Smith C Jeffrey, Sieckman Gary L, Owen Nellie K, Hayes Donald L, Mazuru Dana G, Volkert Wynn A, Hoffman Timothy J
Departments of Radiology and Nuclear Science, Engineering Institute, University of Missouri-Columbia School of Medicine, Columbia, MO, USA.
Anticancer Res. 2003 Jan-Feb;23(1A):63-70.
Bombesin (BBN), a 14 amino acid peptide, is an analogue of human gastrin-releasing peptide (GRP) that binds to GRP receptors (GRPr) with high affinity and specificity. The GRPr is over-expressed on a variety of human cancer cells including prostate, breast, lung, and pancreatic cancers. The specific aim of this study was to develop a 188Re(I)-radiolabeled BBN analogue that maintains high specificity for the GRPr in vivo.
A preselected synthetic sequence via solid phase peptide synthesis (SPPS) was designed to produce a Dpr-BBN (Dpr = Diaminopropionic acid) conjugate with the following general structure: Dpr-X-Q-W-A-V-G-H-L-M-(NH2), where the spacer group, X = Serylserylserine. The new BBN-construct was purified by reversed phase-HPLC (RP-HPLC). The non-radioactive Re(I)-BBN conjugate was prepared by the reaction of [Re(Br)3(CO)3]2- and Dpr-SSS-bombesin(7-14)NH2 with heating. ES-MS was used to determine the molecular constitution of the non-metallated and metallated Re (I)--conjugates. The 188 Re-conjugate was prepared at the tracer level by the pre-conjugation, postlabeling approach from the reaction of [188Re(H2O)3(CO)3]+ and corresponding ligand.
The 188Re- and non-radioactive Re(I)conjugate behaved similarly under identical RP-HPLC conditions. In vitro cell displacement assays showed that the new conjugate has an IC50 value of approximately 1 nM. In vitro cell binding assays showed that the new conjugate is rapidly internalized and exhibits long-term retention, demonstrating the agonistic efficacy of the radiolabel. In vivo targeting of human prostate, PC-3 tumor xenografts indicated uptake and retention of the new radioconjugate for time-point < or = 24 hours.
Results from in vitro and in vivo models demonstrated the ability of these derivatives to specifically target GRP receptors on human, prostate and cancerous PC-3 cells. This new construct holds potential for the development of a therapeutic entity for the treatment of prostate cancer.
蛙皮素（BBN）是一种含14个氨基酸的肽，是人胃泌素释放肽（GRP）的类似物，能以高亲和力和特异性与GRP受体（GRPr）结合。GRPr在包括前列腺癌、乳腺癌、肺癌和胰腺癌在内的多种人类癌细胞上过度表达。本研究的具体目的是开发一种188Re（I）放射性标记的BBN类似物，该类似物在体内对GRPr保持高特异性。
通过固相肽合成（SPPS）设计了一个预选的合成序列，以产生具有以下一般结构的Dpr-BBN（Dpr = 二氨基丙酸）缀合物：Dpr-X-Q-W-A-V-G-H-L-M-(NH2)，其中间隔基团X = 丝氨酰丝氨酰丝氨酸。新的BBN构建体通过反相高效液相色谱（RP-HPLC）纯化。非放射性Re（I）-BBN缀合物通过[Re(Br)3(CO)3]2-与Dpr-SSS-蛙皮素（7-14）NH2加热反应制备。电喷雾质谱（ES-MS）用于确定未金属化和金属化的Re（I）缀合物的分子组成。188Re缀合物通过预共轭、后标记方法，由[188Re(H2O)3(CO)3]+与相应配体反应在示踪剂水平制备。
在相同的RP-HPLC条件下，188Re和非放射性Re（I）缀合物的行为相似。体外细胞置换试验表明，新缀合物的IC50值约为1 nM。体外细胞结合试验表明，新缀合物能迅速内化并表现出长期滞留，证明了放射性标记的激动剂功效。对人前列腺PC-3肿瘤异种移植模型的体内靶向研究表明，新的放射性缀合物在时间点≤24小时时有摄取和滞留。
体外和体内模型的结果表明，这些衍生物能够特异性靶向人前列腺癌和癌性PC-3细胞上的GRP受体。这种新构建体具有开发用于治疗前列腺癌的治疗实体的潜力。
