The above-established subcutaneous tumor xenografts, which expressed both GFP and Luc transgenes under the control of a stem cell-specific Nanog promoter, allow us to in vivo non-invasively optically image and quantify putative CSCs within tumor xenografts in NOD/SCID mice by noninvasively detecting Luc signal via using in vivo bioluminescence imaging. Here, NANOG is linked to neoplasm.