Comparative studies of three 68Ga-labeled [Des-Arg10]kallidin derivatives for imaging bradykinin B1 receptor expression with PET.
Bradykinin B1 receptor (B1R) is a G-protein-coupled receptor that is overexpressed in a variety of cancers. B1R is not expressed in healthy tissues, making it an attractive cancer imaging marker. Previously, we reported selective uptake of (68)Ga-P03034 ((68)Ga-DOTA-dPEG2-Lys-Arg-Pro-Hyp-Gly-Cha-Ser-Pro-Leu) in B1R-positive (B1R+) HEK293T::hB1R tumor xenografts in mice. In this study, we compare (68)Ga-P03034 with (68)Ga-labeled P04158 ((68)Ga-DOTA-dPEG2-Lys-Lys-Arg-Pro-Hyp-Gly-Igl-Ser-D-Igl-Oic) and Z02090 ((68)Ga-DOTA-dPEG2-Lys-Lys-Arg-Pro-Hyp-Gly-Cpg-Ser-D-Tic-Cpg) derived from 2 potent B1R antagonists, B9858 and B9958, respectively, for imaging B1R expression with PET.


METHODS
Peptide sequences were assembled on solid-phase. Cold standards were prepared by incubating DOTA-conjugated peptides with GaCl3. Binding affinity was measured via competition binding assays using hB1R-expressing Chinese hamster ovary-K1 cell membranes. (68)Ga labeling was performed in N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) buffer with microwave heating and purified by high-performance liquid chromatography. Imaging/biodistribution studies were performed in mice bearing wild-type HEK293T (B1R-) and B1R+ HEK293T::hB1R tumors.


RESULTS
P03034, P04158, and Z02090 bound B1R with high affinity, with Ki values at 16.0 ± 2.9, 1.5 ± 1.9, and 1.1 ± 0.8 nM, respectively. (68)Ga-labeled P03034, P04159, and Z02090 were obtained in greater than 50% decay-corrected radiochemical yields with more than 99% radiochemical purity. Biodistribution studies showed that all three (68)Ga-labeled tracers cleared rapidly from the blood and normal tissues, with excretion mainly via the renal pathway. At 1 h after injection, only the kidneys, bladders, and B1R+ HEK293T::hB1R tumors were clearly visualized in PET images. Uptake values of (68)Ga-labeled P03034, P04158, and Z02090 in B1R+ tumors were 2.17 ± 0.49, 19.6 ± 4.50, and 14.4 ± 1.63 percentage injected dose per gram, respectively. Uptake ratios of B1R+ to B1R- tumor, blood, and muscle were 6.23 ± 1.69, 5.72 ± 2.20, and 25.5 ± 13.1 for (68)Ga-P03034; 34.5 ± 10.5, 19.2 ± 8.21, and 66.1 ± 17.0 for (68)Ga-P04158; and 29.3 ± 9.68, 29.9 ± 5.58, and 124 ± 28.1 for (68)Ga-Z02090, respectively.


CONCLUSIONS
All three (68)Ga-labeled B1R-targeting peptides generated specific and high-contrasted images of B1R+ tumors xenografted in mice. With significantly higher tumor uptake and target-to-nontarget ratios, (68)Ga-labeled P04158 and Z02090 are superior to P03034 for imaging B1R expression with PET.
Department of Molecular Oncology, BC Cancer Agency, Vancouver, British Columbia, Canada Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada; and.
Kuo-Shyan
KS
Lin
Department of Molecular Oncology, BC Cancer Agency, Vancouver, British Columbia, Canada.
Guillaume
G
Amouroux
Department of Molecular Oncology, BC Cancer Agency, Vancouver, British Columbia, Canada.
Jinhe
J
Pan
Department of Molecular Oncology, BC Cancer Agency, Vancouver, British Columbia, Canada.
Zhengxing
Z
Zhang
Department of Molecular Oncology, BC Cancer Agency, Vancouver, British Columbia, Canada.
Silvia
S
Jenni
Department of Molecular Oncology, BC Cancer Agency, Vancouver, British Columbia, Canada.
Joseph
J
Lau
Department of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada.
Zhibo
Z
Liu
Department of Molecular Oncology, BC Cancer Agency, Vancouver, British Columbia, Canada.
Navjit
N
Hundal-Jabal
Department of Molecular Oncology, BC Cancer Agency, Vancouver, British Columbia, Canada.
Nadine
N
Colpo
Department of Molecular Oncology, BC Cancer Agency, Vancouver, British Columbia, Canada Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada; and fbenard@bccrc.ca.
François
F
Bénard
D000818:Animals; D016466:CHO Cells; D003287:Contrast Media / Q000737:chemistry; D006224:Cricetinae; D003412:Cricetulus; D005710:Gallium Radioisotopes; D057809:HEK293 Cells; D006801:Humans; D007609:Kallidin / Q000031:analogs & derivatives* / Q000737:chemistry; D008297:Male; D051379:Mice; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D010455:Peptides / Q000737:chemistry; D049268:Positron-Emission Tomography / Q000379:methods*; D043783:Receptor, Bradykinin B1 / Q000378:metabolism*; D014057:Tomography, X-Ray Computed
D003287:Contrast Media; D005710:Gallium Radioisotopes; D010455:Peptides; D043783:Receptor, Bradykinin B1; D007609:Kallidin; C052787:kallidin, des-Arg(10)-
B9858; B9958; antagonist; bradykinin B1 receptor; positron emission tomography