PSCA靶向纳米粒携带新型“联合靶向化学药物”治疗HRPC的生物学效应及其机制

Drug resistance and target deficiency are the challenges in the treatment of hormone refractory prostate cancer(HRPC). Currently, drugs are usually designed to single target, which may have less anti-tumor effectiveness. Our previous studies revealed that the combi-targeting molecule (JDF12) could achieve more potent anti-tumor effect on prostate cancer(PCa) than monotargeted drugs. JDF12 can specifically bind to epidermal growth factor receptor(EGFR) which is highly expressed in PCa and block EGFR-mediated signaling pathway, further decompose into another EGFR tyrosine kinase(TK) inhibitor plus a DNA alkylating moiety. The later two exert synergistic anti-tumor effect with direct blocking of EGFR signaling pathway on HRPC. However, the stability of JDF12 is poor in liquid and it is susceptible to hydrolysis and easily binds to organs with high EGFR expression resulting in side effects. In the present study, this new drug would be employed to synthesize prostate stem cell antigen(PSCA) monoclonal antibody modified nanoparticle by using nanotechnological technique. This modified nanoparticle has favorable soluability and stability and can specifically transport JDF12 to PSCA expressing PCa cells, which increases the targeting effect and reduces the side effect. In vitro and in vivo detection will be performed to investigate the bio-effect of this nanoparticle on HRPC, and to explore the changes in DNA repair following blocking of EGFR signaling pathway and alkylated damage to DNA. This study may provide a new strategy and evidence for the clinical treatment of HRPC.

药物抵抗及缺乏靶向性是HRPC治疗的难点，目前靶向药物主要针对单一靶点设计，抗癌效果有限。我们研究发现，合成的联合靶向化学药物JDF12能产生比单一功能药物更强的抗PCa能力，该药自身能靶向结合PCa高表达的EGFR，阻断EGFR信号通路，并能进一步水解成另一EGFR TK抑制分子和一个DNA烷基化分子，发挥串联级释放协同抗癌分子治疗HRPC的作用，但该药在体液中稳定性较差，容易水解或结合其它高表达EGFR的器官，产生毒副作用。本研究基于这种新型"联合靶向化学药物"，利用纳米技术合成PSCA单克隆抗体修饰载药纳米粒，包裹药物以提高药物水溶性和稳定性，靶向运输JDF12至特异表达PSCA的PCa细胞，增强药物肿瘤靶向性，减少其毒副作用。体内外检测载药靶向纳米粒抗HRPC的生物学效应，研究其阻断EGFR信号通路并烷基化损伤DNA后细胞DNA修复通路的改变，为临床治疗HRPC提供新的手段和依据。

药物抵抗及缺乏靶向性是HRPC治疗的难点，课题组前期合成了新型联合靶向化学药物-JDF12，该药自身能靶向结合PCa高表达的EGFR，阻断EGFR信号通路，并能进一步水解成另一EGFR TK抑制分子和一个DNA烷基化分子，发挥串联级释放协同抗癌分子治疗HRPC 的作用。体外研究发现该药不仅能产生比单一功能药物更强的抗HRPC增殖能力，且比两种单一功能药物等剂量及等效价联合应用具有更强的抗PCa能力。但该药在体液中稳定性较差，容易水解或结合其它高表达EGFR的器官，产生毒副作用。本研究我们应用纳米合成技术将PLGA-b-PEG-Mal与AbPSCA单链抗体相连接，合成PLGA-b-PEG-scAbPSCA载药靶向纳米粒，采用纳米沉淀法使合成的靶向纳米粒包裹JDF12，并进行相关表征和验证，测定载药量和包封率符合设计要求，以提高药物水溶性和稳定性，靶向运输具有强抗HRPC作用的JDF12药物至特异表达PSCA的PCa细胞，增强药物肿瘤靶向性，减少其毒副作用。研究中激光共聚焦显微镜观察显示PCa细胞对载药JDF12的靶向纳米粒具有较好的吞噬作用，证实了载药靶向纳米粒可靶向表达PSCA的PCa细胞。体外及体内实验证实载药靶向纳米粒较对照组能明显提高药物抗HRPC生长增殖效应。针对药物抗HRPC作用机制的研究，我们发现联合靶向化学药物协同抗HRPC作用机制与药物剂量反应性抑制EGFR自体磷酸化，抑制DNA损伤修复蛋白XRCC1及ERCC1的表达，从而更有效地促进肿瘤细胞DNA损伤有关。总之，通过本项目的研究，我们成功在国内合成了PSCA靶向载药纳米粒，并检测纳米粒能提高新型联合靶向化学药物体内运输的稳定性，增强药物肿瘤靶向性及肿瘤杀伤能力，这种肿瘤抗原特异性靶向纳米载药技术可进一步在PCa诊治研究中发挥作用，同时，研究初步阐明新型联合靶向化学药物通过下调DNA损伤修复通路蛋白的表达起协同抗HRPC作用，为临床HRPC的化学靶向治疗研究提供新的手段和理论依据。