H-CRRETAWAC-OH, a lead structure for the development of radiotracer targeting integrin α5β1?
Imaging of angiogenic processes is of great interest in preclinical research as well as in clinical settings. The most commonly addressed target structure for imaging angiogenesis is the integrin α(v)β(3). Here we describe the synthesis and evaluation of [(18)F]FProp-Cys(*)-Arg-Arg-Glu-Thr-Ala-Trp-Ala-Cys(*)-OH, a radiolabelled peptide designed to selectively target the integrin α(5)β(1). Conjugation of 4-nitrophenyl-(RS)-2-[(18)F]fluoropropionate provided [(18)F]FProp-Cys(*)-Arg-Arg-Glu-Thr-Ala-Trp-Ala-Cys(*)-OH in high radiochemical purity (>95%) and a radiochemical yield of approx. 55%. In vitro evaluation showed α(5)β(1) binding affinity in the nanomolar range, whereas affinity to α(v)β(3) and α(IIb)β(3) was >50 μM. Cell uptake studies using human melanoma M21 (α(v)β(3)-positive and α(5)β(1)-negative), human melanoma M21-L (α(v)β(3)-negative and α(5)β(1)-negative), and human prostate carcinoma DU145 (α(v)β(3)-negative and α(5)β(1)-positive) confirmed receptor-specific binding. The radiotracer was stable in human serum and showed low protein binding. Biodistribution studies showed tumour uptake ranging from 2.5 to 3.5% ID/g between 30 and 120 min post-injection. However, blocking studies and studies using mice bearing α(5)β(1)-negative M21 tumours did not confirm receptor-specific uptake of [(18)F]FProp-Cys(*)-Arg-Arg-Glu-Thr-Ala-Trp-Ala-Cys(*)-OH, although this radiopeptide revealed high affinity and substantial selectivity to α(5)β(1) in vitro. Further experiments are needed to study the in vivo metabolism of this peptide and to develop improved radiopeptide candidates suitable for PET imaging of α(5)β(1) expression in vivo.
Department of Nuclear Medicine, Innsbruck Medical University, Anichstraße 35, 6020 Innsbruck, Austria.
Roland
0000-0002-4665-7433
R
Haubner
Department of Nuclear Medicine, Molecular Imaging and Radiochemistry, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Schwabachanlage 6, 91054 Erlangen, Germany.
Simone
S
Maschauer
Department of Chemistry and Pharmacy, Emil Fischer Center, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Schuhstraße 19, 91052 Erlangen, Germany.
Jürgen
J
Einsiedel
Department of Urology, Innsbruck Medical University, Anichstraße 35, 6020 Innsbruck, Austria.
Iris E
IE
Eder
Department of Nuclear Medicine, Innsbruck Medical University, Anichstraße 35, 6020 Innsbruck, Austria.
Christine
0000-0003-1167-9779
C
Rangger
Department of Chemistry and Pharmacy, Emil Fischer Center, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Schuhstraße 19, 91052 Erlangen, Germany.
Peter
P
Gmeiner
Department of Nuclear Medicine, Innsbruck Medical University, Anichstraße 35, 6020 Innsbruck, Austria.
Irene J
IJ
Virgolini
Department of Nuclear Medicine, Molecular Imaging and Radiochemistry, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Schwabachanlage 6, 91054 Erlangen, Germany.
Olaf
0000-0003-0247-3656
O
Prante
D000595:Amino Acid Sequence; D000818:Animals; D045744:Cell Line, Tumor; D004705:Endocytosis; D005434:Flow Cytometry; D005462:Fluorine Radioisotopes; D006801:Humans; D055767:Immobilized Proteins / Q000378:metabolism; D039081:Integrin alpha5beta1 / Q000378:metabolism*; D008297:Male; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008969:Molecular Sequence Data; D010455:Peptides / Q000097:blood / Q000138:chemical synthesis* / Q000737:chemistry; D010456:Peptides, Cyclic / Q000097:blood / Q000138:chemical synthesis* / Q000737:chemistry; D011485:Protein Binding; D055550:Protein Stability; D019275:Radiopharmaceuticals / Q000138:chemical synthesis* / Q000737:chemistry; D014018:Tissue Distribution
C000598756:2-fluoropropionate-cysteinyl-arginyl-arginyl-glutamyl-threonyl-alanyl-tryptophyl-alanyl-cysteine (1-9)-disulfide; D005462:Fluorine Radioisotopes; D055767:Immobilized Proteins; D039081:Integrin alpha5beta1; D010455:Peptides; D010456:Peptides, Cyclic; D019275:Radiopharmaceuticals