Abstract: Objective To investigate the expression of miR-30d in breast cancer tissues and demonstrate the regulative effects of miR-30d ASO on the invasion and migration of breast cancer cells in vitro. Methods The expression of miR-30d in 108 breast cancer tissues and their adjacent tissues were detected by real-time quantitative PCR method. After transfection with miR-30dASO, the biological effects of miR-30d in breast cancer cells was measured by transwell assay and wound healing assay, and invasion-related protein expression was analyzed by western blot. Results The expression level of miR-30d was found to be overexpressed in 50.93%（55/108） of the breast cancer cases (p<0.05). miR-30d expression in breast cancer cells（transfection with miR-30d ASO）was significantly less than control group (p<0.05). Transwell and wound healing assay results showed that the invasion and migration ability decreased greatly after transfection with miR-30d ASO, furthermore,down-regulation of miR-30d resulted in obvious inactivation of MMP2 and MMP9. (p<0.05). Conclusion：miR-30d was overexpressed in human breast cancer. Reduce the expression of miR-30d can effectively inhibit the invasion and migration of breast cancer cells. miR-30d may become a new target for the regulation of invasion and migration in breast cancer.

Key words: miR-30d, breast cancer, Invasion, Migration, Antisense oligonucleotides