Specifically in breast cancer, Rac/Cdc42/PAK signaling is implicated with therapy resistance of HER2-type (Wang et al., 2006; Ebi et al., 2013; Laurin et al., 2013; Dokmanovic et al., 2014; Desai et al., 2016; Hampsch et al., 2017), triple negative (De et al., 2017), and ER(+) cancers (Cai et al., 2003; Gonzalez et al., 2017). This evidence concerns the gene ESR1 and breast cancer.