Prometastatic GPCR CD97 Is a Direct Target of Tumor Suppressor microRNA-126

Tumor suppressor microRNA-126 (miR-126) is often down-regulated in cancer cells, and its overexpression is found to inhibit cancer metastasis. To elucidate the mechanism of tumor suppression by miR-126, we analyzed the proteomic response to miR-126 overexpression in the human metastatic breast cancer cell line MDA-MB-231. To acquire quantitative, time-resolved information, we combined two complementary proteomic methods, BONCAT and SILAC. We discovered a new direct target of miR-126: CD97, a pro-metastatic G-protein-coupled receptor (GPCR) that has been reported to promote tumor cell invasion, endothelial cell migration, and tumor angiogenesis. This discovery establishes a link between down-regulation of miR-126 and overexpression of CD97 in cancer and provides new mechanistic insight into the role of miR-126 in inhibiting both cell-autonomous and non-cell-autonomous cancer progression

Synthesis and Cell Adhesive Properties of Linear and Cyclic RGD Functionalized Polynorbornene Thin Films

Described herein is the efficient synthesis and evaluation of bioactive arginine-glycine-aspartic acid (RGD) functionalized polynorbornene-based materials for cell adhesion and spreading. Polynorbornenes containing either linear or cyclic RGD peptides were synthesized by ring-opening metathesis polymerization (ROMP) using the well-defined ruthenium initiator [(H₂IMes)­(pyr)₂(Cl)₂RuCHPh]. The random copolymerization of three separate norbornene monomers allowed for the incorporation of water-soluble polyethylene glycol (PEG) moieties, RGD cell recognition motifs, and primary amines for postpolymerization cross-linking. Following polymer synthesis, thin-film hydrogels were formed by cross-linking with bis­(sulfosuccinimidyl) suberate (BS³), and the ability of these materials to support human umbilical vein endothelial cell (HUVEC) adhesion and spreading was evaluated and quantified. When compared to control polymers containing either no peptide or a scrambled RDG peptide, polymers with linear or cyclic RGD at varying concentrations displayed excellent cell adhesive properties in both serum-supplemented and serum-free media. Polymers with cyclic RGD side chains maintained cell adhesion and exhibited comparable integrin binding at a 100-fold lower concentration than those carrying linear RGD peptides. The precise control of monomer incorporation enabled by ROMP allows for quantification of the impact of RGD structure and concentration on cell adhesion and spreading. The results presented here will serve to guide future efforts for the design of RGD functionalized materials with applications in surgery, tissue engineering, and regenerative medicine