Unraveling the tumor immune microenvironment in immune quiescent sites

Abstract

The immune system plays an important role in fighting cancer. T cells, a type of immune cell, can kill tumor cells. In the brain, however, T cells are naturally less active, which limits the effectiveness of immunotherapy. To better understand this, we studied how T cells function in tumors in the brain. By growing T cells from brain metastases of skin and lung cancer patients in the laboratory, it became clear that T cells were actually capable of destroying tumor cells outside the body. One challenge seems to be that patient T cell numbers inside the brain are too low to eliminate tumors effectively. In addition, many patients receive dexamethasone to relieve symptoms. This drug suppresses T cell activity, especially upon long-term use. These findings highlight the need to further investigate the balance between T cell activity and dexamethasone use to improve immunotherapy in the brain.