In vivo near-infrared fluorescence imaging of integrin α2β1 in prostate cancer with cell-penetrating-peptide-conjugated DGEA probe.

Abstract

UNLABELLED:

The overexpression of integrin α(2)β(1) has been demonstrated to correlate with prostate tumor aggressiveness and metastatic potential. Recently, we reported that the DGEA peptide is a promising targeting ligand for near-infrared fluorescence and microPET imaging of integrin α(2)β(1) expression in prostate cancers. Here, we aimed to further improve the targeting efficacy of this peptide by incorporating a series of cell-penetrating peptides (CPPs) into the DGEA sequence.

METHODS:

After the conjugation with appropriate fluorescent dyes, the CPP-DGEA peptides were evaluated in human prostate cell lines (PC-3, CWR-22, and LNCaP) that contain different integrin α(2)β(1) expression levels. In addition, to reduce excess kidney uptake, a carboxypeptidase-specific sequence Gly-Lys was incorporated into the probe design, allowing for cleavage by the kidney brush border enzymes of the CPP before uptake by proximal tubule cells.

RESULTS:

Although the CPP motif greatly facilitated the translocation of CPP-DGEA without affecting binding specificity in vitro, fluorescent dye-labeled CPP-DGEA demonstrated extremely high kidney uptake in vivo. Kidney uptake was dramatically decreased after a carboxypeptidase-specific peptide linker (Gly-Lys) had been incorporated into the probe design. The optimized probe demonstrated a prominent accumulation of activity in PC-3 tumor (integrin α(2)β(1)-positive). Receptor specificity was confirmed with blocking experiments and evaluation in a CWR-22 control tumor model with low α(2)β(1) expression.

CONCLUSION:

This study demonstrated that the introduction of a CPP sequence can facilitate the internalization of an integrin-targeted peptide probe in vitro. Moreover, a cleavable peptide linker successfully reduced kidney uptake while preserving good tumor uptake in vivo.

• Authors: Chiun-Wei Huang, Zibo Li, Peter S Conti
• Journal: Journal of nuclear medicine : official publication, Society of Nuclear Medicine (J Nucl Med) Vol. 52 Issue 12 Pg. 1979-86 (Dec 2011) ISSN: 1535-5667 [Electronic] United States
• PMID: 22065876 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Cell-Penetrating Peptides
• Fluorescent Dyes
• Integrin alpha2beta1
• Oligopeptides
• aspartyl-glycyl-glutamyl-alanine

Topics

• Biological Transport
• Cell Line, Tumor
• Cell-Penetrating Peptides (metabolism)
• Fluorescent Dyes (metabolism)
• Humans
• Infrared Rays
• Integrin alpha2beta1 (metabolism)
• Kidney (metabolism)
• Male
• Molecular Imaging (methods)
• Oligopeptides (metabolism)
• Optical Phenomena
• Prostatic Neoplasms (pathology)