Abstract
925
Objectives: Prostate-specific membrane antigen (PSMA) might be the most famous target for prostate cancer nuclear imaging and radio-therapy. Here we radio-labeled DKFZ-PSMA-617 with attractive radio-nuclide 64Cu (T1/2= 12.7h) in order to develop a novel non-invasive PET imaging and radionuclide therapy tracer.
Methods: DKFZ-PSMA-617 was labeled with 64Cu using 0.1 M pH 5.5 NaAc as reaction buffer. 64Cu-DKFZ-PSMA-617 was purified by spe-pak C-18 column using 80% ethanol as elution. The quality control including appearance, Radio-TLC/HPLC, endotoxins, sterility parameter were tested to formulate the 64Cu-DKFZ-PSMA-617. The cell uptake test of 64Cu-DKFZ-PSMA-617 in PSMA over-express LNCap cell and PSMA low-expressed PC-3 cell and BGC 823 cell were conducted. Micro-PET/CT images were acquired until 48 hours. Mice were euthanized after the last PET/CT imaging session, and the biodistribution of the 64Cu-DKFZ-PSMA-617 was performed. Both the autoradiography and immune-histology analysis of dissected PC-3 and BGC-823 tumor tissues were conducted.
Results: 64Cu-DKFZ-PSMA-617 was radio-synthesized in high radiochemical yield over 98% and specific activity upto 17.5 MBq/μg. The novel tracer showed good in vitro stability in each buffers. Cell uptakes of 64Cu-DKFZ-PSMA-617 in human prostate cancerLNCap, human prostate cancer PC-3 and human gastric BGC823 cancer cell were 4.7+0.0%, 2.3+0.5% and 1.7+0.5 %IA/106 cells, at 2 hours after incubation. Coadministration of N-[[[(1S)-1-Carboxy-3-methylbutyl]amino]- carbonyl]-L-glutamic acid (ZJ43) effectively reduced the uptake only in LNCap cells ( p< 0.01), not in PC-3 or BGC-823 cells (p> 0.05) . Micro-PET imaging of 64Cu-DKFZ-PSMA-617 was evaluated in both BGC 823 and PC 3 xenografts nude mice (n=4). BGC 823 and PC3 tumors were visualized on PET images at 30 min, 1h respectively, and better tumor-to-background lever achieved with prolonged time till 24h and 48 h after injection. Coadministration of ZJ43 can also substantial block the uptake in those tumors. Biodistribution studies were performed by injection of 64Cu-DKFZ-PSMA-617 tracer in normal mice, BGC823 and PC3 xenografts mice (n =3). Both the autoradiography and immune-histology analysis of dissected PC-3 and BGC-823 tumor tissues showed the specific uptake of 64Cu-DKFZ-PSMA-617 in those solid tumors .
Conclusion: We successfully synthesis a 64Cu radiolabeled PSMA targeted probes, to the best of our knowledge; it's the first time reported the radio-labeling and evaluation of 64Cu-DKFZ-PSMA-617 for PSMA over-expressed solid tumor 64Cu-DKFZ-PSMA-617 demonstrated specific binding ability to PSMA over-expressed cells and the corresponding solid tumors. All those results suggested 64Cu-PSMA-617 may guarantee as a novel tracer for tumor imaging more than prostate cancer. Acknowledgements: This work was supported, in part, the National Natural Science Foundation of China (No. 81371592, No. 81401467, No. 81501519, No. 81571705 and 81671733), Beijing Natural Science Foundation (No. 7162041 and No.7171002) and Beijing Municipal Commission of Health and Family Planning (215 backbone program).