RT Journal Article SR Electronic T1 Receptor binding assay, biodistribution and micro-SPECT/CT imaging of 111In-AMBA in human prostate tumor-bearing mice JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1524 OP 1524 VO 51 IS supplement 2 A1 Ho, Chung Li A1 Liu, I-Hshiang A1 Chen, Liang-Cheng A1 Lee, Wan-Chi A1 Wu, Yu-Hsien A1 Chen, Chun-Lin A1 Jan, Meei-Ling A1 Lin, Wuu-Jyh A1 Lee, Te-Wei A1 Chang, Chih-Hsien YR 2010 UL http://jnm.snmjournals.org/content/51/supplement_2/1524.abstract AB 1524 Objectives Gastrin-releasing peptide receptors (GRPRs) are overexpressed on a variety of human tumors like prostate, breast, and lung cancer. Bombesin (BN) is a 14 amino acid peptide with high affinity for these GRPRs. We synthesized DO3A-CH2-CO-G-4-aminobenzoyl-Q-W-A-V-G-H-L-M-NH2-(AMBA), a peptide chelated with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), and radiolabeled this BN analogue with 111InCl3. Biological activity of 111In-AMBA was evaluated in PC-3 prostate tumor-bearing SCID mice. Methods A solid phase approach was used to synthesize AMBA. The affinity of AMBA to BBN type 2 receptor was determined by a competitive displacement cell-binding assay using 125I-Tyr4-BN. The PC-3 tumor-bearing SCID mice were imaged by microSPECT/CT and sacrificed for biodistribution at 1, 4, 8, 24 and 48 hr after iv injection of 111In-AMBA. Results The purity of synthesized AMBA was greater than 95%. The IC50 and Ki of AMBA in the human bombesin 2 receptor were 0.33 ± 0.09 nM and 0.26 ± 0.07 nM, respectively. The radiolabeling efficiency of 111In-AMBA was 95.43 ± 1.37 %. In biodistribution, the higher uptake of tumor and tumor/muscle ratio was 3.87 ± 0.65 %ID/g and 11.7 at 8 hours after injection, respectively. The microSPECT/CT imaging studies with 111In-AMBA suggested the higher uptake of tumor was maintained between 8 and 48 hours post-injection. Conclusions Our result revealed AMBA has high affinity with BBN type 2 receptor. The results demonstrated a good uptake in the GRPR-over expression PC-3 tumor-bearing SCID mice. 111In-AMBA is a potential agent for imaging GRPR-positive tumors in humans