To investigate the characteristics of the serum exosomal miRNA expression profile in patients with early-stage lung adenocarcinoma (LUAD) and to screen for microRNA (miRNA) biomarkers with value for early diagnosis.

A total of 255 subjects were enrolled from January 2021 to December 2024, including 154 patients with stage Ⅰ LUAD as the LUAD group, 101 patients with benign pulmonary nodules (BPN) as the BPN group, It was randomly divided into the discovery cohort, the screening cohort and the verification cohort. miRNA sequencing was performed, and differentially expressed miRNAs were screened by comparing them with those in the GES137140 dataset. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to validate the differentially expressed miRNAs. The diagnostic performance of candidate miRNAs was evaluated using receiver operating characteristic (ROC) curves, and target genes and related signaling pathways were predicted through bioinformatics analysis.

The average particle size of serum exosomes was 70.0 nm, with a concentration of 3.66×10⁸ particles/ml. In the discovery cohort, 38 overlapping DEmiRs were identified among the two groups, including 10 upregulated and 28 downregulated DEmiRs. Cross-analysis with the GES137140 dataset screened out seven DEmiRs: hsa-miR-486-5p, hsa-miR-346, hsa-miR-130b-3p, hsa-miR-183-5p, hsa-miR-18a-3p, hsa-miR-625-5p, and hsa-miR-25-3p. In both the screening and validation cohorts, compared with the control and BPN groups, exosomal miR-486-5p and miR-346 were upregulated, and exosomal miR-130b-3p was downregulated in the LUAD group (P<0.05). The area under the curve (AUC) for diagnosing early LUAD was >0.7 for miR-486-5p, hsa-miR-346, and miR-130b-3p, with sensitivities of 76.00%, 88.0%, and 92.80%, and specificities of 82.86%, 59.43%, and 61.32%, respectively. The combined detection of miRNAs yielded an AUC of 0.956 (95%CI: 0.921~0.979), with a sensitivity and specificity of 88.0% and 90.48%. The combination of these three miRNAs with tumor markers achieved an AUC of 0.969 (95%CI: 0.949~0.989). Four tools identified 280, 650, and 26 target genes for miR-486-5p, miR-346, and miR-130b-3p, respectively. KEGG analysis showed enrichment of terms such as the JNK signaling pathway and integrins in angiogenesis and other biological processes.

The miRNA signature composed of serum exosomal miR-486-5p, miR-346, and miR-130b-3p demonstrates good diagnostic efficacy for detecting early LUAD and shows promise as a diagnostic marker for early LUAD.