KLRK1 and cancer: However, an ongoing clinical trial against MUC-1+ solid tumors and one targeting metastatic solid tumors responsive to NKG2D (Table 3), alongside advancements in improving the trafficking of NK cells into solid tumors by engineering chemokine receptors such as CXCR2 [173, 174] into solid tumors, are demonstrating advancements into targeting cancers that have traditionally been difficult to treat with NK cells.