Health & Medicine UT-Led Study Finds Dormant Cancer Cells Block Immune Cells To Disarm Immunotherapy Targeting a signal released by dormant cancer cells could help overcome resistance to immunotherapy and improve cellular therapies for pancreatic cancer. Using mouse models that grow tumors in the pancreas itself, the team tracked a rare population of “quiescent” cells — cancer cells that stop dividing and lie in wait. “Dormant cells make up a minor population of cancer cells within the tumor, which makes them difficult to study. Researchers found that dormant tumor cells protected themselves by recruiting other immune cells. The cells released a protein called EREG that activated nearby macrophages, immune cells that help coordinate the body’s immune response.