Human
tumor cell progression and
metastasis are partially dependent on the ability of a
tumor cell to adhere to the
proteins of the extracellular matrix (ECM) and survive at the distant location. Six novel D-
amino acid-containing
peptides were analyzed for their ability to adhere to human prostate
tumor cells, support
tumor cell adhesion, and inhibit
tumor cell adhesion to ECM
proteins or human dermal fibroblasts. Of these, two
peptides called RZ-3 (kmviywkag) and HYD-1 (
kikmviswkg) bound to
tumor cell surfaces and compared favorably with the previously reported
AG-73 (
RKRLQVQLSIRT) L-
amino acid peptide, as determined by fluorescence-activated cell sorting analysis. A scrambled
peptide derivative of HYD-1, called HYDS-1 (wiksmkivkg), was not active. The RZ-3, HYD-1, and
AG-73 peptides supported maximal
cancer cell adhesion at 5 microg, 10 microg, and 50 microg/well, respectively. The ECM
proteins fibronectin,
laminin 1, and
collagen IV supported maximal cell adhesion at 1 microg, >10 microg, and 50 microg/well, respectively. Prostate
tumor cell adhesion to immobilized RZ-3 and HYD-1
peptides was inhibited by alpha2-6- and beta1-integrin-blocking
antibodies. Conversely,
tumor cell adhesion to a beta1-integrin-specific antibody was blocked by both RZ-3 and HYD-1. Epithelial cell adhesion to dermal fibroblasts was inhibited by HYD-1 and unaffected by the scrambled
peptide, HYDS-1. Cell adhesion to immobilized
peptides was unaffected by
EDTA. The soluble RZ-3 and HYD-1
peptides inhibited
tumor cell adhesion to each of the immobilized four ECM
proteins (1.0 microg/well) in a time- and concentration-dependent manner. The IC(50) of the RZ-3
peptide for blocking adhesion to
fibronectin,
laminin 1,
laminin 5, and
collagen IV was 2.4 microg, 1.8 microg, 4.6 microg, and 2.8 microg/well, respectively. The IC(50) of the HYD-1
peptide for blocking adhesion to
fibronectin,
laminin 1,
laminin 5, and
collagen IV was 6.9 microg, 5.7 microg, >10 microg, and 6.2 microg/well, respectively. Taken together, these results indicate that RZ-3 and HYD-1 are biologically active D-
amino acid-containing
peptides that can themselves support
tumor cell adhesion and can inhibit
tumor cell adhesion to immobilized ECM
proteins or dermal fibroblasts.