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Excerpts from Technology Review:
In one unusual form of biological attack, researchers are engineering viruses to
seek and destroy the cells that run amok in cancer patients. After more than 10
years of lab work, researchers in the field of oncolytic therapy have reached a
sort of critical mass, deploying their designer viruses in a number of human
trials.
The idea is astonishingly simple: let viruses do what they always dobut only
to cancer cells. All viruses infect host cells and trick them into replicating
the virus until the cells burst, releasing the new viruses. But unlike other
viruses, oncolytic, or cancer-bursting, viruses reproduce in and destroy only
cancer cells, leaving normal cells pretty much alone. Viruses are a parasite,
and they want to grow in cells that replicate very effectively to have the
highest opportunity for themselves to replicate, says Matt Coffey, chief
scientific officer of Oncolytics Biotech in Calgary, Alberta. Cancer cells fit
that bill.Several oncolytic viruses have entered human tests. Robert Martuza, a
neurosurgeon at Massachusetts General Hospital and Harvard Medical School and a
pioneer of oncolytic therapy, has done human safety tests of mutated herpes
strains against brain cancer, for instance….Cell Genesys, based in South San Francisco, CA, is developing cancer-targeted
versions of adenovirus, often the culprit behind the common cold; one is already
being tested in prostate cancer patients, and another should enter clinical
trials against bladder cancer early this year.Researchers are exploring ways of coping with patients immune reactions to
oncolytic viruses. One possibility is to administer the virus directly to the
tumor, largely bypassing the blood-based immune system. Or the immune system
might turn out to be as much friend as foe. The immune system will attack the
virus, says Martuza. But at the same time, it will attack the cells the virus is
growing in, so youll get a rejection not only of the virus but also of the
cancer cells.
