Our previous work demonstrated that Epithelial Splicing Regulatory Protein 1 (ESRP1) could inhibit the progression of lung adenocarcinoma (ADC). When ESRP1 was upregulated, the interferon (IFN) pathway was activated and Interferon-stimulated gene 15 (ISG15) expression increased exponentially in our microarray result. In this study, we aim to explore the function of ISG15 and its interactions with ESRP1 and to provide new insights for ADC treatment. ISG15 expression in lung ADC tissues was determined by immunohistochemistry (IHC) staining. The effect of ISG15 on lung ADC progression was examined by in vitro and in vivo assays. The mechanism of action on ESRP1 regulating ISG15 was investigated using Western blotting, RT-qPCR, immunofluorescence staining, chromatin immunoprecipitation, and a dual luciferase reporter system. The ISGylation between ISG15 and ESRP1 was detected by co-immunoprecipitation. Patients with high ISG15 expression were associated with higher survival rates, especially those with ISG15 expression in the nucleus. In vitro and in vivo experiments showed that upregulation of ISG15 inhibited EMT in lung ADC. ESRP1 upregulated the expression of ISG15 through CREB with enriched ISG15 in the nucleus. Importantly, ISG15 promoted ISGylation of ESRP1 and slowed the degradation of ESRP1, which demonstrated that ESRP1 and ISG15 formed a positive feedback loop and jointly suppressed EMT of lung ADC. In conclusion, ISG15 serves as an independent prognostic marker for long-term survival in lung ADC patients. We have revealed the protective effect of ISG15 against lung ADC progression and the combinatorial benefit of ISG15 and ESRP1 on inhibiting EMT. These findings suggest that reconstituting ISG15 and ESRP1 may have the potential for treating lung ADC.

我们以前的工作表明，上皮剪接调节蛋白1（ESRP1）可以抑制肺腺癌（ADC）的进展。当ESRP1上调时，干扰素（IFN）途径被激活，干扰素刺激基因15（ISG15）的表达在我们的微阵列结果中呈指数增加。在这项研究中，我们旨在探索ISG15的功能及其与ESRP1的相互作用，并为ADC治疗提供新的见解。通过免疫组织化学（IHC）染色确定肺ADC组织中ISG15的表达。通过体外和体内测定法检查了ISG15对肺ADC进程的影响。使用蛋白质印迹，RT-qPCR，免疫荧光染色，染色质免疫沉淀和双重萤光素酶报告系统研究了对ESRP1调控ISG15的作用机制。通过共免疫沉淀检测到ISG15和ESRP1之间的ISGylation。ISG15表达高的患者与更高的生存率相关，尤其是细胞核中ISG15表达的患者。体外和体内实验表明，ISG15的上调抑制了肺ADC中的EMT。ESRP1通过CREB上调了ISG15的表达，其中核中ISG15的含量很高。重要的是，ISG15促进了ESRP1的ISGylation并减缓了ESRP1的降解，这表明ESRP1和ISG15形成了正反馈回路并共同抑制了肺ADC的EMT。总之，ISG15可作为肺ADC患者长期生存的独立预后指标。我们已经揭示了ISG15对肺ADC进程的保护作用，以及ISG15和ESRP1在抑制EMT方面的综合益处。