title: Initial characterization of a dually radiolabeled peptide for simultaneous monitoring of protein targets and enzymatic activity.
abstract: OBJECTIVE
  The goal of this study was to develop dually radiolabeled peptides for simultaneous imaging of cancer cell localization by targeting the α(v)β(3) integrin and their pathophysiology by targeting the activity of the proteolytic enzyme MMP2, involved in the metastatic process.
  
  
  METHODS
  A hybrid peptide c(RGDfE)K(DOTA)PLGVRY containing an RGD motif for binding to the α(v)β(3)integrin, a metal chelator (DOTA) for radiolabeling with [(64)Cu], and the MMP2 substrate cleavage sequence PLGVRY with terminal tyrosine for labeling with [(123)I] was synthesized, labeled with [(64)Cu] and [(123)I], and evaluated in vitro as a potential imaging agent.
  
  
  RESULTS
  The peptide was synthesized and labeled with [(64)Cu] and [(123)I] with 300 and 40 μCi/μg (542 and 72.2 mCi/μmol) specific activities, respectively, and radiochemical purity of >98%. c(RGDfE)K(DOTA)PLGVRY demonstrated high affinity for α(v)β(3) integrins (Kd=83.4+13.2 nM) in both substrate competition and cell binding assays. c(RGDfE)K(DOTA)PLGVRY peptide, but not the scrambled version, c(RGDfE)K(DOTA)GRPLVY was specifically cleaved by MMP2.
  
  
  CONCLUSIONS
  These results demonstrate the feasibility of developing dually radiolabeled peptides for the simultaneous imaging of cancer cells and their pathophysiologic activity.
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, Box 8225, St Louis, MO 63110, USA.
authors.forename: Efrem
authors.initials: E
authors.lastname: Mebrahtu
authors.forename: Alexander
authors.initials: A
authors.lastname: Zheleznyak
authors.forename: Minjun A
authors.initials: MA
authors.lastname: Hur
authors.forename: Richard
authors.initials: R
authors.lastname: Laforest
authors.forename: Suzanne E
authors.initials: SE
authors.lastname: Lapi
mesh_terms: D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D003301:Copper Radioisotopes; D004355:Drug Stability; D057075:Enzyme Assays / Q000379:methods*; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry*; D006801:Humans; D006877:Hydroxamic Acids; D007211:Indoles / Q000494:pharmacology; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D007457:Iodine Radioisotopes; D007553:Isotope Labeling; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D061965:Matrix Metalloproteinase Inhibitors / Q000494:pharmacology; D064847:Multimodal Imaging / Q000379:methods*; D009842:Oligopeptides / Q000097:blood / Q000737:chemistry / Q000378:metabolism*; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography; D059748:Proteolysis; D013997:Time Factors; D014057:Tomography, X-Ray Computed
chemical_list: D003301:Copper Radioisotopes; D006573:Heterocyclic Compounds, 1-Ring; D006877:Hydroxamic Acids; D007211:Indoles; D039302:Integrin alphaVbeta3; D007457:Iodine Radioisotopes; D061965:Matrix Metalloproteinase Inhibitors; D009842:Oligopeptides; C071349:1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid; C047981:arginyl-glycyl-aspartic acid; D020778:Matrix Metalloproteinase 2; C119203:ilomastat