以FGF8为靶点的前列腺癌分子显像与治疗研究

It is known that Fibroblast growth factor-8 (FGF8) has proven to be highly expressed in prostate cancer. FGF8 plays an important role in tumorogenesis by inducing angiogenesis under MEK1/2, PI3K pathways. It promotes not only tumorigenesis but also metastasis. Peptide HSQAAVP was isolated as a specific FGF8b-binding phage clones by screening a phage peptide display library. And due to its highly affinity with FGF8b, it is expected to be a new target for prostate cancer treatment. Nuclide tracing technique shows dynamic changes of target molecules in vivo and noninvasively, and helps diagnosis and therapy of diseases by molecular levels. Combined with nuclide tracing technique, we hypothesize the following three points of view. Firstly, 99mTc-HSQAAVP can be radiolabeled and display the expression and distribution of FGF8b in vivo. Secondly, 131I-HSQAAVP can be radiolabeled and serve in targeting therapy of prostate cancer. Thirdly, HSQAAVP suppresses the occurrence and progression of prostate cancer by inhibiting tumor cell proliferation and occurance of EMT. In previous experiments, we found the expression of FGF8b increased in 77.5% of prostate cancer specimens; HSQAAVP and LNCaP cells showed strong green fluorescence signal in Confocal images. SPECT imaging with 99mTc-HSQAAVP in nude mice bearing prostate carcinomas showed clearly uptake in tumors. Based on the former results, in this project we plan to apply molecular biologic technologies, such as Confocal imaging, Western blot, FCM, to clarify the molecular mechanism of HSQAAVP inhibiting tumor development; synthesize 99mTc/131I-HSQAAVP molecular probes to evaluate their functional effects as new biomarkers in early diagnosis and targeting therapy for prostate cancer. We are looking forward that the new molecular probes can offer a new approach to diagnosis and therapy of prostate cancer.

已发现FGF8在前列腺癌中高表达，通过MEK1/2、PI3K等途径诱导肿瘤血管生成，发挥促癌作用。通过噬菌体肽展示文库筛选的多肽HSQAAVP（HAP）与FGF8b具有高亲和力，有望成为肿瘤治疗的新靶点。结合核素示踪技术，我们假设99mTc-HAP能够在动物体内观察到FGF8b的分布和表达量，可用于前列腺癌早期诊断；131I-HAP能够靶向治疗前列腺癌，辐射吸收剂量安全。前期工作中，我们已验证FGF8b在77.5%的前列腺癌中呈高表达，Confocal示HAP与LNCaP细胞呈强绿色荧光信号， 99mTc-HAP在荷瘤裸鼠体内显像效果好。结合前期基础，本项目拟选择不同肿瘤细胞系，通过Confocal、Western blot、FCM技术，拟阐明HAP抑癌机制；合成99mTc/131I-HAP分子探针，评价SPECT/CT分子显像和靶向治疗效果，为前列腺癌早期诊断和靶向治疗提供新的方法。

文献报道称FGF8的高表达与前列腺癌的发生发展及浸润转移密切相关。从噬菌体肽文库中筛选获得的多肽HSQAAVP，可高亲和性、特异性、竞争性结合FGF8b受体，阻断其效应达到对肿瘤治疗的目的。本项目拟选择FGF8为靶点，应运放射性核素131I、99mTc对修饰后多肽HSQAAVP进行标记，制备新型分子探针131I-HSQAAVP、99mTc- HSQAAVP，通过分子生物学手段及活体动物水平的不同层面进行对分子探针的研究。探讨131I-HSQAAVP在前列腺癌荷裸鼠中的中代谢分布、肿瘤显像及治疗中的作用。结果显示：①多肽HSQAAVP易于被131I和99mTc，标记前后多肽生物学活性并未发生改变，但氯胺-T法标记HSQAAVP方法虽简单，易出现标记率低及不易标记成功显像；②激光共聚焦实验发现多肽HSQAAVP不但能与前列腺癌细胞结合，还能与多种肿瘤实质细胞结合，呈现增强的绿色荧光；③细胞划痕实验、MTT实验发现以及CCK-8实验结果均表明制备获得的分子探针对前列腺癌细胞的生长增殖起抑制作用。④99mTc- HSQAAVP的制备与显像较易操作，可应用于荷裸鼠前列腺癌显像，有望成为一种新的针对前列腺癌的肿瘤显像剂。⑤131I-HSQAAVP注射后主要分布于血液、肾脏和肝脏等组织中，在前列腺癌荷裸鼠体内清除迅速。⑥131I-HSQAAVP不仅可用于前列腺癌荷瘤裸鼠显像，也可对的肿瘤生长具有抑制作用，但未能完全杀灭肿瘤，是一具有潜在应用价值的抗前列腺癌靶向治疗药物。加大剂量应用131I-HSQAAVP用于前列腺癌治疗是否效果更佳，是否有毒性反应等方面有待于进一步研究。