Figure 1.

Signals governing the recruitment of innate immune cells in response to tumour initiation. IL-1β is secreted by PNCs in response to oncogenic transformation, activating local immune cells, which in turn express inflammatory cytokines such as IL-1β and TNFα. H₂O₂ released from PNCs acts as a local chemoattractant for the recruitment of inflammatory leukocytes. CSF-1 and Cxcl12 contribute to the recruitment of macrophages through interaction with CSF-1R and Cxcr4 respectively, these signals are both PNC and macrophage derived. IL-8, expressed by both PNCs and neutrophils in response to tumour initiation, is responsible for neutrophil recruitment via Cxcr1/2.