Abstract：
Immune checkpoint inhibitors (ICIs) offer new options for the treatment of patients with solid cancers worldwide. The majority of colorectal cancers (CRC) are proficient in mismatch-repair (pMMR) genes, harboring fewer tumor antigens and are insensitive to ICIs. These tumors are often found to be immune-deserted. We hypothesized that forcing immune cell infiltration into the tumor microenvironment followed by immune ignition by PD1 blockade may initiate a positive immune cycle that can boost antitumor immunity. Bioinformatics using a public database suggested that IFNγ was a key indicator of immune status and prognosis in CRC. Intratumoral administration of IFNγ increased immune cells infiltration into the tumor, but induced PD-L1 expression. A combined treatment strategy using IFNγ and anti-PD-1 antibody significantly increased T cell killing of tumor cells in vitro and showed synergistic inhibition of tumor growth in a mouse model of CRC. CyTOF found drastic changes in the immune microenvironment upon combined immunotherapy. Treatment with IFNγ and anti-PD1 antibody in CT26 tumors significantly increased infiltration of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs). IFNγ had a more pronounced effect in decreasing intratumoral M2-like macrophages, while PD1 blockade increased the population of CD8+Ly6C + T cells in the tumor microenvironment, creating a more pro-inflammatory microenvironment. Additionally, PD1 induced increased expression of lymphocyte activating 3 (LAG3) in a significant fraction of CD8+ T cells and Treg cells, indicating potential drug resistance and feedback mechanisms. In conclusion, our work provides preclinical data for the Combined immunotherapy of CRC using intratumoral delivery of IFNγ and systemic anti-PD1 monoclonoal antibody.
摘要：
免疫检查点抑制剂（ICIs）为全球实体癌患者的治疗提供了新的选择。大多数结直肠癌（CRC）都精通错配修复（pMMR）基因，携带较少的肿瘤抗原，对ICIs不敏感。这些肿瘤通常被发现是免疫缺失的。我们假设，迫使免疫细胞浸润到肿瘤微环境中，然后通过PD1阻断进行免疫点火可能会引发积极的免疫循环，从而增强抗肿瘤免疫力。使用公共数据库的生物信息学表明，IFNγ是CRC免疫状态和预后的关键指标。肿瘤内施用IFNγ增加了免疫细胞浸润到肿瘤中，但诱导PD-L1表达。在CRC小鼠模型中,使用IFNγ和抗PD-1抗体的组合治疗策略显著增加了T细胞对肿瘤细胞的体外杀伤,并显示出肿瘤生长的协同抑制。CyTOF在联合免疫疗法后发现免疫微环境发生了急剧变化。在CT26肿瘤中使用IFNγ和抗PD1抗体治疗显着增加了多形核骨髓来源的抑制细胞（PMN-MDSC）的浸润。IFNγ在减少肿瘤内M2样巨噬细胞方面有更明显的作用，而PD1阻断增加了肿瘤微环境中CD8+Ly6C+T细胞的数量，创造一个更促炎的微环境。此外,PD1诱导淋巴细胞活化3（LAG3）在CD8+T细胞和Treg细胞的显著部分的表达增加，表明潜在的耐药性和反馈机制。总之,我们的工作为使用IFNγ和全身性抗PD1单克隆抗体的肿瘤内递送联合免疫治疗CRC提供了临床前数据.
