Tumor cell recognition of basement membranes is an important consideration in tumor cell invasion and metastasis formation. Despite the well established role for laminin in promoting tumor cell adhesion, there is also an important role for type IV collagen in mediating the adhesion, migration and invasion of transformed and malignant tumors. Published and preliminary data are presented to demonstrate that melanoma cell adhesion and migration on type IV collagen is an important contributing factor to invasion in vitro. Furthermore, cell surface receptors which interact with type IV collagen, including alpha2beta1 integrin and cell surface chondroitin sulfate proteoglycans (expressed with a CD44 core protein) are both important for mediating melanoma cell invasion through reconstituted basement membranes in vitro. The data also suggest that these two structurally distinct cell adhesion receptors collaborate to promote melanoma cell adhesion and motility. The integrin alpha2beta1 has been associated with melanoma progression, and CD44 is well known to modulate the migration of both normal and transformed cell types, including activated leukocytes, melanoma cells, and various other malignant tumors. While it is clear that type IV collagen is an important cell adhesion and motility-promoting component of basement membranes, relatively little is known regarding the structural features of type IV collagen that are important for its ability to promote cell adhesion and motility. We have recently used a novel peptide synthesis strategy to demonstrate that conformationally constraining a linear cell adhesion/motility promoting synthetic peptide from type IV collagen into a homotrimeric mini-triple helix can greatly enhance the cell adhesion promoting properties of the peptide in vitro, consistent with a number of published reports that emphasize the Importance of triple helical structure within collagens for cell adhesion promoting activity. We intend to use this strategy as one approach for further dissecting the molecular basis by which melanoma cells adhere and migrate on type IV collagen. We will initially focus on identifying sites that either promote melanoma cell adhesion and motility and/or interact with integrins (such as alpha2beta1, alpha1beta1, or others) or cell surface chondroitin sulfate proteoglycan/CD44. Structural variants of synthetic peptides, including variants that contain glycosylated hydroxylysine (where appropriate), or heterotrimeric variants (incorporating residues from both alpha1 (IV) and alpha2(IV) collagen chains), will be compared with linear peptides or homotrimeric peptides for their relative efficacy in directly mediating melanoma cell adhesion and motility, or to inhibit motility, invasion or metastasis formation. By systematically evaluating sites within type IV collagen that support melanoma cell adhesion and motility, we propose to further dissect the complex molecular basis of type IV collagen-mediated melanoma cell migration. In addition, these studies may provide a first generation of structurally constrained compounds that could be useful in metastasis management in vivo.
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