Immune cells called macrophages can destroy tumor cells by producing inflammatory proteins that are toxic to the tumor. But the environment inside the tumor somehow halts this production and instead causes the cells to make proteins that promote tumor growth.
The new study identifies a protein, called IKK(beta), that drives this pro-tumor switch. This protein normally stimulates protective inflammation. But in the context of tumors, the study shows, IKK(beta) also blocked the activity of a protein that turns on anti-tumor genes.
When the scientists inactivated IKK(beta) in macrophages from mouse tumors, the tumor-friendly cells went on the attack. These cells also secreted proteins that attracted professional tumor-killing cells that helped to shrink the tumors. The researchers are now conducting clinical trials to determine whether macrophages from cancer patients can be similarly reprogrammed into tumor killers.