Expression studies of the entire HOX gene cluster in breast cancers revealed elevated expression for several members, including HOXA4, B3, B13, C13, D3 and D13. Moreover, HOXB13 overexpression can be used as a component of a two-gene signature predicting poor outcome in tamoxifen-treated patients, and its ectopic expression promotes motility and invasion in vitro[55]. Here, HOXA4 is linked to breast cancer.