Alterations in expression of basement membrane proteins during tumour progression in oral mucosa.

Expression of three basement membrane proteins--collagen IV, laminin and fibronectin--was studied in normal, hyperplastic, dysplastic and neoplastic conditions of the oral mucosa using immunohistochemistry. Collagen IV and laminin exhibited similar staining patterns, while fibronectin showed a different pattern of expression. The expression of collagen IV and laminin also demonstrated an inverse correlation between staining intensity, thickness and basement membrane continuity in various stages of tumour progression. In contrast to the continuous and intense staining of basement membrane in normal oral mucosa with collagen IV and laminin antibodies, severe dysplasia and carcinoma exhibited discontinuous, thin and weakly stained basement membrane. The expression of fibronectin showed a direct correlation with extent of tumour progression. In normal mucosa, expression of fibronectin was almost absent, whereas in carcinoma intense expression of fibronectin was evident in the basement membrane and basal cells. These results emphasize the value of basement membrane proteins as biological markers for assessing oral carcinogenesis.