Therefore, the NPC cell line harboring double reporter genes (i.e., GFP and Luc) under control of a stem cell-specific Nanog promoter allows us to in vitro visualize putative CSCs and to in vivo optically image and quantify putative CSCs within tumor xenograft-bearing mice, which has never been reported in other cancers. Here, NANOG is linked to nasopharyngeal carcinoma.