NK cell counts. NK: natural killer cell; DC: dendritic cell, IL‐10: interleukin 10; IDO: indoleamine 2,3‐dioxygenase; MHC: major histocompatibility complex; ROS:

cells to resist ROS‐related death and gain survival advantage for metastasis [66].

**4. NK cell modulation for cancer therapy**

reactive oxygen species; Th2: T helper cell type 2.

from NK cells.

22 Natural Killer Cells

May Sabry and Mark W. Lowdell\*

\*Address all correspondence to: m.lowdell@ucl.ac.uk

Department of Haematology, University College London Medical School, University College London, London, United Kingdom
