Type IV collagen promotes
integrin-mediated cell adhesion, spreading, and motility. Several regions within the triple-helical domain of
type IV collagen have been identified as
tumor cellular recognition sites. Among these regions, the alpha1(IV)531-543 sequence, designated L-
Hep-III, promotes
integrin-mediated
tumor cell adhesion and directly binds to the
alpha3beta1 integrin [Miles, A. J., et al. (1994) J. Biol. Chem. 269, 30939-30945; Miles, A. J., et al. (1995) J. Biol. Chem. 270, 29047-29050]. We have presently compared the activities of the all-d enantiomeric
peptide model of alpha1(IV)531-543, designated D-
Hep-III, with L-
Hep-III, for promoting the adhesion, spreading, and motility of metastatic
melanoma and
breast carcinoma cells. D-
Hep-III was found to support
melanoma and
breast carcinoma cell adhesion, spreading, and motility in a dose-dependent fashion similar to that of L-
Hep-III. The adhesions of
melanoma and
breast carcinoma cells to both
type IV collagen and
fibronectin were effectively inhibited by L-
Hep-III and D-
Hep-III.
Melanoma cell invasion of the basement membrane was also inhibited by D-
Hep-III. Characterization of the
cell surface receptor for D-
Hep-III was acheived via cell adhesion assays and affinity chromatography using
monoclonal antibodies against
integrin subunits. Immunoprecipitation analysis following
EDTA elution from a D-
Hep-III affinity column indicated that D-
Hep-III binds to the
alpha3beta1 integrin but not to the alpha2 or
alpha6 integrin subunits. In summary, these studies demonstrate that an all-D model of the alpha1(IV)531-543 sequence mimics the
biological activities of the all-L
peptide. D-
Hep-III is the first all-D
peptide that has been shown to promote
tumor cell adhesion, spreading, and migration, inhibit
tumor cell adhesion and migration on
type IV collagen and invasion of the basement membrane, and bind directly to an
integrin. Due to the resistance to proteolysis, all-D receptor-binding
peptides such as D-
Hep-III have great potential for in vivo studies and as therapeutic agents.