A shortcut for early macrophage recruitment into tumors by activated oncogenes

Macrophages play an important role in tumor promotion, usually acting as facilitators of cancer initiation and progression. However, it is not clear how macrophages impact early phases of tumorigenesis. Using genetically modified mouse models, Guo et al. (pp. 247–259) demonstrated that tumor-initiating cells with an activated Hippo pathway are able to recruit macrophages starting from the very early phases of cancer development, mainly through direct activation of genes encoding macrophage chemoattractants and survival factors. The recruited macrophages were of vital importance for protection of tumor-initiating cells against eradication by lymphocyte-mediated immune surveillance. Such a tight link between macrophages and a pathway controlling organ development and size may reflect the normal role of these cells in tissue morphogenesis.