Skin cancer treatment hope

Exposure to sun is risky

Knocking out a key enzyme may provide a new way to prevent and treat skin cancer, say experts.

The enzyme, called JNK2, has been shown to play a pivotal role in the development of nonmelanoma skin cancers.

A team from the University of Minnesota believes that disrupting the function of JNK2 could break a vital link in the complex chain of chemical interactions that lead to the growth of skin tumours.

Lead researcher Dr Zigang Dong said even a few minutes of exposure to ultraviolet sunlight was enough to stimulate JNK activity in the epidermal cells of the skin.

He said: "If you go out for a few minutes, JNK activity doesn't stay elevated.

"But it looks as though if a person gets too much sun exposure, JNK activity becomes permanently elevated and cancers develop.

"This study indicates that some form of JNK activity is a key step in the process by which nonmelanoma cancers grow."

Dr Dong and his team examined mice which had been bred to lack either of one of two enzymes, JNK1 or JNK2.

Cancer agent

When the mice were two months old, the scientists applied a cancer-causing chemical to the skin of their backs, followed by five-times-a-week exposure to the type of ultraviolet light that causes skin cancer.

It is important to realise that the process of skin cancer development in mouse skin is known to be very different at the molecular level from that in human skin Dr Alan Storey

At 31 weeks of age, just 18% of the mice lacking JNK2 had developed tumours.

However, among mice which produced JNK2 the rate was around 50%.

Nine weeks later, the tumour rate in JNK2-deficient mice had risen to 35% - but the rate was much higher in the other mice.

Among those who produced both enzymes the tumour rate was 56% - but among those who were deficient only in JNK1 the rate had soared to 73%.

The researchers say the results indicate that JNK2 plays a key role in the development of skin cancer.

And that when it is missing, the process is either blocked or at least delayed.

Dr Dong said: "Knocking out the JNK2 enzyme could simply delay the response to ultraviolet light, but if so, it would be significant.

"If we age enough, every one of us will get cancer. But if we can delay the process, that's good progress."

Poor understanding

Dr Alan Storey, of the Cancer Research UK Skin Tumour Laboratory, said ultraviolet light had many effects on the skin cells - including damaging effects such as tanning or sunburn.

However, he said the way ultraviolet light triggered changes associated with cancer development were still poorly understood.

"This new work shows that an enzyme, known as JNK2, plays a role where mouse skin cells become cancerous.

"But it is important to realise that the process of skin cancer development in mouse skin is known to be very different at the molecular level from that in human skin.

"If further studies - conducted in humans - show that JNK2 also plays a part in tumour development in people, that would be very significant and could suggest routes of intervention in the future."

Details of the research was presented at a meeting of the American Association for Cancer Research.