全身动态^(18)F-FDG PET/CT Patlak多参数显像监测PD-1抗体联合放射治疗对小鼠B16F10黑色素瘤的协同作用及远隔效应

The use of whole-body dynamic ^(18)F-FDG PET/CT Patlak multiparametric imaging to monitor the synergistic effect and distant effect of PD-1 antibody combined with radiotherapy in the treatment of B16F10 melanoma in mice

目的 采用全身动态^(18)F-脱氧葡萄糖正电子发射计算机断层显像(^(18)F-FDG PET/CT) Patlak多参数显像技术,监测和评价程序性死亡受体-1(PD-1)免疫检查点单抗与放射联合治疗的协同抗肿瘤效应。方法 建立B16F10黑色素瘤小鼠双瘤模型,按照随机数字表法分为4组:空白对照组、PD-1单抗组、单纯放疗组、PD-1单抗+放疗(联合治疗)组,每组6只,分别于治疗前和治疗完成后24 h对小鼠行全身动态^(18)F-FDG PET/CT Patlak多参数显像。显像完后之后,分析比较四组肿瘤最大标准化摄取值(SUV_(max))、葡萄糖净摄取速率(MR_(FDG))的变化,以颈椎脱臼的方法处死小鼠,取出四组肿瘤进行苏木精-伊红(HE)染色及肿瘤浸润T淋巴细胞(CD8)、细胞核增殖抗原(Ki67)免疫组化分析肿瘤组织免疫细胞浸润情况及肿瘤组织增殖情况。治疗期间记录远端肿瘤体积变化情况。结果 治疗后24 h,原位肿瘤中,空白对照组SUV_(max)及MR_(FDG)值较治疗前升高(P<0.000 1),联合治疗组SUV_(max)及MR_(FDG)值较治疗前降低(P<0.000 1);远端肿瘤中,空白对照组、PD-1单抗组、单纯放疗组SUV_(max)及MR_(FDG)值较治疗前升高,但仅空白对照组治疗前后SUV_(max)差异有统计学意义(P<0.001),远端肿瘤中MR_(FDG)值上述三组差异均有统计学意义(P<0.01或P<0.000 1)。远端肿瘤联合治疗组SUV_(max)及MR_(FDG)值较治疗前降低(P<0.000 1)。远端肿瘤治疗后比较各组SUV_(max)及MR_(FDG)值,除单纯放疗组和PD-1单抗组外,其余各组间SUV_(max)及MR_(FDG)值差异均有统计学意义(均P<0.05)。免疫组化结果显示,远端肿瘤CD8 T淋巴细胞平均吸光度值高于其他三组(P<0.001);远端肿瘤增殖指数Ki-67免疫组化平均吸光度值低于其他三组(P<0.001)。结论 联合治疗发挥出的协同作用可以降低远端肿瘤生长速度,全身动态^(18)F-FDG PET/CT Patlak多参数显像能够作为PD-1抗体与放射联合治疗远隔效应对小鼠B16F10黑色素瘤的协同作用的监测方法,可为优化联合治疗方案提供可靠的影像学评估参数,对改善肿瘤患者预后具有重要意义。

Objective To monitor and evaluate the synergistic antitumor effects of programmed death-1(PD-1)checkpoint inhibitor combined with radiation therapy through whole-body dynamic ^(18)F-Fluorodeoxy glucose positron emission computed tomography(^(18)F-FDG PET/CT)and Patlak multi-parametric analysis.Methods B16F10 melanoma dual-tumor mouse model was established and randomly divided into control,PD-1 monoclonal antibody,radiation-only,and combination groups(n=6).Whole-body ^(18)F-FDG PET/CT imaging was performed before and 24 hours post-treatment.The changes of maximum standardized uptake value(SUV_(max))and metabolic rate of FDG(MR_(FDG))changes were analyzed and compared.Mice were then euthanized,tumors excised and underwent histopathology with HE,CD8,Ki-67 staining to assess immune infiltration and proliferation.Distal tumor volumes were monitored during treatment.Results At 24 hours post-treatment,in the primary tumors,SUV_(max) and MR_(FDG) values increased compared to pre-treatment in the control group(P<0.0001),while they decreased in the combination treatment group(P<0.0001),with statistically significant differences.In the distal tumors,SUV_(max) and MR_(FDG) values increased compared to pre-treatment in the control group,PD-1 monoclonal antibody group,and radiotherapy-alone group.The SUV_(max) differences were statistically significant in the control group before and after treatment(P<0.0001).MR_(FDG) values in the distal tumors showed statistically significant differences in all three groups(P<0.01 or P<0.0001).In the combination treatment group,SUV_(max) and MR_(FDG) values in the distal tumors decreased significantly compared to pre-treatment(P<0.0001).Post-treatment comparison of SUV_(max) and MR_(FDG) values in the distal tumors showed that statistically significant differences in SUV_(max) and MR_(FDG) values were observed among all groups except between the radiotherapy-alone and PD-1 monoclonal antibody groups(all P<0.05).Immunohistochemistry results showed that the mean absorbance value of CD8 T lymphocytes in the distal tumor was significantly higher than that in the other three groups(P<0.001);the mean absorbance value of Ki-67 immunohistochemistry in the distal tumor proliferation index was significantly lower than that in the other three groups(P<0.001).Conclusion The synergistic effects of combined treatment reduced distal tumor growth.Whole-body ^(18)F-FDG PET/CT Patlak multi-parametric imaging can monitor the synergistic effects of PD-1 antibody and radiotherapy in B16F10 melanoma,providing reliable imaging parameters for optimizing combinatorial therapies.