Tumor cell
metastasis involves a complex series of interdependent events, including repeated invasion of basement membranes. Studies from several laboratories have implicated
tumor cell adhesion and migration in response to
laminin as a major contributing factor in
tumor cell invasion. The current studies address the direct role of
type IV collagen in promoting
tumor cell adhesion, spreading, and migration. The observations of
type IV collagen-mediated cellular behavior are contrasted with cellular behavior on
type I collagen. The highly metastatic K1735 M4
melanoma cell line adhered, spread, and migrated in response to
type IV collagen in a concentration-dependent manner. Functional assays using well-defined proteolytic fragments of
type IV collagen demonstrated that
melanoma cells interact with multiple domains of this
protein. Highly metastatic
melanoma cells adhered, spread, and exhibited motile behavior in response to 0.2 to 200 nM concentrations of a purified
pepsin-generated, triple helix-rich domain of
type IV collagen. In contrast, cells adhered and spread but were essentially nonmotile in response to a purified major noncollagenous domain of the
protein. In addition, de novo
protein synthesis was required for cell adhesion to the major noncollagenous domain, whereas adhesion to the helical domain was less dependent upon de novo
protein synthesis.
Arg-Gly-Asp (RGD)-related
peptides were used to study the adhesion and spreading of
melanoma cells on
type IV collagen. The results demonstrated that a
serine containing RGD-related
peptide (
GRGDSP) has virtually no effect on
melanoma cell adhesion on
type IV collagen-coated substrata, whereas this
peptide inhibited
melanoma cell adhesion to
fibronectin-coated substrata in a concentration-dependent manner. In contrast, when
threonine was substituted for
serine (
GRGDTP), cell adhesion to
type IV collagen was significantly (45%) inhibited. The
threonine-containing
peptide virtually eliminated cell adhesion on substrata coated with
type I collagen. These data demonstrate that adhesion, spreading, and migration of
melanoma cells on
type IV collagen have a complex molecular basis which is partially dependent on RGD-related sequences.