Epithelial stem cells and malignancy

Oral cancer stem cells - properties and consequences

Research on cancer stem cells (CSCs) has greatly increased in the field of medicine and pathology; however, some conceptual misunderstandings are still present among the public as well as within the general scientific community that is not yet familiar with the subject. The very first problem is the misinterpretation of CSCs as a synonym of their normal counterparts, the well-known stem cells (SCs). Particularly in Dentistry, another common mistake is the misinterpretation of oral CSCs as normal tooth-derived SCs. The present review aims to clarify important concepts related to normal SCs and CSCs, as well as discuss the relevance of CSCs to the development, metastasis and therapy resistance of oral squamous cell carcinoma.

The low-affinity nerve growth factor receptor p75NTR identifies a transient stem cell-like state in oral squamous cell carcinoma cells

BACKGROUND

Although several markers have been used for enrichment of cells with stem cell-like properties in oral squamous cell carcinoma (OSCC), isolation of a pure subpopulation is still a challenging task. Normal oral and esophageal keratinocyte stem cells have been previously isolated using the low-affinity nerve growth factor receptor p75NTR.

OBJECTIVE

To investigate the potential of p75NTR as a marker for identification and isolation of oral cancer cells with stem cell-like properties.

METHODS

Subpopulations of cells with high or low expression of p75NTR were sorted from OSCC-derived cells and compared for sphere/colony formation, in vivo tumor formation ability, expression of stem cell-related molecules, cell cycle distribution and drug resistance.

RESULTS

p75NTR(High) cells exhibited statistically significant higher stem cell properties than p75NTR(Low) cells in all assays performed. Nevertheless, p75NTR(Low) subpopulation did also exhibit some stem cell features, but to a lesser extent. Propagation of p75NTR(Low) cells for several passages in culture showed that the expression of p75NTR could rise spontaneously. This finding was also supported by the similar expression of p75NTR by the xenografts generated by both subpopulations in NOD\SCID IL2Rg(null) mice.

CONCLUSION

p75NTR can be used for isolating a subpopulation enriched for cells with stem cell-like properties in OSCC. De novo generation of p75NTR(High) cells from p75NTR(Low) cells suggests either that there is another subpopulation with stem cell features within the p75NTR(Low) cells, or that the p75NTR(Low) cells can dedifferentiate due to a contextually regulated equilibrium between stem cell-like cells and transit-amplifying neoplastic progenitors.