Researchers Encouraged by Cancer Therapy Advance

For the first time, researchers have blocked the activity of a cancer gene to halt the growth of cancer cells in a test tube.

Because the new approach, reported Friday by researchers from the University of Texas, would affect only cancer cells, it would virtually eliminate the side effects now associated with radiation treatments and chemotherapy.

The Texas researchers caution, however, that the therapy will not be available to humans for years.

Industrial and academic researchers throughout the country have been intensively experimenting with the new approach, which involves the use of synthetic molecules called “antisense RNA,” because it is so promising. But their results have been disappointing so far, experts said, because the treatment seemed to work only sporadically.

Molecular biologist Jack A. Roth and his colleagues at the university’s M. D. Anderson Cancer Center in Houston, however, reported in Friday’s issue of the journal Cancer Research that their variation of the technique seemed to work almost every time.

They hope to start testing it shortly on tumors in mice.

Antisense RNA disrupts the normal flow of genetic information within the cell by binding tightly to a genetic intermediate called “messenger RNA” (ribonucleic acid), a sort of working blueprint for the cell to produce proteins and other products.

The binding prevents the messenger RNA from producing a protein.

In this case, the messenger RNA is a blueprint for an oncogene called K-ras. Oncogenes stimulate the production of tumors, and K-ras is crucial for the initiation and spreading of tumors in the lungs, breasts, colon and pancreas.

Roth and his colleagues devised a gene for K-ras antisense RNA that would produce large quantities of the antisense RNA within the tumor cells. When they introduced the gene into human lung cancer cells in the test tube, the cells lost their ability to grow rapidly and “their size and shape changed back to normal,” Roth said in a telephone interview.

“We’re very excited about this,” he said. “It’s an opportunity to begin to specifically inhibit genes we know can lead to the causation of cancer. If we can affect the fundamental process of cancer . . . we can treat these cancers more effectively and with fewer side effects.”

But, he cautioned, “we don’t want to raise false hopes. This is an advance, not a breakthrough or a cure.”