Proteomics- and bioinformatics-based identification of regulators of radiosensitivity in lung cancer

Background Radiotherapy resistance is a major challenge in lung cancer (LC) treatment, affecting patient outcomes. The protein networks underlying radiotherapy response remain incompletely understood. Objective This study aimed to identify key proteins regulating radiosensitivity and immune-mediated anti-tumor responses. Methods Proteomic data from CPTAC were analyzed to identify differentially expressed proteins (DEPs). Weighted gene co-expression network analysis (WGCNA) was used to identify tumor-related modules. DEPs, WGCNA hub proteins, and radiotherapy-related genes were integrated, and key targets were screened using machine learning algorithms. Associations with immune cell infiltration were assessed using CIBERSORT. Protein expression was validated by Western blotting, and functional effects on proliferation, invasion, migration, viability, apoptosis, and clonogenic capacity were evaluated using EdU, transwell, wound healing, CCK8, flow cytometry, and clonogenic assays. Results WGCNA identified six protein modules. Based on module membership and gene significance, 553 core proteins were obtained. Integration of WGCNA core proteins, DEPs, and radiotherapy-related genes yielded 46 candidate proteins, and machine-learning analyses further identified three hub proteins (ERG, PDLIM2, SYNM). Immune infiltration analysis revealed significant associations between these hub proteins and multiple immune cell subsets. PDLIM2 was markedly downregulated in radiotherapy-resistant LC cells and negatively correlated with PD-L1 expression. Functional assays demonstrated that PDLIM2 overexpression suppressed the proliferation, migration, and invasion of resistant cells and enhanced T cell-mediated cytotoxicity through inhibition of PD-L1. Conclusion This study identified PDLIM2 as a candidate regulator in LC. PDLIM2 reduced tumor aggressiveness and enhanced T cell-mediated cytotoxicity by suppressing PD-L1, indicating its potential value in overcoming LC radioresistance.