To confirm the importance of NSCs expressing CD and/or IFN-β genes in the metastatic breast cancer animal model, we used three types of GESTECs, HB1.F3 as a parental cells, HB1.F3.CD as a representative expressing one suicide gene, and HB1.F3.CD.IFN-β cells as a representative expressing a suicide gene and a cytokine. Here, IFNB1 is linked to breast cancer.