Targeting gelatinases with a near-infrared fluorescent cyclic His-Try-Gly-Phe peptide.
OBJECTIVE
The purpose of the study is to synthesize and characterize near-infrared (NIR) fluorescence imaging probes targeted to gelatinases.


METHODS
A phage display-selected cyclic peptide containing the His-Try-Gly-Phe (HWGF) motif was used as the lead compound. Structure-activity relationship analysis was used to identify stable and potent gelatinase inhibitors suitable for NIR imaging applications.


RESULTS
Replacing the S-S bond in cyclic peptide c(CTTHWGFTLC)NH(2) (C1) with an amide bond between the epsilon-amino group of Lys and the side chain of Asp resulted in a significant increase in stability and a fourfold increase in gelatinase inhibition of the resulting peptide, c(KAHWGFTLD)NH(2) (C6). Conjugation of Cy5.5 to C6 led to Cy5.5-C6, which was selectively taken up by MMP-2 expressing human glioma U87 cells. In vivo, selective accumulation of Cy5.5-C6, but not Cy5.5-C1 or a Cy5.5-scrambled peptide conjugate, was visualized in intratibial prostate PC-3 tumors 48 h after their intravenous injection. Moreover, Cy5.5-C6 was readily visualized in orthotopically inoculated U87 brain tumors.


CONCLUSIONS
Cy5.5-C6 may be a useful agent for molecular imaging of gelatinases. The approach of producing stable cyclic peptides through side chain amide linkage should be applicable to other peptide-based imaging agents.
Department of Experimental Diagnostic Imaging, Unit 59, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
Wei
W
Wang
Ruping
R
Shao
Qingping
Q
Wu
Shi
S
Ke
John
J
McMurray
Frederick F
FF
Lang
Chusilp
C
Charnsangavej
Juri G
JG
Gelovani
Chun
C
Li
D000595:Amino Acid Sequence; D002232:Carbocyanines / Q000378:metabolism; D045744:Cell Line, Tumor; D055598:Chemical Phenomena; D005456:Fluorescent Dyes / Q000737:chemistry; D018093:Gelatinases / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D005910:Glioma / Q000473:pathology; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology; D008297:Male; D015394:Molecular Structure; D008970:Molecular Weight; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000302:isolation & purification; D011471:Prostatic Neoplasms / Q000473:pathology; D011485:Protein Binding; D055550:Protein Stability; D019265:Spectroscopy, Near-Infrared; D013329:Structure-Activity Relationship
C098793:CY5.5 cyanine dye; D002232:Carbocyanines; D005456:Fluorescent Dyes; D010456:Peptides, Cyclic; D018093:Gelatinases