We found that tumour-associated macrophages and metastatic HER1-positive colon cancer in liver biopsies expressed a ligand/receptor repertoire that was consistent with our hypothesis and that in vitro CXCL12 could trigger a GM-CSF/HB-EGF paracrine loop whereby mononuclear phagocytes support cancer survival. The gene discussed is CXCL12; the disease is cancer.