Proteins that block cell death and help cells to integrate with blood vessels are crucial in the spread of cancer to the brain.

Brain metastasis is often deadly, but most cancer cells that invade the brain die without establishing a tumour. To find ways in which successful invaders bypass the brain's defences, Joan Massagué of the Memorial Sloan Kettering Cancer Center in New York and his colleagues looked at a set of genes expressed in brain metastases, focusing on two proteins called serpins.

These serpins inhibit another protein called plasminogen activator, which, the authors found, kills cancer cells in the brain. Serpin expression shielded cancer cells from cell death and helped them to spread on the surface of capillaries, establishing a blood supply in their new home.

Cell 156, 1002–1016 (2014)