Targeting miR-9 in gastric cancer cells using locked nucleic acid oligonucleotides

Joana Filipa Lima, Joana Carvalho, Inês Pinto-Ribeiro, Carina Almeida, Jesper Wengel, Laura Cerqueira, Céu Figueiredo, Carla Oliveira, Nuno Filipe Azevedo

Gastric cancer is the third leading cause of cancer-related mortality worldwide. Recently, it has been demonstrated that gastric cancer cells display a specific miRNA expression profile, with increasing evidence of the role of miRNA-9 in this disease. miRNA-9 upregulation has been shown to influence the expression of E-cadherin-encoding gene, triggering cell motility and invasiveness. In this study, we designed LNA anti-miRNA oligonucleotides with a complementary sequence to miRNA-9 and tested their properties to both detect and silence the target miRNA. We could identify and visualize the in vitro uptake of low-dosing LNA-based anti-miRNA oligonucleotides without any carrier or transfection agent, as early as 2 h after the addition of the oligonucleotide sequence to the culture medium. Furthermore, we were able to assess the silencing potential of miRNA-9, using different LNA anti-miRNA oligonucleotide designs, and to observe its subsequent effect on E-cadherin expression. The administration of anti-miRNA sequences even at low-doses, rapidly repressed the target miRNA, and influenced the expression of E-cadherin by significantly increasing its levels.