miR-491-5p functions as a tumor suppressor by targeting JMJD2B in ERα-positive breast cancer.

The involvement of miR-491-5p in breast cancer development is unclear. This study showed that miR-491-5p is significantly downregulated in ERα-positive breast cancer tissues and cell lines and is generally hypermethylated in ERα-positive breast cancer. MiR-491-5p overexpression significantly suppressed estrogen signaling and estrogen-stimulated proliferation of breast cancer cells. Furthermore, the histone demethylase JMJD2B was identified as a direct target of miR-491-5p. The ectopic expression of JMJD2B abrogated the phenotypic changes induced by miR-491-5p in breast cancer cells. Collectively, our data indicate that miR-491-5p plays a tumor suppressor role in the development and progression of breast caner and may be a novel therapeutic target against ERα-positive breast cancer.