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N-4-[18F]Fluorobenzoyl-c(RGDyK) .

Authors

Leung K1.

Source

Molecular Imaging and Contrast Agent Database (MICAD) [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2004-2013.
2006 Mar 06 [updated 2008 Mar 11].

Author information

1
National for Biotechnology Information, NLM, NIH, Bethesda, MD, Email: micad@ncbi.nlm.nih.gov

Excerpt

Integrins are a family of heterodimeric glycoproteins on cell surfaces that mediate diverse biological events involving cell-cell and cell-matrix interactions (1). Integrins consist of an α and a β subunit and are important for cell adhesion and signal transduction. αvβ3 integrin is the most prominent receptor affecting tumor growth, tumor invasiveness, metastasis, tumor-induced angiogenesis, inflammation, osteoporosis, and rheumatoid arthritis (2-7). Expression of αvβ3 integrin is strong on tumor cells and activated endothelial cells, whereas expression is weak on resting endothelial cells and most normal tissues. αvβ3 antagonists are being studied as antitumor and antiangiogenic agents and the agonists as angiogenic agents for coronary angiogenesis (6, 8, 9). A tripeptide sequence consisting of Arg-Gly-Asp (RGD) has been identified as a recognition motif used by extracellular matrix proteins (vitronectin, fibrinogen, laminin, and collagen) to bind to a variety of integrins, including αvβ3. Various radiolabeled antagonists have been introduced for imaging of tumors and tumor angiogenesis (10). Most of the cyclic RGD peptides are monomeric and composed of five amino acids. Haubner et al. (11) reported that various cyclic RGD peptides exhibit selective inhibition of binding to αvβ3 (IC50, 7-40 nM) but not to αvβ5 (IC50, 600-4,000 nM) or αIIbβ3 (IC50, 700-5,000 nM) integrin. [18F]FB-c(RGDyK) was synthesized to study in vivo biodistribution of the tracer in tumor-bearing mice. [18F]FB-c(RGDyK) was found to have high accumulation in tumors, but it also had a high tumor washout and biliary excretion into the gallbladder and intestines (12). A dimeric analog was also synthesized as [18F]FB-E[c(RGDyK)]2, which was shown to have higher tumor uptake than the monomer and predominantly renal excretion (13).

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