CXCR4 and gastric cancer: NK signature consists of a 12-gene NK cell-associated signature (CXCR4, RDH8, MAGEA11, CYP19A1, SHOX2, GRB14, SLC35E4, NEK5, AKAP5, MSI2, KYNU, PLCL1) and can predict both the prognosis of GC patients and the efficacy of immunotherapy.