Moreover, DOCK4 functions as a guanine nucleotide exchange factor for the GTPase Rac1, a key regulator of motility 14, 19, 20 and localises at actin‐rich protrusions in migrating breast cancer cells 19, while SNPs within the promoter region of DOCK4 have been detected in breast cancer 22. The gene discussed is RAC1; the disease is breast carcinoma.