KLRK1 and cancer: We have found that NKAE cells exhibit a highly cytotoxic phenotype, with high expression of cytotoxic receptors, such as NKG2D, and SP cells can be destroyed to a greater extent through the NKG2D receptor, which we have already shown to be essential for NK cell activity against total tumor cells and whose ligands (MICA, MICB, and ULBPs) are overexpressed under stress conditions that occur in cancer, and specifically in MM [43].