title: Molecular imaging of breast tumors using a near-infrared fluorescently labeled clusterin binding peptide.
abstract: Several reports have shown that secreted clusterin (sCLU) plays multiple roles in tumor development and metastasis. Here, we report on a 12-mer sCLU binding peptide (designated P3378) that was identified by screening a phage-display peptide library against purified human sCLU. Differential resonance perturbation nuclear magnetic resonance using P3378 and a scrambled control peptide (designated P3378R) confirmed the P3378-sCLU interaction and demonstrated that it was sequence specific. P3378 and P3378R peptides were conjugated to an Alexa680 near infrared fluorophore (NIRF) and assessed for their tumor homing abilities in in vivo time-domain fluorescence optical imaging experiments using living 4T1 tumor bearing BALB/c mice. When injected in separate animals, both peptides accumulated at the tumor site, however the NIRF-labeled P3378 peptide was retained for a significant longer period of time than the P3378R peptide. Similar observations were made after simultaneously injecting the same tumor-bearing animal with a peptide mixture of P3378 DyLight (DL)680 and the P3378R-DL800. Coinjection of P3378-DL680 with excess unlabeled P3378 blocked tumor accumulation of fluorescent signal while excess P3378R control peptide did not confirming the sequence specificity of the tumor accumulation. Finally, ex vivo fluorescence microscopy of these tumors confirmed the presence of P3378-DL680 in the tumor and its colocalization with CLU. These results confirm the tumor targeting specificity of the P3378 CLU-binding peptide and suggest its usefulness for the in vivo monitoring of solid tumors secreting detectable levels of CLU.
authors: Receptors, Signaling and Proteomics Group, Biotechnology Research Institute, National Research Council of Canada, Montréal, QC, Canada.
authors: Rana
authors: R
authors: Filfil
authors: Béatrice
authors: B
authors: Paul-Roc
authors: Christiane
authors: C
authors: Cantin
authors: Umar
authors: U
authors: Iqbal
authors: Dmitri
authors: D
authors: Tolkatchev
authors: Anna
authors: A
authors: Vinogradova
authors: Ping
authors: P
authors: Xu
authors: Feng
authors: F
authors: Ni
authors: Maureen D
authors: MD
authors: O'Connor-McCourt
authors: Anne E G
authors: AE
authors: Lenferink
mesh_terms: D000818:Animals; D015153:Blotting, Western; D051152:Clusterin / Q000378:metabolism*; D005260:Female; D005455:Fluorescent Antibody Technique; D005456:Fluorescent Dyes; D006801:Humans; D015674:Mammary Neoplasms, Animal / Q000175:diagnosis* / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008856:Microscopy, Fluorescence; D057054:Molecular Imaging; D015335:Molecular Probes; D010446:Peptide Fragments / Q000378:metabolism*; D019151:Peptide Library; D019265:Spectroscopy, Near-Infrared; D014407:Tumor Cells, Cultured
chemical_list: C495242:CLU protein, human; D051152:Clusterin; D005456:Fluorescent Dyes; D015335:Molecular Probes; D010446:Peptide Fragments; D019151:Peptide Library