An ironclad role in metastasis

Abstract

Cancer![Figure][1] Neutrophils can aid and abet metastasis. IMAGE: DAVID MCCARTHY/SCIENCE SOURCE In the body's defense against cancer, immune cells are generally viewed as friends, not foes. One exception is neutrophils, which promote the growth of metastatic tumor cells. Liang et al. explored the signaling mechanism underlying this effect and identified a surprising culprit. Studying lung metastases in mice, they found that the tumor growth–promoting signal secreted by neutrophils is transferrin, an iron-transporting protein previously thought to be expressed mainly in liver cells. Transferrin synthesis in neutrophils was stimulated by a specific growth factor, called granulocyte-macrophage colony-stimulating factor (GM-CSF), produced by tumor cells in the metastatic microenvironment. Drugs blocking the activity of GM-CSF and its signaling pathway are already available and conceivably could be repurposed as treatments for metastatic disease. Proc. Natl. Acad. Sci. U.S.A. 115 , 11060 (2018). [1]: pending:yes