@misc{oai:repo.qst.go.jp:00069526,
 author = {Sogawa, Chizuru and Tsuji, Atsushi and Sugyou, Aya and Sudou, Hitomi and Okada, Keiichirou and Arano, Yasushi and Koizumi, Mitsuru and Furukawa, Takako and Harada, Yoshinobu and Saga, Tsuneo and 曽川 千鶴 and 辻 厚至 and 須尭 綾 and 須藤 仁美 and 岡田 圭一郎 and 荒野 泰 and 小泉 満 and 古川 高子 and 原田 良信 and 佐賀 恒夫},
 month = {Oct},
 note = {Aim: Gastrointestinal stromal tumor (GIST) is a most common mesenchymal tumor arising from the human gastrointestinal tract. Overexpression of c-kit, encoding type III receptor tyrosine kinase, and its functional mutation is present in most GIST. 18F-fluoro-deoxyglucose (FDG) has been reported to highly accumulate in GISTs, and positron emission tomography using FDG (FDG-PET) is very useful for tumor detection and also for the assessment of early response to treatments using Imatinib (Gleevec). However, FDG-PET, in some cases, fails to detect relapse of GIST at early time point. If we could develop a specific method to detect c-kit expression, it can be used for the evaluation of the early response and relapse of GISTs. In this study, we labeled anti-c-kit antibodies with 125I and 111In, and assessed its in vitro and in vivo characteristics.
Materials & methods: We constructed an expressing vector of mutated c-kit and transfected it to HEK293 human embryonic kidney cells and isolated several stable clones. To select highly expressing cell clones, we determined c-kit expression using western blot analysis and immunofluorescent staining. The cell suspension (1x107) was mixed with Matrigel, and injected subcutaneously in BALB/c-nu/nu male mice. We radiolabeled two anti-c-kit murine monoclonal antibodies (Mab1 and Mab2) with 125I using the chloramine-T or 3'-lodohippuryl-Ne-maleoyl-L-lysine (HML), and 111In using the 2-(p-isothiocyanatobenzyl) cyclohexyl-diethyl-enetriaminepentaacetic acid (CHX-A"-DTPA). We performed cell binding, competitive inhibition and internalization assays in vitro, and biodistribution and SPECT imaging in tumor-bearing mice.
Results: We isolated 18 c-kit stably expressing cell clones, and determined 6 of them highly express c-kit using western blotting analysis. Immunofluorescent staining of c-kit highly expressing cells showed that c-kit is primarily localized on the cell membrane like the original GIST cell line, and developed tumors in mice. 125I-MAb1, 125I-MAb1(HML), 125I-Mab2, 111In-MAb1 and 111In-MAb2 specifically bound to c-kit expressing cells with affinity constants of 4.3x108M-1, 5.2x108M-1, 3.5x108M-1, 3.4x108M-1 and 3.9x108M-1, respectively. These antibodies were internalized, and 111In-labeled Mab1 highly accumulated in xenografted tumors, which were visualized by SPECT.
Conclusion: These results showed that the radiolabeled c-kit antibody specifically accumulated in xenografted tumors and would be useful for the PET/SPECT imaging of GIST., Annual Congress of the European Association of Nuclear Medicine 2008},
 title = {Development of anti c-kit monoclonal antibody probe for SPECT imaging of gastrointestinal stromal tumor},
 year = {2008}
}