Anti-PD-1/PD-L1 Immunotherapy Response Prediction Signature Construction And Drug Resistance Mechanism Exploration In Non-small Cell Lung Cancer

Non-small cell lung cancer(NSCLC),which includes lung squamous cell carcinoma(LUSC)and lung adenocarcinoma(LUAD),is a health concern in China and worldwide.Due to its superior clinical therapeutic effects,anti-PD-1/PD-L1 antibody immunotherapy has recently caught the attention of many oncologists and researchers.Unfortunately,not all patients respond effectively to this therapy,some suffer from drug resistance.Therefore,it is crucial to identify the characteristics of immunotherapy-responsive patients,analyze the underlying mechanisms of drug resistance,and develop solutions to overcome resistance.Anti-tumor immunity is complexly regulated by various factors such as immunerelated genes,epigenetics,and immune microenvironment.The purpose of this study is to explore the predictive markers for the efficacy of anti-PD-1/PD-L1 immunotherapy and the mechanism of drug resistance from the perspective of immune regulation.The first part of this study found that currently used predictive markers like PD-L1 cannot meet clinical needs,and predictive models constructed based on immune-related gene expression are rarely used in clinical practice due to technical inaccuracies brought by absolute quantification.Here we use a strategy based on the relative expression level of immune-related genes to build a new prediction model—Benefit-Related Gene Pairs Index(BRGPI).BRGPI was significantly associated with progression-free survival in NSCLC patients receiving immunotherapy in internal and external cohort validation.BRGPI was identified as an independent prognostic factor in multivariate regression analysis.BRGPI also performed well in analysis stratified by PD-L1 expression and pathological type.Combined analysis showed that patients in the BRGPI low-PD-L1 high subgroup obtained more clinical benefit from immunotherapy.The BRGPI demonstrated solid and reliable predictive value,showing potential for clinical practice.The underlying mechanisms of LUAD immunotherapy resistance was explored at the epigenetic level in the second part of this study.Adenosine-to-Inosine(A-to-I)RNA editing,a common epigenetic modification mainly caused by the adenosine deaminases acting on RNA(ADAR)family,has been intensively focused for its role in the regulation of innate immune tolerance and cancer progression.Here we found that A-to-I RNA editing levels were upregulated in LUAD based on public data and Sanger sequencing analysis which was associated with ADAR1.A mouse model was constructed to explore the role of ADAR1 in LUAD immunotherapy and the results showed that the ADAR1 knockdown group was more sensitive to anti-PD-L1 immunotherapy.Suppressive tumor microenvironment(TME)characterized by reduced CD8+ T cell infiltration and reduced PD-L1 expression was identified in ADAR1 knockdown group.Mechanism exploration showed more dsRNA was accumulated in cells when ADAR1 was knocked down,accompanied by dsRNA receptors(such as RIG-I,MAVS)and activation of downstream IFN-P signaling.In the final clinical validation,patients with LUAD who had low ADAR1 expression benefited more from immunotherapy.Therefore,ADAR1-mediated A-to-I RNA editing is involved in LUAD immunotherapy resistance through the IFN pathway and is expected to become a new predictive marker and therapeutic target.In summary,this study aims to explore the efficacy predictive markers and drug resistance mechanism of anti-PD-1/PD-L1 immunotherapy in NSCLC.Firstly,a model defined as BRGPI was constructed and verified based on the relative expression of immune-related genes to predict immunotherapy response in NSCLC.The BRGPI model not only showed reliable predictive power at both the RNA and protein levels,but also performed well in both stratification and combination analysis.Then we explored epigenetic ADAR 1-mediated A-to-I RNA editing induced suppressive TME and promoted immunotherapy resistance in LUAD by inhibiting dsRNA-triggered type I IFN signaling.This study provides new ideas for screening patients suitable for immunotherapy,overcoming immunotherapy drug resistance to develop more effective precision treatment strategies and improve the prognosis of NSCLC patients.