The role of KRT18 in lung adenocarcinoma development: integrative bioinformatics and experimental validation

Lung adenocarcinoma (LUAD) represents one of the most common subtypes of lung cancer with high rates of incidence and mortality, which contributes to substantial health and economic demand across the globe. Treatment today mainly consists of surgery, radiotherapy, and chemotherapy, but their efficacy in advanced stages is often suboptimal and emphasizes the clear need for new biomarkers and therapeutic targets. Using comprehensive bioinformatics analyses consisting of the Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), Human Protein Atlas (HPA) and Clinical Proteomic Tumor Analysis Consortium (CPTAC), immune infiltration analysis and functional enrichment analysis, and single-cell analysis, we examined the potential of keratin 18 (KRT18) as a candidate biomarker in advanced LUAD. KRT18 was significantly elevated in LUAD tissue relative to normal adjacent tissue (p < 0.05), and its expression was correlated with poor clinical-pathological features and inferior prognostic outcome. Furthermore, KRT18 expression was associated with several populations of immune cells, suggesting KRT18 may contribute to the local tumor microenvironment and potentially pathways of immune evasion. Survival analysis indicated that elevated KRT18 expression correlated with poor overall survival (OS), disease-specific survival (DSS), and progression-free interval (PFI), reinforcing its legitimacy as a prognostic tool (AUC = 0.846). Importantly, gene enrichment analysis found KRT18-associated genes enriched for pathways associated with lymphocyte differentiation and immune response pathways, which provides mechanistic insight into biological effects attributed to KRT18. Notably, NU.1025 has demonstrated the capability of reversing KRT18-modulated oncogenic features, and targeted therapeutic strategies can be developed moving forward. In conclusion, our data demonstrate that KRT18 has utility as a potential biomarker but may also serve as a therapeutic target in LUAD and merit further investigation into underlying mechanistic functions and potential therapeutic roles in the clinic.