Combination of four serum exosomal miRNAs as novel diagnostic biomarkers for early-stage gastric cancer

The aim of this study was to identify and evaluate exosomal miRNAs in serum as early diagnostic markers for gastric cancer (GC). Methods: Using next-generation sequencing (NGS) and bioinformatics, we identified candidate serum exosomal miRNA markers for early detection of GC in patients. The candidates were further validated by qRT-PCR in 50 newly recruited early-stage GC patients and matched healthy individuals. Results: NGS revealed that the average mappable reads in the RNA libraries were about 6.5 million per patient. A total of 66 up and 13 down-regulated exosomal miRNAs were found in the screened cohort after removal of log2 transformed read counts <5 and p >0.05. In the validation cohort, by comparing candidate exosomal miRNAs levels in early-stage GC patients and healthy individuals, higher levels of miR-92b-3p, let-7g-5p, miR-146b-5p and miR-9-5p were found to be significantly associated with GC. Diagnostic power of the combined panels of the exosomal miRNAs or the combination of exosomal miRNAs and CEA outperformed that of single exosomal miRNA marker for establishing a diagnosis of early-stage GC. In addition, serum levels of exosomal miR-92b-3p were significantly associated with low adhesion, let-7g-5p and miR-146b-5p were significantly correlated with nerve infiltration, and miR146b-5p was statistically correlated with tumor invasion depth in early-stage GC. Conclusions: Serum exosomal miR-92b-3p, -146b-5p, -9-5p, and let-7g-5p may serve as potential noninvasive biomarkers for early diagnosis of GC. Further validation of these candidate exosomal miRNAs in larger experimental cohorts are required in order to confirm the diagnostic values. Overall design: Serum exosomal miRNA profiles of early gastric cancer patients were generated by deep sequencing, in triplicate, using Illumina Hiseq 2500/2000 platform.