RESUMO
Emerging evidence suggests that microRNAs (miRNAs) serve an important role in tumorigenesis and development. Although the low expression of miR-125a-5p in gastric cancer has been reported, the underlying mechanism remains unknown. In the current study, the low expression of miR-125a-5p in gastric cancer was verified in paired cancer tissues and adjacent non-tumour tissues. Furthermore, the GC islands in the miR-125a-5p region were hypermethylated in the tumour tissues. And the hypermethylation was negatively correlated with the miR-125a-5p expression. Target gene screening showed that the histone methyltransferase Suv39H1 was one of the potential target genes. In vitro studies showed that miR-125a-5p could directly suppress the Suv39H1 expression and decrease the H3K9me3 levels. On the other hand, the Suv39H1 could induce demethylation of miR-125a-5p, resulting in re-activation of miR-125a-5p. What is more, overexpessing miR-125a-5p could also self-activate the silenced miR-125a-5p in gastric cancer cells, which suppressed cell migration, invasion and proliferation in vitro and inhibited cancer progression in vivo. Thus, we uncovered here that the epigenetic silenced miR-125a-5p could be self-activated through targeting Suv39H1 in gastric cancer, suggesting that miR-125a-5p might be not only the potential prognostic value as a tumour biomarker but also potential therapeutic targets in gastric cancer.