Differential Modulation of Human Melanoma Cell Metalloproteinase Expression by α2β1 Integrin and CD44 Triple-helical Ligands Derived from Type IV Collagen

Abstract

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 ␣ 1 ␤ 1 , ␣ 2 ␤ 1 , and ␣ 3 ␤ 1 integrins, as well as cell surface proteoglycan receptors, such as CD44/chondroitin sulfate proteoglycan (CSPG). The role of ␣ 2 ␤ 1 integrin and CD44/CSPG receptor binding on human melanoma cell activation has been evaluated herein using triple-helical peptide ligands incorporating the ␣1(IV)382-393 and ␣1(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 ␣ 2 ␤ 1 -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 ␣ 2 ␤ 1 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.Melanoma is one of the most rapidly increasing malignancies in the world in both young and old patients, with over 50,000 newly diagnosed patients each year (1). 1 Mortality from cancer is frequently due to metastasis, given that surgical excision of the primary tumor considerably enhances the prognosis of a patient and prolongs survival (2). Metastasis is a complex series of finely coordinated events that results in cancer cells circulating in lymph and blood vascular systems to invade remote tissues and establish secondary sites of tumor growth (3). Extravasation of the tumor cell into secondary tissues requires alterations in cellular behaviors, resulting from specific adhesion to components of the basement membrane. Tumor cells respond to each of the various components of the ECM, 2 including the collagens; noncollagenous glycoproteins, such as fibronectin and laminin; and proteoglycans, such as decorin and syndecan (4). These interactions are known to occur through several families of cell surface receptors, including the integrins and cell surface proteoglycans.Integrins are heterodimeric proteins composed of one ␣ and one ␤ subunit and are the best described of the cell surface adhesion molecules. To date, there are 18 different ␣ subunits and 8 distinct ␤ subunits identified that combine to form at least 24 heterodimers (5-7). Although the specific integrin expression profile can fluctuate with tumor type and stage of progression, highly metastatic melanoma cells are known to up-regulate expression of, and ␣ 6 ␤ 4 integrins while down-regulating the expression ...

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