SOX2 and neoplasm: As an alternative method, the use of reporter systems where the expression of a fluorescent protein is driven by the SOX2 and/or OCT4 promoter or by SOX2/OCT4 response elements has proved the tumor-propagating potential of cells expressing pluripotency factors in several tumor models [4,8,22,24,25,26,27,28,29,30,31].