Research unravelling the body’s immune response to the human papilloma virus (HPV), the major cause of cervical cancer, has given scientists important clues to new targets for vaccines against the disease.
HPV has been linked to almost all cases of cervical cancer and researchers are currently trying to develop effective vaccines against the virus to both prevent and treat the disease.
The research is published today (Tuesday) in the British Journal of Cancer (BJC).
Carried out by Cancer Research UK scientists at the University of Birmingham, the study shows that patients who are able to clear HPV infection have a different immune response to those whose infection progresses to cervical cancer.
Understanding more about these differences should help researchers narrow down which proteins potential vaccines should target in order to trigger the immune response that clears HPV infection, and stops cervical cancer from developing.
Cervical cancer is the second most common female cancer worldwide, with an estimated half a million new cases diagnosed each year.
One of the researchers, Dr Jane Steele from the Cancer Research UK Institute for Cancer Studies at the University of Birmingham, says:
“Little was understood about how the immune system’s defence mechanisms work to clear HPV infection. So, to find out more, we studied 41 women at different stages of progression of the disease from HPV infection to cervical cancer. We measured the response of their immune system cells to proteins from the most common type of HPV.
“We found that the patients with pre-cancerous lesions most likely to progress to cervical cancer showed less immune activity from a population of immune cells called helper T cells than the women who were at much less risk.
“This could mean that helper T cells, which are known to play a central role in the immune response, are critical in disease progression. Vaccines aimed to re-activate helper T cell responses to the relevant proteins should be considered.”
Professor John Toy, Medical Director of Cancer Research UK, which owns the BJC, says: “Vaccines are likely to play an important role in helping us control certain cancers in the future and scientists are hopeful that vaccines against HPV might be able to prevent cervical cancer altogether. This research opens up new avenues of investigation for the development of possibly better vaccines.”
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British Journal of Cancer, Volume 93, Issue 2.
The human papilloma viruses (HPVs) are a group of more than 70 different types of virus. They are given numbers to distinguish them. HPVs can be transmitted through sexual intercourse. Some of the HPV viruses can cause genital warts – those numbered HPV 6 and HPV 11. These two are sometimes called low risk because they are not associated with cervical cancer. Some types of HPV are linked to cervical cancer, particularly numbers 16, 18, 30 and 33. They are called high risk because just about all cervical cancers are positive for high risk HPV.
The researchers in this study looked at HPV 16 because it is the most prevalent type, present in up to 70 per cent of cervical cancers.
Cervical cancer is the eleventh most common cancer in the UK. The major cause of the disease is sexually transmitted infection of HPV, although smoking has also been linked as a causal factor.
During 2001 around 2,950 new cases of invasive cervical cancer were diagnosed in the UK, and in 2002 the disease caused 1,120 deaths. Each year 274,000 die from the disease worldwide. Cervical cancer is among the most common female cancers in many countries in the developing world.
Screening for pre-malignancy of the cervix was introduced in the UK in 1964.
A scraping of cells is taken from the surface of the cervix and examined under the microscope to see if any of them are showing signs of becoming cancerous. This is a test for pre-cancer. A positive smear does not mean you have cancer. It means you have cells that, if not treated, might go on to develop into cancerHPV infection/progression to cervical cancer.
Cervical cancer vaccines
Two types of vaccine are being investigated:
- HPV vaccines are being developed to stop HPV infection. If effective vaccines against the strains known to be high risk for cervical cancer could be developed, it might be possible to prevent the disease altogether.
- One UK trial has now recruited all the women it needs. It has been testing a vaccine against 2 of the HPV strains that together cause about 70% of cervical cancers. The researchers hope to develop this vaccine in future so that it will protect against 4 strains – together causing 90% of cervical cancer.
- A worldwide trial of a vaccine closed in June 2005. The aim of the trial is to see if cervarix can prevent HPV infection. It recruited nearly 19,000 women aged 15 to 25. It will be several years before the results are known.
- Another trial is due to start recruiting later in 2005. This trial will recruit 26 to 55 year olds. The aim of the will be to find out the effect of the vaccine on long term HPV infection.
- Cervical cancer vaccines. These are for women who have cervical cancer that has spread or come back after treatment. These types of vaccines try to produce an immune system reaction to the proteins that are involved in the abnormal growth of the cancer cells. The idea is that the immune response will destroy the cancer cells or prevent them from growing. This type of treatment is highly experimental. At this time, cancer vaccines are still largely unproven and still being developed. Cancer Research UK does not know of any cervical cancer vaccine trials recruiting patients in the UK at the moment.
Cancer Research UK
Cancer Research UK’s vision is to conquer cancer through world-class research.
The charity works alone and in partnership with others to carry out research into the biology and causes of cancer, to develop effective treatments, improve the quality of life for cancer patients, reduce the number of people getting cancer and to provide authoritative information on cancer. Cancer Research UK is the world’s leading independent charity dedicated to research on the causes, treatment and prevention of cancer.
For further information about Cancer Research UK’s work or to find out how to support the charity, please call 020 7009 8820.
For further information about Reduce the Risk please visit the Reduce the Risk website.
For more information about different types of cancer, diagnosis and treatment for patients and their families, visit Cancer Research UK’s CancerHelp website.