基于细胞表面GRP78为靶点的胰腺癌精准分子显像与疗效评估研究

Pancreatic cancer is known as the "king of cancer", 90% patients were metastatic when diagnosed with pancreatic cancer. The survival rate is less than 10% in five years.The early and accurate diagnosis method are urgent for clinical work.Cancer cells are characterized by metabolic alterations and the tumor microenvironment is often marked with impaired blood flow and hypoxia, all of which can elicit endoplasmic reticulum (ER) stress. Tumor cells adapt to these adverse conditions by activating the unfolded protein response (UPR), with induction of GRP78 as a major pro-survival arm of the UPR signaling pathways. While traditionally GRP78 has been regarded as an ER lumenal protein, GRP78 has been identified in multiple intracellular organelles, which is correlated with facilitating cell adaptation to stress for survival. In particular, ER stress promotes GRP78 export from ER to cell surface: the upregulation of cell surface GRP78 (csGRP78) protein level have been observed in many types of cancer cells and correlated with malignancy, metastasis, and drug resistance. Indeed, accumulating evidence suggests that csGRP78 can interact with other cell surface proteins to regulate cell proliferation and survival, which allows the modulation of the csGRP78 only without altering its normal intracellular functions. In this proposal, we aim to develop a new PET imaging probe 64Cu-Sar-MAb159, the MAb159 of which is the the specific antibody of csGRP78 to monitor csGRP78 expression non-invasively and repetitively. We hypothesize that the amount of csGRP78 in the tumor predicts the aggressiveness of the tumor, the treatment response to GRP78-targeted therapy, and the development of chemoresistance. The imaging probes developed in this research could be fully integrated into patient screening and treatment monitoring, which would finally lead to personalized medicine.

胰腺癌被称为“癌中之王”，90%的胰腺癌在诊断时已有转移，5年存活率小于10%。因此临床急需早期精准的诊断方法来提高胰腺癌的诊疗效果。肿瘤细胞的特性是代谢异常和恶劣的肿瘤微环境，这会引起细胞内质网的应激反应，癌细胞常引入GRP78蛋白，内质网的应激反应促使GRP78蛋白被运送到细胞膜表面和其他蛋白作用，使癌细胞得以生存和生长。研究发现胰腺癌细胞表面的GRP78（csGRP78）与胰腺癌的恶性程度、转移侵入及耐药性相关。csGRP78的特性使其成为一个有前景的诊疗靶点，本研究拟以csGRP78为靶点，对其特异性抗体Mab159进行系统改造，开发出高亲和力和高特异性的靶向csGRP78的分子探针64Cu-Sar-MAb159 ，对胰腺癌荷瘤鼠进行csGRP78靶向诊断PET显像，并通过动态显像监测化疗和靶向治疗后胰腺癌csGRP78的表达变化，进行疗效评估，为临床提供一种诊疗胰腺癌的新策略。

根据项目申请书收集临床胰腺癌、慢性胰腺炎及胰腺内分泌肿瘤标本,免疫组化方法检测GRPR的表达差异；胰腺癌GRPR的表达阳性率为79.4%，胰腺内分泌肿瘤及慢性胰腺炎的GRPR表达阳性率分别为33.3%与 22.7%。以csGRP78为靶点，对其特异性抗体Mab159进行系统改造，开发出高亲和力和高特异性的靶向csGRP78的分子探针64Cu-Sar-MAb159，构建PANC-1移植瘤模型，进行64Cu-Sar-MAb159 小动物PET/CT显像，胰腺癌荷瘤病灶清晰可见64Cu-Sar-MAb159 高摄取灶，并且能够被未标记前体有效抑制。密切结合前沿热点研制靶向GRPR的光学探针GRP-IRDye800，对移植瘤进行光学显像，并在光学显像指导下对裸鼠实施移植瘤切除手术，完成胰腺癌术中导航疗效的评估。.在完成该项目后，课题组拓展了研究内容，经免疫组化检测前列腺癌患者组织标本，发现前列腺癌也高表达GRPR，由于核素64Cu来源比较受限，因此后续课题组改用68Ga，合成探针68Ga-NOTA-P2-RM26进行前列腺癌移植瘤的靶向显像及组织学验证。