Molecular mechanisms underlying the functions of cellular markers associated with the phenotype of Cancer Stem Cells.

Cancer Stem Cells (CSC) generally constitute a minor cellular population within tumors that exhibits some capacities of normal stem cells. The existence of CSC, able to self-renew and differentiate, influences central aspects of tumor biology. In part because they are the ones that can continue tumor growth, give rise to metastasis, and acquire drug and radio resistance, which opens new avenues for therapeutics. It is well known that Stem Cells (SC) constantly interact with their niche, which includes mesenchymal cells, extracellular ligands, and the Extracellular Matrix (ECM). These interactions regularly lead to homeostasis and maintenance of SC characteristics. However, the exact participation of each of these components for CSC maintenance is not clear, as they seem to be context- or cell-specific. In the recent past, surface cellular markers have been fundamental molecular tools for identifying CSC and distinguish them from other tumor cells. Importantly, some of these cellular markers have been shown to have functional roles that impact central aspects of CSC. Likewise, some of these markers can participate in regulating the interaction of CSC with their niche, particularly the ECM. We focused this review on the molecular mechanisms of surface cellular markers commonly employed to identify CSC, highlighting the signaling pathways and mechanisms involved in CSC-ECM interactions, through each one of the cellular markers commonly used in the study of CSC, such as CD44, CD133, CD49f, CD24, CXCR4 and LGR5. The presence of each one does not necessarily implicate them in CSC biology.