基因与纳米探针协同介导的前列腺癌分子级磁共振可视化诊疗研究

The success of focal ablation in prostate cancer (PCa) is greatly dependent on accurate localization and precise visualization of tumor lesions and confidence in the absence of malignancy elsewhere. However, the complex biological behaviors of PCa, like multiple focalities and high heterogeneity, present great challenges for the current imaging technology to make accurate pre-operative definition of all tumor lesions, which impedes the use of focal therapy in the clinic. To address this issue, our preliminary work has introduced a human-derived protein-based nanoprobe Gd@Tf as a novel class of magnetic contrast agents and achieved specific MR signal enhancement of ultrasmall PCa lesions and their metastasis. Such magnetic nanoprobe Gd@Tf demonstrated excellent ability to act as a carrier of nanoscale prodrugs for MRI-visualizing PCa-targeting therapy. In combination with our ongoing work that optimized the specificity and efficiency of the Tf-TfR based nanoparticle tumor-homing by a synergistic application of PCA3-driven gene probes, this project aims to introduce a gene-nano probes synergistically mediated MRI visualization strategy to realize the in vivo PCA3 gene activity detection, tumor risk assessment and sensitive MRI localization of early PCa in a non-invasive manner at the molecular level, and then facilitate the accurate ablation of localized tumor lesions under the guidance of MRI visualization. Overall, the success of this project will provide a new and rational strategy for the early diagnosis, treatment, and simultaneous monitoring of prostate cancer.

肿瘤的可视化是前列腺癌早期治疗，特别是局部治疗的关键，但多灶性和高肿瘤异质性等病理特点，使目前的影像学方法尚无法全面、精准显示前列腺癌灶。前期我们利用课题组开发的首个人源蛋白基磁共振探针Gd@Tf，实现了微小前列腺癌、前列腺癌转移瘤的精准成像，并以该探针为载体构建了磁共振可视化前列腺癌靶向化疗前药。本研究计划进一步结合课题组近期研究中，通过协同应用含PCA3启动子的基因探针，显著增强Tf类纳米探针的前列腺癌特异性和靶向递送效率的研究成果，实现基因与纳米探针协同介导的、早期前列腺癌磁共振可视化下PCA3基因表达的在体检测、前列腺癌的超早期诊断、肿瘤分级和精准成像引导下的局部治疗，进而在磁共振上实现分子级别的前列腺癌可视化研究，为前列腺癌的早诊早治和诊、疗、监测一体化提供新的方式。

课题组前期实现了基因协同纳米探针增强前列腺癌靶向MRI成像的研究，并发现基因探针中PCA3启动子介导的TfR表达水平在不同病理类型前列腺癌中存在较显著差异。本研究中，课题组首先通过数据库分析和细胞实验阐释了其原因：即由于AR在不同前列腺癌的表达有明显差异，PCA3的表达受AR调控，因此PCA3启动子介导的基因探针的TfR表达在不同病理类型的前列腺癌中表达量不同。.在此基础上，课题组构建了rAAV-pPCA3-TfR-WPRE基因探针，并证实了其在且仅在前列腺癌组织中特异性表达TfR，不同病理类型的前列腺癌TfR表达量不同。另一方面，在活体水平应用Gd@Tf纳米探针后，T1值变化与前列腺癌中TfR表达呈线性、正相关，证实Gd@Tf探针可在磁共振上放大基因探针介导的TfR表达差异，进而用于间接评价、预估前列腺癌的病理类型。综上，课题组建立了不同类型的前列腺癌移植瘤小鼠模型，通过基因与纳米探针联合处理，获取不同病理类型肿瘤的T1WI信号强度、肿瘤的T1值；通过ICP-MS定量肿瘤中的Gd3+含量；分析T1值定量结果、Gd含量与病理类型之间的联系，获取区分激素依赖与去势抵抗型前列腺癌的T1值变化率作为诊断阈值；再通过双盲法验证该T1值诊断阈值在活体水平区分不同类型前列腺癌的诊断效能。最后，通过基因与纳米探针协同靶向前列腺癌的方法，实现了微小前列腺癌的精准磁共振成像，完成了磁共振成像引导下的射频治疗，并对术后的瘤鼠进行了磁共振可视化疗效监测。.研究成果：1.rAAV-pPCA3-TfR-WPRE基因探针可在前列腺癌特异性表达TfR，其在不同类型前列腺癌细胞中介导的TfR表达量存在差异，该表达差异与前列腺癌病理类型相关；2.联合应用基因与纳米探针，Gd@Tf可通过磁共振放大基因探针介导的TfR表达差异，实现磁共振可视化下T1值定量TfR表达，从而间接反应前列腺癌的病理类型，课题组在活体水平获取了区分激素依赖与去势抵抗型前列腺癌的T1值变化率诊断阈值；在双盲法验证中准确率可达70%；3.协同应用基因和纳米探针，可实现早期、微小、多灶前列腺癌磁共振的可视化，并据此进行精准的前列腺癌局部治疗和可视化疗效监测。