(64)Cu-labeled CB-TE2A and diamsar-conjugated RGD peptide analogs for targeting angiogenesis: comparison of their biological activity.

Abstract

OBJECTIVES:

The alpha(v)beta(3) integrin is a cell adhesion molecule known to be involved in stages of angiogenesis and metastasis. In this study, the chelators CB-TE2A and diamsar were conjugated to cyclic RGDyK and RGDfD and the biological properties of (64)Cu-labeled peptides were compared.

METHODS:

CB-TE2A-c(RGDyK) and diamsar-c(RGDfD) were labeled with (64)Cu in 0.1 M NH(4)OAc (pH=8) at 95 degrees C and 25 degrees C, respectively. PET and biodistribution studies were carried out on M21 (alpha(v)beta(3)-positive) and M21L (alpha(v)-negative) melanoma-bearing mice. Binding affinity of the Cu-chelator-RGD peptides to alpha(v)beta(3) integrins was determined by a competitive binding affinity assay.

RESULTS:

Biological studies showed higher concentration of (64)Cu-CB-TE2A-c(RGDyK) in M21 tumor compared to M21L tumor at 1 and 4 h pi. Tumor concentration of (64)Cu-CB-TE2A-c(RGDyK) was higher than that of (64)Cu-diamsar-c(RGDfD). The difference is not due to differing binding affinities, since similar values were obtained for the agents. Compared to (64)Cu-diamsar-c(RGDfD), there is more rapid liver and blood clearance of (64)Cu-CB-TE2A-c(RGDyK), resulting in a lower liver and blood concentration at 24 h pi. Both (64)Cu-labeled RGD peptides show similar binding affinities to alpha(v)beta(3). The differences in their biodistribution properties are likely related to different linkers, charges and lipophilicities. The M21 tumor is clearly visualized with (64)Cu-CB-TE2A-c(RGDyK) by microPET imaging. Administration of c(RGDyK) as a block significantly reduced the tumor concentration; however, the radioactivity background was also decreased by the blocking dose.

CONCLUSIONS:

Both (64)Cu-CB-TE2A-c(RGDyK) and (64)Cu-diamsar-c(RGDfD) are potential candidates for imaging tumor angiogenesis. For diamsar-c(RGDfD), a linker may be needed between the Cu-chelator moiety and the RGD peptide to achieve optimal in vivo tumor concentration and clearance from nontarget organs.

• Authors: Lihui Wei, Yunpeng Ye, Thaddeus J Wadas, Jason S Lewis, Michael J Welch, Samuel Achilefu, Carolyn J Anderson
• Journal: Nuclear medicine and biology (Nucl Med Biol) Vol. 36 Issue 3 Pg. 277-85 (Apr 2009) ISSN: 1872-9614 [Electronic] United States
• PMID: 19324273 (Publication Type: Comparative Study, Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• (4,11-bis(carboxymethyl)-1,4,8,11-tetraazabicyclo(6.6.2)hexadecane)copper(II)
• Chelating Agents
• Dipeptides
• Heterocyclic Compounds
• Integrin alphaVbeta3
• Oligopeptides
• Organometallic Compounds
• alanyltyrosine
• arginyl-glycyl-aspartic acid
• diamsar chelate
• Sarcosine

Topics

• Animals
• Binding, Competitive
• Chelating Agents (chemistry)
• Dipeptides (chemistry)
• Heterocyclic Compounds (chemistry)
• Humans
• Integrin alphaVbeta3 (metabolism)
• Male
• Melanoma (diagnostic imaging, metabolism, pathology)
• Mice
• Neovascularization, Pathologic (diagnostic imaging, metabolism)
• Oligopeptides (chemistry, metabolism, pharmacokinetics)
• Organometallic Compounds (chemistry)
• Positron-Emission Tomography
• Sarcosine (analogs & derivatives, chemistry)
• Staining and Labeling
• Tissue Distribution