The utility of CD44, CD117 and CD133 in identification of cancer stem cells (CSC) in oral squamous cell carcinomas (OSCC)

One of the theories regarding oral carcinogenesis is that the tumor growth is dependent on cancer stem cells (CSCs) that have the capacity of self-renewal and of giving rise to more differentiated tumor cells, like the stem cells do in normal tissues. The most used methods of CSCs isolation are based on their identification based on the expression of different cell surface markers. The markers qualified for this purpose have been described originally in studies involving hematopoietic or embryonic stem cells. Thus, we were interested to study the expression of the most used CSCs surface markers for formalin fixed paraffin embedded tissue samples from oral squamous cell carcinoma (OSCC). We investigated by immunohistochemistry thirty tissue samples of OSCCs with different degrees of differentiation and different oral locations. We were interested to establish the tissular localization pattern for cells expressing CD44, CD133 and CD117 in tumoral samples. The results indicated that with the exception of CD44, the other two surface markers were expressed only in tumoral stromal cells. When we looked at their origin (by double immunohistochemistry for cytokeratins AE1-AE3, vimentin and CD34) we concluded that they are of mesenchymal nature. Also, we proved that some of these cells also co-expressed CD44 but were negative for CK5/6. Moreover, some of the stromal cells that were positive to CD133 and especially for CD117 also had reactivity to tryptase showing their mast cell nature. In conclusion, our study proved that CD44 has limited utility in identifying oral CSCs, while CD117 and CD133 expression appears to be limited more in identifying mesenchymal stem cells.