RAC1 and cancer: MARCO overexpression in peritoneal murine macrophages led to the increased expression of SYK, PI3K and Rac-1, and facilitated macrophage-mediated phagocytosis of SL4 (colon carcinoma cell line) via binding to integrin β5 on cancer cells and activation of SYK-PI3K-Rac1 signaling pathway in TAMs in the co-culture system (28) (Figure 4).