In the study of lung metastasis, Lu et al. (2020) reported that circEHMT1 was decreased in human BC tissues, and the overexpression of circEHMT1 inhibited lung metastasis of BC in vitro and in vivo, emphasizing the importance of circEHMT1 in inhibiting BC metastatic potential by reducing MMP2 levels through modulating circEHMT1/miR-1233-3p/KLF4 axis. This evidence concerns the gene KLF4 and breast cancer.