Using viruses to fight cancer

Contract the common cold to fight cancer � does it sound loony?

Not really, not if cutting-edge research being done by British scientists were to see results. They are readying to launch human trials of the technique of killing tumours by infecting them viruses like that of common cold, reports The Guardian, London.

Currently, there are two weapons in the war against Big C � radiotherapy and chemotherapy. If successful, virotherapy could emerge as the third arm in the war.

Leonard Seymour, professor of gene therapy at Oxford University, will lead the trials later this year. 'In principle, you have got something that could be many times more effective than regular chemotherapy,' he said.

Those who have seen a loved one undergo chemotherapy, or went through the ordeal themselves, know how debilitating the process is. Virotherapy, on the other hand, promises none of it.

The new therapy uses cancer's own working � of suppressing the body's local immune system � as its Achilles heel. Viruses find tumours a great nesting place since there is no immune system to stop them from replicating. What's more, it's not like a great amount of the virus needs to enter the tumour. 'They replicate, you get a million copies in each cell and the cell bursts and they infect the tumour cells adjacent and repeat the process,' Prof Seymour was quoted by The Guardian as saying. He should know, for he has been working with viruses that kill cancer but don't harm healthy tissue.

It's been known for some time that viruses can kill tumour cells; in fact scientific journals have published some aspects of the work. In America viruses have been directly injected into tumours but this technique has one major flaw: it will not work if the cancer is either inaccessible or spread throughout the body.

Where Prof Seymour's solution differs is to mask the virus a la a stealth bomber, away from the radar of the body's immune system which will seek and destroy it otherwise. His technique allows the viruses to work like chemotherapy drugs � reach the tumour through the blood stream. This is done by giving the virus a polymer coat after some chemical modifications.
The virus replicates after infecting the tumour, but hearteningly the copies lack the chemical modifications. The challenge is to contain them within the tumour, otherwise they will be finished by the immune system.

Preliminary research on mice has shows the virus working on tumours that are otherwise resistant to standard cancer drugs.

Virotherapy is expected to be particularly useful in the case of secondary cancers, known as metastases.

The human clinical trials are expected to use two viruses: adenovirus, which gives you a cold-like illness if you have contracted it, and vaccinia, which causes cowpox. The viruses will be uncoated during the trials, delivering them locally to liver tumours in order to find out if the treatment works in humans. The trials, later involving polymer-coated viruses, are expected to take several years.

Researchers hope that some day viruses will become an important part of the arsenal against cancer, a disease that has dogged the human race for centuries.