Jia Fang, Figueroa Said Daibes, Gallazzi Fabio, Balaji Baghavathy S, Hannink Mark, Lever Susan Z, Hoffman Timothy J, Lewis Michael R
Department of Veterinary Medicine and Surgery, University of Missouri-Columbia, Columbia, Missouri 65211, USA.
J Nucl Med. 2008 Mar;49(3):430-8. doi: 10.2967/jnumed.107.045138. Epub 2008 Feb 20.
The bcl-2 gene is overexpressed in non-Hodgkin's lymphoma (NHL), such as small lymphocytic lymphoma (SLL), and many other cancers. Noninvasive imaging of bcl-2 expression has the potential to identify patients at risk for relapse or treatment failure. The purpose of this study was to synthesize and evaluate radiolabeled peptide nucleic acid (PNA)-peptide conjugates targeting bcl-2 gene expression. An (111)In-labeled PNA complementary to the translational start site of bcl-2 messenger RNA was attached to Tyr(3)-octreotate for somatostatin receptor-mediated intracellular delivery.
DOTA-anti-bcl-2-PNA-Tyr(3)-octreotate (1) and 3 control conjugates (DOTA-nonsense-PNA-Tyr(3)-octreotate (2), DOTA-anti-bcl-2-PNA-Ala[3,4,5,6]-substituted congener (3), and DOTA-Tyr(3)-octreotate (4) [DOTA is 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid]) were synthesized by standard solid-phase 9-fluorenylmethoxycarbonyl (Fmoc) chemistry. In vitro studies were performed in Mec-1 SLL cells, which express both bcl-2 messenger RNA and somatostatin receptors. Biodistributions and microSPECT/CT studies were performed in Mec-1-bearing SCID (severe combined immunodeficiency) mice, a new animal model of human SLL.
(111)In-Labeled conjugate 1 was taken up by Mec-1 cells through a somatostatin receptor-mediated mechanism. Biodistribution studies showed specific tumor uptake of conjugate 1, the somatostatin analog 4, and the PNA nonsense conjugate 2, but not of the mutant peptide conjugate 3. Mec-1 tumors could be detected by microSPECT/CT using (111)In-labeled DOTA-Tyr(3)-octreotate (4) and the targeted anti-bcl-2 conjugate (1), but not using the 2 negative control conjugates 2 and 3.
A new (111)In-labeled antisense PNA-peptide conjugate demonstrated proof of principle for molecular imaging of bcl-2 expression in a new mouse model of human SLL. This imaging agent may be useful for identifying NHL patients at risk for relapse and conventional treatment failure.
bcl-2基因在非霍奇金淋巴瘤（NHL）如小淋巴细胞淋巴瘤（SLL）以及许多其他癌症中过度表达。对bcl-2表达进行无创成像有可能识别出有复发或治疗失败风险的患者。本研究的目的是合成并评估靶向bcl-2基因表达的放射性标记肽核酸（PNA）-肽缀合物。将与bcl-信使核糖核酸翻译起始位点互补的（111）In标记的PNA连接到Tyr(3)-奥曲肽上，用于生长抑素受体介导的细胞内递送。
通过标准的固相9-芴甲氧羰基（Fmoc）化学方法合成了DOTA-抗bcl-2-PNA-Tyr(3)-奥曲肽（1）和3种对照缀合物（DOTA-无义-PNA-Tyr(3)-奥曲肽（2）、DOTA-抗bcl-2-PNA-Ala[3,4,5,6]-取代类似物（3）和DOTA-Tyr(3)-奥曲肽（4）[DOTA是1,4,7,10-四氮杂环十二烷-N,N',N'',N'''-四乙酸]）。在同时表达bcl-2信使核糖核酸和生长抑素受体的Mec-1 SLL细胞中进行体外研究。在携带Mec-1的SCID（严重联合免疫缺陷）小鼠（一种人类SLL的新动物模型）中进行生物分布和微型SPECT/CT研究。
（111）In标记的缀合物1通过生长抑素受体介导的机制被Mec-1细胞摄取。生物分布研究显示缀合物1、生长抑素类似物4和PNA无义缀合物2有特异性肿瘤摄取，但突变肽缀合物3没有。使用（111）In标记的DOTA-Tyr(3)-奥曲肽（4）和靶向抗bcl-2缀合物（1）通过微型SPECT/CT可以检测到Mec-1肿瘤，但使用2种阴性对照缀合物2和3则检测不到。
一种新的（111）In标记的反义PNA-肽缀合物在人类SLL的新小鼠模型中证明了bcl-2表达分子成像的原理。这种成像剂可能有助于识别有复发和传统治疗失败风险的NHL患者。
