Issues

Spiegel and colleagues investigated the function of neutrophils in the intermediate stages of the invasion–metastasis cascade. Splenectomy to reduce the reservoir of myeloid cells suppressed pulmonary metastases in a murine mammary carcinoma model, and was associated with neutrophilia. Further, G-CSF overexpression phenocopied the neutrophilia and metastatic potential of the cancer cells, and G-CSF–induced neutrophils enhanced metastasis after intravasation but before postextravasation colonization. Neutrophils protected cancer cells from natural killer (NK) cell–mediated clearance while still within the lumina of the microvessels. Overall, these results indicate that neutrophils can suppress the activity of NK cells and promote tumor cell extravasation. For details, please see the article by Spiegel and colleagues on page 630. Cover image courtesy of Asaf Spiegel.