Targeting cytosolic helicases with modified siRNA for immunotherapy of hepatocellular carcinoma

免疫应答能够影响肝癌的肿瘤生长。I型干扰素（IFN）与其他炎症细胞因子在肿瘤免疫监视和增强肿瘤免疫中起关键作用。普遍表达的RIG-I样解旋酶（RLH）视黄酸诱导基因I （RIG-I）和黑色素瘤分化相关蛋白5 （MDA-5）是免疫受体，它们通过I型IFN激活细胞细胞质中病毒RNA的存在，并激活先天和适应性免疫。此外，RLH激活肿瘤细胞内在的线粒体凋亡途径。通过RLH配体联合免疫激活和诱导细胞凋亡在癌症治疗中具有很大的潜力。在5'端含有三磷酸基团的合成RNA分子（ppp-RNA）诱导RIG-I信号传导。将siRNA修饰为pp-siRNA可以将基因沉默与RIG-I激活结合起来，并在几种肿瘤模型中显示出治疗效果。该项目旨在评估RLH作为肝癌治疗靶点和特异性RLH配体的疗效。双功能ppp-siRNA分子将被设计用于特异性沉默肿瘤促进靶点，调节血管生成、增殖和免疫抑制，并将在小鼠肝癌模型中进行开发和验证。此外，将研究优化siRNA递送以有效靶向肿瘤的方法。我们的目标是临床前开发双功能siRNA分子作为HCC患者的新治疗选择。

Immune responses are able to influence tumor growth in HCC. Type I interferon (IFN) in conjunction with other inflammatory cytokines plays a key role in tumor immune surveillance and boosts tumor immunity. The ubiquitously expressed RIG-I-like helicases (RLH) retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated protein-5 (MDA-5) are immunoreceptors that signal the presence of viral RNA in the cytosol of cells and activate innate and adaptive immunity via type I IFN. Furthermore, RLH activate the intrinsic, mitochondrial pathway of apoptosis in tumor cells. The combination of immune activation and apoptosis induction via RLH ligands has great potential in cancer therapy. Synthetic RNA molecules containing a triphosphate group at the 5' end (ppp-RNA) induce RIG-I signaling. Modifying siRNA to ppp-siRNA allows to combine gene silencing with RIG-I activation and has shown therapeutic efficacy in several tumor models. The proposed project aims at evaluating RLH as targets and specific RLH ligands as therapeutic agents for HCC. Bi-functional ppp-siRNA molecules designed to specifically silence tumor promoting targets regulating angiogenesis, proliferation and immune suppression will be developed and validated in mouse models of HCC. In addition, means for optimizing siRNA delivery for effective tumor targeting will be investigated. Our goal is the preclinical development of bi-functional siRNA molecules as novel therapeutic option for patients with HCC.