Role of miR-140-3p and miR-140-5p in lung cancer invasion

The precursor of miR-140 is located on chromosome 16q22.1 and produces two mature single strands named miR-140-3p and miR-140-5p, which have been associated with several cancers including non-small cell lung cancer (NSCLC). I aim to investigate the differential expression of these two miR-140 strands in NSCLC and their roles in the invasion of lung cancer cells. My hypothesis is that these two miR-140 strands suppress the progression of the NSCLC by targeting specific gene transcripts. MiR-140-3p and miR-140-5p were downregulated in tissues from NSCLC patients and lung cancer cell lines (A549 and SK-MES-1). The sequencing of the miR-140 precursor indicated two DNA variants in SK-MES-1 cells but not in A549 cells. This might affect the biogenesis of its mature strands because the expression levels of both miR-140-3p and miR-140-5p were lower in SK-MES-1 than in A549 cells. Mimics of miR-140-3p and miR-140-5p reduced the invasive properties of A549 cells and enhanced their adhesion to laminin and collagen, two of the main components of the extracellular matrix. In SK-MES-1 cells, both miR-140-3p and miR-140-5p mimics reduced invasion but only miR-140-5p decreased the migration of the cells. The conditioned media from lung cancer cells treated with the miR-140-3p mimics impaired the tubule formation of primary endothelial cells, suggesting its role as an angiogenesis inhibitor. By using bioinformatic tools, the integrin β 3 (ITGB3) was predicted as a novel target of miR-140-3p, which was validated by Dual-Luciferase miRNA Target Expression Vectors and western blotting. By combining the global data from Kinex™ Antibody Microarray (with 878 antibodies) and RNA-Sequencing, I speculate that miR-140-3p inhibits lung cancer invasion and limits the angiogenic potential of the endothelial cells through the epidermal growth factor receptor (EGFR) signalling pathway. In contrast, miR-130-5p may target cyclin-dependent kinase 3 (CDK3) and sulfatase 2 (SULF2) in NSCLC