Nicolas Floquet

The Antitumor Properties of the α3(IV)-(185-203) Peptide from the NC1 Domain of Type IV Collagen (Tumstatin) Are Conformation-dependent

Tumor progression may be controlled by various fragments derived from noncollagenous 1 (NC1) C-terminal domains of type IV collagen. We demonstrated previously that a peptide sequence from the NC1 domain of the α3(IV) collagen chain inhibits the in vitro expression of matrix metalloproteinases in human melanoma cells through RGD-independent binding to αvβ3 integrin. In the present paper, we demonstrate that in a mouse melanoma model, the NC1 α3(IV)-(185-203) peptide inhibits in vivo tumor growth in a conformation-dependent manner. The decrease of tumor growth is the result of an inhibition of cell proliferation and a decrease of cell invasive properties by down-regulation of proteolytic cascades, mainly matrix metalloproteinases and the plasminogen activation system. A shorter peptide comprising the seven N-terminal residues 185-191 (CNYYSNS) shares the same inhibitory profile. The three-dimensional structures of the CNYYSNS and NC1 α3(IV)-(185-203) peptides show a β-turn at the YSNS (188-191) sequence level, which is crucial for biological activity. As well, the homologous MNYYSNS heptapeptide keeps the β-turn and the inhibitory activity. In contrast, the DNYYSNS heptapeptide, which does not form the β-turn at the YSNS level, is devoid of inhibitory activity. Structural studies indicate a strong structure-function relationship of the peptides and point to the YSNS turn as necessary for biological activity. These peptides could act as potent and specific antitumor antagonists of αvβ3 integrin in melanoma progression.

The YSNSG cyclopeptide derived from tumstatin inhibits tumor angiogenesis by down-regulating endothelial cell migration

We previously demonstrated that the CNYYSNS peptide derived from tumstatin inhibited in vivo tumor progression. The YSNS motif formed a β‐turn crucial for biological activity. More recently, a YSNSG cyclopeptide with a constrained β‐turn on the YSNS residues was designed. Intraperitoneal administration of the YSNSG cyclopeptide inhibited in vivo melanoma progression more efficiently than the native linear peptide. In the present article, we showed that the YSNSG cyclopeptide also triggered an inhibition of in vivo tumor neovascularization and we further analyzed its in vitroantiangiogenic effect. The YSNSG cyclopeptide did not alter endothelial cell proliferation but inhibited cell migration by 83% in an in vitro wound healing model. The inhibition was mediated by a decrease in active MT1‐MMP at the migration front as well as a decrease in u‐PA and u‐PAR expression. The cyclopeptide also altered β1‐integrin distribution in endothelial cell lamellipodia, induced a strong decrease in the phosphorylated focal adhesion kinase (p125FAK), disorganized F‐actin stress fibers and decreased the number of lamellipodia, resulting in a non migratory phenotype. Our results confirm the YSNSG cyclopeptide as a potent antitumor agent, through both the inhibition of invasive properties of tumor cells and the antiangiogenic activity.

Interaction between the elastin peptide VGVAPG and human elastin binding protein

Background: The interaction of the peptide VGVAPG with the elastin binding protein is critically involved in aneurysm progression. Results: A molecular model of this interaction is proposed and explored using a site-directed mutagenesis strategy. Conclusion: Three residues, Leu-103, Arg-107, and Glu-137, of elastin binding protein are critical players in this interaction. Significance: Our data now allow the design of antagonists of VGVAPG. The elastin binding protein (EBP), a spliced variant of lysosomal β-galactosidase, is the primary receptor of elastin peptides that have been linked to emphysema, aneurysm and cancer progression. The sequences recognized by EBP share the XGXXPG consensus pattern found in numerous matrix proteins, notably in elastin where the VGVAPG motif is repeated. To delineate the elastin binding site of human EBP, we built a homology model of this protein and docked VGVAPG on its surface. Analysis of this model suggested that Gln-97 and Asp-98 were required for interaction with VGVAPG because they contribute to the definition of a pocket thought to represent the elastin binding site of EBP. Additionally, we proposed that Leu-103, Arg-107, and Glu-137 were essential residues because they could interact with VGVAPG itself. Site-directed mutagenesis experiments at these key positions validated our model. This work therefore provides the first structural data concerning the interaction of the VGVAPG with its cognate receptor. The present structural data should now allow the development of EBP-specific antagonists.