Immune cells called macrophages are supposed to serve and protect, but cancer has found ways to put them to sleep. Now researchers at the Abramson Cancer Center say they’ve identified how to fuel macrophages with the energy needed to attack and eat cancer cells. Macrophages can either support cancer cell growth and spread or hinder it. But most tumors also express a signal called CD47, which can lull macrophages into a deep sleep and prevent them from eating. Researchers have found that rewiring macrophage metabolism can overcome this signal and act like an alarm clock to rouse and prepare macrophages to go to work. Their findings were published in Nature Immunology.