Abstract: Background and purpose: miRNA is a type of single-stranded non-coding RNA molecule with a length of about 21-23 nucleotides, which mainly functions by targeting the 3’ untranslated region (3’UTR) of mRNA so as to inhibit the expression of its target gene. miRNA plays a key role in the occurrence and development of cancer. This study aimed to explore the effect of miR-26b-3p on the biological characteristics of breast cancer and its mechanism. Methods: Real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR) was used to detect the expression level of miR-26b-3p in MCF-7, MDA-MB-231 and MDA- MB-453 breast cancer cell lines. miR-26b-3p mimics were transfected in the breast cancer cells with the lowest expression of miR-26b-3p. Cell proliferation was detected by cell counting kit-8 (CCK-8) assay, and cell migration and invasion abilities were detected by transwell migration and invasion assay. The effects of miR-26b-3p on the growth and metastasis of breast cancer xenografts in nude mice were detected by in vivo imaging system and in vivo metastasis model. Dual luciferase reporter assay was used to detect the interaction between miR-26b-3p and zinc finger E-box binding homeobox 1 (ZEB1). RTFQ-PCR and Western blot were used to detect the expression of ZEB1. Results: The expression of miR-26b-3p was the lowest in MDA-MB-453 cells. After transfection with miR-26b-3p mimics, the expression level of miR-26b-3p was significantly increased (P<0.05). After miR-26b-3p was overexpressed in MDA-MB-453 cells, the cell proliferation (P<0.05), migration (P<0.001) and invasion abilities (P<0.01) were significantly decreased. Overexpression of miR-26b-3p inhibited the growth and metastasis of breast cancer xenografts in nude mice. miR-26b-3p could bind the 3’UTR of ZEB1, and inhibit the expression of ZEB1. Conclusion: miR-26b-3p directly targets ZEB1 and inhibits the proliferation, migration and invasion of breast cancer cells. miR-26b-3p inhibits breast cancer growth and metastasis.

Key words: Breast cancer, miR-26b-3p, Proliferation, Migration, Invasion