A、How to find a way to deliver viruses to tumours effectively. B、How to inject viruses directly into tumours. C、How to allow vir

British scientists are preparing to launch trials of a radical new way to fight cancer, which kills tumours by infecting them with viruses like the common cold. If successful, virus therapy could eventually form a third pillar alongside radiotherapy and chemotherapy in the standard arsenal against cancer, while avoiding some of the side-effects.
    Leonard Seymour, a professor of gene therapy at Oxford University, will lead the trials later this year. One of the country’s leading geneticists, Prof Seymour has been working with viruses that kill cancer cells directly, while avoiding harm to healthy tissue. "In principle, you’ve got something which could be many times more effective than regular chemotherapy," he said.
    Preliminary research on mice shows that the viruses work well on tumours resistant to standard cancer drugs. "It’s an interesting possibility that they may have an advantage in killing drug-resistant tumours, which could be quite different to anything we’ve had before."
    Researchers have known for some time that viruses can kill tumour cells and some aspects of the work have already been published in scientific journals. American scientists have previously injected viruses directly into tumours but this technique will not work if the cancer is inaccessible or has spread throughout the body.
    Prof Seymour’s innovative solution is to mask the virus from the body’s immune system, effectively allowing the viruses to do what chemotherapy drugs do—spread through the blood and reach tumours wherever they are. The big hurdle has always been to find a way to deliver viruses to tumours via the bloodstream without the body’s immune system destroying them on the way.
    The therapy would be especially useful for secondary cancers, which sometimes spread around the body after the first tumour appears. "There’s an awful statistic of patients in the west with malignant cancers; 75％ of them go on to die from secondary cancers," said Prof Seymour.
    Several more years of trials will be needed, before the therapy can be considered for use in the NHS. Though the approach will be examined at first for cancers that do not respond to conventional treatments, Prof Seymour hopes that one day it will be applied to all cancers.
    20.What’s the possible advantage of virus therapy according to Prof Seymour?
    21.What’s the big challenge facing virus therapy?
    22.What does Prof Seymour want to do with virus therapy?