Increased expression of Smad proteins, and in particular Smad3, in oral lichen planus compared to normal oral mucosa

Backgound: Oral lichen planus (OLP) is a chronic inflammatory disease of the oral mucosa which the World Health Organisation (WHO) considers a premalignant condition. One step in malignant development is so called epithelial mesenchymal transition (EMT), a process whereby epithelial cells acquire mesenchymal characteristics. EMT occurs during embryogenesis and wound healing but also in some human diseases such as cancer and fibrosis. A factor known to induce EMT is transforming growth factor-beta (TGF-beta), which uses the Smad proteins as mediators for its signalling. TGF-beta is also often over-expressed in squamous cell carcinoma of the head and neck (SCCHN). Methods: In the present study we mapped expression of Smad proteins in OLP lesions by immunohistochemistry, and compared to expression in normal and sensitive oral mucosa. The latter group of patients had developed SCCHN after shorter or longer periods of diffuse oral symptoms. The aim was to see if there were any signs of EMT related changes in the OLP lesions, as judged by changes in the TGF-beta pathway. Conclusion: Changes in the TGF-beta pathway related to EMT are seen in the very earliest stages of oral malignancy and become more severe as lesions progress.