Elongation assays showed that, like DOCK4-depleted cells (Fig. 3d, e), cells lacking either DOCK9 or CDC42 did not elongate upon EGF stimulation as control cells (Fig. 5a–d), suggesting that DOCK9 and CDC42, together with DOCK4 and RAC1, are essential for the elongation and subsequent intercalation of breast cancer cells. Here, DOCK4 is linked to breast cancer.