Previous studies done in mammary epithelial and breast cancer cell lines have shown that ERK3 promotes cell migration by acting as a guanine exchange factor for CDC42 and Rac1 and by phosphorylating the ART3 subunit of the ARP2/3 complex, leading to filopodia formation at the leading edge and actin polymerisation (15). This evidence concerns the gene CDC42 and breast carcinoma.