Abstract: Objective To investigate the effect of miR-4443 expression on migration and invasion of breast cancer. Methods We examined the expression of miR-4443 in breast carcinoma in situ and paired adjacent tissues from 3 breast cancer patients with high-throughput sequencing and verified the results using TCGA database. We also detected miR-4443 expressions using real-time quantitative PCR (RT-qPCR) in low invasive and highly invasive breast cancer cells (MCF-7 and MDA-MB-231 cells, respectively). The changes in apoptosis, migration and invasion of MCF-7 and MDA-MB-231 cells after transfection with miR-4443 mimics, mimics-NC, miR-4443 inhibitor or inhibitor-NC were analyzed using flow cytometry, wound healing assay and Transwell invasion assay. The target
gene of miR-4443 was predicted by bioinformatics software and validated by a dual luciferase reporter gene system. RT-qPCR and Western blotting were performed to detect the expression of recombinant human phosphatidyl ethanolamine binding protein 1 (PEBP1) in the transfected cells. Results The expression of miR-4443 was significantly higher in the breast cancer tissues than in the adjacent tissues (P<0.01), and was significantly up-regulated in MDA-MB-231 cells as compared with MCF-7 cells (P<0.01). Transfection with miR-4443 mimics or inhibitors did not obviously affect apoptosis rate of the breast cancer cells (P>0.05), but significantly enhanced or weakened the migration and invasion abilities of the cells, respectively (P<0.01). Bioinformatic analysis identified PEBP1 as the target gene of miR-4443 with a close correlation with metastasis of breast cancer (P<0.01), and the result was confirmed by double luciferase reporter gene assay. The mRNA and protein expression of PEBP1 were significantly lower in MDA-MB-231 cells than in MCF-7 cells (P<0.01), and miR-4443 over-expression or knockdown significantly down-regulated or up-regulated PEBP1 expressions in the cells, respectively (P<0.01). Conclusion MiR-4443 promotes the migration and invasion of breast cancer cells by inhibiting the expression of PEBP1, suggesting the possibility of suppressing miR-4443 expression as a potential therapeutic strategy for breast cancer.

Key words: microRNAs; phosphatidylethanolamine binding protein 1; neoplasm metastasis; breast neoplasms