Light activated magic bullets zap out cancers

Oct 30 2007

Scientists in Britain believe they may be able to use ultra-violet light to render cancer-fighting drugs far more effective.

The ultra-violet (UV) light they say can be used to target tumours far more effectively by activating monoclonal antibodies.

Monoclonal antibodies are considered to be a key weapon in the fight against cancer, but they can also attack healthy tissue; but now Newcastle University researchers say they have found a way to make antibodies only respond when light is shone.

Antibodies are proteins produced by the immune system to help tackle infections and disease.

The researchers say the UV light is shone at the site of the tumour to activate the antibodies with unprecedented precision; other treatments, such as radiotherapy and chemotherapy, often cause serious side-effects by killing off healthy tissues as well as cancer cells.

The body does not as a rule automatically generate the antibodies which are needed to fight cancer, as it does so often with other diseases.

Therapeutic antibodies work either by attacking the disease itself, or by stimulating the body's own T-cells, which regulate the production of its own antibodies.

Such radical therapies while very powerful can be dangerous as was seen in the case of the six volunteers who became seriously ill after drug trials at an independent research unit in the London.

The men's immune systems went into overdrive during a trial of such a therapy at Northwick Park hospital.

The problem is that it is very difficult to make the antibodies specifically target the tumour and they get into places where they are not wanted.

Some however have been safely harnessed into drugs for cancer such as Herceptin for breast cancer and Avastin.

Many others remain unused because a safe way of delivering them to the site of the tumour has yet to be developed.

Professor Colin Self, who led the Newcastle team, developed the treatment over an 11 year period and he says getting the antibodies to specifically target the tumour is very difficult.

The team addressed the problem of delivery, by devising a way of "cloaking" the antibodies with a light-sensitive organic oil which stops them from working until they come into contact with light.

The UV light is then shone at the site of the tumour, and the antibodies kick into action.

When tests were conducted on six mice who had been given ovarian cancer, the treatment killed the tumours in five of the six rodents.

In an ongoing series of experiments, the researchers have designed antibodies that latch directly on to tumours as they circulate in the bloodstream and Professor Self, describes the therapy as the equivalent of ultra-specific magic bullets.

The team suggest the therapy might be particularly effective against prostate cancer, which can be partially removed by surgery, but is a delicate operation because of the danger of damaging a key nerve that could leave the patient becoming impotent or incontinent.

He says his "vision of the future" was one in which someone could be treated as an outpatient, arriving for an injection of cloaked antibodies and then waiting no more than an hour for a few minutes of light therapy.

It is hoped that funding will ensure that clinical trials on humans will begin next year, which will be on secondary skin cancers and not internal tumours.

However experts say even if these and the next stage of clinical trials are successful, it could be more than a decade before such treatment becomes available.

The research appears in the journal ChemMedChem.