PKC-δ attenuates the cancer stem cell among squamous cell carcinoma cells through down-regulating p63.

Protein kinase C delta (PKC-δ) has been identified as a tumor suppressor. However, the effects of PKC-δ on the cancer stem cells in squamous cell carcinomas (SCC) have not been clarified. The purpose of this study was to detect the regulation of PKC-δ on cancer stem cell among SSC cells and the role of p63 during the regulation. Immunohistochemistry of human cutaneous SCC tissues was performed to detect the expression of PKC-δ. After the human SCC13 cells infected by recombinant adenoviruses, the cell proliferation were determined. The correlation of PKC-δ and p63 was detected by western blot. The colony forming activity and the number of cancer stem cells (CSCs) in SCC identified by double-staining with anti-integrin α and anti-CD71 antibodies were detected. The expression of PKC-δ was obviously decreased in SCC tissues compared with that in normal skin tissues. The higher protein level of p63 in SCC was attenuated by the transfection of PKC-δ. The higher proliferation capacity of SCC13 cells, the higher activity and expression of CSCs in SCC13 cells induced by p63 were significantly suppressed by the transfection of PKC-δ. In conclusion, PKC-δ played as a protective role in SCC partly by down-regulating p63, leading to the suppression of SCC cell proliferation, attenuation of the activity and expression of CSCs in SCC cells.