Differential modulation of human melanoma cell metalloproteinase expression by α₂β₁ integrin and CD44 triple-helical ligands derived from type IV collagen

Tumor cell binding to components of the basement membrane is well known to trigger intracellular signaling pathways. Signaling ultimately results in the modulation of gene expression, facilitating metastasis. Type IV collagen is the major structural component of the basement membrane and is known to be a polyvalent ligand, possessing sequences bound by the α1β 1, α2β1 and α 3β1 integrins, as well as cell surface proteoglycan receptors, such as CD44/chondroitin sulfate proteoglycan (CSPG). The role of α2β1 integrin and CD44/CSPG receptor binding on human melanoma cell activation has been evaluated herein using triple-helical peptide ligands incorporating the α1(IV)382-393 and α1(IV) 1263-1277 sequences, respectively. Gene expression and protein production of matrix metalloproteinases-1 (MMP-1), -2, -3, -13, and -14 were modulated with the α2β1-specific sequence, whereas the CD44-specific sequence yielded significant stimulation of MMP-8 and lower levels of modulation of MMP-1, -2, -13, and -14. Analysis of enzyme activity confirmed different melanoma cell proteolytic potentials based on engagement of either the α2β1 integrin or CD44/CSPG. These results are indicative of specific activation events that tumor cells undergo upon binding to select regions of basement membrane collagen. Based on the present study, triple-helical peptide ligands provide a general approach for monitoring the regulation of proteolysis in cellular systems.