Stemness in Cancer: Stem Cells, Cancer Stem Cells, and Their Microenvironment

Table 1

Comparison of traits of normal Stem Cells and Cancer Stem Cell biology.

Trait	Normal Stem Cells	Cancer Stem Cells
Self-renewal	High capacity [27, 28]	High capacity [10, 64, 70, 71]
Cell cycle duration	Long. Tissue-regulated generation of transit amplifying progenitors [28]	Redundant self-renewal pathways become activated. Pathological self-renewal balance over differentiation [72]
Genome repair abilities	Yes [73, 74]	Altered (constant generation of new mutations and epigenetic profiles to generate clones with strong adaption capacity to aggressive environments) [46, 73]. Hypoxia mediated cell cycle lengthening and DNA repair [75, 76]. Shorter cell cycle contribution [12]
Microenvironmental protection by niche from noxious agents	Yes [77]	Yes [11, 23]
Location at hierarchy	Basal compartment [27]	Basal compartment [72]
Transit amplifying compartment	Progenitor cells have short cycles to generate enough numbers of normal differentiated cells [47, 78]	It seems to be present as the basis for rapid growth of tumors. Progenitor cells have short cycles [10]
Plasticity	Can go back and forth between differentiation and dedifferentiation states [79]	Epithelial mesenchymal transition and self-renewal acquisition [10, 80, 81] Dedifferentiation and mutation accumulation in committed cells [22]