Turning Off Cancer Gene Shuts Down Cancer in Mice

By Alison McCook

NEW YORK (Reuters Health) - When a particular cancer-causing gene is turned off for a few days at a time in mice, former cancer cells become healthy cells, and the disease does not return when the gene is turned back on, according to new study findings.

Researchers led by Dr. Dean W. Felsher of Stanford University in California report that when they turned off the gene, MYC, in cancerous mouse bone cells, the cells became healthy, and matured.

Furthermore, when the researchers turned MYC back on, the tumor cells appeared to commit suicide, a cellular process known as apoptosis.

"When you turned off one of those broken genes (such as MYC), even for a short time, the cells change," Felsher told Reuters Health. "And in that new state, the cancer goes away."

The researcher emphasized that this process cannot yet be considered a treatment, which is likely a long ways off. Rather, these results simply demonstrate that a treatment based on this concept might work. "This isn't a treatment--it's an idea," Felsher said.

Reporting in the July 5th issue of Science, Felsher and his colleagues tested the idea by conducting a series of experiments, all based on turning MYC off in mouse bone cancer cells. When the investigators turned off the gene in mice, they found that former tumor bone cells developed into mature healthy bone cells.

In another experiment, Felsher and his team shut off the MYC gene for 10 days, then turned it back on to see if, as they expected, the tumors would grow back. To their surprise, the researchers found that the number of tumor cells dropped significantly 14 days after MYC was turned back on, and most of the cells appeared to have died from apoptosis.

In an interview with Reuters Health, Felsher said that many different genes cause cancer, but removing the gene that "started the ball rolling" changes the entire makeup of the cell. As such, the immature tumor cells can say, "Oh, okay, now I can get back to my normal goal," which is to mature and become normal, healthy cells, the researcher explained. Once those cells become healthy adults, Felsher added, MYC can no longer make them become cancerous.

In an accompanying editorial, Dr. I. Bernard Weinstein of Columbia University in New York proposed that many tumor cells become "addicted to" the activity of certain genes in order to stay malignant. He notes that researchers will have to discover these critical targets in different cancer cells, and if this treatment becomes available, patients may still have to take a combination of different drugs.

SOURCE: Science 2002;297:102-104.