Natural killer cell engineering - a new hope for cancer immunotherapy.

Natural killer (NK) cells are an important component of the innate immune system, particularly for metastasis immunosurveillance. They can rapidly recognize and kill transformed cells without the requirement of specific neo-antigen recognition. Their effector functions are modulated by a range of stimulatory and inhibitory surface receptors that regulate their cellular activation, differentiation and homeostasis. However, cancer cells can evade NK cell detection by receptor interaction or secretion of soluble immunosuppressant molecules. Therefore, genetic reprogramming of these immune suppressing or activating receptors of NK cells is a promising strategy to augment NK cell tumoricidal functions. In this review, we highlight the current clinical trials of chimeric antigen receptor engineered NK cells with redirected antigen specificity to eliminate hematological cancers and solid tumors. New alternative strategies that are advancing NK cell engineering for cancer treatment are also outlined. Lastly, different NK cell transgenesis approaches are reviewed and compared, and we discuss how these methods can be employed to maximize their anti-tumor effector functions.