UK researchers have used a gene editing technique to stop cancer cells from escaping the immune system, in a new approach that could reduce side effects seen with many current immunotherapies.

The PD-1 switch - found on T cells - is a safety device that stops immune cells from attacking healthy human cells. However, this mechanism can be exploited by cancer cells, allowing them to remain hidden from the immune system.

According to a new Cancer Research UK-funded study, published in the journal Cancer Research, cutting off this sleep-switch awakens these killer T cells and enables them to hunt down and target diseased tissue.

The team, from University College London’s Cancer Institute, took T cells from cancerous tumours in mice, used a gene editing technique to remove PD-1, multiplied the T cells and put them back into the mice. They found that the immune system was then able recognise and destroy the cancer cells.

“This is an exciting discovery and means we may have a way to get around cancer’s defences while only targeting the immune cells that recognise the cancer,” said Sergio Quezada, Cancer Research UK scientist and co-lead author of the study.

“While drugs that block PD-1 do show promise, this method only knocks out PD-1 on the T cells that can find the tumour which could mean fewer side effects for patients.”

The next step will be to test this approach in clinical trials, the researchers said.