Purpose: The microRNA (miR)-31 and miR-143 are pleiotropic anti-metastatic miRs, with an expression that decreases significantly in metastatic breast cancer cells. The aim of this study was to investigate the effect of miR-31 and miR-143 inhibition on metastasis and invasion in both MDA-MB231, MDA-MB468 as well as the MCF-7 breast cancer cell lines and 5-week old female mice.
Methods: Following the cloning of miR-31 and miR-143 into vectors, their expressions were determined before treatment with constructs of miR-31 and miR-143 in cancer cell lines and normal breast cells. Then miR-31 and miR-143 were transfected to the cell lines and the expression was assessed after 48 hrs. Moreover, the levels of migration and invasion were determined in cell lines. These experiments were performed in 5-week old female mice.
Results: The results showed that miR-31 expression before the transfection of miR-31 construct was decreased 4, 70 and 100 times in MCF-7, MDA-MB468 and MDA-MB231 cell lines, respectively, in comparison to normal breast cells; but after the transfection of miR-31 construct, the expression of miR-31 increased 80 times. Additionally, invasion and migration decreased by 15 and 10 times in MDAMB-468. All of the modifications in miR-143 were low in comparison to miR-31. The results of the in vivo experiments were approximately the same as in the in vitro experiments.
Conclusions: It appears that the use of miR-31 is highly efficient than miR-143 in the inhibition of invasion and metastasis in breast cancer. Our study improved our conception about miR-31 and miR-143 and their roles in the identification and therapy of breast cancer.