Channelling potassium to fight cancer

Potassium released from dying tumour cells has now been found to suppress the activity of T cells of the immune system. Enhancing the removal of potassium from T cells restores their ability to attack cancer. See Letter p.539 Cell death in tumours is frequently associated with a poor prognosis, a phenomenon that has previously been attributed to rapidly dividing cancer cells in a resource-limited environment. Robert Eil et al. demonstrate that intratumoural cell death in fact plays an active part in suppressing anti-tumour immunity. They show that elevated extracellular potassium in human and mouse tumour interstitial fluid inhibits T-cell-receptor-induced anti-tumour functions in human and mouse T cells. In addition, this immune suppression can be reversed by enabling tumour-specific T cells to efflux potassium through overexpression of the exporter Kcna3.