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结直肠癌是消化道最常见的恶性肿瘤之一,大多数结直肠癌患者就诊时已属中晚期。结肠癌局部转移相对频繁,肿瘤可穿透肠壁并使区域淋巴结受累[1-3]。中晚期结直肠癌的标准治疗模式以直肠癌根治术为基础,辅以放疗。放疗通过破坏DNA将肿瘤杀灭,可以提高结直肠癌的局部控制率,增加保肛机率,提高患者生存率及生活质量,但仍存在辐射剂量高、对健康组织损伤较大等缺点。具有高度选择性的内照射治疗(selective internal radiotherapy,SIRT)可以降低局部复发率,使肿瘤缩小,减少癌周浸润,同时可以降低放疗所致的生物毒性,减轻放疗引发的不良反应。
由于阻断T细胞免疫检查点程序性死亡受体1(programmed death receptor, PD-1)/程序性死亡受体-配体1(programmed death receptor-ligand 1, PD-L1)通路的免疫疗法具有高度特异性,因此其在癌症免疫治疗中的重要性被广泛认可[4]。有研究结果证实,结肠癌周间质主要由大量T淋巴细胞浸润[5],所以结直肠癌也成为PD-1/PD-L1治疗的重要应用方向之一。由于PD-1与PD-L1的高度相关性,靶向PD-1的诊疗一体化核素标记的单克隆抗体可用于PD-1表达的评估,同时SIRT作用于T细胞浸润的肿瘤组织有望成为PD-1/PD-L1免疫疗法的有效补充。
本研究拟合成一种PD-1抗体导向的免疫放疗诊疗剂。在SIRT的同时,131I释放的γ射线可用于SPECT评估PD-1的表达,成为PD-1相关SIRT的诊疗一体化试剂。
131I-Tyr-Nivolumab用于结肠癌PD-1表达相关诊疗一体化的初步研究
Preliminary study of 131I-Tyr-Nivolumab for PD-1-related theranostics of colon cancer
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摘要:
目的 研制靶向程序性死亡受体1(PD-1)的131I-Tyr-Nivolumab诊疗剂,并研究其在高表达PD-1的原位结肠癌小鼠模型中的初步应用。 方法 采用间接标记法制备131I-Tyr-Nivolumab,测量产物的放射化学纯度及评估体外稳定性。PD-1高表达原位结肠癌小鼠10只,随机分成治疗组和对照组。治疗组尾静脉注射131I-Tyr-Nivolumab(11.1 MBq/10 μg)后,通过SPECT/CT观察在给药后不同时间点(2、4、24、65 h)诊疗剂在小鼠体内的分布情况。治疗5 d后,采用免疫组织化学法量化治疗组肿瘤组织中Bax、Bcl-2蛋白的表达。 结果 131I-Tyr-Nivolumab放射化学纯度>99%,24 h的体外稳定性>90%。131I-Tyr-Nivolumab主要分布于心脏、肝脏及肠道肿瘤,通过肾脏代谢清除,给药后2 h,肿瘤组织摄取131I-Tyr-Nivolumab逐渐增加,给药后4 h可见肝脏显影,给药后24 h肠道疑似肿瘤区显影清晰,给药后65 h肝脏非特异性摄取几乎被排出;给药后4、24、65 h肠道疑似肿瘤区放射性计数与全身总放射性计数的比值分别为(2.8±0.3)%、(8.4±0.2)%和(1.8±0.5)%。治疗组比未治疗组的Bax蛋白表达率明显增高[(22.23±1.61)% vs.(13.64±2.43)%,t=−5.476,P=0.006],治疗组比未治疗组的Bcl-2蛋白表达率明显降低[(13.81±4.64)% vs.(25.57±2.33)%,t=3.902,P=0.017)]。 结论 成功合成靶向PD-1的131I-Tyr-Nivolumab诊疗剂,其可作为结肠癌SPECT显像及内照射的诊治试剂,为实现诊疗一体化提供了依据。 Abstract:Objective We synthesized theranostic agent 131I-Tyr-Nivolumab, which targets programmed cell death-1 (PD-1), and studied its preliminary application in the mouse model with orthotopic colon cancer and high PD-1 expression. Methods 131I-Tyr-Nivolumab was prepared through indirect labeling, and the radiochemical purity and stability of products were evaluated. Ten mice with high expression of PD-1 colon neoplasm in situ were randomly categorized into the treatment and untreated groups. In the treatment group, 131I-Tyr-Nivolumab (11.1 MBq/10 μg) was injected into the tail vein, and SPECT/CT was then performed to observe the distribution of the theranostic agent in mice at different time points (2, 4, 24, and 65 h) after injection. After 5 days of treatment, the expression of Bax and Bcl-2 proteins in tumor tissues were quantified by immunohistochemistry. Results 131I-Tyr-Nivolumab had radiochemical purity greater than 99% and in vitro stability greater than 90% for 24 h. The theranostic agent was mainly distributed in the heart, liver, and intestinal tumors, and was eliminated by renal metabolism, and its uptake by the tumor tissue increased gradually at 2 h post-injection. The liver was visualized at 4 h post-injection, and the suspected tumor area of the intestine was clear at 24 h post-injection. Liver non-specific uptake was almost eliminated at 65 h post-injection. The ratios of radioactivity counts in the intestinal suspected tumor area to the whole-body radioactivity counts at 4, 24, and 65 h post-administration were (2.8±0.3)%, (8.4±0.2)%, and (1.8±0.5)%, respectively. The treatment group had significantly higher expression rate of Bax protein [(22.23±1.61)% vs. (13.64±2.43)%, t=−5.476, P=0.006] bur significantly lower expression rate of Bcl-2 protein [(13.81±4.64)% vs. (25.57±2.33)%, t=3.902, P=0.017] compared with the untreated group. Conclusion 131I-Tyr-Nivolumab targeting PD-1 was successfully synthesized and can be used as a theranostic agent for SPECT imaging and internal irradiation therapy. This method could provide a new idea for the theranostics of colon cancer. -
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