There is increasing evidence that the body s ability to mount an immune response to cancer cells may dictate which patients are cured of cancer by conventional therapy. Macrophages have a central role in both innate and adaptive immunity; both human and experimental cancers become infiltrated by macrophages, however tumour-associated macrophages (TAM) are corrupted by the tumour microenvironment to promote survival, invasion and metastasis of cancer cells. TAM also contribute to immune-suppression in cancer and evasion of anti-tumour immunity. It is not clear what factors promote the pro-tumour TAM phenotype or the signalling pathways involved. The intrinsic anti-tumour potential of macrophages as innate immune cells and their abundance in solid tumours makes them an attractive therapeutic target. The challenge is to block the cancer-promoting function of these cells and restore their anti-tumour effects. We have previously shown that NF-ºB inhibits the classical activation of macrophages in the context of inflammation and cancer and our preliminary data show that NF-ºB activation in TAM inhibits anti-tumour immunity in transplantable models of cancer. Further studies have shown a subset of IKK²-regulated genes in macrophages are dependent on p38 MAP Kinase (MAPK14) and targeting p38 activity in macrophages also blocks the TAM phenotype. These data suggest IKK²-p38 signalling maintains the pro-tumour phenotype of TAM and inhibits anti-tumour immunity.In this project we will extend our preliminary observations in transplantable tumour models to clinically relevant genetic models of spontaneous cancer in mice. We will also map IKK² and p38 target genes in TAM and investigate IKK²/p38 dependent mechanisms of gene regulation.