KCTD1 and breast cancer: To address this, we used a Tet-On inducible lentiviral overexpression system to overexpress KCTD1-5 or KILR (Supplementary Fig. 3b), and showed that individual overexpression of KILR but not KCTD1-5 promoted apoptosis, again only in the breast cancer cell lines but not normal breast cells (Fig. 2d, e and Supplementary Fig. 3c-e).