GAS6 and colonic neoplasm: GAS6 expression was also upregulated in murine macrophages in response to treatment with the chemotherapeutic agent 5-fluorouracil and co-culture with macrophages or treatment with GAS6 reduced the impact of treatment with 5-fluorouracil on human colon cancer cells, revealing a chemo-protective role for GAS6 produced by macrophages in the tumor microenvironment [36].