RAC1 and breast carcinoma: Those results also indicated that the mechanism of HGF-induced CXCR4 expression in the MDA-MB-436 breast cancer cell line involved a pathway of activation of the PKCζ and PI 3K/Akt, and that signals stimulated by HGF passed on from PI 3K/Akt to Rac1 and then to PKCζ.