Transcriptome Analyses Reveal the Important miRNAs Involved in Immune Response of Gastric Cancer.

MicroRNAs (miRNAs) are crucial factors in gene regulation, and their dysregulation plays important roles in the immunity of gastric cancer (GC). However, finding specific and effective miRNA markers is still a great challenge for GC immunotherapy. In this study, we computed and analysed miRNA-seq, RNA-seq and clinical data of GC patients from the TCGA database. With the comparison of tumour and normal tissues in GC, we identified 2056 upregulated and 2311 downregulated protein-coding genes. Based on the miRNet database, more than 2600 miRNAs interact with these genes. Several key miRNAs, including hsa-mir-34a, hsa-mir-182 and hsa-mir-23b, were identified to potentially play important regulatory roles in the expression of most upregulated and downregulated genes in GC. Based on bioinformation approaches, the expressions of hsa-mir-34a and hsa-mir-182 were closely linked to the tumour stage, and high expression of hsa-mir-23b was correlated with poor survival in GC. Moreover, these three miRNAs are involved in immune cell infiltration (such as activated memory CD4 T cells and resting mast cells), particularly hsa-mir-182 and hsa-mir-23b. GSEA suggested that the changes in their expression may possibly activate/inhibit immune-related signal pathways, such as chemokine signalling pathway and CXCR4 pathway. These results will provide possible miRNA markers or targets for combined immunotherapy of GC.