干扰素诱导基因IFIT家族分子促进I型干扰素抗肝癌作用的机制与应用基础研究

Interferon, especially IFN-α, is widely used in the treatment of malignancies, but for hepatocellular carcinoma patients, it have showed diverse curative outcomes among different patients. Thus, it is clearly urgent to search potential biomarkers for predicting the response to IFN-α adjuvant therapy and to identify the well-responders. Moreover, it is also essential to clarify the underlying molecular mechanisms influencing the response to IFN-α therapy and to open new avenues to improve it. The biological functions of IFN-α rely on the functions of interferon-stimulated genes (ISGs). And our group had applied cDNA microarray and focused on differentially expressed ISGs in HCC tissues, and compared to those in matched nontumor liver tissues, through which we identified RIG-I as a potential candidate. In the following studies, we have demonstrated that RIG-I could enhance response to IFN-α therapy in HCC and the RIG-I expression in HCC tissues may be useful as an independent predictor for IFN-α treatment response. This works has already been published as the cover story of Cancer Cell, with an impact factor of 25.6. Besides RIG-I, we also noticed IFIT family members, including IFIT1\2\3\5 were dramatically downregulated in HCC tissues, and despite the antiviral effects of IFIT family members, its antitumor effect or its effect on IFN pathway are still largely unknown. Thus, we will use hepatocellular carcinoma as a model and focus on the effects and mechnisms of IFITs in the IFN pathway, hoping to identify whether IFITs could also predict the curative outcomes of IFN-therapy as well as providing clues to improve the treatment.

I型干扰素广泛应用于治疗恶性肿瘤，但在肝癌患者中有较大疗效差异，寻求IFN-α疗效预判的分子靶标、探求IFN-α疗效的影响因素并进行相应干预以提高患者对IFN-α治疗的反应性成为亟待解决的重要问题。IFN-a的生物学效应依赖干扰素诱导基因(ISG)的表达，申请人所在课题组通过系统筛选ISG在肝癌中的差异表达，发现RIG-I和IFIT家族分子在肝癌组织中表达均有显著降低，且已证实RIG-I能够促进IFN对肝癌的疗效并作为肝癌IFN治疗疗效预测的分子靶标(Cancer Cell 2014)。IFIT家族分子的作用则有待确定。本研究拟以肝癌为模型，系统研究IFIT家族分子是否通过影响IFN下游效应信号通路影响其他ISG产生，从而对I型干扰素的抗肝癌作用产生影响，并研究IFIT家族分子表达水平是否影响IFNα治疗敏感性，以期提出新的IFN治疗疗效预判的分子靶标，为提高IFNα疗效提供新思路。

抵御病毒感染和诱导细胞凋亡是I型干扰素的重要生物学功能，故而I型干扰素尤其是IFN-α长期以来被广泛应用于病毒感染性疾病和恶性肿瘤的临床治疗。但其在应用于肝细胞肝癌的治疗时的疗效在不同患者中存在较大差异，因此寻求预判治疗疗效的分子靶标以及如何提高患者对IFN-α治疗的反应性就成为后续继续应用IFN-α治疗肝细胞肝癌的应用中亟待解决的重要问题。. I型IFN与细胞表面受体结合并活化JAK-STAT信号通路促使一系列干扰素诱导基因（IFN-stimulated genes，ISG）表达，从而完成IFN的主要生物学效应。于是，我们在肝细胞肝癌的病理组织和癌旁正常组织中筛查了干扰素诱导基因的表达情况，发现IFIT（interferon-induced proteins with tetratricopeptide repeats)家族中IFIT1、2、3、5均在肿瘤组织中低表达。进一步，我们基于用IFN-α治疗肝细胞肝癌的两个临床研究队列中的病历、肿瘤标本和临床疗效数据，验证了IFIT家族分子在肿瘤组织中的表达水平与患者对干扰素治疗疗效的关系。我们发现在IFIT家族分子中，仅有IFIT3在肝细胞肝癌组织中的高表达预示着患者对IFN-α治疗的疗效反应更佳。. 在反复从体内外实验验证IFIT3可以促进IFN-α信号通路从而增强IFN-α的抗肿瘤作用这一现象后，我们对其分子机制进行了探索。我们发现，在应用IFN-α后，IFIT3通过结合STAT1和STAT2并促进STAT1-STAT2的二聚化和磷酸化入核过程，从而增强IFN-α信号通路。