Fibrillary co-deposition of laminin-5 and large unspliced tenascin-C in the invasive front of oral squamous cell carcinoma in vivo and in vitro

Purpose: Invasion of oral squamous cell carcinoma (OSCC) is associated with laminin-5 (Ln-5) synthesis, focal Ln-5 loss from the basement membrane (BM), and Ln-5 depositions in the stroma beneath invading carcinoma cell complexes. Methods: The study is focused on the laminin-5 matrix reorganisation within the stroma of the OSCC invasive front outside the basement membrane region as well as in OSCC-fibroblast co-culture in relation to unspliced tenascin-C (Tn-C-L) and ED-B+ fibronectin (ED-B+ fn) using confocal laser scanning microscopy. Resulrs: In vivo Ln-5 was demonstrated as fibrillary deposition in the invasive front. It was co-localised to Tn-C-L. In pure OSCC cultures, Ln-5 was synthesised and deposited as a spot-like matrix. Fibrillary structures were not found. In contrast, in the OSCC-fibroblast co-culture, a fibrillary Ln-5 matrix organisation was revealed within the interface of OSCC cell-fibroblast complexes exclusively in co-distribution with Tn-C-L and ED-B+ fn. Conclusion: At least in vitro, a carcinoma cell-stroma fibroblast intel action is indispensable for fibrillary Ln-5/Tn-C-L matrix organisation. Behind the parallels to the initial basement membrane formation in organotypic cultures, the fibrillary multiprotein complexes at the OSCC cell-fibroblast interface are suggested as provisional basement membrane fragments with a possible supportive role for invasive tumour behaviour.