In an interesting proof-of-concept study of an affinity-optimized, second generation CD38-targeting CAR (see later for more details about CAR-NK cells) with a costimulatory CD28 domain, retrovirally transduced into the KHYG-1 NK cell line, Stikwoort et al. observe an intense killing of CD38high multiple myeloma (MM) cell lines and primary cells, whereas nonmalignant hematopoietic cells with low or absent CD38 expression are spared. This evidence concerns the gene CD38 and plasma cell myeloma.