Cancers constitute a leading cause of mortality. Chimeric antigen receptor (CAR) cell therapies provide breakthrough solutions for various cancers while posing considerable risks of immunological side reactions. Of various cytotoxic lymphocyte subsets, natural killer (NK) cells are considered the least immunogenic. Obtaining viable NK cells with stable phenotypes in quantities sufficient for modification is technologically challenging. The candidate sources include primary mononuclear cell cultures and immortalized NK cell lines
alternatively, the clinical-grade NK cells can be differentiated from induced pluripotent stem cells (iPSCs) by a good manufacturing practice (GMP)-compatible xeno-free protocol. In this review, we analyze existing protocols for targeted differentiation of human iPSCs into NK cells with a focus on xeno-free requirements.