Among the 16 common overexpressed genes in both chemoresistant tumors and MCF-7DR cells, Rac1 overexpression was particularly noted, because Rac1 was not only expressed higher in breast tumors than in normal tissues (Supplementary Fig. 1C), but also its overexpression correlated with advanced tumor stage (Supplementary Fig. 1D) and poor survival in breast cancer patients (Supplementary Fig. 1E) in TCGA database. This evidence concerns the gene RAC1 and breast cancer.