负载siRNA的MR可视化纳米胶束靶向沉默VEGF/Snail基因抑制肝癌射频消融术后复发转移

Radiofrequency ablation (RFA) has been considered as one of the main means for the treatment of hepatocellular carcinoma (HCC) because of its efficacy and relatively less invasion. However, the high HCC recurrence rate after RFA has been a challenge for the clinical treatment. During the RFA procedure, heat ablation not only could kill HCC cells, but also might activate HCC cells invasion and metastasis processes, particularly for those received sublethal heat treatment at the peripheral zone of the tumor. Sublethal heat treatment could skew HCC cells towards a series of biological transformation, which may be the sources of HCC recurrence. Up to now, the mechanism underling the RFA-induced HCC recurrence still remains unexplored. According to the recent researches, hypoxia inducing factor-1α/vascular endothelial growth factor（HIF-1α/VEGF）and epithelial-mesenchymal transition (EMT) may play the key roles for the HCC recurrence. Aiming at VEGF and Snail, the key factors of the HIF-1α/VEGF and EMT signal paths, we want to build a novel nano-carrier targeting HCC cells based on our previous experiences of building multifunctional nano-carriers, which can transfer siRNAs (VEGF siRNA and Snail siRNA) into HCC cells and silence VEGF and Snail genes synergistically, to achieve the goal of antagonizing HCC recurrence and metastasis after RFA. Besides these, super paramagnetic iron oxide nanoparticles (SPION) will be embedded into the nano-carrier for the vivo MR monitoring of the genes silencing effects. The expected results of this study will be of great significance in illuminating the mechanism of RFA-induced HCC recurrence and metastasis, and providing important information for exploring an effective molecular targeted therapy.

射频消融术（RFA）因其创伤小、疗效显著，已成为肝癌治疗的主要手段之一。然而，术后高复发率成为临床治疗的难题。RFA可杀死肝癌细胞，但同时也可能激活部分癌细胞侵袭转移程序，尤其是接受亚致死温度的肿瘤周边区域的肝癌细胞，可能发生一系列生物学变化，并成为术后复发的根源。缺氧诱导因子/血管内皮生长因子（HIF-1α/VEGF）和上皮间质转化（EMT）在RFA术后肝癌细胞侵袭转移机制中可能起着关键作用。本课题针对上述信号通路中的关键因子VEGF和Snail，在前期成功制备多功能纳米载体的基础上，赋予纳米载体对肝癌细胞的靶向性，利用siRNA技术，靶向传输siRNA到肝癌细胞，协同沉默VEGF、Snail基因，达到拮抗肝癌复发转移的目的；同时在纳米胶束内包埋超顺磁性氧化铁纳米颗粒，实现对基因沉默效果的MR监测。本课题预期结果对阐明RFA术后肝癌复发转移的机制并寻求有效的分子靶向治疗方法具有重要意义。

肝癌（HCC）射频消融（RFA）术后高复发率成为临床治疗的难题，RFA可能激活残癌细胞侵袭转移程序，尤其是接受亚致死温度的肿瘤周边区域的肝癌细胞，可能发生一系列生物学变化，并成为术后复发的根源。（1）本课题在成功构建HCC体外、体内不完全消融模型的基础上，证实不完全消融可促进残余HCC细胞发生EMT转变，但同时我们发现snail及VEGF-A的表达水平变化与不完全消融诱导的EMT并无明显相关性；也发现利用siRNA联合索拉非尼不能有效抑制HCC不完全消融后的侵袭行为，提示以snail及VEGF为靶点拮抗RFA术后肝癌复发转移的效果欠佳。（2）研究中我们发现由糖基化转移酶OGT催化的O-GlcNAc糖基化修饰与HCC热耐受性及不完全消融后的EMT转变具有高度的相关性。因此，我们将糖基转移酶OGT作为新的治疗靶点，构建负载OGT siRNA的纳米载体，实现了对HCC细胞OGT基因的高效靶向沉默。体内外实验研究表明，纳米靶向OGT治疗通过削弱HCC细胞的热耐受性抑制不完全消融后肿瘤进展，从而显著延长了荷瘤小鼠模型的生存期。该研究在国际上首次通过阐明不完全消融后HCC代谢重编程机制，为研究HCC消融术后复发与转移提供了新的思路及方向。（3）研究中我们还成功设计了一种可生物降解的 mPEG-PBLA复合物，通过自组装稳定地将抗癌药物DOX和MRI 诊断剂SPION包含在复合物的核心中。我们在负载HepG-2皮下瘤的BALB/c裸鼠模型上，证实MR可视化纳米载体可实现非侵入性的肿瘤细胞成像和示踪。该研究为实时评估基因治疗的效果建立了一种MR活体监测手段。