Crucial gene is the key to skin cancer

A single gene may play a major role in nearly all cases of the most commonly diagnosed human cancer, according to a report published today (Saturday 1st October 2005)*.

Scientists funded by Cancer Research UK and the Association for International Cancer Research (AICR) have shown that cells in over 90 per cent of basal cell carcinomas (BCC), the commonest form of skin cancer, have genetic damage in the same place. They have pinpointed the location to an area of the genome that contains ‘Patched’ (PTCH), a gene already known to be involved in skin and other types of cancer. Genetic damage is caused by UV waves present in sunlight.

But the team, based at Barts and The London, Queen Mary’s School of Medicine and Dentistry, now suggest that PTCH is the “first hit” in a chain of events that leads to BCC, and is, therefore, essential to the development of the disease.

Basal cell carcinoma is the most common form of cancer, affecting tens of thousands of people each year in the UK**. Although most people who develop BCC survive the disease, it can be particularly difficult to cope with. Because it tends to affect areas of the skin exposed to sunlight, such as the face, treatment often leaves highly visible scars or damaged features.

The PTCH gene has been implicated in BCC before, but previous studies were unable to show the full extent of its importance. This study used new technology to pick up the genetic differences between BCC cells and the patient’s healthy cells in much greater detail.

Lead researcher, Professor David Kelsell, says: “We used a technology called a gene chip array that detects any difference between two sets of genes. It’s a vast improvement on previous technologies, which could not pick up certain differences. By comparing a BCC patient’s tumour cells with their healthy cells, we were able to see all of the genetic events that played a part in the development of disease in that individual.

“In about 90 per cent of patients, there was a genetic difference in the same area on chromosome 9 – the location of a number of genes, including the PTCH gene. This means it’s extremely likely the same genetic changes are involved in the majority of cases. As 70 per cent of these tumours were found to have mutations in the PTCH gene, we think this gene is probably the ‘first hit’ in the development of most BCC.”

Dr Muy-Teck Teh, lead author, says: “A ‘signature fingerprint’ for BCC has been identified, which has very few genetic changes compared to that seen in non-skin epithelial cancers like breast and colon. Though PTCH is the major gene in BCCs, other genes may play additional roles in BCC development. Our current studies are trying to find out how mutations in PTCH can lead to the development of this common skin tumour.”

Dr Mark Matfield, AICR’s Scottish scientific consultant says: “There are over two hundred different types of cancer and each one is caused by a handful of key genetic changes. This new gene-testing technology means we will be able to identify them all and that means we can soon start developing treatments aimed at the actual cause of the cancers. What Professor Kelsell and his colleagues have discovered for skin cancer will, we expect, be followed by similar discoveries on many different types of cancer, pushing the study of cancer into the next stage of genetic research.”

Professor John Toy, Cancer Research UK’s Medical Director, says: “The interesting thing about this research is that it suggests a single gene plays an integral role in nearly all cases of BCC. Unravelling how mutations in PTCH play a role in causing this common cancer will provide yet further insights into how cancers arise. But avoiding excess sun exposure will remain the priority in preventing skin cancer.”

ENDS

For media enquiries, please contact the Cancer Research UK press office on 020 7061 8300, or, out of hours, the duty press officer on 07050 264 059. For the AICR contact Dr Matfield on mobile 07990 906145 or Susan Osborne on mobile 07836 229208.