Following the first discovery that mature adult cells can be reprogrammed to become pluripotent stem cells (iPSCs) by introduction of a set of four stemness factors (Oct4, SOX2, KLF4 and MYC) through retroviral transduction [7], it has been shown that cancer stem cells (CSCs) and relatively differentiated cancer cells are subject to bidirectional conversion [8]. This evidence concerns the gene KLF4 and cancer.