A study funded by Cancer Research UK has provided a surprising insight into the development of a form of skin cancer called squamous cell carcinoma, or SCC.

Researchers based at the charity's London Research Institute and King's College London, working with colleagues at Yale University in the US, found that a supposedly beneficial immune cell appears, under some circumstances, to be involved in SCC development.

The cells, known as Langerhans cells, are widely thought to help protect the body from the disease by removing naturally occurring toxins from tissues.

However, the new research suggests the immune cells also have a darker side.

Skin cancers, including SCC, are caused by damage to DNA by various factors. Ultraviolet light is a major cause of DNA damage, but chemical carcinogens like tobacco smoke and industrial pollution also play a role.

Researchers studies mice that lacked Langerhans cells, and found they were completely resistant to DNA damage when exposed to synthetic toxins. As a result, the mice did not develop skin cancer.

The team then confirmed this finding in human tissues, finding the same effect as that seen in the mice. The research was published in the journal Science.

Professor Adrian Hayday, based both at King's College London and Cancer Research UK's London Research Institute, said the results of the research could influence the approach to treatments of certain types of cancer.

He said: "Langerhans cells may activate immunoprotective components of the immune system and so are often regarded as useful in preventing cancer.

"Here we have actually shown that the opposite is also true - they can also play a role in facilitating development of the disease.

"It is seldom recognised that Langerhans cells are primarily 'scavenging garbage collectors', that identify and try to break down harmful compounds.

"They successfully deal with natural toxins that we come into contact with all the time, such as many in food, but they cannot deal well with some common synthetic toxins from sources such as industrial air pollution.

"This study showed that when these cells attempt to process synthetic toxins, their role changes and their attempt to break down these toxins instead creates even more harmful carcinogenic products that spread to neighbouring cells.

Dr Safia Danovi, senior science information officer at Cancer Research UK, said: "We're used to thinking that cancer arises from one rebel cell working alone, but this research challenges that view and shows that the immune system can sometimes trigger skin cancer when the skin is exposed to certain toxins.

"So although immune cells usually help protect us against diseases, the system isn't foolproof and things can go wrong. We need to study this glitch and perhaps, in the future, we'll be able to harness this knowledge to help cancer patients."

Source: CRUK