Molecular Markers and Networks for Cancer and Stem Cells

Stem cell differentiation and self-renewal are regulated by several factors, including molecules that each cell expresses both inside and on its surface. Cancer stem cells (CSCs) exist in some populations of cancer cells, however, the origin and characteristics of CSCs remain incompletely understood; thus, a deeper analysis of the essence of CSCs is required. Since the CSCs exhibit the properties to initiate tumor and be resistant to anti-cancer drugs, inquiries into the molecular mechanisms in CSCs may lead to the discovery of novel therapeutic targets for cancer. Epithelial-mesenchymal transition (EMT), in which cells transit from epithelial-like into mesenchymal-like cell features, is an important phenotype of CSCs and cancer metastasis. In this review article, the molecules and signaling pathways involved in CSCs, with a focus on molecules so-called CD antigens, of which combinations represent cancer types and CSCs, are summarized and described for further investigation of CSCs as well as the stem cell properties of cancer. Considering that CSCs and stem cells may have similar properties, and cancer and stem cells exhibit similar signaling pathway activation in self-renewing, the phenotypes of CSCs including EMT may confer tumorigenic properties to the stem cells. From overviewing the literatures, it is suggested that CSCs are defined with combinations of several markers, and investigation of EMT network is important.