Newly-discovered watchmen DCs instruct T cells to attack and destroy cancer cells

Discovery of potent vaccine target in body's natural defence system

Cancer Research UK scientists have discovered sophisticated 'watchman' cells in humans that can instruct the immune system to destroy foreign invaders like viruses and cancer cells, according to research published in The Journal of Experimental Medicine.

The team, based at Cancer Research UK's London Research Institute, examined human tissues and white blood cells to identify a superior group of dendritic cells (DC) - key players in the body's defences - in humans for the first time.

'Watchmen' DCs hunt down foreign bodies and flag them up for destruction by T cells in the immune system. The newly-discovered DCs are better than ordinary DCs at instructing the T cells to attack and destroy cancer cells and cells infected with viruses.

This finding opens up opportunities for scientists to investigate the potential of these superior DCs in the development of new vaccines for many diseases, including cancer.

Scientists had already discovered a superior subset of DCs in mice, called CD8a+ DC. But until now this group of cells had not been identified in humans.

The team used a new technique to discover human equivalent DCs - called DNGR-1+ DC - in human tissues and developed a method to grow the
DNGR-1+ 'watchmen' DCs from human blood stem cells.

Lead author, Dr Caetano Reis e Sousa, head of the Immunobiology Laboratory at Cancer Research UK's London Research Institute, said: "Our discovery is a crucial step towards harnessing the power of the immune system to fight disease.

"We know these cells are effective 'watchmen' in mice. We now know that these 'watchmen' also exist in humans, which paves the way for the development of better vaccines for diseases such as cancer, tuberculosis and HIV infection.

"We're excited to see whether research that follows on from this discovery will lead to a vaccine we can use to treat cancer patients, but we can't yet say whether this will be the case."

Dr Lesley Walker, director of cancer information at Cancer Research UK, said: "There is a new sophisticated player in the immune system that can now be targeted for use in vaccines to treat cancer. These exciting results open a door for researchers to develop an effective therapy that uses the body's own immune system to fight disease.

"Cancer Research UK is already investing in early clinical trials of experimental vaccines to treat a range of cancers - including bowel, lung, breast and pancreatic cancers - and this new discovery will help us develop more new and efficient ways to target different cancers as effectively as possible with fewer side effects."