Mutant cold virus kills cancer cells
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From: Peter Langston <psl>
Date: Fri, 28 Mar 97 15:22:19 -0800
Subject: Mutant cold virus kills cancer cells
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Researchers use mutant cold viruses to attack cancer cells
March 25, 1997 Web posted at: 8:15 p.m. EST
RESTON, Virginia (AP) -- In a novel experiment to stop cancer, 27 patients
have received mutant cold viruses designed to infect their tumor cells
and destroy them.
The idea is to turn the adenovirus, a usually mild-mannered microbe that
causes colds and intestinal upsets, into a kind of hunter that selectively
attacks cancer cells that are fueled by a bad gene.
The strategy was developed by scientists at Onyx Pharmaceuticals of
Richmond, California, and described Tuesday at a meeting sponsored by the
American Cancer Society.
Over the past year, it has been tested mostly in people terminally ill
with head and neck cancer. The results of initial safety studies will be
presented at a conference in Denver in May.
"We are encouraged and are designing a phase 2 study that we hope to start
in the middle of the year," said Christopher A. Maack, who heads
development of the approach at Onyx.
A phase 2 study is intended to determine whether the treatment actually
Protein kills cancer cells
The human studies are being conducted by Drs. Daniel Von Hoff of the San
Antonio Cancer Therapy and Research Center and Stanley Kaye of the Beatson
Oncology Center in Glasgow, Scotland.
Cancers are triggered by a series of genetic mutations that make cells
divide over and over. Often the last mutation to occur is one in the p53
tumor suppresser gene.
Ordinarily, this gene is a sort of genetic watch dog. It makes a protein
that stops the cell from reproducing if any of its other genes are
damaged. Without p53, the cell loses its built-in control over
cancer-causing mutations. About half of all cancers involve harm to p53.
When adenoviruses infect a cell, they produce a protein that disarms the
p53 gene's protein so it can take over the cell's reproductive machinery
and make new copies of itself. Then it releases thousands of new viruses
and kills the cell.
The Onyx researchers have created a form of the adenovirus that is missing
the ability to disarm p53. So if it infects a healthy cell that is making
normal amounts of the p53 protein, it does nothing.
Technique tried on ovarian cancer
But if it invades a cancer cell that lacks p53, it will kill the cell and
release more virus that in turn attacks neighboring cancer cells.
The technique appears to work well when the virus is injected into lab
animals that have tumors.
In the human experiments, researchers have injected the mutant adenovirus
directly into head and neck tumors, as well as into pancreatic cancer
during surgery. On Monday, they tried the approach on the first patient
with ovarian cancer.
Maack said if all goes well, researchers hope to try the treatment on
victims of brain, bladder and liver cancer, too.
Dr. Vincent DeVita Jr. of the Yale Cancer Center raised the possibility
that it may be possible to give people yearly injections of the virus to
cleanse the body of cells with bad p53 genes.
© 1997 Peter Langston