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room temperature, and this probe was radiochemically stable for
the time of one PET scan. These analytical results were in compli-
ance with our in-house quality control/assurance specifications.
To determine brain radioactivity (expressed as standardized up-
take value: SUV), we performed PET with [11C]1 on wild-type and
Pgp/Bcrp knockout mice using a small-animal PET scanner.24
Figure 2A and B shows representative brain PET images of coronal
and horizontal views in a wild-type mouse. The brain uptake of
radioactivity in wild-type mice was quite low. Figure 2C and D
shows representative brain PET images in P-gp/Bcrp knockout
mice, in which radioactivity accumulation was seen. The brain up-
take in the knockout mice was higher than that in wild-type mice.
Figure 2E shows the time-activity curves in the brains of two
groups. The radioactivity levels, represented as values of area un-
der the time-activity curves (AUC0–60 min, SUV Â min), in the brain
between 0 and 60 min after injection of [11C]1 were 18.83 1.80
(n = 3) for P-gp/Bcrp knockout mice and 6.72 0.40 (n = 3) for
wild-type mice, respectively. The difference in the AUC0–60 min val-
ues of brains was statistically significant between the two groups
(P <0.05, Student’s paired t-test). As a control, there was no signif-
icant difference in the AUC0–60 min values of the cardiac blood pool
between the two groups of mice (data not shown).
15. Kawamura, K.; Yamasaki, T.; Yui, J.; Hatori, A.; Konno, F.; Kumata, K.; Konno, F.;
Irie, T.; Fukumura, T.; Suzuki, K.; Kanno, I.; Zhang, M.-R. Nucl. Med. Biol. 2009,
36, 239.
16. Yamasaki, T.; Fujinaga, M.; Kumata, K.; Kawamura, K.; Yui, J.; Hatori, A.; Zhang,
17. Roeda, D.; Dollé, F. Curr. Top. Med. Chem. 2010, 10, 1680.
18. Ogawa, M.; Takada, Y.; Suzuki, H.; Nemoto, K.; Fukumura, T. Nucl. Med. Biol.
2010, 37, 73.
These results indicated that the brain uptake related to [11C]1
was limited by P-gp and Bcrp at the BBB. The brain uptake of radio-
activity in P-gp/Bcrp knockout mice was increased by deficiency of
P-gp and Bcrp functions at the BBB. This Letter may enable evalu-
ation of the bioavailability of 1 in combination chemotherapy
against brain tumors. PET study with [11C]1 may provide useful
information for the treatment of renal cell carcinoma patients with
brain metastases, because a dual Bcrp and P-gp inhibitor, such as
elacridar,25,26 may improve brain permeability and thereby the
therapeutic efficacy of 1. Moreover, PET with [11C]1 may be used
to evaluate anticancer therapeutic effects of other molecular target
drugs, such as gefitinib15,27 and imatinib,28 which are also sub-
strates for P-gp and Bcrp.
19. Takada, Y.; Ogawa, M.; Suzuki, H.; Nemoto, K.; Fukumura, T. Appl. Radiat. Isot.
2010, 68, 1715.
20. Link, J. M.; Krohn, A. J. Labelled Compd. Radiopharm. 1997, 40, 306.
21. Compound
3 [4-(4-aminophenoxy)-N-methylpyridine-2-carboxamide]: mp:
105–106 °C. 1H NMR (300 MHz, CDCl3) d: 2.78 (3H, d, J = 4.77 Hz), 5.17 (2H, dd,
J = 8.80, 1.83 Hz), 6.64 (2H, dd, J = 8.80, 1.83 Hz), 6.86 (1H, dd, J = 8.80, 1.83 Hz),
7.05–7.08 (1H, m), 7.34 (1H, d, J = 2.20 Hz), 8.45 (1H, d, J = 5.50 Hz), 8.73 (1H,
br). FAB-MS calcd for C13H13N3O2: 243.27; found: 244 (M+H+).
22. Conway, T.; Diksic, M. J. Nucl. Med. 1988, 29, 1957.
23. Dollé, F.; Martarello, L.; Bramoullé, Y.; Bottlaender, M.; Gee, A. D. J. Labelled
Compd. Radiopharm. 2005, 48, 501.
24. A mouse was secured in a custom-designed chamber and placed in a small-
animal PET scanner (Inveon; Siemens Medical Solutions, Knoxville, TN). Body
temperature was maintained with a 40 °C water circulation system (T/Pump
TP401, Gaymar Industries, Orchard Park, NY). The mouse was kept under
anesthesia with 1.5% isoflurane during the scan. To inject [11C]1, a 29-gauge
needle with 12–15 cm of PE 10 tubing was placed into a tail vein of the mouse.
A dynamic emission scan in 3D list-mode was performed for 60 min (1 min  4
scans, 2 min  8 scans, 5 min  8 scans). A bolus of 11–16 MBq of [11C]1 in
In conclusion, [11C]1 was successfully labeled with carbon-11 at
its urea site using [11C]COCl2 as a labeling agent, via the intermedi-
ate preparation of isocyanate [11C]6. The preliminary results indi-
cated that [11C]1 is a promising PET probe for evaluating the
therapeutic efficiency of 1 for brain tumors. Studies on the effect
of P-gp or/and Bcrp modulators on the penetration of 1 into brain
tumors and imaging of modeled animals bearing tumor are in
progress.
100
lL saline was injected through the tail vein catheter. Wild-type (male; 17–
18 w.o.; 30–32 g; n = 3) and P-gp/Bcrp knockout (Abcb1a/1bÀ/ÀAbcg2À/À
;
male; 17–18 w.o.; 31–33 g; n = 3) mice (FVB; Taconic Farm; Hudson, NY) were
used in the PET experiments. Region-of-interest (ROI) analysis and image
reconstruction were performed using the software ASIPro (Siemens Medical
Solutions). Visual analysis was performed by individuals experienced in PET
interpretation using coronal, horizontal, and sagittal reconstructions. ROIs
were manually placed across image planes for time-activity curves.
Radioactivity was decay-corrected to the injection time and expressed as a
standardized uptake value (SUV), normalized for injected radioactivity and
Acknowledgments
We are grateful to Mrs. Y. Yoshida and N. Nobuki (SHI Acceler-
ator Service Co. Ltd) for technical support with radiosynthesis, and
to Mr. H. Wakizaka (National Institute of Radiological Sciences) for
assistance with PET scans. We also thank the staff of the National
Institute of Radiological Sciences for support with the cyclotron
operation and radionuclide production.
body
weight:
SUV = (radioactivity
per
milliliter
tissue/injected
radioactivity) Â body weight in grams. The area under the time–activity
curve of the ROIs in the brain (AUC0–60
starting from 0 to 60 min.
,
SUV Â min) was calculated
min
25. Yamasaki, T.; Kawamura, K.; Hatori, A.; Yui, J.; Yanamoto, K.; Yoshida, Y.;
Ogawa, M.; Nengaki, N.; Fukumura, T.; Zhang, M.-R. Nucl. Med. Commun. 2010,
31, 985.
26. Kawamura, K.; Yamazaki, T.; Konno, F.; Yui, J.; Hatori, A.; Yanamoto, K.;
Wakizaka, H.; Fukumura, T.; Zhang, M.-R. Mol. Imaging Biol. 2011, 13,
152.
27. Zhang, M.-R.; Kumata, K.; Hatori, A.; Takai, N.; Toyohara, J.; Yanamoto, K.;
Yamasaki, T.; Yui, J.; Kawamura, K.; Koike, S.; Ando, K.; Suzuki, K. Mol. Imaging
Biol. 2010, 12, 181.
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