Synthetic peptides inhibit adhesion of human tumor cells to extracellular matrix proteins

Human tumor cell progression and metastasis are partially dependent on the ability of a tumor cell to adhere to the proteins of the extracellular matr ix (ECM) and survive at the distant location. Ex novel D-amino acid-contain ing peptides were analyzed for their ability to adhere to human prostate tu mor cells, support tumor cell adhesion, and inhibit tumor cell adhesion to ECR;I proteins or human dermal fibroblasts. Of these, two peptides called R Z-3 (kmviywkag) and HYD-1 (kikmviswkg) bound to tumor cell surfaces and com pared favorably with the previously reported AG-73 (RKRLQVQLSIRT) L-amino a cid peptide, as determined by fluorescence-activated cell sorting analysis. A scrambled peptide derivative of HYD-1, called HYDS-1 (wiksmkivkg), was n ot active. The RZ-3, HYD-1, and AG-73 peptides supported maximal cancer cel l adhesion at 5 mug, 10 mug, and 50 mug/well, respectively. The ECM protein s fibronectin, laminin I, and collagen IV supported maximal cell adhesion a t 1 mug, >10 mug, and 50 mug/well, respectively. Prostate tumor cell adhesi on to immobilized RZ-3 and HYD-1 peptides was inhibited by alpha2-6- and be ta1-integrin-blocking antibodies. Conversely, tumor cell adhesion to a beta 1-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 ce ll adhesion to each of the immobilized four ECM proteins (1.0 mug/well) in a time- and concentration-dependent manner. The IC50 of the RZ-3 peptide fo r blacking adhesion to fibronectin, laminin 1, laminin 5, and collagen TV w as 2.4 mug, 1.8 mug, 4.6 mug, and 2.8 mug/well, respectively. The IC50 of t he HYD-1 peptide for blocking adhesion to fibronectin, laminin 1, laminin 5 , and collagen IV was 6.9 mug, 5.7 mug, >10 mug, and 6.2 mug/well, respecti vely. Taken together, these results indicate that RZ-3 and HYD-1 are biolog ically 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.