基于乳腺癌PDX个体化模型的高亲和力融合肽靶向探针“显像-治疗”体系的构建

Recurrence and metastatic breast cancer is still difficult to cure, and the prognosis is poor. At this moment of challenge, tumor targeted radiotherapy provides a new idea for the treatment of advanced breast cancer.But in vivo models used so far for therapeutic studies were derived mainly from established cancer cell lines. These cell lines have been cultivated for a long time in monolayers on plastic dishes and have lost most of their original tumour tissue specificity. We make our study with patient-derived xenograft（PDX）models which could highly simulate human breast cancer individualized molecular characteristics. [18F] NOTA-RGD-ATWLPPR，synthesized by our research group in the preliminary work，has been proved to be a better new probe which has a higher targeting activity and better biology distribution properties in glioma cells. Both the integrin αvβ3 and VEGF receptor are also over expressed in breast cancer cells ，we will verify the feasibility and validity of this new probe as a imaging probe for breast cancer.Through radiolabeling with 177Lu, we are going to evaluate whether the dual-targeted heterodimer could exhibit significantly improved breast cancer-targeting efficiency and enhance lethality for tumors in PDX models.Through this investigation, we wish to establish a new pattern of the “prescreening-therapy” high affinity binding heterodimeric peptide probe for targeting recurrence and metastasis of breast cancer on PDX models

复发、转移性乳腺癌目前临床仍治疗困难，预后不佳。放射性核素靶向治疗为晚期乳腺癌的治疗提供了新思路。但以往筛选探针多用的肿瘤细胞移植模型不能反应原发肿瘤的个体化特性而导致难以准确评估药物在临床试验中的真正作用。本项目选择能高度模拟原发肿瘤分子特征的人源性肿瘤组织异种移植 (PDX) 模型为基础进行研究。课题组前期工作已成功制备出一种新型融合肽正电子探针[18F] NOTA-RGD-ATWLPPR，并验证了其较单肽探针对于脑胶质瘤细胞有更佳的靶向性和生物学分布性质。针对乳腺癌高表达整合素αvβ3与VEGF为靶标，本项目将验证该探针作为乳腺癌显像探针的可行性,同时采用治疗核素[177Lu]标记同一靶向分子（RGD-ATWPPR）构建内照射靶向治疗探针，以期通过融合肽的双靶点结合作用，增强该探针对肿瘤的杀伤作用。目标为构建一个基于乳腺癌PDX模型的“显像筛查-靶向内照射治疗”精准个体化诊疗新模式。

对于复发和转移性乳腺癌目前临床上仍缺乏有效的治疗方法，预后不佳。放射性核素靶向治疗为晚期乳腺癌的治疗提供了新思路。业已证实乳腺癌高表达整合素受体αVβ3和VEGF受体。申请人课题组前期工作已成功制备出一种靶向胶质瘤细胞内整合素受体αVβ3和VEGF受体的新型融合肽正电子探针18F-NOTA-RGD-ATWLPPR。本研究进一步对探针进行优化，通过68Ga标记，制备双靶点正电子成像探针68Ga-DOTA-RGD- ATWLPPR。我们通过体内外实验论证该探针较之单肽探针68Ga-DOTA-RGD和68Ga-DOTA-ATWLPPR对于乳腺癌具有更好的靶向性能。同时采用治疗核素177Lu标记同一靶向分子（RGD-ATWLPPR）成功构建内照射靶向治疗探针177Lu-DOTA-RGD-ATWLPPR，完成对乳腺癌荷瘤鼠模型核素治疗及初步的疗效评估。结果显示与对照组，单剂量7.4MBq或18.5MBq相比， 29.6MBq 177Lu-DOTA-RGD-ATWLPPR可使肿瘤生长显著延迟。治疗组7.4MBq、18.5MBq、29.6MBq治疗后均未在短期内出现荷瘤裸鼠的死亡，并在治疗后的短期内体重恢复至较稳定、正常的水平。通过治疗后重要器官和组织的苏木精-伊红染色法实验也印证了177Lu-DOTA-RGD-ATWLPPR治疗的安全性。本项目还在还原患者肿瘤异质性的乳腺癌PDX模型上做了177Lu-DOTA-RGD-ATWLPPR个体化治疗的初步实验尝试，结果证明其对乳腺癌肿瘤具有有效的抑制作用。本项目实现了乳腺癌高亲和力融合肽靶向探针“显像筛查-靶向内照射治疗”一体化体系的构建并且具有良好的临床转化应用前景。