MicroRNAs in colorectal cancer stem cells: new regulators of cancer stemness?

Recently, the hypothesis that colorectal tumors originate from a subpopulation of cells called ‘cancer stem cells' (CSCs) or tumor-initiating cells, which exhibit stem-like features, has been confirmed experimentally in various human cancers. Several studies have confirmed the existence of colorectal CSCs (CRCSCs) and have demonstrated that this rare cell population can be isolated by the expression of specific cell surface biomarkers. MicroRNAs (miRNAs) are a class of small non-coding RNAs, which are crucial for post-transcriptional regulation of gene expression and participate in a wide variety of biological functions, including development, cell proliferation, differentiation, metabolism and signal transduction. Moreover, new evidences suggest that miRNAs could contribute to preserve stemness of embryonic stem cells and could be involved in maintaining stemness of CSCs. Recent studies have begun to outline the role of miRNAs in regulation of CRCSCs. This review aims to summarize the recent advancement about the roles of miRNAs in CRCSCs that may represent a step forward in understanding the molecular mechanisms and the possible approaches for colorectal cancer therapy.