Background: Although much progress has been made in the diagnosis of early-stage lung adenocarcinoma (ES-LUAD), the prognosis for ES-LUAD patients with rapid recurrence is still poor. Importantly, there is currently no effective and precise method to screen patients who may develop rapid recurrence. Therefore, it is necessary to identify potential differentially expressed genes (DEGs) in ES-LUAD patients with rapid recurrence and non-rapid recurrence.
Methods: Affymetrix GeneChip Human Transcriptome Array was used to identify DEGs between ES-LUAD patients with rapid recurrence and non-rapid recurrence. Rapid recurrence was defined as recurrence-free survival (RFS) ≦ 1 year and non-rapid recurrence was defined as RFS ≧ 3 years. The biological functions of the DEGs were analyzed by GO and KEGG pathway enrichment analyses. The protein-protein interaction (PPI) network of identified DEGs was conducted by STRING and Cytoscape software. The expression level of crucial hub genes and tumor-infiltrating lymphocytes (TILs) was verified by immunohistochemistry (IHC).
Results: A total of 416 DEGs were identified between ES-LUAD patients with and without rapid recurrence. The results of GO analysis revealed that 2 of the top 10 categories in the domain of cellular component, 2 of the top 10 in the domain of molecular function, and 9 of the top 10 in the domain of biological process were functionally related to immunity. The results of KEGG analysis showed that 6 of the top 8 pathways were functionally involved in immune regulation and inflammatory response. The PPI network analysis identified ten crucial nodal protein, including EGFR, MMP9, IL-1β, PTGS2, MMP1, and 5 histone proteins, which constituted 25 key interactions. IL-1β and PTGS2 expression were closely related to immunity and IHC analysis further revealed that low expression of IL-1β and PTGS2 is associated with rapid recurrence. Kaplan-Meier analysis further revealed that LUAD patients with lower IL-1β or PTGS2 expression had a worse RFS. When the TIL density of CD3+, CD4+, CD8+ and CD20+ subsets was less than 20%, ES-LUAD patients have a higher probability of rapid recurrence.
Conclusion: There were significant differences in the expression of immune-related genes between patients with rapid recurrence and patient with non-rapid recurrence. Immune-related genes such as IL-1β and PTGS2 and TIL density (20%) play important roles in rapid recurrence of ES-LUAD. This study provided a theoretical basis for distinguishing the two types of patients from an immunological perspective.
Keywords: Differentially expressed genes; Early-stage lung adenocarcinoma; IL-1β; Microarray; PTGS2; Rapid recurrence; Tumor-infiltrating lymphocytes.