Fig 2: NOX2 mRNA and protein expression levels are downregulated in LUAD cells and tissues. (A) Immunohistochemical analysis of LUAD tumor tissue and matching para-carcinoma tissue. (B) H-score of NOX2 determined by immunohistochemistry; analyzed by paired t-test. (C) Western blotting and (D) reverse transcription-quantitative PCR of the human bronchial epithelial BEAS-2B cell line and human lung cancer NCI-H1975 cell line. **P<0.01 and ***P<0.001. LUAD, lung adenocarcinoma; NOX2, NADPH oxidase isoform 2.

Fig 3: PPI network and univariate Cox analysis. (A) PPI network of NOX2 was generated using the STRING platform. Local clustering coefficient, 0.879. (B) First 30 genes in the PPI network ordered by number of adjacent nodes. (C) Univariate Cox regression analysis. P<0.05 considered to indicate a statistically significant difference. (D) Intersection of (B) and (C) was combined in a Venn diagram. PPI, protein-protein interaction; NOX2, NADPH oxidase isoform 2.

Fig 4: Analysis of the association between NOX2 expression and survival and clinicopathological characteristics. (A) Paired differentiation analysis of NOX2 expression in tumor and normal groups derived from the same patients (n=54). (B) Kaplan-Meier analysis of NOX2 expression. The red and blue lines represent the proportion of surviving patients at each time node. The survival rate decreased over time and the group with high NOX2 expression demonstrated better survival. (C) Kruskal-Wallis rank sum test indicated that NOX2 expression was associated with T classification. (D) The enriched gene sets in the C2 dataset with high NOX2 expression levels. Particular signaling pathways were presented using different colored lines. The graph indicated the enrichment pathways and the vertical lines below indicated the number of genes enriched in each pathway. FDR< 0.05 was identified to be significant. (E) Enriched gene sets in the C7 collection of immunologic gene sets, in samples with high BTK expression. NOX2, NADPH oxidase isoform 2; GSEA, Gene Set Enrichment Analysis; FDR, false discovery rate.

Fig 5: Analysis of TIC proportion in LUAD samples. (A) Bar plot of the proportions of the 22 types of TICs in each LUAD sample. Each column presented the data for a single sample ID. (B) Violin plot showing analysis between the infiltration level of immune cells, and low (green) and high (red) NOX2 expression level groups; the expression groups were split according to the median NOX2 expression level. The Wilcoxon rank sum test was used to assess statistical significance. TIC, tumor-infiltrating immune cells; LUAD, lung adenocarcinoma; NOX2, NADPH oxidase isoform 2.