Aim: Accumulating evidence indicates that RUNX3 is an important tumour suppressor that is inactivated in many cancer types. This study aimed to assess the role of microRNA (miRNA) in the regulation of RUNX3.
Methods: Four bioinformatic algorithms were used to predict miRNA binding to RUNX3. The correlation between candidate miRNAs and RUNX3 expression in cell lines was determined by real-time reverse transcriptase quantitative PCR (RT-qPCR) and Western blot. Candidate miRNAs were tested for functional effects through transfection of miRNA precursors and inhibitors, and monitoring cell viability, apoptosis and Bim expression. miRNA and RUNX3 expression, RUNX3 methylation and RUNX3 protein levels were assessed in gastric tissue by RT-qPCR, Methylight analysis and immunohistochemistry, respectively.
Results: Bioinformatics, gene and protein expression analysis in eight gastric cell lines identified miR-130b as the top candidate miRNA for RUNX3 binding. Overexpression of miR-130b increased cell viability, reduced cell death and decreased expression of Bim in TGF-beta mediated apoptosis, subsequent to the downregulation of RUNX3 protein expression. In 15 gastric tumours, miR-130b expression was significantly higher compared to matched normal tissue, and was inversely associated with RUNX3 hypermethylation.
Conclusion: Attenuation of RUNX3 protein levels by miRNA may reduce the growth suppressive potential of RUNX3 and contribute to tumourigenesis.
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