[Expression of circRNA_051778 in Lung Adenocarcinoma-Associated Malignant and Tuberculous Pleural Effusions and Its Clinical Significance].

Objective: To investigate the expression and clinical significance of circular RNA (circRNA) 051778 in lung adenocarcinoma-malignant pleural effusion (LA-MPE) and tuberculous pleural effusion (TPE).

Methods: This is a cross-sectional study. A total of 212 patients were recruited from the Jiangxi Chest Hospital between October 2018 and September 2019, and their pleural effusion samples and/or plasma samples were collected. The exosomal circRNA profile was sketched by circRNA microarray. Differentially expressed circRNAs (DECs) were verified by droplet digital PCR. In addition, a putative circRNA-miRNA-mRNA network was constructed, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to predict the functions of the DECs. The diagnostic value of circRNA_051778 was evaluated by binary logistic regression and receiver operating characteristic curve.

Results: The expression level of circRNA_051778 in the LA-MPE samples was (3.92±0.48) copies/100 ng cDNA, while that in the TPE samples was (21.53±2.22) copies/100 ng cDNA. Compared to that in the TPE samples, circRNA_051778 was significantly downregulated in the LA-MPE samples (<0.001). The potential targets of circRNA_051778 were enriched in positive regulation of GTPase activity, cytoplasm, protein binding, and cancer-related pathways. The area under the curve (AUC) for the combined assessment of circRNA_051778 with liquid-based thin-layer cytology (TCT), erythrocyte sedimentation rate (ESR), and tuberculosis antibody (TBA) was 0.98 (95% confidence interval: 0.97-1.00), with the sensitivity being 88.0% and the specificity being 100.0%.

Conclusion: Exosomal circRNA_051778 is downregulated in LA-MPE. According to the findings from the GO and KEGG analyses, exosomal circRNA_051778 may play a role in cancer development and has the potential to serve as a marker for differential diagnostic of LA-MPE and TPE when it is used in combination with TCT, ESR, and TBA.