miR-34b Inhibits Breast Cancer Cell Epithelial-Mesenchymal Transition (EMT) and Invasion via Targeting Glioma-Associated Oncogene Protein 1 (Gli1)

Decreased expression of miR-34b is associated with breast cancer. Bioinformatics analysis revealed that miR-34b has a complementary binding site to the 3'-UTR region of glioma-associated oncogene protein 1 (Gli1) mRNA. This study investigated whether miR-34b can target Gli1, then affect EMT and invasion of breast cancer cells. miR-34b and Gli1 expression was measured in normal mammary gland epithelial MCF-10A cells, low metastatic MCF-7 cells, or high metastatic MDA-MB-231 cells. MDA-MB-231 cells were divided into two groups: miR-NC group and miR-34b mimic group followed by analysis of Gli1, E-cadherin and N-cadherin level by Western blot and cell invasion by Transwell assay. There was a targeted relationship between miR-34b and Gli1 mRNA. miR-34b in MCF-7 and MDA-MB-231 cells was significantly downregulated and Gli1 was significantly upregulated, compared that in MCF-10A cells. miR-34b mimic transfection significantly reduced Gli1 and N-cadherin expression and upregulated E-cadherin, and then inhibited EMT. The decreased expression of miR-34b plays a role in increasing Gli1 express and promoting EMI and breast cancer cell invasion. miR-34b overexpression can reverse the above effect on breast cancer cells.