Background: USP5, a deubiquitinating enzyme, is linked to various cancers. However, its relationship with immune infiltration and its prognostic significance in non–small-cell lung cancer (NSCLC) remains to be determined. Methods: USP5 expression patterns in NSCLC were analyzed using data sourced from the Gene Expression Omnibus and The Cancer Genome Atlas databases. Functional enrichment analyses were performed to predict the role of USP5 in NSCLC development, and Hub genes were identified through a protein–protein interaction (PPI) network. Immune cell infiltration was assessed via single-sample gene set enrichment analysis, while the prognostic significance of USP5 was evaluated using the Kaplan–Meier method and Cox regression analysis. To facilitate survival rate predictions at different time points, a prognostic model was developed. Previous findings were validated using real-time PCR and in vitro functional assays in NSCLC cell lines. Results: USP5 expression was found to be markedly elevated in NSCLC tissues when compared to normal tissues. Functional enrichment analysis revealed the involvement of USP5 in regulating key pathways linked to lung adenocarcinoma development. PPI network analysis revealed several potential interactions contributing to NSCLC progression. A correlation was observed between higher USP5 levels and the reduced presence of immune cells (e.g., macrophages, CD8+T cells, NK cells, and iDCs) within the tumor microenvironment. ROC curves confirmed the prognostic value of USP5 for NSCLC. Functional studies in NSCLC cell lines confirmed the molecular effects of USP5 on NSCLC development. Conclusions: USP5 appears to be a reliable marker for diagnosing NSCLC and predicting its prognosis. Further investigation into the role of USP5 in immune responses may aid in the development of immunotherapies for NSCLC.

Loss of heterozygosity in HLA-I (HLA-I LOH) may facilitate immune evasion. However, the large population study of HLA-I LOH in Chinese pan-cancer patients remains to be explored. In this study, analysis was performed in 1504 advanced pan-cancer patients and 134 early-stage NSCLC patients using a 1021-gene panel. The consistency between the 1021-gene panel and whole-exome sequencing (WES) was evaluated in 45 samples, where concordant results were obtained in 95.6% (43/45) of the samples. Analytical results revealed that the prevalence of HLA-I LOH presents considerable differences across cancer types. HLA-I LOH was relevant to genomic instability, reflected in higher tumor mutation burden (TMB) level. The incidence of HLA-I LOH in MSS samples was significantly higher than that in MSI-H samples. The alteration frequencies of p53 pathway, RTK/RAS pathway, Notch pathway, Hippo pathway, and Nrf2 pathway in HLA-I LOH group were significantly higher than that in HLA-I stable group (p<0.0001, p<0.0001, p=0.032, p=0.013, p=0.003, respectively). In DNA damage response (DDR) pathways, alterations in CPF pathway and FA pathway are enriched in HLA-I LOH group (p<0.0001, p=0.023, respectively). Besides, HLA-I LOH was accompanied by higher mutation rates of several tumor suppressors, including TP53 and LRP1B. These results may shed light on follow-up research.