Although Rad9 is a potential tumor suppressor in breast and lung cancers, and can selectively regulate genes that contribute to DDR or EMT, such as p21 [12], NEIL1 [13], and Slug [11], other Rad9-targeting genes and factors that may down- or up-regulate the transcription of Rad9 are not yet to be identified [14]. This evidence concerns the gene RAD9A and lung cancer.