Expression of laminin-5 and integrins in actinic cheilitis and superficially invasive squamous cell carcinomas of the lip.

The progression of carcinogenesis entails the detachment of cells, invasion and migration of neoplastic cells. Alterations in epithelial adhesion and basement membrane proteins might mediate the early stages of carcinogenesis. This study investigated the expression of adhesion molecules and the basement membrane protein laminin-5 in actinic cheilitis (AC) and incipient squamous cell carcinoma of the lower lip to understand early photocarcinogenesis. Ln-5γ2 chain as well as α3, ß1 subunits of α3ß1 heterodimer and ß4 subunit of integrin α6ß4 were evaluated by immunohistochemistry in 16 cases of AC and 16 cases of superficially invasive squamous cell carcinoma (SISCC). Most AC cases showed reduced expression of ß1, ß4 and α3 integrins, and SISCCs lacked ß1, ß4 and α3 integrins in the invasive front. AC cases were negative for the Ln-5γ2 chain. Five cases of SISCC (31%) showed heterogeneous Ln-5γ2 chain expression in the invasive front of the tumor. Integrin ß1, ß4 and α3 expression is lost during the early stages of lip carcinogenesis. Expression of Ln-5γ2 in the invasive front in cases and its correlation with tumor progression suggest that it mediates the acquisition of the migrating and invading epithelial cell phenotype.