Fibroblasts and extracellular matrix differently modulate MMP activation by primary and metastatic head and neck cancer cells

A genetically related pair of human head and neck cancer (HNSCC) cell lines derived from the same patient at different stages of disease was used to investigate the role of extracellular matrix, integrin, and CXCL12–CXCR4 receptor interactions and their signal pathways in MMP-2 and MMP-9 activation and cell invasion. We found that collagen I enhanced MMP-2 and MMP-9 secretion in both primary and metastatic HNSCC cells. Collagen I acted through α₂β₁ integrin to activate tyrosine kinases, protein kinase C, ERK1/2, and p38, which in turn activated MMP-2 and MMP-9 production. The signaling function was also involved in the enhancement of cell invasion. Experiments using cocultures between live and fixed cells demonstrated that direct contact between tumor and fibroblast cells was required to activate MMP-2 and MMP-9 secretion in both tumor cells and fibroblasts. The augmentation appears specific for MMP-2. Fibroblasts seem to be responsible for the increased MMP-2 in the coculture. In addition, fibroblast or tumor cell-conditioned media upregulated the secretion of MMP-2 and MMP-9 in HNSCC cells. These findings indicate that autocrine and paracrine factors are involved in the augmented secretion of MMPs in coculture. We also found that CXCL12-enhanced HNSCC cell invasion through paracrine-activated CXCR4, which triggered MMP-dependent cell invasion. Together, our results suggest that cell–matrix and cell–cell interactions including autocrine and paracrine factors play important roles in the invasive behavior of HNSCC via upregulation of MMP-2 and MMP-9.