Reduced miR-125a-5p level in non-small-cell lung cancer is associated with tumour progression.

Emerging evidence suggests that microRNAs (miRNAs) serve an important role in tumourigenesis and development. Although the low expression of miR-125a-5p in non-small-cell lung cancer (NSCLC) has been reported, the underlying mechanism remains unknown. In the current study, the low expression of miR-125a-5p in NSCLC was verified in paired cancer tissues and adjacent non-tumour tissues. Furthermore, the CpG island in the miR-125a-5p region was hypermethylated in the tumour tissues, and the hypermethylation was negatively correlated with 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 Suv39H1 expression and decrease the H3K9me3 levels. On the other hand, 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 NSCLC cells, which suppressed cell migration, invasion and proliferation in vitro and inhibited cancer progression in vivo Thus, we found that the epigenetic silenced miR-125a-5p could be self-activated through targeting Suv39H1 in NSCLC, suggesting that miR-125a-5p might not only have the potential prognostic value as a tumour biomarker but also be a potential therapeutic target in NSCLC.