Finally, we employed GFP+ putative CSCs sorted from CNE2 and SUNE1 cells harboring PNanog-GFP-T2A-Luc transgene to examine whether addition of anti-NKG2D antibody could block the direct killing effect of CIK cells against putative CSCs of NPC by colony formation assay and tumor sphere formation assay. The gene discussed is KLRK1; the disease is nasopharyngeal carcinoma.