Stromal laminin chain distribution in normal, hyperplastic and malignant oral mucosa: relation to myofibroblast occurrence and vessel formation

Background: The contribution of stromal laminin chain expression to malignant potential, tumour stroma reorganization and vessel formation in oral squamous cell carcinoma (OSCC) is not fully understood. Therefore, the expression of the laminin chains alpha 2, alpha 3, alpha 4, alpha 5 and gamma 2 in the stromal compartment/vascular structures in OSCC was analysed. Methods: Frozen tissue of OSCC (9x G1, 24x G2, 8x G3) and normal (2x)/hyperplastic (11x) oral mucosa was subjected to laminin chain and alpha-smooth muscle actin (ASMA) immunohistochemistry. Results were correlated to tumour grade. The relation of laminin chain positive vessels to total vessel number was assessed by immunofluorescence double labelling with CD31. Results: Stromal laminin alpha 2 chain significantly decreases and alpha 3, alpha 4, alpha 5 and gamma 2 chains and also ASMA significantly increase with rising grade. The amount of stromal alpha 3, alpha 4 and gamma 2 chains significantly increased with rising ASMA positivity. There is a significant decrease in alpha 3 chain positive vessels with neoplastic transformation. Conclusions: Mediated by myofibroblasts, OSCC development is associated with a stromal up-regulation of laminin isoforms possibly contributing to a migration promoting microenvironment. A vascular basement membrane reorganization concerning alpha 3 and gamma 2 chain laminins during tumour angioneogenesis is suggested.