Scientists uncover virus's role in skin cancer
Researchers are a step closer to understanding how the HPV virus1 might play a role in the development of some cases of non-melanoma skin cancer (NMSC).
Scientists have known HPVs to be present in some NMSCs for a number of years. But the role they might play in causing these skin cancers has remained a mystery.
Professor Alan Storey, of the Cancer Research UK Skin Tumour Laboratory in London, and colleagues have shown that a protein found in HPV causes skin cells to invade underlying skin tissue. This is a key stage in the development of malignant skin cancer.
They report the findings in today's edition of the journal Cancer Research2.
Over 62,000 cases of NMSC are registered in the UK each year, making it one of the most common forms of cancer.
NMSC is primarily caused by repeated exposure to UV (ultra-violet) light. However, recent studies have shown that a significant number of NMSCs contain DNA from certain types of HPV.
Professor Storey says: "Some types of HPV cause cervical cancer, so finding papillomaviruses in many skin tumours has led scientists to believe HPV might also play a role in causing some skin cancers.
"We made a model of human skin in the laboratory using human skin cells. This enabled us to infect the cells with proteins from HPV to see how they affected the cells' behaviour."
HPV infects the outer layer of the skin - known as the epidermis - which is made of cells called keratinocytes. The deeper layer of skin - called the dermis - is separated from the epidermis by a barrier known as the basement membrane.
When the team inserted an HPV protein called E7 into keratinocytes, they multiplied and migrated down into the dermis, away from the skin surface. In doing so they crossed the basement membrane, which forms the initial barrier against the invasion of skin cancer cells into other tissues.
Professor Storey explains: "Normally, old keratinocytes eventually become the outermost layer of skin and flake off. These are replaced from below by new keratinocytes.
"A key stage of cancer development is when cells begin to spread from their normal place in the body into neighbouring tissues. In the case of NMSC, keratinocytes migrate downwards into the dermis instead of upwards towards the skin surface.
"We have discovered that infection with the HPV E7 protein can kick start this process. In cases of skin cancer where HPV has played a role, we suspect it does so in tandem with the cancer-causing effects of UV light.
"Knowing more about how skin cancer develops could ultimately lead to new ways of preventing and treating this disease in the future.
"The research could also increase our understanding of how other types of cancer begin to spread into neighbouring tissues and around the body. Cancers tend to become much more difficult to treat once they have spread in this way."
Professor Robert Souhami, Cancer Research UK's Director of Policy and Communication, says: "This work contributes to our knowledge of how viruses might play a part in the development of some skin cancers, and may lead to new ways of arresting the viruses' effects.
"It is important to remember that the major cause of skin cancer is over-exposure to the sun's rays. Avoiding excessive exposure, as advised by Cancer Research UK's SunSmart campaign, is still the best way to avoid the cell damage that can lead to most forms of skin cancer."
- Human papillomavirus
- Cancer Research (2005) 60: 2216-2223
Notes to Editor
The team used the E7 protein of HPV strain 8 for this study.
Cervical cancer is primarily caused by HPV strains 16 or 18.
The key messages of Cancer Research UK's SunSmart campaign are:
- Stay in the shade between 11am-3pm
- Make sure you never burn
- Always cover up with a T shirt, wide brimmed hat and sunglasses
- Remember to take extra care with children
- Then use factor 15 plus sunscreen.
For more information, please visit the SunSmart website.
Visit our website CancerHelp UK for clear, easy to understand information about cancer and cancer treatments.