Gluc-Lys([Al^(18)F]NOTA)-KE108的制备及初步生物学评价

Preparation and preliminary biological evaluation of Gluc-Lys([Al^(18)F]NOTA)-KE108

放射性核素标记的生长抑素类似物可与神经内分泌肿瘤(Neuroendocrine Tumors,NETs)细胞表面的生长抑素受体(Somatostatin Receptor,SSTR)特异性结合,对NETs进行显像或治疗。本研究设计合成了一种新型生长抑素类似物Gluc-Lys([Al^(18)F]NOTA)-KE108探针——活性分子片段KE108多肽,通过偶联双功能螯合剂(1,4,7-Triazacyclononane-1,4,7-Triacetic Acid,NOTA)螯合Al^(18)F进行放射性核素标记以靶向SSTR阳性肿瘤。经测定,总合成时间约为20 min,探针标记率为(30±5)%(n=6)(未校正),放射化产率为(20±5)%(n=6)(未校正),Sep-pak C-18 light柱纯化之后放化纯可达95%以上,比活度大于1.37 GBq∙μmol−1。Gluc-Lys([Al^(18)F]NOTA)-KE108呈水溶性(logP=−2.172±0.03(n=5)),在体外具有良好的稳定性,在生理盐水及小牛血清中2 h之内,放化纯大于95%。在细胞实验中,该探针在SSTR阳性AR42J和BON1肿瘤细胞中表现出纳摩尔级别的结合亲和力(Kd值分别为(152.3±49.1)nmol∙L^(−1)和(45.5±13.6)nmol∙L^(−1)),并且能够被特异性抑制,展现出较高的SSTR靶向能力。Gluc-Lys([Al^(18)F]NOTA)-KE108在AR42J荷瘤鼠正电子发射断层显像(Positron EmissionTomography,PET)显像中肿瘤部位具有较高的放射性摄取,具有高的肿瘤与肌肉摄取比值。研究表明,Al^(18)F标记的生长抑素类似物Gluc-Lys([Al^(18)F]NOTA)-KE108可作为SSTR阳性肿瘤的潜在显像剂。

[Background]Radionuclide labeled somatostatin analogs can specifically bind to somatostatin receptors(SSTRs)on the cell surface of neuroendocrine tumors(NETs),hence be used for imaging or treatment of NETs.[Purpose]This study aims to label glycosylated KE108 protein with^(18)F nuclide,and to investigate the distributions and PET imaging of this probe in mice in vivo.[Methods]A novel^(18)F-radiolabeled somatostatin analogue probe Gluc-Lys([Al^(18)F]NOTA)-KE108 was designed and synthesized,which linked^(18)F nuclide and glycosylated KE108 protein by coupling bifunctional chelator(NOTA)to target SSTR positive tumors.The in vitro physicochemical properties,in vitro cell binding,ex vivo biodistribution and in vivo imaging of Gluc-Lys([Al^(18)F]NOTA)-KE108 were further investigated to evaluate the SSTR targeting ability and feasibility of PET imaging in the diagnosis of NETs.[Results]The efficiency of Gluc-Lys([Al^(18)F]NOTA)-KE108 obtained with moderate labelling is(30±5)%without corrected(n=6),and the radiochemical purity is higher than>95%.The radiochemical yield is((20±5)%,uncorrected)(n=6),and the total synthesis time is about 20 min.The specific activity is more than 1.37 GBq∙μmol^(−1).The probe shows expected nanomolar binding affinity in SSTR-positive AR42J and BON1 tumor cells,which Kd values are(152.3±49.1)nmol∙L^(−1)and(45.5±13.6)nmol∙L−1,respectively,and can be specifically inhibited,showing high SSTR targeting ability.In PET imaging of AR42J tumor bearing mice,Gluc-Lys([Al^(18)F]NOTA)-KE108 has a high uptake of radioactivity and a high ratio of tumor to muscle uptake.[Conclusions]Gluc-Lys([Al^(18)F]NOTA)-KE108 has high hydrophilicity and good stability in vitro,hence be served as a potential imaging agent for SSTR positive tumors.