FOXK2 and breast cancer: To further confirm the role of FOXK2 in paclitaxel sensitivity and response, we overexpressed FOXK2 in the moderately paclitaxel-resistant MDA-MB-231 breast cancer cells (Supplementary Figure S6a) and found the FOXK2-overexpressing MDA-MB-231 cells were more sensitive to paclitaxel treatment compared with control MDA-MB-231 cells (Supplementary Figure S6b) and had decreased colony-formation capacities in response to paclitaxel (Supplementary Figure S6c).