One of the main pro-inflammatory and neo-angiogenesis promoting cytokines responsible for our observations in Stat3-deficient tumours is Cxcl1. Cxcl1, the murine orthologue to human IL-8 and CXCL1, is known to be RAS dependent40, to directly attract myeloid cells and to stimulate endothelial cells to promote angiogenesis35, 36. This evidence concerns the gene CXCL8 and neoplasm.