GRB2 and breast cancer: Furthermore, studies conducted with the use of an MDA-MB-231 cell line highlighted that upon EGF stimulation, p66Shc together with Grb-2 not only enhance proliferation but also promote breast cancer cell migration by activating small GTPases: ARF1 (ADP-ribosylation factor 1) and ARF-6 (ADP-ribosylation factor 6) [32].