Acting as a tumour suppressor gene, FOXN3 is reduced in several types of tumours, such as HCC, colon cancer and osteosarcoma,9, 10, 19 but it is upregulated in ovarian cancer and breast cancer, where it acts as an oncogene.11, 29 One explanation for the diverse effects of FOXN3 may be due to the specific cellular and tissue environment.30, 31 In our previous studies, the forced expression of FOXN3 inhibited cell proliferation, the induction of apoptosis, and cell cycle arrest.21 These results indicated that FOXN3 may participate in the malignant transformation of leukaemia cells. Here, FOXN3 is linked to breast cancer.