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Thursday, 7 November, 2002, 00:11 GMT
Cervical cancer 'hides' in the body
Smear test
Smear tests detect cervical cancer
A virus that causes cervical cancer disguises itself so it can hide from the immune system, researchers have found.

The human papillomavirus (HPV) causes around 99% of cervical cancers and up to 50% of vulval cancers.

Although the link was known, HPV is difficult to treat because after the initial infection, it can lie undetected in cells for years before becoming active.


By preventing women developing the earliest stages of infection we can block the route of the cancer's development

Dr Lesley Walker, Cancer Research UK
Researchers from Cancer Research UK say that now HPV's disguise has been discovered, new treatments for early stages of cervical cancer could be developed.

About 3,200 women are diagnosed with cervical cancer each year in the UK. It is the second commonest cancer in women under 35.

Alarm signal

The mystery was uncovered through research into bovine papillomavirus (BPV), which acts on cows in the same way HPV acts in humans.

A protein called E5 provides the "cloak" for the virus to hide itself in.

It means that the immune system cannot spot the infection early and deal with it.

E5 works by stopping a molecule called MHC class 1 being transported to the surface of a cell.

The molecule normally acts as an alarm signal to the body's immune system to warn that the cell is infected and needs to be attacked.

There are over 70 types of HPV but only some high risk types can cause changes in the cells covering the cervix or vulva, making them more likely to become cancerous.

Pushing figures down

Professor Saveria Campo at the Institute of Comparative Medicine, Glasgow University, who led the research, said: "We know the viral E5 protein is present in high risk types of HPV.

"Now we understand how it works it could lead to treatments that will target this protein and inhibit it.

"The body will then make an effective immune response - stopping infection early and preventing the development of cancer."

Dr Lesley Walker, director of science information at Cancer Research UK, which funded the research with the Medical Research Council, said: "Particularly with cervical cancer we've seen a huge drop of 33% in the number of cases since 1982, largely due to screening.

'Great importance'

"An effective HPV treatment that allows the immune system to do its job could really push these figures down further.

"By preventing women developing the earliest stages of infection we can block the route of the cancer's development."

Sir Paul Nurse, chief executive of Cancer Research UK, said: "The cervical screening programme has been highly successful. The prevention of cancer at as earlier point as possible is of great importance.

"Professor Campo's study of the masking mechanism is another step towards achieving this goal for cervical cancer."

The research is published in the journal Oncogene.

See also:

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