Janus-faced Kupffer cells in tumor metastasis

Kupffer cells are the resident liver macrophages of the liver; other tissues also have resident immune cells e.g., microglia in the brain. These cells have a distinct embryonic lineage when compared with circulating myeloid cells. In both the liver and brain micro-environments activation of their resident immune cells results in the synthesis of multiple growth factors and cytokines which stimulate tumor growth and that in part provide the permissive "soil" in which the tumor "seed" grows. In the manuscript by Wen et al., studies defined whether liver localized Kupffer cells supported or inhibited the growth of colorectal tumor metastases in an immune competent animal model. The authors also determined whether the most important changes in the biology of metastatic tumors were associated with the numbers of CD3-positive T cells and the numbers of VEGF and iNOS expressing cells.