S100A6 as a Constituent and Potential Marker of Adult and Cancer Stem Cells

Adult or tissue stem cells are present in various tissues of the organism where they reside in a specific environment called the niche. Owing to their ability to generate a progeny that can proliferate and differentiate into specialized cell types, adult stem cells constitute a source of new cells necessary for tissue maintenance and/or regeneration. Under normal conditions they divide with a frequency matching the pace of tissue renewal but, following tissue damage, they can migrate to the site of injury and expand/divide intensively to facilitate tissue repair. For this reason much hope is being placed on the use of adult stem cells in regenerative therapies, including tissue engineering. Identification and characterization of tissue stem cells has been a laborious process due to their scarcity and lack of universal markers. Nonetheless, recent studies, employing various types of transcriptomic analyses, revealed some common trends in gene expression pattern among stem cells derived from different tissues, suggesting the importance of certain genes/proteins for the unique properties of these cells. S100A6, a small calcium binding protein, has been recognized as an important factor influencing cell proliferation and differentiation. Accumulating results show that S100A6 is a constituent of adult stem cells and, in some cases, may even be considered as their marker. Thus, in this review we summarize literature data concerning the presence of S100A6 in adult and cancer stem cells and speculate on its potential role and usefulness as a marker of these cells.