Development of radiolabeled bis(zinc(II)-dipicolylamine) complexes for cell death imaging
作者:Miho Aoki、Akira Odani、Kazuma Ogawa
DOI:10.1007/s12149-019-01339-8
日期:2019.5
Although it has been traditionally surmised that phosphatidylserine (PS) externalization is a hallmark of apoptosis, most other non-apoptotic modes of cell death, such as necrosis, are also associated with PS externalization. Bis(zinc-dipicolylamine) (ZnDPA) complexes have been reported to exhibit affinity for PS. The present study aimed to develop novel radiolabeled ZnDPA derivatives for cell death imaging in tumor after treatment with anticancer drugs. [125I]IB-EG2-ZnDPA and [99mTc]Tc-MAG3-EG2-ZnDPA were designed and prepared. The stabilities of these radiotracers were determined in 0.1 M phosphate buffer (pH 7.4) or murine plasma at 37 °C, and their 1-octanol/water partition coefficients (logP) were measured. The uptake of radioactivity in cancer cells, which were preincubated in a normal medium or in a medium containing 5-FU, was measured after incubation with radiotracers. Accumulation of [99mTc]Tc-MAG3-EG2-ZnDPA in the tumor was evaluated in tumor-bearing mice treated with or without 5-FU, and then TUNEL staining was performed to detect dead cells in the tumor tissue sections. The radiochemical purities of [125I]IB-EG2-ZnDPA and [99mTc]Tc-MAG3-EG2-ZnDPA exceeded 95%. Although [125I]IB-EG2-ZnDPA gradually decomposing with time, more than 90% of [99mTc]Tc-MAG3-EG2-ZnDPA remained in its intact form in phosphate buffer through 6 h of incubation. Neither [125I]IB-EG2-ZnDPA nor [99mTc]Tc-MAG3-EG2-ZnDPA decomposed so much after 6-h incubation in murine plasma. [125I]IB-EG2-ZnDPA could not specifically recognize PS on the cell surface because of its high lipophilicity. Conversely, [99mTc]Tc-MAG3-EG2-ZnDPA accumulated in cancer cells after treatment with an anticancer drug both in vitro and in vivo, and its accumulation was correlated with the number of TUNEL-positive cells. However, the biodistribution of [99mTc]Tc-MAG3-EG2-ZnDPA was not suitable for imaging because of its low accumulation in tumor and high uptake in abdomen organs. [99mTc]Tc-MAG3-EG2-ZnDPA could be useful for the early detection of treatment effects after chemotherapy. Since the signal-to-noise ratio is not enough for single photon emission computed tomography imaging, further modification is needed to improve its biodistribution and affinity for PS.
尽管传统上认为磷脂酰丝氨酸(PS)外化是细胞凋亡的标志,但大多数其他非凋亡性细胞死亡模式(如坏死)也与 PS 外化有关。据报道,双(锌-二羟基胺)(ZnDPA)复合物对 PS 具有亲和力。本研究旨在开发新型放射性标记 ZnDPA 衍生物,用于抗癌药物治疗后的肿瘤细胞死亡成像。研究人员设计并制备了[125I]IB-EG2-ZnDPA 和[99mTc]Tc-MAG3-EG2-ZnDPA。在 0.1 M 磷酸盐缓冲液(pH 7.4)或小鼠血浆(37 ℃)中测定了这些放射性racer的稳定性,并测量了它们的 1-辛醇/水分配系数(logP)。癌细胞在正常培养基或含有 5-FU 的培养基中预处理后,在与放射性核素孵育后测量了癌细胞对放射性的摄取。在接受或不接受 5-FU 治疗的肿瘤小鼠体内评估[99mTc]Tc-MAG3-EG2-ZnDPA 在肿瘤中的积累情况,然后进行 TUNEL 染色以检测肿瘤组织切片中的死亡细胞。[125I]IB-EG2-ZnDPA和[99mTc]Tc-MAG3-EG2-ZnDPA的放射化学纯度均超过95%。虽然[125I]IB-EG2-ZnDPA 会随着时间的推移而逐渐分解,但在磷酸盐缓冲液中培养 6 h 后,90% 以上的[99mTc]Tc-MAG3-EG2-ZnDPA 仍保持完整形态。[125I]IB-EG2-ZnDPA和[99mTc]Tc-MAG3-EG2-ZnDPA在小鼠血浆中培养6小时后的分解程度都不高。由于[125I]IB-EG2-ZnDPA具有很高的亲脂性,因此它不能特异性地识别细胞表面的 PS。相反,[99mTc]Tc-MAG3-EG2-ZnDPA 在体外和体内经抗癌药物处理后会在癌细胞中积累,其积累与 TUNEL 阳性细胞的数量相关。然而,[99m锝]Tc-MAG3-EG2-ZnDPA 的生物分布不适合成像,因为它在肿瘤中的蓄积量低,而在腹部器官中的摄取量高。[99m锝]Tc-MAG3-EG2-ZnDPA可用于化疗后治疗效果的早期检测。由于其信噪比不足以用于单光子发射计算机断层扫描成像,因此需要进一步改进其生物分布和对 PS 的亲和性。