Gene editing could in future help the body's immune system overcome cancer, research suggests.

Findings from an early mouse study have shown that altering the DNA in immune system cells can turn them into potent tumour killers.

Cancer often shields itself from the body's natural defences by exploiting a safety device designed to put brakes on the immune system and stop it running out of control.

By editing out the gene that controls this process in immune system T-cells, scientists left tumours vulnerable to attack.

New drugs called "checkpoint inhibitors" suppress the switch and perform a similar function, but can have severe side effects.

The gene-editing approach only affects those T-cells that target cancer, and so avoids any risk of unchecked cells damaging the body's own tissues.

In the new study, scientists took T-cells from a tumour, removed the safety switch - a protein called PD-1 - multiplied the cells and put them back in the mice. With no PD-1 for the cancer to activate, the T-cells were now free to target and shrink the tumours.

Dr Sergio Quezada, from University College London's Cancer Institute, who co-led the research, said: "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.

"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."

Professor Peter Johnson, chief clinician at charity Cancer Research UK, which funded the study, said: "We know that some cancers can switch off the cells of our immune system, and this interesting laboratory research suggests a new way that we might be able to get around the problem, although this is still some way away from use in the clinic."

The findings are published in the journal Cancer Research.