Integrated bioinformatics and single-cell analyses reveal the clinical and immunological significance of S100P in lung adenocarcinoma

S100P is a member of the S100 calcium-binding protein family and has been implicated in the development of several human malignancies. However, its clinical significance and potential role in the tumor immune microenvironment of lung adenocarcinoma (LUAD) remain incompletely understood. This study aimed to evaluate the prognostic value of S100P and explore its association with immune infiltration in LUAD. LUAD transcriptomic data and clinical information were downloaded from TCGA and GEO databases. Differential expression, survival, clinicopathological correlation, and functional enrichment analyses were conducted to characterize S100P. Immune infiltration was evaluated using ESTIMATE and ssGSEA algorithms. Associations between S100P expression and immune checkpoints, tumor heterogeneity, genetic alterations, and drug sensitivity were further investigated. Single-cell sequencing data were analyzed to determine the cellular distribution of S100P within the tumor microenvironment. S100P expression was significantly elevated in LUAD tissues compared with normal lung tissues and was associated with poorer overall survival. Increased S100P expression was correlated with advanced T stage and pathological stage. Functional enrichment analysis indicated that S100P-related genes were involved in several cancer-related pathways, including neutrophil extracellular trap (NET) formation. Immune analyses revealed that elevated S100P expression exhibited weak‑to‑moderate correlations with the infiltration levels of several immune cell subsets. Single-cell analysis further revealed that S100P was predominantly enriched in neutrophil-associated cell populations. S100P is highly expressed in LUAD and is associated with unfavorable clinical outcomes and alterations in the immune microenvironment. These findings suggest that S100P may serve as a potential biomarker for evaluating disease progression and immune status in patients with LUAD.