French researchers have discovered a new human gene that may play a key role in the progression of breast cancer, according to a report being published in today's issue of Nature, a British scientific journal.
The gene, known as stromelysin-3, has been active in all of the 30 breast cancers that the researchers have examined so far, suggesting that it "may be one of the molecular events required for breast cancer progression," said the researchers from the INSERM Institute of Biological Chemistry in Strasbourg, France.
The gene directs the production of a protein, known as a protease, that is capable of destroying the tissue that surrounds a breast cancer.
As researchers learn more about the protein, they hope to learn how to block the destruction it causes and eventually use this knowledge to design new approaches to breast cancer therapy.
The protein is likely to attract considerable scientific interest because it is so novel. Unlike other cancer proteins, it appears to be produced by the stromal cells that surround the tumor, not the tumor itself
The protein "is seemingly the first example of a protease specifically produced by breast cancer stromal cells," the report said.
Dr. William Stetler-Stevenson of the National Cancer Institute in Bethesda, Md., called the findings new and interesting.
Proteases "have a critical role in tumor invasion and metastasis," Stetler-Stevenson said. The action of these enzymes can "allow tumor cells to escape from the primary tumor into the bloodstream." Eventually, tumor cells "exit the bloodstream and establish a distant metastasis."
If researchers can find a way to block proteases, we "may have a way to prevent metastases," said Dr. Yves DeClerck, an expert on tumor invasion at County-USC Medical Center in Los Angeles.
Over the last decade, researchers have learned a great deal about the initial stages of tumor development on a molecular level. But the precise steps involved in tumor progression have been less certain. One theory has been that tumor cells stimulate destructive changes in the cells that surround them by secreting substances called growth factors.
Using recombinant DNA techniques, the French researchers searched for human genes that were abundant in samples of human breast cancers as compared to non-cancerous tissues. They were able to determine that the new gene was active in the cells surrounding the breast cancer, not the cancer itself. Other experiments suggested that the tumor cells make a substance that triggers the activation of the gene.
According to the American Cancer Society, there were about 150,000 new breast cancer cases in women in the United States in 1990 and 44,000 deaths. The vast majority of the deaths were from metastatic disease, which strikes organs such as the bone, brain and liver.