IFN-g是抗肿瘤关键效应分子，在肿瘤免疫检查点抑制剂治疗中起到重要作用。IFN-g除了具有广泛的免疫调节作用，还能够直接抑制肿瘤生长。本项目从IFN-g抑制肿瘤增殖这个现象出发，探讨IFN-g抑制肺癌细胞增殖的分子机制以及被IFN-g抑制的这部分肺癌细胞生物学特征和临床意义。前期研究表明肺癌肿瘤组织IFN-g的表达水平不仅和细胞周期通路有关，而且与DNA复制以及p53通路存在联系。最近研究发现IFN-g可以引发肺癌细胞DNA损伤并激活修复通路，还可以诱导肺癌细胞出现衰老样改变。我们推测IFN-g抑制肺癌细胞增殖，同时引发细胞DNA损伤修复，导致部分癌细胞形成衰老细胞。这些衰老细胞产生衰老相关分泌表型等变化，其分泌的炎症因子影响肿瘤免疫微环境和T细胞免疫应答。我们的研究目标是通过系统性研究IFN-g对肿瘤的影响，寻找提高肿瘤免疫治疗疗效和预防治疗耐药发生的关键靶点。

IFN-g is the most important cytokine implicated in anti-tumor immunity. Targeting PD-1 and CTLA-4 immune checkpoints have shown remarkable anti-tumor effects. The blockade of PD-1 and CTLA-4 in the treatment of cancers leads to a significant upregulation of IFN-g gene expression. More recent findings suggest that loss of IFN-g associated genes in tumor cells serves as a mechanism of resistance to anti-CTLA-4 and PD-1 blockade therapies in melanoma. It is well known that IFN-g inhibits tumor cell proliferation. Recently, using Agilent microarray, we found that the regulatory molecules of cell cycle including E2F1, Cyclin B1, Cyclin E, which play essential role in promoting cell proliferation, were dramatically downregulated in IFN-g highly expressed tumor tissues compared to the ones expressing low level of IFN-g. Interestingly, growth arrest and DNA damage-24 alpha (GADD45a) was significantly upregulated in IFN-g highly expressed tumor tissues. Besides regulating the cell cycle progression, GADD45A plays a critical role in induction of DNA damage and repair signaling. Our preliminary studies showed that lung cancer cells exposure to IFN-g resulted in increased phosphorylation of H2AX, which is a specific biomarker for DNA damage. Furthermore, IFN-g treated lung cancer cells expressed increased level of phosphorylated ATM. ATM is the key sensor for DNA damage and the key initiator of DNA repair signaling. Our results indicate that IFN-g can induce DNA damage and repair signaling in lung cancer cells. DNA damage and repair signaling not only blocks cell cycle progression but also induces cell senescence. Senescent cells produce multiple types of cytokines including several inflammatory cytokines such as IL-6, IL-8 and IL-1. These inflammatory cytokines can directly inhibit T cell mediated immune response. In addition, IL-6 and IL-8 play critical role in recruiting myeloid derived suppressor cells infiltrating into tumor tissues. As a result, it inhibits adaptive immune responses. In this proposal, we hypothesize that IFN-g induces lung cancer cell DNA damage and repair signaling and results in cell senescence. Cell senescence associated inflammatory cytokines regulate T cell mediated immune function. On the one hand, senescent cells display cell cycle arrest, which represents the anti-tumor effect of IFN-g. On the other hand, cell senescence associated secretory phenotype could affect the T cell function and the status of immune components in tumor microenvironment. Such effect of IFN-g could lead to a new paradigm for tumor immune escape. Investigation of how IFN-g regulates the biological features of tumor cells and how that alternations affect anti-tumor immunity could facilitate identification the key molecule or signaling pathway to manipulate so as to improve the anti-tumor efficacy of IFN-g as well as to prevent the resistance of PD-1 inhibitor based immunotherapy.