To elucidate the function of IFT20 in breast cancer cell lines, the mouse breast cancer epithelial cell line, 4T1, was used since the expression level of IFT20 in 4T1 cells was comparable to that in ciliated MEF cells (Supplementary Figure 2A) and no cilia were formed in 4T1 cells treated with or without serum starvation for 36 h (Figure 2A and Supplementary Figure 2B). This evidence concerns the gene IFT20 and breast cancer.