Gd/Mn配合物修饰的鸟嘌呤核苷酸分子对K-Ras蛋白的活性调节及影像分析

K-Ras protein can be used as markers of many human tumors, indicating the occurrence of cancer. Regulating the activity of K-Ras protein can control tumor growth. Development of chemical small molecule inhibitors with K-Ras protein targeting and imaging capabilities can achieve image-guided diagnosis and treatment of tumor related to K-Ras proteins. Guanine nucleotide (GDP) can be effectively incorporated into the nucleotide binding pocket of the K-Ras protein, to inactivate K-Ras proteins. Paramagnetic Gd/Mn complexes can increase the MRI contrast in lesions with a superior spatial resolution. This project intends to take K-Ras protein as targets, design and prepare K-Ras inhibitors through reasonably modifying the molecular skeleton of GDP with Gd/Mn complexes to achieve nuclear magnetic resonance (NMR) and fluorescence multiple responses with the structural and functional synergy. The interaction of marked GDP and K-Ras protein will be detected by imaging techniques to study inhibitors anti-tumor activity in tumor cells and the model objects. Its multidimensional comprehensive imaging analysis can provide a wealth of useful information for the diagnosis and treatment of cancer caused by K-Ras protein dysfunction.

K-Ras蛋白可作为人类许多肿瘤的标志物，预示肿瘤的发生。调节K-Ras蛋白的活性可以控制肿瘤的发展。开发靶向K-Ras蛋白且具有影像功能的化学小分子抑制剂可实现K-Ras蛋白相关肿瘤的影像导引诊断、治疗。鸟嘌呤核苷酸（GDP）可有效结合到K-Ras蛋白的核苷酸结合口袋并灭活K-Ras蛋白。顺磁性的Gd/Mn配合物可高分辨率地增加病变组织的核磁共振成像对比度。本项目拟以K-Ras蛋白为靶标，通过合理设计将Gd/Mn配合物修饰到鸟嘌呤核苷酸（GDP）分子骨架上，制备具有核磁共振和荧光多模式响应，结构与功能协同的K-Ras蛋白抑制剂。利用影像技术探测标记后GDP与K-Ras蛋白的相互作用，研究抑制剂在肿瘤细胞、模型物中抗肿瘤活性。对其进行多层次全方位成像分析，为K-Ras蛋白功能异常所致肿瘤的诊断、治疗提供丰富有用的信息。

KRAS蛋白主要通过GTP水解生成GDP，在效应蛋白作用下实现GTP-GDP-GTP的循环。因此将KRAS蛋白稳定在GDP的失活状态可实现KRAS蛋白的活性调节。由于KRAS突变肿瘤会造成GTP浓度异常，项目合成了基于GTP的核磁共振成像造影剂用于体内体外影像分析，该方法可实现KRAS蛋白活性间接评估。以GDP为模板通过GDP β-磷原子进行Gd配合物修饰和α，β-不饱和烯烃修饰，但其与KRAS的结合率很低，可能原因是在β-磷原子引入大基团修饰会影响磷酸链与KRAS蛋白的G结合口袋各氨基酸残基的氢键网络和镁离子与磷酸根配位，这些结果表明，KRAS蛋白光滑表面对于直接靶向的小分子抑制剂是极大挑战。目前基于KRASG12C的共价键合抑制剂只能在12%KRAS突变体外实验有效，因此探索普适性KRAS突变肿瘤治疗将是后续工作的目标。