Since our previously published study has demonstrated that Rad9 functions as a tumor suppressor by attenuating cellular migration and invasion, and simultaneously inhibiting the EMT in breast and lung cancer cell lines, the involvement of Rad9 in RSV-inhibited cell mobility and induced mesenchymal-epithelial transition (MET) in MCF-7 and A549 cells is further examined. Here, RAD9A is linked to lung cancer.