多功能核酸靶向STAT3/PD-L1介导的抑制性免疫微环境治疗肝细胞肝癌的研究

The immunosuppressive microenvironment protects hepatocellular carcinoma (HCC) from immune clearance, such as dysfunctional immune surveillance, immune checkpoints and activated STAT3 etc., which determine the efficacy of immunotherapy. Our and other studies suggested that 5’-triphosphate small interfering RNA (ppp-siRNA) is the specific ligand of the pattern recognition receptor retinoic acid-inducible gene I (RIG-I), and can effectively activates antitumor immune surveillance. However, our further study showed that ppp-siRNA also triggered several negative immune feedbacks, such as upregulation of PD-L1 and STAT3 activation, which may compromise its antitumor efficacy. The nucleic acid aptamer targeting PD-L1 is the next generation of immune checkpoint blockers. The antisense oligonucleotide inhibitor of STAT3 significantly inhibits the activation of IL-6/STAT3 pathway, and has entered phase I clinical trial in HCC patients. In this study, we intend to construct a novel chimeric nucleic acid, PD-L1apt-STAT3pppsiRNA. On the one hand, it activates immune surveillance by its ppp-siRNA, on the other hand, it blocks the intrinsic and induced negative immune regulation by blockage of PD-L1 and silence of STAT3. Therefore, PD-L1apt-STAT3pppsiRNA may integrate the multiple mechanisms of antitumor immunotherapy and effectively breakdown the immunosuppressive microenvironment of HCC. The results of this study attempt to solve the problem of lack of effective immunotherapy strategies for HCC, and explores a novel targeted delivery of ppp-siRNA for antitumor immunotherapy.

抑制性免疫微环境是肝细胞肝癌逃脱抗肿瘤免疫清除的保护伞，例如免疫监视功能不足、免疫检查点以及STAT3介导的免疫抑制性环路等，阻碍了肿瘤免疫疗法的功效。研究证实，模拟RNA病毒的5’端三磷酸小干扰RNA（ppp-siRNA）能有效激活抗肿瘤免疫。同时，该核酸也上调了PD-L1和STAT3等免疫负反馈信号。我们设想构建一个嵌合型多功能核酸分子(PD-L1apt-STAT3pppsiRNA)，其一端为PD-L1特异性核酸适配体，另一端为特异性沉默STAT3的ppp-siRNA，能够在激活免疫监视的同时，靶向阻断PD-L1和STAT3介导的负性免疫调控，“一石三鸟”，彼此协同，优势互补，更有效地突破肝癌免疫抑制微环境，活化抗肿瘤免疫应答。本课题将在肝癌细胞和活体动物模型中，验证该嵌合体的靶向性、免疫诱导、基因沉默及抗肿瘤的功能和机制。研究结果将为RNAi疗法和肝癌免疫治疗提供新思路和研究基础。

抑制性免疫微环境是肝细胞癌逃脱抗肿瘤免疫清除的保护伞，阻碍了肿瘤免疫疗法的功效。为此，我们设计构建了嵌合型多功能核酸分子（PD-L1apt-STAT3pppsiRNA），其一端为PD-L1特异性核酸适配体，另一端为特异性沉默STAT3的ppp-siRNA。试验结果证实该嵌合体在激活RIG-I介导的免疫监视的同时，靶向阻断PD-L1和STAT3介导的负性免疫调控，有效突破肝癌免疫抑制微环境，活化抗肿瘤免疫应答。其次，我们还拓展探索了导致肿瘤免疫耐受的其它靶点，合成了靶向IDO1和SMG1的ppp-IDO1和ppp-SMG1，并构建了核酸嵌合体，验证了其功能和抗肿瘤效果。此外，在此基金资助下，我们还发现二氯乙酸以及生酮饮食都能够增强溶瘤新城疫病毒（NDV）介导的抗肿瘤免疫应答；提出了一种基于糖酵解和酮体代谢基因的代谢亚型分类，作为预测患者生酮饮食抗肿瘤效果和预后的生物标志；证实了靶向抑制GOT2能够促进谷氨酰胺代谢重编程，并使肝细胞癌对谷氨酰胺酶抑制剂更加敏感。我们的研究成果一方面为靶向STAT3的肿瘤免疫治疗提供一个更有效的武器，另一方面为恶性肿瘤的免疫治疗提供了多个新的联合策略和实验基础。