A comparative quantitative analysis of laminin-5 in the basement membrane of normal, hyperplastic, and malignant oral mucosa by confocal immunofluorescence imaging

Laminin-5 (Ln-5) is a heterotrimeric basement membrane (BM) molecule (alpha 3 beta3 gamma2), It is a principal protein constituent of the anchoring fil aments, which connect the BM with the hemidesmosomes of the basal keratinoc ytes and possess a crucial function in keratinocyte adhesion. Confocal immu nofluorescence imaging is introduced for a quantitative evaluation of the L n-5 content in the BM of oral squamous epithelium. The BM of normal oral mu cosa was used as a reference (100%) for comparative analysis and showed a n early uniform Ln-5 immunofluorescence intensity (99-100%). In all hyperplas tic lesions of oral mucosa, the Ln-5 immunofluorescence intensity was incre ased (107-141%). The increased Ln-5 content in the BM of hyperplastic lesio ns suggests an increased keratinocyte-BM adhesion, possibly resulting in a higher stability of the oral mucosa. In contrast, in the oral squamous cell carcinoma (OSCC) invasive front, the remaining BM segments were characteri zed by a decrease in Ln-5 immunofluorescence intensity (35-74%). A stronger decrease of Ln-5-linked kerationocyte-BM adhesion correlates with a higher tumor grade. Because in central areas of carcinoma BM segments with a norm al Ln-5 content could be demonstrated, the fundamental Ln-5 diminution in B M segments of the invasive front should be considered as an invasion-associ ated phenomenon.