Tumorigenic OS521 cells were engineered to activate an Oct-4 promoter/GFP reporter and the GFP+ cells were at least 100-fold more tumorigenic and metastatic, capable of forming tumors at less than 300 cells, whereas only 1 of 8 mice developed a tumor at 3,000 cells in the GFP-depleted group [57, 58]. This evidence concerns the gene POU5F1 and neoplasm.