Trencsényi György, Dénes Noémi, Nagy Gábor, Kis Adrienn, Vida András, Farkas Flóra, Szabó Judit P, Kovács Tünde, Berényi Ervin, Garai Ildikó, Bai Péter, Hunyadi János, Kertész István
Department of Medical Imaging, Nuclear Medicine, University of Debrecen, Debrecen, Hungary; Scanomed LTD, Debrecen, Hungary.
Department of Medical Imaging, Nuclear Medicine, University of Debrecen, Debrecen, Hungary.
J Pharm Biomed Anal. 2017 May 30;139:54-64. doi: 10.1016/j.jpba.2017.02.049. Epub 2017 Mar 1.
Malignant melanoma is the most aggressive form of skin cancer. The early detection of primary melanoma tumors and metastases using non-invasive PET imaging determines the outcome of this disease. Previous studies have shown that benzamide derivatives (e.g. procainamide) conjugated with PET radionuclides specifically bind to melanin pigment of melanoma tumors. Ga chelating agents can have high influence on physiological properties of Ga labeled bioactive molecules, as was experienced during the application of HBED-CC on PSMA ligand. The aim of this study was to assess this concept in the case of the melanin specific procaindamide (PCA) and to compare the melanin specificity of Ga-labeled PCA using HBED-CC and NODAGA chelators under in vitro and in vivo conditions. Procainamide (PCA) was conjugated with HBED-CC and NODAGA chelators and was labeled with Ga-68. The melanin specificity of Ga-HBED-CC-PCA and Ga-NODAGA-PCA was investigated in vitro and in vivo using amelanotic (MELUR and A375) and melanin containing (B16-F10) melanoma cell lines. Tumor-bearing mice were prepared by subcutaneous injection of B16-F10, MELUR and A375 melanoma cells into C57BL/6 and SCID mice. 21±2days after tumor cell inoculation and 90min after intravenous injection of the Ga-labelledlabeled radiopharmacons whole body PET/MRI scans were performed. Ga-NODAGA-PCA and Ga-HBED-CC-PCA were produced with excellent radiochemical purity (98%). In vitro experiments demonstrated that after 30 and 90min incubation time Ga-NODAGA-PCA uptake of B16-F10 cells was significantly (p≤0.01) higher than the Ga-HBED-CC-conjugated PCA accumulation in the same cell line. Furthermore, significant difference (p≤0.01 and 0.05) was found between the uptake of melanin negative and positive cell lines using Ga-NODAGA-PCA and Ga-HBED-CC-PCA. In vivo PET/MRI studies using tumor models revealed significantly (p≤0.01) higher Ga-NODAGA-PCA uptake (SUVmean: 0.46±0.05, SUVmax: 1.96±0.25,T/M ratio: 40.7±4.23) in B16-F10 tumors in contrast to Ga-HBED-CC-PCA where the SUVmean, SUVmax and T/M ratio were 0.13±0.01, 0.56±0.11 and 11.43±1.24, respectively. Melanin specific PCA conjugated with NODAGA chelator showed higher specific binding properties than conjugated with HBED-CC. The chemical properties of the bifunctional chelators used for Ga-labeling of PCA determine the biological behaviour of the probes. Due to the high specificity and sensitivity Ga-labeled PCA molecules are promising radiotracers in melanoma imaging.
恶性黑色素瘤是最具侵袭性的皮肤癌形式。使用非侵入性正电子发射断层扫描（PET）成像对原发性黑色素瘤肿瘤和转移灶进行早期检测决定了这种疾病的治疗结果。先前的研究表明，与PET放射性核素共轭的苯甲酰胺衍生物（如普鲁卡因酰胺）能特异性结合黑色素瘤肿瘤的黑色素。镓螯合剂对镓标记的生物活性分子的生理特性可能有很大影响，就像在将HBED-CC应用于前列腺特异性膜抗原（PSMA）配体时所经历的那样。本研究的目的是在黑色素特异性普鲁卡因酰胺（PCA）的情况下评估这一概念，并在体外和体内条件下比较使用HBED-CC和NODAGA螯合剂的镓标记PCA的黑色素特异性。将普鲁卡因酰胺（PCA）与HBED-CC和NODAGA螯合剂共轭，并用Ga-68进行标记。使用无黑色素（MELUR和A375）和含黑色素（B16-F10）的黑色素瘤细胞系在体外和体内研究了Ga-HBED-CC-PCA和Ga-NODAGA-PCA的黑色素特异性。通过将B16-F10、MELUR和A375黑色素瘤细胞皮下注射到C57BL/6和SCID小鼠中制备荷瘤小鼠。在肿瘤细胞接种后21±2天以及静脉注射镓标记的放射性药物90分钟后进行全身PET/MRI扫描。制备的Ga-NODAGA-PCA和Ga-HBED-CC-PCA具有优异的放射化学纯度（98%）。体外实验表明，在孵育30分钟和90分钟后，B16-F10细胞对Ga-NODAGA-PCA的摄取显著（p≤0.01）高于同一细胞系中Ga-HBED-CC共轭PCA的积累。此外，使用Ga-NODAGA-PCA和Ga-HBED-CC-PCA时，在黑色素阴性和阳性细胞系的摄取之间发现了显著差异（p≤0.01和0.05）。使用肿瘤模型进行的体内PET/MRI研究显示，与Ga-HBED-CC-PCA相比，B16-F10肿瘤中Ga-NODAGA-PCA的摄取显著（p≤0.01）更高，其中Ga-HBED-CC-PCA的平均标准摄取值（SUVmean）、最大标准摄取值（SUVmax）和肿瘤/肌肉比值（T/M ratio）分别为0.13±0.01、0.56±0.11和11.43±1.24，而Ga-NODAGA-PCA的SUVmean为0.46±0.05，SUVmax为1.96±0.25，T/M ratio为40.7±4.23。与HBED-CC共轭相比，与NODAGA螯合剂共轭的黑色素特异性PCA显示出更高的特异性结合特性。用于PCA镓标记的双功能螯合剂的化学性质决定了探针的生物学行为。由于高特异性和高灵敏度镓标记的PCA分子是黑色素瘤成像中有前景的放射性示踪剂。
