131I-Tyr-Nivolumab用于结肠癌PD-1表达相关诊疗一体化的初步研究

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。

Preliminary study of 131I-Tyr-Nivolumab for PD-1-related theranostics of colon cancer

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.