Furthermore, CRISPR (clustered regularly interspaced short palindromic repeats)-Cas9-mediated knockout of MALAT1 (~650 bp deletion of the 5′ end) in the MDA-MB-231 breast cancer cell line promoted cell migration and invasion in vitro and lung metastasis in vivo, which could be reversed by ectopic expression of mouse Malat1. Conversely, overexpression of Malat1 in LM2 human breast cancer cells and in 4T1 mouse mammary tumor cells led to a pronounced reduction of their lung metastatic ability in experimental metastasis assays [29]. Here, MALAT1 is linked to breast cancer.