In addition, if the patient are administered with autologous cancer cells, they enhance the anti-tumor immunity in patients, especially when the cells were engineered to secrete granulocyte-macrophage colony stimulating factor (GM-CSF), which indicate that circulating cancer cells are better recognized by immune cells and they mount anti-tumor response (30, 31), so metastasis make the tumor cells more accessible to immune cells. Here, CSF2 is linked to cancer.