Pluripotency transcription factors and cancer stem cells: small genes make a big difference

Cancer stem cells (CSCs) are thought to drive uncontrolled tumor growth, and the existence of CSCs has recently been proven by direct experimental evidence, including tracing cell lineages within a growing tumor. However, CSCs must be analyzed in additional cancer types. Cancer stem cell-like cells (CSCLCs) are a good alternative system for the study of CSCs, which hold great promise for clinical applications. OCT4, NANOG, and SOX2 are three basic transcription factors that are expressed in both CSCLCs and embryonic stem cells (ESCs). These transcription factors play critical roles in maintaining the pluripotence and self-renewal characteristics of CSCLCs and ESCs. In this review, we discuss the aberrant expression, isoforms, and pseudogenes of OCT4, NANOG, and SOX2 in the CSCLC niche, which contribute to the major differences between CSCLCs and ESCs. We also highlight an anticancer therapy that involves killing specific cancer cells directly by repressing the expression of OCT4, NANOG, or SOX2. Importantly, OCT4, NANOG, and SOX2 provide great promise for clinical applications because reducing their expression or blocking the pathways in which they function may inhibit tumor growth and turn-off the cancer "switch." In the future, a clear understanding of transcription factor regulation will be essential for elucidating the roles of OCT4, NANOG, and SOX2 in tumorigenesis, as well as exploring their use for diagnostic and therapeutic purposes.