The Role of MicroRNAs in Regulating Cancer Stem Cells

Abstract

Stem cells are a rare population of cells that have the ability to self-renew (to replenish the stem cell pool) and to differentiate (to produce daughter cells that will perform the physiological functions of tissues and organs). Although stem cells exist in different tissues, organs, and developmental stages. However, stem cells differ to some degree with regard to their developmental potency; life span, and notably their potential for self-renewal and proliferation capacity. Stem cell self-renewal and differentiation is regulated by signaling pathways, transcription factors, and micro RNAs (miRNAs). Some key transcription factors directly regulate the expression of miRNAs in stem cells. Meanwhile, miRNAs target key transcription factors and either repress or induce their expression in stem cells to regulate self-renewal and differentiation. Thereby, the miRNA regulatory network and the signaling pathways crosstalk to each other to orchestrate stem cell maintenance and cell fate decision. Dysregulation of core signaling pathways, transcription factors and miRNAs associated with normal stem cells can lead to carcinogenesis. Thus, understanding the regulation of normal stem cell is crucial for understanding the molecular mechanisms underline carcinogenesis. In this chapter, we review the characteristics and functions of miRNAs and cancer stem cells (CSCs), focusing on the roles of miRNAs in regulating CSCs. First, we provide an introduction to stem cells and CSCs. Then, we describe the signaling pathways that regulate stem cell self-renewal and differentiation. In particular, we review the Wnt/┚-catenin, Hedgehog (HH), and Notch pathways. Next, we discuss the epithelial–mesenchymal transition (EMT), CSCs, and miRNAs that play roles in regulating stem cells. Finally, we summarize the current status and discuss future perspectives.