Introduction

MicroRNAs (miRNAs) are small, non‑coding RNAs that regulate gene expression and play pivotal roles in carcinogenesis. Distinct miRNA expression signatures can discriminate among tumours and normal tissue, and have emerged as promising, minimally invasive diagnostic biomarkers.

Aims & Methods

To characterise the miRNome of advanced gastric adenocarcinoma (AGC), early gastric cancer (EGC) and its precancerous lesions (GPL) in comparison to normal gastric mucosa, and to identify candidate miRNA biomarkers for early diagnosis.
Gastric mucosa samples were prospectively collected from 60 participants in the EpiGASTRIC/EDGAR consortium: 20 with AGC, 20 with EGC/GPL and 20 tumour‑free controls. During the discovery phase, small‑RNA libraries were prepared from tissue samples and sequenced by next‑generation sequencing (NGS). Reads were processed with miRDeep2 against miRBase, and differential expression was analysed with DESeq2, applying a false discovery rate (FDR) < 0.05. Selected miRNAs were then validated in gastric tissue by reverse‑transcription quantitative PCR (RT‑qPCR) and subsequently in matched serum samples by RT‑qPCR.

Results

A total of 823 miRNAs were detected. Compared with controls, 292 miRNAs were significantly deregulated in AGC and 233 in EGC/GPL, with 170 miRNAs commonly deregulated in both tumour groups. For biomarker prioritisation we applied ≥ 4-fold change and mean read count > 400 and we found 20 miRNAs that were consistently differentially expressed and discriminated AGC, EGC and GPL from normal mucosa. 17 of these 20 miRNAs were successfully validated by RT‑qPCR in gastric tissue. In a subsequent serum analysis, two miRNAs – 148a-3p and 223-3p – showed statistically significant differential expression in serum, distinguishing patients with AGC or EGC/GPL from individuals with histologically normal gastric mucosa.

Conclusion

Deep sequencing followed by RT‑qPCR validation identified a 17‑miRNA signature capable of differentiating normal gastric tissue from AGC and EGC/GPL. Within this set, 148a-3p and 223-3p discriminated serum of patients with AGC or EGC/GPL from those with normal mucosa. External validation and further assessment of their diagnostic performance are required, but these miRNAs are promising non‑invasive biomarkers of prevention and diagnosis of gastric cancer.