Abstract: Objective To detect the expression of miR-4719 in breast cancer tissues and cells and explore its role in regulating invasion and migration of breast cancer cells. Methods qRT-PCR was used to detect the expression of miR-4719 and ARHGAP36 in 30 pairs of human breast cancer tissues and adjacent tissues, two breast cancer cell lines (BT549 and MDA-MB-231) and normal breast cells (MCF-10A). Bioinformatic methods were utilized to analyze the relationship between miR-4719 expression and overall survival of breast cancer patients and predict the potential target gene miR- 4719. miR-4719 mimics, ARHGAP36 shRNA and ARHGAP36 plasmids were transfected into breast cancer cells to test the effects of miR-4719 overexpression, ARHGAP36 knockdown and ARHGAP36 overexpression on cell migration and invasion using wound healing assay and Transwell assay. A dual-luciferase reporter assay was used to verify the direct binding between miR-4719 and 3'-UTR of ARHGAP36. Results Compared with those in adjacent tissues or normal breast cells, the expressions of miR-4719 were significantly decreased and the expression of ARHGAP36 was increased in breast cancer tissues (P<0.001) and breast cancer cell lines (P<0.01). A low expression of miR-4719 was correlated with a poorer overall survival of breast cancer patients (P< 0.05). Overexpression of miR-4719 and ARHGAP36 knockdown both significantly attenuated the invasion and migration abilities of breast cancer cells (P<0.05). The expression of miR-4719 was inversely correlated to that of ARHGAP36 in breast cancer tissues (P<0.01). Dual-luciferase reporter assay confirmed that ARHGAP36 was the target gene of miR-4719 (P<0.01), and exogenous miR-4719 could significantly lower the expression of ARHGAP36 (P<0.05). ARHGAP36 overexpression significantly reversed the inhibitory effects of miR-4719 mimics on migration and invasion of breast cancer cells (P<0.05). Conclusion The expression of miR-4719 is aberrantly decreased in breast cancer tissues to promote migration and invasion of breast cancer cells by up-regulating ARHGAP36 expression.

Key words: breast cancer; miR-4719; ARHGAP36; migration; invasion