Cold viruses used to invade, destroy cancer cells

5/20/98

DENVER (AP) - Two treatments that use cold viruses to invade and destroy cancer cells are showing promise in experiments on gravely ill patients.

Both approaches involve one of the hottest ideas in cancer research - finding ways to exploit the genetic flaws that allow cancer cells to divide and spread endlessly.

Cells become cancerous when they develop a series of genetic errors that let them escape the body's standard repair and surveillance machinery. The most common of these flaws - present in about half of all cancers - are in a gene called p53. This gene is a kind of genetic watch dog that ordinarily stops cells from reproducing if any of their other genes are damaged.

The two experimental approaches were described Tuesday at a meeting of the American Society for Clinical Oncology. Both use cold viruses to carry in genes that exploit cancer's reliance on a damaged p53 gene.

The treatments are in very early stages of development, but both have shown at least some effect against tumors when given to patients who have failed all standard treatments.

''I'm excited by this, but there is a lot of work left to do before this has any effect on the way cancer patients are treated,'' said Dr. Mace Rothenberg of the University of Texas in San Antonio.

The new approaches were developed by researchers at M.D. Anderson Cancer Center in Houston and Onyx Pharmaceuticals of Richmond, Calif. Both involve genetically manipulating the adenovirus, a usually modest microbe that causes colds and intestinal upsets.

At M.D. Anderson, scientists weakened the adenovirus and gave it a normal copy of the p53 gene. Then they injected it into the tumors of 20 patients with advanced lung cancer. The intention was to supply a good p53 gene that would take over for the bad one.

''We hope this will induce the cells to kill themselves,'' said Dr. Stephen Swisher, one of the researchers.

The approach has been licensed to Introgen Therapeutics in Houston, which is expected to sponsor a larger study involving 50 to 100 patients with less advanced disease.