title: Peptide-based MRI contrast agent and near-infrared fluorescent probe for intratumoral legumain detection.
abstract: Recent studies suggest that intratumoral legumain promotes tumorigenesis. To monitor legumain activity in tumors, we developed a new MRI contrast agent ([Gd-NBCB-TTDA-Leg(L)]) and a NIR fluorescence probe (CyTE777-Leg(L)-CyTE807). The MRI contrast agent was prepared by introduction of cyclobutyl and benzyl group residues to TTDA (3,6,10-tri(carboxymethyl)-3,6,10-triaza-dodecanedioic acid), followed by the attachment of a legumain-specific substrate peptide (Leg(L)). The NIR fluorescence probe was designed by conjugating two NIR fluorochromes (CyTE777 and CyTE807) with Leg(L). Peptide cleavage of the MRI contrast agent by legumain can increase its hydrophobicity and promote rotational correlation time (τ(R)). Peptide cleavage of the NIR probes by the legumain relieves the self quench of the probe. Peptide cleavage of the MRI contrast agent and the NIR fluorescence probe by legumain were confirmed by T1 relaxometric studies and by fluorescence studies, respectively. In vivo MR images showed that [Gd-NBCB-TTDA-Leg(L)] attained 55.3 fold (254.2% versus 4.6%, at 2.0 h post-injection) higher imaging enhancement, as compared with control contrast agent bearing a noncleaveable peptide ([Gd-NBCB-TTDA-Leg(D)], in the CT-26 (legumain(+)) tumors. Similarly, optical imaging probe CyTE777-Leg(L)-CyTE807 attained 15.2 fold (3.34 × 10(9) photons/min versus 0.22 × 10(9) photons/min, at 24.0 h post-injection) higher imaging enhancement in the CT-26 (legumain(+)) tumors, compared to a NIR control probe (CyTE777-Leg(D)-CyTE807). These data indicate that the [Gd-NBCB-TTDA-Leg(L)] and the CyTE777-Leg(L)-CyTE807 probes may be promising tools to image the legumain-expressing cancers for diagnoses and targeted treatments.
authors.affiliation: Department of Biological Science and Technology, National Chiao Tung University, 75 Bo-Ai Street, Hsinchu 300, Taiwan.
authors.forename: Yu-Jen
authors.initials: YJ
authors.lastname: Chen
authors.forename: Shou-Cheng
authors.initials: SC
authors.lastname: Wu
authors.forename: Chung-Yung
authors.initials: CY
authors.lastname: Chen
authors.forename: Shey-Cherng
authors.initials: SC
authors.lastname: Tzou
authors.forename: Tian-Lu
authors.initials: TL
authors.lastname: Cheng
authors.forename: Ying-Fang
authors.initials: YF
authors.lastname: Huang
authors.forename: Shyng-Shiou
authors.initials: SS
authors.lastname: Yuan
authors.forename: Yun-Ming
authors.initials: YM
authors.lastname: Wang
mesh_terms: D000818:Animals; D003287:Contrast Media; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D005456:Fluorescent Dyes; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D008819:Mice, Nude; D009374:Neoplasms, Experimental / Q000378:metabolism*; D010455:Peptides / Q000008:administration & dosage*; D013050:Spectrometry, Fluorescence; D019265:Spectroscopy, Near-Infrared; D000099240:Asparaginyl Endopeptidase
chemical_list: D003287:Contrast Media; D003546:Cysteine Endopeptidases; D005456:Fluorescent Dyes; D010455:Peptides; D000099240:Asparaginyl Endopeptidase
keywords: Contrast agent; Legumain; MRI; Optical imaging