Role of Cathepsin B as a Marker of Malignant Transformation in Oral Lichen Planus: An Immunohistochemical Study.

INTRODUCTION: Malignant transformation of Oral Lichen Planus (OLP) remains a much discussed but very less understood realm. Various hypotheses and theories have been put forward to explain the same. Malignant transformation is a complex interplay of epithelial mesenchymal factors acting in tandem. This study tries to identify and asses the stromal changes that pave the way for epithelial migration using Cathepsin B (CB) a cysteine protease belonging to the Cathepsin family. Various studies have been done to study its role in human cancers which have proven that CB helps mark and identify tissue digestion.

AIM: The purpose of this study was to evaluate the expression of CB, in OLP and examine its possible role in malignant transformation.

MATERIALS AND METHODS: Immunohistochemical analysis of CB expression was done in 50 OLP tissues along with 10 normal mucosa tissue and 10 Oral Squamous Cell Carcinoma (OSCC) cases (control groups). Evaluation was done on the basis of intensity of staining. The intensity was graded in all the cases by assigning values of 0 to 4 in ascending order. Two other observers evaluated the staining and intensity independently and the average of the observations was taken.

RESULTS: A variable staining pattern in both the stroma and the cytoplasm of the epithelial cells was noticed. The staining intensity was clearly increased in OLP tissues when compared to normal control tissue and OSCC which served as our positive control. The staining patterns in tissues of OLP and OSCC to Cathepsin B were similar. The staining intensity of Cathepsin B was observed to be increased in both these groups of tissues.

CONCLUSION: This study demonstrated a significantly increased expression of CB in OLP. This may be correlated to a possible indicator for its eventual malignant transformation. This overexpression of CB amounts to an array of stromal changes that take place and different mechanisms that get activated underneath the epithelium leading to the formation of what is known as a tumour microenvironment, a well proven entity. We hypothesize that it is this which felicitates the invasion of the overlying epithelial cells.