Development of microRNA-145 for therapeutic application in breast cancer.

MicroRNAs, small non-coding RNAs, are key regulators of tumorigenesis and cancer metastasis through inhibition of gene expression. Therefore, there is increasing interest in developing anti-cancer therapies using microRNAs. In this study, we determined the therapeutic potency of microRNA-145(miR-145) against breast cancer. We found a reverse-correlation between the expression of miR-145 and its target genes, such as fascin-1, c-myc, SMAD2/3 and IGF-1R in breast cancer cell lines and breast cancer patient tissues. Transfected miR-145 mimicking double-stranded oligonucleotides was directly reduced cell proliferation and motility via interaction with 3'UTR of target gene and also indirectly regulates Wnt signaling. An inhibitor of miR-145 nullified this decreasing effect of miR-145 on cell proliferation and motility. We prepared an adenoviral constructed miR-145(Ad-miR-145) and subjected it to breast cancer cells in vitro and orthotopic breast cancer mice in vivo. Ad-miR-145 suppressed cell growth and motility in both the in vitro and in vivo systems. Furthermore, a treatment combining Ad-miR-145 with 5-FU significantly showed anti-tumor effects, compared to treating alone. In conclusion, this study demonstrated that miR-145 suppresses tumor growth by inhibition of multiple tumor survival effectors, and more we suppose that miR-145 is potentially useful in the therapy of breast cancers.