9 Matrix remodeling in head and neck squamous cell carcinomais

Abstract

Extracellular matrix (ECM) remodeling is an inherent characteristic of invasive head and neck squamous cell carcinoma (HNSCC). We investigated the regulation of gene expression, synthesis and activation of ECM components and matrix remodeling enzymes in a co-culture model of head and neck squamous cell carcinoma (HNSCC) and in HNSCC tissue. Periodontal ligament fibroblasts (PDL) and SCC-25 HNSCC cells were co-cultured for seven days, followed by mRNA and protein expression analysis of ECM components, ECM receptors, matrix metalloproteinases (MMPs) and proteinase inhibitors. The activity of MMPs was analyzed using gelatinase zymography. MMP-9, fibronectin and “antiadhesion proteins” were investigated by immunohistochemistry in HNSCC tissue. In co-cultured fibroblasts, in addition to fibronectin (FN), the “antiadhesion proteins” tenascin C (TSC), thrombospondin 1 (TSP1) and latent TGF-beta binding protein 2 (LTBP2) were upregulated. In lower levels: FN, TSC and TSP1 were also produced by the tumor cells. In co-cultured fibroblasts, alpha 1 and 5 and beta 1 integrins, in co-cultured tumor cells alpha 3 and 5 integrins were upregulated. MMP-1 was upregulated in both co-cultured tumor cells and fibroblasts, MMP-2 in co-cultured fibroblasts, and MMP-9 in co-cultured tumor cells. MMP inhibitors were mainly produced in fibroblasts. The activation of MMP-2 required the co-culture with tumor cells. MMP-9 was exclusively produced in tumor cells. In sections of formalin-fixed paraffin embedded HNSCC tissue, FN and LTBP2 were detected in fibroblastic stroma surrounding tumor cell nests; TSP1 was detected both in tumor cell nests and in the surrounding fibroblastic stroma. Extended MMP-9 immunohistochemical staining was found in 27 of 280 HNSCC tissue samples, in a subpopulation of cells in tumor cell nests. Fibroblast – tumor cell communication is a major pathway of matrix remodeling in HNSCC tumor tissue. Carcinoma-associated fibroblasts produce new matrix elements as TSP1, TSC and LTBP2, both tumor cells and fibroblasts upregulate integrin receptors, and they also share tasks in synthesis and activation of matrix remodeling enzymes. Intensive matrix re-organization takes place at the borders of tumor cell nests.