Identification and validation of blood miRNAs as diagnostic markers of gastric cancer
Authors: Xu Zhouhan , Yang Xuesi , Zhao Ruiqi , Li Xueling , Li Shujie , Wang Qingyu , Li Xize , Liu Fen , Zeng Jiping 
Published: June 2022

Abstract
Objective: Gastric cancer (GC) is one of the leading causes of cancer-related deaths. MicroRNAs (miRNAs) have been identified to play an important role in gastric carcinoma. It can provide a new direction for the diagnosis and treatment of gastric cancer to evaluate the blood-based miRNAs that are differentially expressed in gastric carcinoma.Methods: The gastric cancer patients' blood-based miRNAs datasets GSE113486，GSE112264 and GSE113740 were obtained from the Gene Expression Omnibus (GEO) database. The miRNAs which were differentially expressed in gastric cancer patients' blood compared with the corresponding normal ones were analyzed by the SangerBox. The target genes of the differentially expressed miRNAs were predicted through three miRNA - target genes prediction websites which are Targetscan, Mirtarbase and miRDB, respectively. Subsequently，Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG）functional enrichment analyses were performed using DAVID 6.8 to acquire key biological pathways associated with the differentially expressed miRNAs - target genes. The STRING database and Cytoscape were selected to analyze and visualize the interaction network between the encoded proteins of the target genes. QRT-PCR was used to detect the expression of the selected out possible key miRNAs in human blood species. The correlation of the key miRNAs expression with prognosis of gastric cancer patients and the corresponding diagnostic value were also analyzed by survival prognosis and receivers operating characteristic (ROC) curve. Results: This study identified potential novel blood miRNA biomarkers of gastric cancer. There are a total of 5654 data of the statistically significant abnormal blood miRNAs of gastric cancer patients obtained from GEO database. Combined the data of the three datasets with the RRA method, 20 miRNAs which have the maximum changes were chosen as the differentially expressed miRNAs, 10 up-regulated and 10 down-regulated, respectively. On this basis, 691 up-regulated differentially expressed target genes and 1074 down-regulated ones were selectively predicted. The main biological processes involved in up-regulated genes included autophagosomes maturation, cytosol and protein binding. While for 1074 down-regulated ones, the main biological functions were negative regulation of transcription from RNA polymerase II promoter, nucleoplasm and protein binding. With the help of the protein network analysis, five key blood-based miRNAs were determined, including hsa-miR-125a-3p, hsa-miR-124-3p, hsa-miR-29b-3p, hsa-miR-4276 and hsa-miR-575. The check in human blood species and analysis of patient prognosis and diagnostic value confirmed the prediction could be useful for the early diagnosis and efficacy monitoring. Conclusion: The key blood-based miRNAs in gastric carcinoma determined by bioinformatics and human blood species detection may give a new possibility of the important biomarkers for the diagnosis and prognosis of gastric cancer.