Role of downregulated ADARB1 in lung squamous cell carcinoma

Abstract

Non‑small cell lung cancer (NSCLC) is prevalent worldwide. Lung squamous cell carcinoma (LUSC) is one of the main subtypes of NSCLC yet, currently, few biomarkers are available for the diagnosis of LUSC. The present study aimed to investigate the expression and role of adenosine deaminase RNA specific B1 (ADARB1) in lung squamous cell carcinoma (LUSC). Integrative bioinformatics analysis was used to identify the effects of ADARB1 expression on the occurrence and prognosis of LUSC. The expression of ADARB1 was further examined by immunohistochemistry (IHC). Bioinformatics analysis suggested that ADARB1 was downregulated in LUSC, serving as a potential tumor suppressor, and these results were verified by IHC performed on a lung cancer tissue array. Clinical studies suggested that ADARB1 expression and methylation levels were significantly associated with patient characteristics in LUSC. Moreover, ADARB1 global methylation levels were upregulated in LUSC tissues compared with normal lung tissues. Higher methylation levels of cg24063645 were associated with shorter overall survival time of patients with LUSC. A negative correlation was identified between ADARB1 and epidermal growth factor receptor (EGFR) expression in LUSC. Using the Gene Expression Omnibus database, it was suggested that the expression of ADARB1 in LUSC was significantly different compared with that in lung adenocarcinoma. Furthermore, protein‑protein interactions were studied and a biological process annotation analysis was conducted. The present study suggested that ADARB1 was downregulated in LUSC; therefore, ADARB1 may serve as a specific biomarker and a potential therapeutic target for LUSC.

Keywords: adenosine deaminase RNA specific B1; expression; methylation; survival; therapeutics.

Figure 1.

Downregulation of ADARB1 in LUSC tissues and cell lines, as indicated by several databases. The expression of ADARB1 was analyzed by the (A) Genome Mining, (B) Cancer Cell Line Encyclopedia, (C) Oncomine, (D) University of Alabama Cancer Database and (E) Gene Expression Profiling Interactive Analysis databases. ADARB1, adenosine deaminase RNA specific B1; LUSC, lung squamous cell carcinoma; TPM, transcripts per million.

Figure 2.

Downregulation of ADARB1 in the lung cancer tissue array. (A) Immunohistochemistry was used to examine the level of ADARB1 expression in a commercial lung cancer tissue array. (B) Protein levels of ADARB1 were significantly downregulated in the lung tissue of patients with LUSC or LUAD compared with normal lung tissue. ADARB1 expression was significantly decreased in LUSC tissues compared with LUAD tissue samples. ADARB1, adenosine deaminase RNA specific B1; LUAD, lung adenocarcinoma; LUSC, lung squamous cell carcinoma.

Figure 3.

ADARB1 expression is significantly different between LUSC and LUAD. (A) Dataset GSE10245, obtained from Gene Expression Omnibus, suggested that ADARB1 was expressed at a lower level in LUSC compared with LUAD. (B) Difference in ADARB1 expression in LUSC and LUAD cell lines, as determined by Cancer Cell Line Encyclopedia analysis. ADARB1, adenosine deaminase RNA specific B1; LUAD, lung adenocarcinoma; LUSC, lung squamous cell carcinoma.

Figure 4.

Methylation values of ADARB1 in patients with LUSC. (A) Global methylation of ADARB1 in LUSC samples compared with normal samples, using DiseaseMeth. (B) Heat map () acquired from MethSurv described the methylation sites of ADARB1 in LUSC. Red represents upregulation and blue represents downregulation. (C) Relationship between methylation values of cg24063645 of ADARB1 and overall survival time in LUSC. ADARB1, adenosine deaminase RNA specific B1; HR, hazard risk; LR, log rank; LUSC, lung squamous cell carcinoma.

Figure 5.

ADARB1 expression is negatively correlated with EGFR expression in LUSC. The Gene Expression Profiling Interactive Analysis database identified an association between the transcript levels of ADARB1 and EGFR in tissues derived from patients with LUSC. ADARB1, adenosine deaminase RNA specific B1; EGFR, epidermal growth factor receptor; LUSC, lung squamous cell carcinoma; TPM, transcripts per million.

Figure 6.

Functional enrichment analysis of ADARB1-associated co-DEGs in LUSC samples. (A) Volcano plot displayed the genes co-expressed with ADARB1 in LUSC (red represents upregulation, green represents downregulation and black is no change). (B) A protein-protein interaction network of ADARB1-associated co-DEGs was generated using the Search Tool for the Retrieval of Interacting Genes/Proteins database and Cytoscape software (square nodes represent hub genes, round nodes represent co-expression genes; the color represents the degree score; degree score <0.5 represent low values (colored yellow), degree score ≥0.5 represent high values (other colors). (C) Gene Ontology analysis of ADARB1-associated co-DEGs. ADARB1, adenosine deaminase RNA specific B1; co-DEGs, co-differentially expressed genes; LUSC, lung squamous cell carcinoma.