Previous studies have predominantly reported on prognostic biomarkers for intermediate and advanced-stage LUAD patients [13, 14]. However, with increased awareness of health check-ups and widespread use of CT scans, more early-stage lung adenocarcinomas are being detected, particularly stage I lung adenocarcinoma. The immune system has been demonstrated to play a crucial role in cancer initiation and progression [15]. Recent research has proposed the use of immune-related genes to predict the prognosis of lung adenocarcinoma [16, 17]. However, limited sample sizes, lack of external independent validation, or effective validation have hindered the predictive capabilities of these prognostic markers, and few studies have focused on the predictive value of immune-related genes for stage I lung adenocarcinoma.
In this study, we selected 29 key genes associated with the prognosis of stage I lung adenocarcinoma from immune-related genes. Subsequently, we constructed a prognostic risk model and evaluated its accuracy, validating it in two independent cohorts. Our results demonstrate that the prognostic risk model predicts the prognosis status of stage I lung adenocarcinoma patients with high accuracy across all included data, including GEO and TCGA datasets. Using nomograms to determine the survival probabilities for each stage I lung adenocarcinoma patient, we confirmed the clinical utility of the 29 immune-related prognostic genes. Based on median risk scores, we stratified patients with significantly different overall survival (OS) into high-risk and low-risk groups. The results indicate that higher risk scores correlate with poorer prognosis, while lower risk scores correlate with better prognosis. Additionally, to explore the distinct prognoses of high-risk and low-risk patients, we conducted differential gene analysis and further investigated the identified differentially expressed genes through enrichment analysis and immune infiltration analysis.
In GO analysis, the functions of these differentially expressed genes are significantly related to immunity, regardless of cellular components, molecular functions, or biological processes. KEGG enrichment analysis highlights the importance of pathways such as systemic lupus erythematosus (SLE) formation, neuroactive ligand-receptor interactions, neutrophil extracellular trap formation, and cell adhesion molecules. Interestingly, SLE ranks first. SLE is an autoimmune disease where the immune system erroneously attacks normal tissues and organs in the body. B cell dysfunction is a typical feature of SLE and B cells are major players in humoral immunity, suggesting a close association with humoral immunity in stage I LUAD patients [18]. Both tumors and immune cells have the ability to produce various neurotransmitters, which directly or indirectly impact tumor cell proliferation, migration, invasion, and cancer development [19, 20]. Research has found that neutrophil extracellular traps (NETs) can create a favorable environment for tumor cells, promoting tumor growth, invasion, and metastasis [21]. Cell adhesion can influence tumor cell growth in situ and their ability to spread to other sites. Some tumor-expressed adhesion molecules can enhance tumor cell adhesion to surrounding tissues, thereby promoting tumor growth and dissemination [22]. GSEA analysis reveals significant inhibition of inflammatory responses, complement, immune cells, interferon gamma response and cytokines. Interferon-gamma (IFN-γ) plays a critical role in cell-mediated immune activation and subsequent stimulation of antitumor immune responses, exerting inhibitory, pro-apoptotic, and antiproliferative effects on tumor cells. Additionally, IFN-γ may suppress tumor angiogenesis, induce regulatory T cell apoptosis, and stimulate M1 pro-inflammatory macrophage activity to inhibit tumor progression [23]. The complement system is one of the inflammatory mechanisms activated in the tumor microenvironment. Besides its antitumor mechanisms, such as complement-dependent cytotoxicity and phagocytosis induced by therapeutic monoclonal antibodies, the complement system can also promote immune suppression and tumor growth and invasiveness, particularly through targeting leukocytes and cancer cells with anaphylatoxins [24]. The IL-2/STAT5 signaling pathway plays a crucial role in tumor development and therapy. IL-2 can activate the STAT5 signaling pathway, promoting the activation and proliferation of immune cells, especially CD8 + T cells and natural killer (NK) cells [25]. These immune cells can recognize and eliminate tumor cells, thus inhibiting tumor growth and dissemination [26].
Furthermore, there is a correlation between immune-related genes and tumor immune infiltration. Tumor purity describes the proportion of actual cancer cells within a tumor. Higher purity tumors typically indicate a higher concentration of cancer cells, often necessitating more aggressive treatment strategies to control or eradicate these cancer cells [27]. Our study found that patients with high-risk scores had significantly higher tumor purity compared to those with low-risk scores, while the other three immune scores were significantly lower in high-risk patients, indicating a poorer prognosis. Combining enrichment analysis results, we discovered that immune-related genes impact lung adenocarcinoma in multiple ways, encompassing almost the entire process of tumor development. We further investigated the relationship between immune-related genes and immune cells, finding that tumors in high-risk individuals exert an immunosuppressive effect on the immune microenvironment, impairing the body’s antitumor capabilities and promoting tumor growth.
However, our study has limitations. Firstly, it is not a prospective study. All stage I lung adenocarcinoma patients were selected from public databases. Secondly, the limited number of clinicopathological variables reduces the statistical power of multivariate Cox regression analysis and the prognostic model. Lastly, the predictive performance of the model requires validation in large-scale multicenter cohorts and more patient samples, or through experimental studies to verify the related mechanisms.